fJass 3T"9T3 Book ^M^_ CQPXRIGHT DEPOSIT. ^ ^ HOG CHOLERA f^)^ THE MACMILLAN COMPANY NEW YORK • BOSTON • CHICAGO • DALLAS ATLANTA • SAN FRANCISCO MACMILLAN & CO.. Limited LONDON • BOMBAY • CALCUTTA MELBOURNE THE MACMILLAN CO. OF CANADA, Ltd. TORONTO HOG CHOLERA ITS NATURE AND CONTROL BY RAYMOND R. BIRCH, B.S., D.V.M., Ph.D. PROFESSOR IN CHARGE OF THE NEW YORK STATE VETERINARY COLLEGE EXPERIMENT STATION AT CORNELL UNIVTERSITY, ITHACA, NEW YORK THE MACMILLAN COMPANY 1922 All rights reserved PRINTED IN THE UNITED STATES OF AMERICA ^ Copyright, 1922, By the MACMILLAN COMPANY. Set up and printed. Published September, 1922. (y)CI.A681947 Press of J. J. Little & Ives Company New York, U. S. A. SfP 21 1922 PREFACE My object in preparing this book has been to place in the hands of those who handle hog cholera definite and authoritative information regarding the disease. There are abundant publications dealing with hog cholera but for the most part they consist of technical papers covering certain restricted phases of the disease, or of attempts to circumscribe the entire subject in the scope of a few pages. Neither meets the needs of the man who must handle hog cholera in the field. More- over these publications appear as bulletins or as special papers in technical journals, and usually they are not at the veterinarian's command at the time he needs them. We are rapidly discarding the old belief that any one who can use a hypodermic syringe can cope with hog cholera. Questions constantly arise regarding diagnosis, complications, when or whether to immunize, which method to use, the subsequent care of the herd, the handling of young pigs, slaughtering from infected herds under inspection, and many other individual prob- lems. The effective handling of hog cholera, like the handling of other diseases, is founded on exact knowledge of the malady itself, but hog cholera differs from other in- fectious diseases in that preventive vaccination against it has served to open the new field of swine practice. VI PKEFACE The result is that there are many veterinarians who will not attempt to cope with the disease, or who, making the attempt, feel the need for guidance. This volume is in no sense a compilation. For the most part it reflects personal experiences gained during ten years of intimate contact with hog cholera in the capacity of practicing and consulting veterinarian, anti- hog-cholera serum producer and research worker, but acknowledgment is due many other members of the veterinary profession whose researches and observations have revealed many of the foundation facts on which the subject matter rests. For statistical and other data I have consulted other authors freely, relying for sta- tistics especially on the numerous and excellent publi- cations of the United States Bureau of Animal Industry. I am indebted to Dr. E. A. Cahill, Director of the Pit- man-Moore Biological Laboratories, Zionsville, Indiana, for some of the illustrations. Dr. y. A. Moore, Dean of the New York State Veteri- nary College at Cornell University, and Dr. J. W. Benner of the College Experiment Station Staff have read the manuscript, and each has offered many valuable sug- gestions which are deeply appreciated. Great care has been taken to make the book a conserva- tive and accurate guide for the practicing veterinarian who must accept farm conditions as he finds them and handle hog cholera so as to secure and retain the con- fidence of his clients. If among other imperfections there are departures from this ideal I trust that my readers will direct my attention to them. R. R. B. CONTENTS CHAPTER PAGE I History and Economic Importance .... 1 II Nature and Cause of Hog Cholera .... 7 III Methods of Dissemination 17 IV Complications 21 V Symptoms and Lesions 35 VI Diagnosis, Differential Diagnosis, Prognosis 58 VII Preparation of Anti-hog-cholera Serum and Hog Cholera Virus 76 VIII Methods of Using Anti-hog-cholera Serum . 118 IX Handling Hog Cholera in the Field . . . 158 X Hog Cholera, Meat Inspection and Garbage Feeding 197 XI Control and Eradication of Hog Cholera . 230 ILLUSTRATIONS PAGE 1. Shoats affected with acute hog cholera 37 2. Lung of pig showing eeehymoses due to acute hog cholera 46 3. Left auricle of pig's heart showing peteehiae due to acute hog cholera 48 4. Spleens showing hemorrhages which are rather typ- ical of acute hog cholera 49 5. Kidney of pig showing numerous peteehiae due to acute hog cholera 51 6. Lymph glands of pig showing hemorrhages caused by acute hog cholera 54 7. Bleeding room in anti-hog-cholera serum laboratory. (Courtesy Pitman-Moore Biological Laboratories) 77 8. Corner of anti-hog-cholera serum laboratory. New York State Veterinary College at Cornell Uni- versity 79 9. Post-mortem room where autopsies on virus pigs are held 88 10. A close view showing the hypering process ... 91 11. Bleeding unit, and hog prepared for bleeding . . 99 12. Bleeding for serum 101 13. Testing anti-hog-cholera serum 107 14. Injecting anti-hog-cholera serum in the ham . . . 119 ix ILLUSTKATIONS PAGE 15. Method of holding shoat for injecting serum in axillary space 120 16. An improvised method of holding shoats for immun- izing 121 17. Convenient hog holder made from ^/2 inch gas pipe, and flexible clothes wire 123 18. Method of preparing snout rope for confining large hogs 124 19. Method of noosing the snout of hog 125 20. Injecting serum behind the ear 129 HOG CHOLERA CHAPTER I HISTORY AND ECONOMIC IMPORTANCE Hog cholera seems to have appeared first on American soil in 1833, at which time an outbreak of the disease was reported in the Ohio valley. It is not definitely known whether the malady orig- inated in this country or in Europe, but it is a rather significant fact that the wild hog has flourished in Eurasia, and not in North America, in spite of the fact that the fauna of the two continents are in most other respects very closely related. It is also of special significance that the earliest authentic report we have of the disease in this country was made at a time when railroads were first being put into operation. It is there- fore possible that it really existed in America prior to that time, and that lack of facilities for its rapid spread prevented it from assuming the proportions of an epizootic. It is true that as early as 1822 an epizootic dis- ease resembling hog cholera was reported in 2 HOG CHOLEEA France, and there is evidence that prior to 1833 outbreaks of a similar nature occurred in other parts of continental Europe. But even with pres- ent-day knowledge hog cholera and other infec- tious swine diseases are sometimes difficult to differentiate, and we are thus in the dark relative to the true causes of all the earlier outbreaks. According to the most authentic records, hog cholera appeared in England in 1862, and from there, in 1887, it was carried to Sweden in a ship- ment of boars. In this same year the disease ap- peared in France and Denmark, and its spread was so rapid and persistent that all European countries have suffered severely from its ravages. To-day, no large area devoted extensively to swine raising is entirely free from hog cholera, and so far as we have been able to ascertain, no country, once invaded, has succeeded in freeing itself of the malady. The Scandinavian countries seem to have suffered least from its effects. Because of its rapid spread and high mor- tality hog cholera has caused and is causing enor- mous losses, the estimate being that in the United States it is responsible for ninety per cent of the deaths from all swine diseases. In this country the annual losses caused by it during the last four decades have ranged between $13,000,000 and $200,000,000, and in the two decades ending "with the year 1914 the average annual loss per one HISTORY AND ECONOMIC IMPORTANCE 6 thousand hogs has been approximately 66. In 1897, the loss per thousand ran as high as 130. Since 1914, the losses due to the disease have been gradually diminishing, and it is believed that more effective sanitary measures and more extensive and judicious use of protective serum have been responsible for this decline. Naturally a disease of such great economic im- portance has been the object of close and pro- longed study. In 1875, Dr. James Law furnished the United States Department of Agriculture with a report setting forth accurately the symptoms and lesions of the disease, and speaking for its transmissibility. Three years later, as a member of a commission of nine men appointed by the De- partment to investigate the disease, he succeeded in transmitting it by inoculation experiments. Dr. Detmers, acting as a member of the same commis- sion, isolated an organism which he regarded as its cause, but his findings were not confirmed. In 1885, Dr. Daniel Elmer Salmon and Dr. Theo- bald Smith isolated an organism, now kno^vn as B, suipestifer, which they believed to be the true cause of hog cholera. Their work was confirmed by trained investigators in this country and Eu- rope, but all attempts to produce immunity to field outbreaks by using B. suipestifer as an im- munizing agent ended in failure. Thus during the late nineties considerable doubt had developed 4 HOG CHOLERA among some scientists relative to the true signifi- cance of this organism in its relation to epizootic hog cholera. This doubt was aroused because hogs that sickened as a result of injections of B, siiipestifer cultures failed to transmit disease to checks, because those that survived injection with cultures of the organism were not immune when exposed in field outbreaks, and because these cul- tures did not always produce disease, while blood from hogs sick as a result of natural infection proved to be quite generally infectious. In 1903, de Schweinitz and Dorset of the United States Bureau of Animal Industry demonstrated that the true cause of epizootic hog cholera is a filterable virus, and this marked an epoch in the history of the disease. Proceeding in the light of this new knowledge, Dorset, Niles and McBryde succeeded, in 1908, in adapting to hog cholera the principles employed by Kolle and Turner, NicoUe and Adil-Bey in pro- ducing a protective serum against rinderpest, a disease of cattle caused by a filterable virus. The work of Dorset and his associates was con- firmed by numerous investigators, among whom were Uhlenhuth, Hutyra and Xylander, and the epochal field experiments conducted in this coun- try by Dr. Niles and described by him in the re- port of the United States Bureau of Animal In- dustry, 1908, fully established the great practical HISTORY AND ECONOMIC IMPORTANCE O usefulness of anti-hog-cholera serum in checking the inroads of hog cholera in the field. Since 1908, rapid advances have been made in providing for an adequate supply of serum, in refining it, in working out methods for its use in the field, and in regulating its production so as to prevent sale of that which is contaminated or im- potent. All important hog-raising states in the Union have made provision to manufacture serum, and scores of private laboratories which have been established are being operated under super- vision of the Bureau of Animal Industry. In the refinement of the serum the aim has been to pro- duce, at low cost, a clear, sterile, potent product with good keeping qualities. This ideal is rapidly being attained, but there are still serious questions regarding uniform potency and keeping qualities of the clear serum, and the equipment required in making it is rather crude, and cannot be said to have passed the developmental stage. Finally, it should be related that with the knowledge that hog cholera can be controlled, there has appeared a quickened interest in all other maladies that affect swine, especially those frequently complicated with hog cholera. Undue importance has sometimes been attached to some of these diseases, and such extravagant claims have been made for certain biologies used as pro- phylactic or therapeutic agents that there has 6 HOG CHOLERA been a sharp reaction, and there are indications at present that the trend of opinion may even swing too far in the opposite direction. The dis- eases that complicate hog cholera present very real problems, and experimental work looking to- ward a deeper understanding of them is one of the immediate needs of the present day. I CHAPTER II NATURE AND CAUSE OF HOG CHOLERA Hog cholera is an acute, communicable, febrile disease which attacks swine of all breeds and ages, but does not afPect other domesticated animals, or man. It is a septicemia. Occasionally a per- acute form of the disease is recognized during the first days of an outbreak and chronic hog cholera is frequently observed among the stragglers that survive the more severe and rapidly terminating forms. In the individual, the disease is charac- terized by sudden onset, inappetence, chilling^ very high fever, arched back, a disposition to hide in the litter, constipation followed by diarrhea, general weakness in the later stages, accompanied by purplish discolorations of the skin covering the belly, ears and snout. In the herd, the onset is relatively slow, the first death usually preceding subsequent ones several days, but after the first week the outbreak rapidly gains momentum, and in a comparatively short time all hogs become in- fected. The mortality ranges between 80 and 100 per cent with a strong tendency to approach the latter figure. 7 8 HOG CHOLEEA Young pigs, especially those farrowed and nursed by immune mothers, are often immune to cholera during the first few weeks of life, and a general impression that all pigs nursing immune sows are likewise immune seems to have gained ground. This impression is not in accord Avith the facts, for we have seen individual pigs born of immune mothers and suckled by them, dead of hog cholera on the seventh day following birth, and under like conditions of birth and sustenance we have frequently seen entire litters succumb to the disease before attaining an age of four weeks. Among older hogs raised in localities where hog cholera is not prevalent, the ^'natural immunes'' so frequently mentioned are by no means common, and it is probable that in places where they are found in considerable numbers they owe their im- munity to the fact that they are exposed to cholera as young pigs, and suffering only a slight reac- tion, are rendered immune. As a general rule, young shoats, old hogs, and sucking pigs are most susceptible to cholera in the order named, and, as would be expected, recoveries from the disease are less frequent among young shoats, and more frequent among old sows and sucking pigs. The cause of hog cholera is a filterable virus, probably an organism too small to be visible with the highest magnification now obtainable, and pos- sibly possessed of characteristics which prevent it NATURE AND CAUSE OF HOG CHOLERA \) from taking stains that render bacteria more plainly visible. The virus readily passes porce- lain and infusorial earth filters which retain all visible bacteria, but it is itself retained by the finest porcelain filters. It does not pass through colloid membranes. In the human subject, mea- sles, mumps, scarlet fever and smallpox are among the diseases caused by filterable viruses, while among animals rinderpest, foot-and-mouth dis- ease and rabies are some of the diseases that fall in the same group. The classification is a rather loose one, being based entirely on the fact that these viruses will pass filters that retain visible bacteria, rather than on morphological or cultural characteristics. There is no conclusive evidence that hog cholera virus has been propagated outside the bodies of infected swine. After a hog has been exposed to the disease and actually infected, the virus ap- pears in the blood stream in about four days, and thus all vascular organs harbor it during the at- tack. In the later stages of a few chronic cases, we have found the blood free of the virus, but we do not know whether this is the rule, nor is there definite knowledge of the part played by '^ car- riers'' in harboring it. It is eliminated through the excretions. The urine is regularly infectious, the feces may or may not contain it, and the dis- charge from the eyes and skin ulcers is infectious 10 HOG CHOLERA at least in some instances. Just how any one of the filterable viruses operates to produce disease is quite unknowm, but it is certain that hog cholera virus has a selective action for epithelial and en- dothelial cells. Virulence. Hog cholera virus produces speci- fic disease only in swine, and very small quantities of infected material are sufficient to cause death in susceptible animals. According to King, sub- cutaneous injections of 1/86 of a mil of virulent blood produced the disease, while lesser amounts produced only a mild reaction, or none at all. Natural infection usually occurs by way of the digestive system, but the disease is readily pro- duced by subcutaneous, intravenous or intra-abdo- minal injections of small quantities of virulent material. Resistance. Most of the natural influences to which hog cholera virus is subjected do not oper- ate to destroy it rapidly. Drying, sunlight, and low temperatures seem to have no immediate at- tenuating effects, although it is a fact that most infected yards which remain uninhabited from three to six months do not endanger susceptible pigs placed in them. There is, though, a consid- erable tendency for hog cholera to recur on old infected farms, and this fact indicates that there are exceptional cases in which the span of life of the virus is greatly prolonged. NATURE AND CAUSE OF HOG CHOLERA 11 Putrefaction is the only natural influence which operates to destroy the virus rapidly. Ac- cording to Uhlenhuth it will live in putrefying car- casses for about eight days, but undoubtedly the many influences which govern putrefactive proc- esses render data of this kind of value merely in establishing tendencies. It is certain that decom- posing carcasses do not harbor the virus regu- larly, and likewise it is true that virus kept in bot- tles in the laboratory often is killed when putre- faction develops. When sufficient preservative is added to prevent the growth of putrefactive or- ganisms, the virus regularly lives several months, and may even exist for years. Moderate degrees of heat attenuate or destroy the virus, and under no circumstances has it been found to survive temperatures near the boiling point. The following rather incomplete table pre- pared by the German Imperial Board of Health laboratories gives a fair idea of the effects pro- duced by various degrees of heat. Degrees Material Centigrade Time Liquid serum filtrate 45 24 hours Liquid serum filtrate 46.5 24 hours Results Not killed or weakened Not killed or weakened 12 HOG CHOLERA Degrees Material Centigrade Time Results Liquid serum filtrate 46 48 hours Killed Liquid serum filtrate 55 24 hours Killed Liquid serum filtrate 60 10 hours Killed Liquid serum filtrate 58 2 hours Not killed Liquid serum filtrate 78 1 hour Killed Dried blood 65 2 hours Not killed Dried blood 72 1 hour Killed Dried blood 72 1/2 hour Killed Urine 58 1 hour Killed Urine 58 % hour Not killed Low temperatures act to prevent growth of putrefactive organisms and are thus instrumental in prolonging the life of the virus. In our oami experiments, hams removed from cholera infected pigs and frozen hard ninety-three days still har- bored virus sufficient to produce the disease when small portions of them Avere fed to susceptible pigs. Disinfectants. Hog cholera virus readily re- sists ordinary disinfectants in dilutions that are rapidly fatal to most bacteria. When % per cent phenol is added to virulent blood, the virus mil remain alive for months, and all of the coal tar disinfectants must be prepared in strong solutions in order to destroy it. Liquor cresolis compositus NATURE AND CAUSE OF HOG CHOLERA 13 in 5 per cent aqueous solution, when allowed to act for an hour or more, has proved effective in killing it. Following is a table prepared by the German Imperial Board of Health laboratories, which fur- nishes additional information relative to the efP ec- tiveness of various disinfectants when used to kill hog cholera virus. Most of the tests were made by mixing 10 mils of the virus with an equal quantity of aqueous dilution of the disinfectant. Dilution applied Result Disinfectant Corrosive sublimate Corrosive sublimate Corrosive sublimate Carbolic acid Carbolic acid Carbolic acid Carbolic acid 0.3 per cent solution Serum filtrate not killed in 8 days. 0.5 per cent solution Serum filtrate virus not killed in 4 days. 0.2 per cent solution Urine virus killed in 15 minutes in one trial. In another trial not killed. 0.5 per cent solution Serum filtrate virus not killed in 8 days. 1.0 per cent solution Serum filtrate virus not killed in 4 days. 3.0 per cent solution Failed to kill blood virus in 8 days. 2.5 per cent solution Failed to kill urine virus in 15 minutes. 14 HOG CHOLERA Dilution Disinfectant applied Chloroform Full strength Sodium taurocholate Formaldehyd 2.5 per cent solution Lugol 's solution Urea 0.25 per cent solution 20.0 per cent solution Glycerin 33.0 per cent solution Ozone Hydrogen peroxid 10.0 per cent solution Antiformin 5.0 per cent solution Antiformin 2.0 per cent solution Result Serum filtrate virus not killed in 24 hours. Blood virus not killed in 4 days. Serum filtrate virus alive after one hour. Dead in 15 days. Failed to kill serum filtrate virus in 2 hours. Did not kill serum filtrate virus in 1 month. Failed to kill serum filtrate virus in 1 month. Blood virus not killed. Serum virus not killed in two hours. Serum filtrate virus killed in one hour. Urine virus not killed in 10 minutes. Killed in 15 min- utes. Antiformin 1.0 per cent solution Serum filtrate virus not killed in 24 hours. NATURE AND CAUSE OF HOG CHOLERA 15 Disinfectant Antiformin Milk of lime Chlorid of lime Lysol Dilution applied Result 2.5 per cent solution Serum filtrate virus killed in 2 hours. Blood virus not killed in two hours. Failed to kill in one hour. In other ex- periments killed in 20 min. 5.0 per cent solution 3.0 per cent solution Serum virus killed in 114 hours. Serum filtrate virus usually killed in 1 hour. Cresol soap solution 3 — 6 per cent solution Always killed virus in 1 hour. Cresol soap solution 3 — 4 per cent solution Serum filtrate virus not killed in % hour. Cresol soap solution 3.0 per cent solution Killed urine virus m hour. Since a filterable virus has been incriminated as the true cause of hog cholera, various investiga- tors have from time to time attempted to isolate it, stain it, and grow it on artificial culture media. King has made an exceedingly careful study of a spirochaete (Spirochaeta hyos) which to him has seemed to possess etiological significance, but his 16 HOG CHOLERA work has never been verified. More recently Proescher and Sell have described a diplococcus which they are inclined to regard as the virus of hog cholera, but as yet they have not submitted substantial proof to justify such a claim. Certain cell inclusions which in cholera-infected hogs ap- pear in the epithelial cells of the conjunctival sac have also been regarded as possible possessors of pathogenic powers, but it now seems probable that these exist as an effect rather than as a cause. There are various organisms which, acting as secondary invaders, exert profound influence on the course of hog cholera and on the lesions which develop, but which should in no way be confused with the filterable virus that produces the dis- ease. These will be considered in another chap- ter. CHAPTER III METHODS OF DISSEMINATIOIT Hog cholera virus exists only in infected hogs and in material contaminated by their excretions, and this is the fundamental fact to which we must repeatedly refer in accounting for new outbreaks. There are numerous exceptions to the rule, but the individual outbreak can usually be traced to a definite source, and this fact is important in its relation to measures for control. Shipping infected animals is probably the one practice responsible for most new herd infections. It is not uncommon for a breeder to become dis- couraged when his hogs begin to die and to ship all seemingly well animals to a distant market. During the fall of the year especially one has but to stand for a few hours at the unloading chutes of some of our large stockyards in order to realize how nearly universal this practice has become. Thus most public stockyards harbor hog cholera virus, and all hogs unloaded in them and later taken to farms for feeding or breeding become potential sources of danger. In the eastern states garbage feeding is re- sponsible for more outbreaks of hog cholera than 17 18 HOG CHOLERA all other factors combined, and in the country as a whole this practice plays an exceedingly im- portant part in the spread of the virus from local- ity to locality. Many hogs are killed while they are in the incubation period of cholera, and pork that comes from their carcasses, even though it is fit for human food, will produce hog cholera when fed in small portions to hogs. Bits of this in- fected pork find their way into garbage which is fed to susceptible swine, and the cycle is com- plete. The use of hog cholera virus in the field in serum- virus immunization has now become a rou- tine measure, and despite the advantages that re- sult from this practice, it must in truth be said that it is responsible for many new outbreaks of hog cholera. The practice of giving feeding shoats serum-virus treatment and shipping them immediately to distant points operates to infect much new territory, and is often the cause of heavy losses among the hogs thus handled. ^^Vaccination cholera," as these ^ ^breaks" follow- ing serum-virus treatment are called, although it usually runs a less rapid course which invites sec- ondary infection, is not fundamentally different from hog cholera contracted as a result of natural infection, but there is a marked tendency in some quarters to avoid the issue and attribute the deaths to causes other than hog cholera virus. METHODS OF DISSEMINATION 19 The practice of taking breeding hogs to dis- tant points to mate them is a fruitful source of new herd infections, and in more than one instance we have known the virus to be carried from one farm to another as a result of neighbors exchang- ing help during butchering time. Small streams to which many hogs have access may also become polluted and carry destruction to herds below the one in which the original infection occurs. Show hogs returned from fairs often contract hog chol- era en route or during their contact with other hogs in the show ring, only to infect the herds they represent when they return home. Besides the regular channels of infection which we have already indicated, and which severally are responsible for most new outbreaks of hog cholera, there are almost an infinite number of casual carriers of the virus, such as crows, spar- rows, buzzards, pigeons, and various predatory animals. These, by feeding in infected yards or on carcasses of hogs dead of cholera, may carry the infection to clean territory, but the probabili- ties are that in most localities the number of herds thus infected is relatively small. In recent experiments Dr. Marion Dorset has found it difficult to transmit hog cholera from herd to herd by employing attendants, pigeons and sparrows as agents of transmission, and in our own experiments we have failed in a surpris- 20 HOG CHOLEKA ing percentage of cases to infect yards with hogs sick of cholera so that susceptibles placed in them subsequently will contract the disease. In spite of these facts, though, we must in handling hog cholera be guided by the practically universal clinical experience which teaches that when hog cholera once finds its way into a farm herd it will eventually infect all individuals in it, irrespective of the fact that the herd may consist of several pens of hogs kept some distance apart. It is impossible, and indeed unnecessary, to dis- cuss in detail the various influences which occa- sionally are instrumental in carrying hog cholera virus from herd to herd, and like^\ise it is impos- sible to assign to each influence a relative import- ance. It is much more important, in concluding this chapter, to call attention again to the fact that in the great majority of cases hog cholera virus travels in certain quite definite channels, and that new outbreaks are usuall}^ the direct or in- direct result of shipping or moving infected hogs, or else they originate from the practice of garbage feeding, or that of using hog cholera virus indis- criminately in seeking to immunize against the disease. CHAPTER IV COMPLICATIONS Before we consider the symptoms, lesions and diagnosis of hog cholera, it is necessary that we shall discuss briefly some of the organisms that complicate the disease, and which at times exert such profound influence on its course that autop- sies become a continual source of surprise and perplexity to the diagnostician. No attempt will be made to give complete morphological and cul- tural characteristics of these organisms, which in- formation may be found in various standard works on bacteriology. The scope and purpose of this book require that we shall deal only in a general way with most biological characteristics, confining our attention chiefly to disease produc- ing power, especially in swine. Bact. suisepticum is the most important of the organisms that complicate hog cholera. It was isolated and described by Loeffler and Schiitz in 1885, and in 1886 Dr. Theobald Smith recovered it from various organs of many hogs dead of an epizootic disease in this country. Moore showed that it is present in the upper air passages of 21 22 HOG CHOLERA many healthy swine. In the absence of knowledge of the filterable hog cholera virus, all these investi- gators were inclined to regard the organism as the cause of epizootic swine plague, and to ascribe repeated failures in causing it to produce trans- missible disease, to the fact that field conditions could not be duplicated in the laboratory. The organism is rod-shaped varying in length from .8 to 2 microns, and in width from .4 to 1.2 microns. Often the ends are rounded giving it an oval shape, but it is not uncommon for the rods to be so short as to resemble micrococci. Some- times involution forms are observed. In cover- glass preparations made direct from the tissues and stained with basic aniline dyes, Bact. suisepti- cum often stains heavily at the ends and around the periphery, and very lightly or not at all in the center. Preparations made from cultures do not as a rule exhibit this bipolar staining. The organism is subject to wide variation in virulence. Rabbits, mice and guinea-pigs readily succumb to injections of minute quantities of cul- tures or suspensions containing it. Eabbits are especially susceptible, usually dying in less than thirty-six hours of an acute bacteremia. Like cul- tures or suspensions injected subcutaneously into cholera immune pigs produce as a rule a transient local reaction. Small doses injected intravenously may or may not prove fatal, but large intrave- COMPLICATIONS 23 nous doses produce death from septicemia quite regularly. The pigs that die in less than seventy- two hours may show as lesions congestion of the lymph glands and various parenchymatous or- gans, or, more rarely, petechial hemorrhages in the kidneys and heart, indistinguishable from those observed in acute hog cholera. In the cases in which the disease runs a less rapid course, there is a rather constant tendency for joint lesions of an inflammatory nature to form, and, contrary to what might be expected, pleuritis and pneumonia appear much less frequently than these joint le- sions. Earely do checks kept with these experi- mental animals contract disease.^ The symptoms that appear in pigs artificially infected with large intravenous doses of Bact. suisepticum are observed in a very few hours after the injection. There is rapid breathing, sometimes an extreme degree of dyspnea, or the respiratory disturbance may manifest itself in ^ ' thumping. ' ' The appetite is suspended, the tem- perature is moderately high (104°-105.5° F.) and there is an anxious facial expression. A general stiffness is practically always observed, and *In our own experiments, in which more than 100 pigs were exposed in pens with pigs artificially infected with intravenous injections of Bact. suisepticum, 3 contracted disease and 2 died. Bact. suisepticum was recovered from the blood and various parenchymatous organs of the dead animals. We know of no other well authenticated instances in which like transmission has occurred. 24 HOG CHOLERA lachrymation often is pronounced. If death or recovery does not take place in two or three days, the tendency is for the disease to assume a chronic type. One or more of the joints, usually the knee or hock, becomes hot, painful, and swollen, render- ing it difficult or impossible for the animal to stand. In spite of this, the temperature falls and is maintained close to normal, the appetite returns and is surprisingly good considering the condition of the animal and the fact that progressive ema- ciation is taking place. Pneumonia sometimes appears in these chronic cases, adding its train of symptoms, but it fails to develop in a surprising percentage of cases, thus presenting a striking comparison with field outbreaks formerly thought to be caused solely by Bact. suisepticum, in which pneumonia is the most constant manifesta- tion. These facts lead us to doubt that the or- ganism, acting alone, is the cause of a rapidly transmissible disease in the field. Field observations are in almost perfect accord with these experimental data. We have frequently had outbreaks of ''pure swine plague" reported to us, and in those we have investigated, in which there was evidence of transmissible disease, we have without exception succeeded in positively demonstrating or establishing the probable pres- ence of the filterable hog cholera virus. It is also significant that in the East, at least, cholera im- COMPLICATIONS 25 mune hogs do not suffer from *^ swine plague'^ if we except the cases in which it is said to appear in the first month subsequent to serum- virus treat- ment, and which in reality have their origin in the hog cholera virus used. Acting as a secondary invader in hogs suffering with cholera, in those badly infested with lung worms, and very probably as a primary microbian cause in those weakened as a result of shipping, Bact. suisepticum regularly produces a rather characteristic bronchopneumonia, and hastens or causes death. In those cases in which it acts as a secondary invader it produces pneumonia so rap- idly and regularly that the lesions due to the pri- mary cause are often obscured or overlooked. Cholera immune farm hogs kept in exceedingly bad sanitary surroundings and exposed regularly to damp and inclement weather, have not been shown to suffer from a rapidly transmissible and fatal pneumonia caused by this organism. There is, though, some experimental evidence that it oc- casionally produces pleuritis or possibly slight pneumonic lesions from which most hogs recover. B. suipestifer (B. cholerce suis) is another or- ganism which may often be isolated from various parenchymatous organs of hogs dead in outbreaks of cholera. It is a short, motile rod, belonging to the colon group. In 1885 it was described by Salmon and Smith as the cause of epizootic hog 26 HOG CHOLEEA cholera. In later years Uhlenhuth and his co- workers reported finding it in the intestinal tracts of many healthy smne. Jordon, in this country, was unable to identify it in any normal hogs which he examined, and neither Avas Tenbroeck. Both of these investigators regard Uhlenhuth 's work as inconclusive owing to the fact that he did not differentiate correctly between B. suipestifer and B. paratyphoid B. Smith states that the only dis- tinction that can be made between the two is that the former is pathogenic for rabbits, while the latter is not. Eabbits and guinea-pigs succumb to small sub- cutaneous injections of cultures of B. suipestifer, rabbits being somewhat more susceptible. Swine are not easily infected with subcutaneous injec- tions, but large intravenous doses prove fatal. According to Welch, small doses may lead to for- mation of the ^^ button ulcers" observed in chronic hog cholera, and Smith secured like results by feeding pigs bouillon cultures. The part played by this organism in producing swine disease in the field is not well defined, as most work with it ceased as soon as the filterable virus was accepted as the cause of epizootic hog cholera. There is good evidence that it is one cause of the ^'button ulcers'' just mentioned, and it is likemse probable that, acting in the role of secondary invader, it is responsible for the en- COMPLICATIONS 27 larged, dark, and somewhat pulpy spleens ob- served in individual hogs dead in outbreaks of cholera. It also seems to intensify hemorrhagic lesions produced by the filterable virus. Its pathogenic powers in relation to cholera immune pigs will bear further investigation, but it is prob- able that for the most part it acts to complicate diseases produced by other causes. B. pyocyaneus, or, according to Migula's classi- fication, Pseudomonas pyocyaneus, is a motile rod 2 to 6 microns long and .3 to 1 micron broad. It is widely distributed in nature, and there has been a tendency to regard it chiefly as a saprophyte. It is included frequently in the flora of wounds, it appears at times in abscesses in swine and other animals, and it has been described as the cause of an outbreak of dysentery in man. In Germany it is said to be the cause of an infectious nasal catarrh in pigs, and we have found it associated with outbreaks of pneumonia in swine, as the prob- able cause. The organism is an aerobe, it grows luxuriantly on the common culture media, tending to over- whelm other bacteria associated with it. It has a marked tendency to produce green color in any cul- ture medium, and the sweetish odor produced by it in bouillon cultures is quite characteristic. It takes the aniline stains regularly, and is Gram negative. 28 HOG CHOLERA B. pyocyaneus is pathogenic for pigeons, guinea pigs and rabbits. In swine, it is not regularly so, but under certain conditions it assumes great pathogenic significance. We have failed to pro- duce disease by feeding cultures of it or by spray- ing them into the nostrils of healthy pigs, while subcutaneous doses produced nothing more than an occasional local abscess. Moderate intrave- nous doses of suspensions containing it cause dyspnea, chilling or spasms to appear immedi- ately, and death, preceded by paralysis, usually of the hind quarters, often takes place in a day or two. This paralysis is observed in rabbits as well, and must be regarded as a more or less constant but nevertheless specific action on the part of the organism. According to Hutyra, cultures of B, pyocyaneus inoculated directly into the ethmoid mucosa in young pigs, produce disease similar to the catarrhal rhinitis observed in Germany. Under natural conditions certain predisposing factors, among which early age, lung worms, hog cholera virus and long confinement in very dusty quarters are most important, prepare the ground so that J5. pyocyaneus exerts its pathogenic pow- ers. We have observed its effects following hyperimmunization during the process of anti-hog- cholera serum preparation, the hypers developing a fatal pneumonia in a few days following a large intravenous dose of hog cholera virus. COMPLICATIONS 29 The lesions produced in swine experimentally infected by means of intravenous injections of material containing B. pyocyaneus are those char- acteristic of septicemia, congestion and dark col- oration of the lymph glands, lungs, kidneys and other organs appearing regularly. We have ob- served no such effects where natural infection rules. Here the constant lesion produced is pneu- monia, acute or chronic, and the constant symp- toms that appear are those that may be referred to this condition. Dyspnea, abdominal breathing and other marked evidence of respiratory distress charac- terize the disease. Paroxysms of coughing occur when the hog is required to move, the alae of the nostrils are drawn backward, giving the snout a peculiar pointed appearance, and it is not uncom- mon for the affected animals to assume a dog- sitting position, with the forelegs placed widely apart. Thumping appears frequently. Some- times there is a yellowish purulent discharge from the nostrils. The appetite may or may not be affected, while the temperature, as a rule, remains normal or is only slightly elevated. The typical lesion which we have found associ- ated with natural infection due to B. pyocyaneus consists of a semi-chronic type of bronchopneu- monia, affecting first the ventral and cephalic portions of the lungs, or if lung worms are pres- 30 HOG CHOLERA ent, the posterior border of the diaphragmatic lobe as well. The solidified portions may be red but are often rather light in color, macroscopically resembling the surface of a salivary gland. There is a marked tendency for necrosis to develop from numerous foci, and multiple abscesses occur, appearing as slightly elevated yellow areas dotted over the surface of the pneumonic lung. Pleuritis is somewhat constant, and a high degree of em- physema appears in the dorsal nonpneumonic por- tion, giving it a pale white color as compared to the normal pink. Often there is distinct evidence that as a final cause of death an acute pneumonia is superimposed over a more chronic type, in which cases all parts of the lungs are pneumonic, while the lesions in the dorsal and posterior por- tions are of more recent origin. B. necrophonis is another organism that some- times complicates hog cholera. Although subject to wide variations in form, it usually appears as a long, slender, nonmotile rod. It is a strict anaer- obe, it stains with the ordinary aniline dyes, and is Gram negative. Evidently it is quite widely distributed in nature, for it appears in numerous necrotic lesions in practically all domesticated ani- mals. It is regarded as a normal inhabitant of the intestinal tract in swine, and it exists in soil con- taminated with manure. It is the exciting cause of calf diphtheria, lip and leg ulceration in sheep, COMPLICATIONS 31 and a necrotic stomatitis of calves and pigs, each of which partakes somewhat of the nature of a specific infectious disease, but none of which, with the possible exception of calf diphtheria, tends to be reproduced regularly, in typical form, by arti- ficial means. In swine, B. necrophorus may be the. primary, and usually is the exciting cause of various ne- croses which appear in the mouth, stomach and intestines, nasal passages, skin, and lungs, and are designated, respectively, according to loca- tion, necrotic stomatitis, enteritis, rhinitis (bull nose), dermatitis and pulmonary bacillosis. The typical lesion consists of a dark brown necrotic patch which spreads slowly and tends to penetrate the deeper structures. Frequently a yellowish- broA\Ti scab or false membrane is formed. In ne- crotic stomatitis and enteritis especially, numer- ous lesions often coalesce until large areas are af- fected, and, depending on location, even the man- dible itself may be involved or the intestinal wall penetrated. A foul odor is usually detected. In the mouth, the lesions usually take origin from teething wounds or other slight abrasions ; in the stomach and intestines, hog cholera lesions and various irritants prepare the ground for their development; in the nasal passages they follow rhinitis due to other causes ; in the skin, they ap- pear especially on the teats and udders of sows 32 HOG CHOLERA which are chapped or wounded as a result of nurs- ing litters. We know less regarding the primary cause of necrotic lesions that appear in the lungs. It is still an open question whether B. necropho- rus is really capable of penetrating normal mu- cous membrane and producing its characteristic effects, but usually it does not. Likewise there is doubt as to whether it releases a toxin, the prob- ability being that at times it does, for especially in young pigs suffering with necrotic stomatitis, death often takes place suddenly, before it can be explained on the basis of the existing local lesion. On the other hand, some pigs will harbor surpris- ingly extensive lesions without marked systemic disturbances. Some regard B. necrophorus as a secondary invader that may cause the * ^button ulcers'^ which appear in chronic hog cholera, but there is at least a distinct difference between the button ulcer in which degenerative and regenera- tive processes coexist, and the usual lesion pro- duced by B. necrophorus, in which a progressive necrosis prevails as long as the exciting cause re- mains active. There is also somewhat meager evidence that the organism may in rare instances cause petechial hemorrhages in the serous mem- branes and kidneys. Bad. suisepticum, B. sidpestifer, B. pyocya- neus, and Bad, necrophorus have two characteris- COMPLICATIONS 33 tics in common. All are of a subvirulent nature, usually depending on other influences or predis- posing causes to enable them to exert their patho- genic powers, and all frequently take advantage of the lesions produced by hog cholera virus, in which they establish themselves, changing the course of the disease, and rendering autopsies puzzling and inconclusive. There are several other organisms that have been associated with hog cholera, either as com- plicating influences or probable causes, but some of these normally lead a saprophytic existence, and with our present knowledge we are unable to assign to any one of them a definite pathogenic role. B. coll communis and other members of the group, together with various streptococci and micrococci may often be found in lungs of hogs that have died of a terminal pneumonia brought on by hog cholera. Spirochceta hyos (King) is sometimes found in the blood and intestinal le- sions of hogs suffering with cholera, and B. py- ogenes suis is found in various suppurating lesions in swine, some of which have died in hog cholera outbreaks. The collective primary and secondary effects of all the organisms considered in this chapter, together with the changes produced by hog cholera virus go to make up the symptom- complex which, conveniently but unfortunately, has come to be known as ^^ mixed infection,'' and 34 HOG CHOLERA handled as a single entity. Only when we begin to inquire more closely into the disease-producing powers of each organism will real progress be made. CHAPTER V SYMPTOMS AND LESIONS Following the subcutaneous injection of a small quantity of hog cholera virus, or the feeding of material containing it, symptoms of the disease usually appear between the fifth and eighth days. In herds through which the disease is spreading, several weeks are often required for it to reach all individuals, but this delay must be regarded as due to failure of some of the hogs to take up the virus, rather than as a prolonged incubation period. The incubation period usually given va- ries between four and twenty-one days, but in the vast majority of cases symptoms will appear in less than nine days following definite exposure (feeding or inoculation) of susceptible pigs. Three forms of hog cholera are recognized, per- acute, acute and chronic. The peracute form is relatively infrequent, but it occurs occasionally among the first few hogs that succumb in an out- break. No definite symptoms have been asso- ciated with this form of the disease, for the af- fected animals are found dead with no history of previous sickness. 35 36 HOG CHOLEKA The acute form, which includes the great ma- jority of cases, begins with high fever (105°-109° F.), arched back, chilling, rough coat, drooping ears and tail, and general depression. The appe- tite is impaired. The affected animals may crowd to the trough in the usual greedy fashion, but after drinking sparingly of any liquid that may be contained in the feed, they return languidly to the nest in advance of their associates, slowly draw the litter backward with alternating fore- feet, and then settle to sternal recumbency with the snout hidden beneath the litter, seemingly in an etfort to keep warm. Intermittent attacks of chilling shake the body, the reflexes are dulled, the eyes closed, and a general stupor prevails. Conjunctivitis, mild or severe, is practically al- ways present, causing an exudate of a seromucous or seropurulent type to appear, gumming the eye- lids together, or forming crusts which remain in the internal canthus and on the margins of the lids. Early in the attack, constipation is noted. The fecal balls, usually dark in color and often cov- ered with mucus, are voided with difficulty. Later, if death does not ensue, diarrhea sets in, and continues pending the advent of death or con- valescence. The character of the food determines the color of the feces. As the sick hog lies undisturbed in the nest 'o bJO o 03 o 37 38 HOG CHOLERA there is often noted a scarcely audible, high- pitched, complaining expiratory grunt, but if the animal is seized suddenly it struggles feebly and emits a weak, hoarse squeal. The gait may be unchanged, but often staggering is noticed, and sometimes there is a characteristic unsteadiness or wea\ing in the hind quarters, best observed in well advanced cases when the animals are caused to move without undue excitement. Convulsions appear somewhat infrequently, and may be regarded as the only violent hog cholera symptom. The attack usually occurs at feeding time or under stress of other excitement, more often in young pigs. The pig comes to the trough as if to eat, but suddenly backs away, squealing, with the snout drawn low between the forelegs. The muscles stiffen in spasm, the pig falls on its side, the eyeballs roll upward, the legs are in con- stant motion, and the snout is gradually extended with a jerky, convulsive movement. The attack lasts less than a minute and terminates either in death or complete return of nervous function. Early in an attack of hog cholera, the skin is flushed, hot and sensitive, the flush being appar- ent only in clean white pigs. Later, as death ap- proaches, a diffuse purplish discoloration some- times appears in the skin covering the ears, snout, belly and inner surfaces of the legs, and is less frequently observed at the extremity of the tail. SYMPTOMS AND LESIONS 39 on the vulva, and in the perineal region. Depend- ing on whether the color results from hyperemia or hemorrhage, it will or will not disappear on pressure. Sometimes congestion and hemorrhage coexist, in which case the color disappears for the most part, revealing the presence of ecchymoses in the pressure-whitened area. Less frequently ecchymoses exist alone. Somewhat infrequently skin ulcers appear on the throat and between the forelegs, very rarely elsewhere on the body. They are light brown, irregularly round or oval in shape, 1/2-2 centimeters in diameter, and cov- ered with scabs. A rusty yellow, very sticky exu- date, most apparent on the ventral scantily-haired body surfaces, is noted in some individuals. Cough is observed in many field outbreaks, but it is by no means a constant symptom in uncom- plicated hog cholera. We have failed to establish a definite relation between this symptom and the petechial hemorrhages which appear in the laryn- geal mucosa. Respiratory symptoms are not prominent in hog cholera unless it is complicated with pneumonia, but dyspnea develops frequently under forced exertion. The superficial inguinal lymph glands are fre- quently enlarged so as to attract attention, and another common symptom is the collection of urine in the sheath of the male pig, causing marked dis- tention. When pressed out manually, the urine 40 HOG CHOLEEA has a very offensive odor, and may be cloudy white in appearance, or otherwise abnormal. As the disease progresses, emaciation is quite rapid, and general weakness prevails. Frequently a terminal pneumonia develops during the last few hours, and death may result from heart or respiratory failure. Chronic hog cholera occurs, for the most part, among stragglers that survive the acute form, but it may exist independently among semisusceptible young pigs. Emaciation, cough, depraved appe- tite, diarrhea, unsteady gait, drooping ears and tail, tucked-up flank, and even sloughing of the skin are among the symptoms that appear. Some animals recover, but complete return to normal health is not the rule. LESIONS Peracute hog cholera does not usually produce characteristic macroscopic lesions, but congestion of the lymph glands, mesenteric vessels and var- ious parenchymatous organs may often be ob- served. It is in the acute uncomplicated form that the most t^^pical lesions occur. These con- sist of congestion, hemorrhages and degeneration, hemorrhages being the only ones which, by virtue of character or location, are highly characteristic of the disease. These appear as petechias in the kidneys, serosa of the intestines, mucosae of the SYMPTOMS AND LESIONS 41 bladder and larynx, in the pericardium, epicar- dium, and on the auricles of the heart, especially the left. Exceptionally they are seen in the dia- phragm, in the parietal pleura and peritoneum, and subjacent connective tissue. In the lungs, the hemorrhages usually appear beneath the pleura as ecchymoses, more often in the ventral portions of the cephalic and cardiac lobes, but at other times unconfined to particular areas. In the spleen they appear as well-defined slightly raised black areas 14 to ll^ centimeters in diameter, practically always at the edge of the organ and visible beneath its capsule from the dorsal aspect. Some of the lymph glands are practically always congested or hemorrhagic. The hemorrhage ap- pears first around the periphery as the sectioned surface will show, later extending to the trabec- ulse, and finally in some cases progressing so far that the entire structure becomes infiltrated, show- ing on section a uniform dark color. Petechiae and ecchymoses in the lymph glands are excep- tional. The nodes most regularly involved in- clude the gastric, hepatic, lumbar, superficial in- guinal, mediastinal and submaxillary. The hemorrhages which are found in and be- neath the alimentary mucosa may appear in the form of petechiae or ecchymoses, but there is a marked tendency, due probably to constant me- chanical irritation, for them to become more 42 HOG CHOLEKA diffuse in character. The pharynx and esophagus are rarely affected, the stomach and small intes- tines frequently are, while the mucosa of the cecum and upper colon usually is involved. The skin lesions may consist of congestion or hemorrhage of circumscribed or diffuse nature, the latter type being by far the most common, and appearing as a purplish discoloration usually con- fined to the ears, belly, snout, inner surfaces of the legs, tip of tail, vulva, and perineal region. Small skin ulcers less than two centimeters in diameter, irregularly round or oval in shape, brown in color and scabbed over, appear somewhat infrequently on the throat, very exceptionally elsewhere on the body. These seemingly take origin from previous hemorrhages. Some have considered all these changes as due to secondary invasion, holding to the belief that hog cholera virus in itself does not produce mac- roscopic lesions. To this view we are unable to subscribe, for one may transport filtered virus hundreds of miles, and it will still produce, regu- larly, some or all of the leions just described, and it is inconceivable that the same secondary in- fluences should be present in all localities. In order to place in relief the more character- istic macroscopic lesions which, according to our conception, are due usually to unaided action of the filterable hog cholera virus, we have for the SYMPTOMS AND LESIONS 43 moment neglected discussion of less characteris- tic changes which frequently take place. If we consider each organ separately, extending our ob- servations to include less characteristic changes, as well as those produced by secondary invaders discussed in a previous chapter, a more complete picture, and a more accurate interpretation^ of the pathological anatomy encountered in field cases can be presented. Mouth and pharynx. Mucosa usually normal. Hog cholera virus may be primary cause of ulcers. These are sometimes present in hog cholera out- breaks, and appear as dark brown necrotic patches on gums, lips, tongue and other parts. Probably due to primary injuries caused by the filterable virus, and certainly caused by B. necrophorus as a secondary invader. B. necrophorus ulcers oc- cur independent of filterable virus infection. Stomach. Mucosa frequently normal. Filter- able virus causes petechiae, ecchymoses or larger suffusions in fundus. Congestion due to the same cause usually present. Ulceration relatively rare, ^ We are fully aware that with our present knowledge such an interpretation can be only approximately correct, but nevertheless there are certain well-defined tendencies which should be indicated. Our conception of the primary filterable virus lesion has been gained, during the last ten years, by performing autopsies on hundreds of pigs which were killed about a week subsequent to injection with virus. The virus was obtained from several sources in various states, some was filtered, some was not. We have also investigated several of the secondary invaders, and the combined results of these investigations with those of similar nature con- ducted by other workers, are reflected in the remarks which follow. 44 HOG CHOLERA but necrotic patches due to secondary infection with Bact. necrophorus may appear. Serosa usu- ally normal. Exceptionally studded with puncti- form hemorrhages, due to filterable virus. Small intestine. Mucosa sometimes normal. Congestion rather common, also hemorrhages sim- ilar to those observed in stomach, and due to filter- able virus. Lymphoid nodules often congested, less frequently hemorrhagic, due to filterable vir- us. Those in ilium most frequently involved. Ulceration rather uncommon, except in extreme posterior portion of ileum. Serosa usually nor- mal. Petechial hemorrhages appear infrequently, mesentery often congested. Changes due to filter- able virus. Caecum and upper colon. Mucosa most con- stant seat of digestive canal lesions, especially region of iliocecal valve. Congestion, petechiae, ecchymoses' and larger suffusions common. Strong tendency toward ulceration. Pitlike patches denuded of epithelium. Necrptic ulcers or patches, dark brown in color, sometimes false membrane ; ulcers tending to broaden and deepen, little tendency toward regeneration. '' Button ulcers ' ' ^ occur in chronic hog cholera. Serosa * The ulcers may be isolated and appear as circular, slightly projecting masses stained yellowish or blackish or both in alter- nate rings, or they may be slightly depressed and somewhat ragged in outline. When the superficial slough is scraped away many ulcers show a grayish or w'hite base. A vertical section reveals a rather firm neoplastic growth, extending usually to the inner mus- SYMPTOMS AND LESIONS 45 often normal, petechiae not infrequent. Hemor- rhages and destruction of epithelial cells probably due to filterable virus. ^'Button ulcers'' due to B. siiipestifer, possibly to other organisms. Necrotic patches usually due to Bad. necro- pliorim. Lower colon and rectum. Usually normal or nearly so. Sometimes congested. Infrequently the lower colon shows the same change as the upper colon. Lar5aix. Mucosa frequently normal. Some- times congested, more often dotted with petechias caused by filterable virus. Trachea and bronchi. Mucosa often normal. Sometimes congested. Probably due to filterable virus. Lungs. Very often normal. Primary lesions sometimes caused by filterable virus consist of ecch}Tnoses visible beneath the pleura. These ap- pear most frequently on the cephalic and cardiac lobes, but are not confined to these parts. Terminal pneumonia due to filterable virus plus nonspecific secondary invaders. Often affects all cular coat. When sections of such an ulcer are stained with aniline dyes and examined under the microscope, the submucous tissue is very much thickened, infiltrated with round cells and con- taining a large number of dilated blood vessels. Resting upon this thickened submucosa, is a line of very deeply stained amor- phous matter, and upon this is situated the necrotic mass which fails to retain the coloring matter and which is permeated by a very large number of bacteria of various kinds. Frequently the eggs of trichocephalus are imbedded in the slough. ' ' — Moore, Pathology of Infectious Diseases. 46 HOG CHOLERA lung tissue. Lung solidified, red. Pneumonia of recent origin. Swine plague pneumonia due to filterable virus Plate 2. Lung of pig showing ecchymoses due to acute hog cholera. These appear in greater numbers on the apical and cardiac lobes plus Bad. suisepticum. Cephalic and cardiac lobes first to be affected, later other parts may solidify. Solidified portion usually red or reddish gray. Usually bronchopneumonia. Interlobular SYMPTOMS AND LESIONS 47 spaces well defined macroscopically, due to infil- tration of leucocytes or blood. Tendency toward necrotic and caseous masses in cases of longer standing. Pleuritis constant. Pleurae often thickened, rough, white, adherent. Pneumonia, characterized by necroses which start from various foci, tending to involve all structures alike, sometimes spreading to the heart by contiguity. Filterable virus plus Bad, necro- phorus. Pneumonia, often semichronic, tending toward formation of multiple abscesses visible beneath the pleura, as slightly raised, yellow areas. Visi- ble on section in deeper parts. Pneumonic lung may be red. More often grayish in color. Due to filterable virus plus B. pyocyaneus} Heart. Usually normal. Filterable virus le- sions consist of petechias and ecchymoses which are visible on the surfaces of the auricles, usually the left. Sometimes congestion of coronary ves- sels. Heart itself rarely the seat of secondary le- sions. Epicarditis and pericarditis often result from secondary infection with Bad. suisepticum. Spleen. Sometimes normal or slightly en- larged. Very small bright-red protruding hem- ^ Hog cholera virus is only one of several influences capable of producing primary changes which, in the presence of secondary invasion with either Bad. necro phorus or B. pyocyaneus may re- sult in the lung lesions mentioned in connection with these organ- isms. For instance, we regard lung worms in combination with B. pyocyaneus as a frequent cause of pneumonia in pigs. 'o o ■73 be _bJC 'S. o 48 Plate 4. Spleens showing^ hemorrha,2:es which are rather typical of acute hog cholera. These hemorrhages are observed in. only a small per- centage of cases 49 50 HOG CHOLERA orrhages beneath capsule are normal. These are frequently on ventral surface near the hilus, not so often along the borders and on the dorsal sur- face. Characteristic filterable virus lesions con- sist of black, well defined slightly raised hemor- rhages 1/4 to 2 centimeters in diameter, located practically always somewhere on the margin. Spleen may be enlarged, dark, friable, engorged with blood. Due usually to secondary invasion with B. siiipestifer, sometimes to other causes. Not of much diagnostic value as related to hog cholera. Liver. Macroscopic appearance usually nor- mal. Very exceptionally ecchymoses, seemingly due to hog cholera virus, are visible beneath the capsule. Often shows degenerative changes, probably due to hog cholera virus, but by no means characteristic, as they may be due to a variety of causes. Kidney. Very rarely normal. Seat of the most characteristic and constant hog cholera le- sions, consisting of petechias. Organ may be changed as follows: Normal in color, capsule peels easily. Surface of kidney studded with petechiae w^hich appear beneath the capsule, involving the glomeruli as well as other parts. On section, the petechiae are seen variously distributed in the cortex, in the medulla, and sometimes in the membrane of the Plate 5. Kidney of pig showing numerous petechia due to acute hog cholera. Often these petechias are so small and few in num- ber that it is necessary to examine the kid- ney very closely in a good light in order to observe them. The capsule is removed in order to make them more plainly visible 51 52 HOG CHOLEEA renal pelvis. They are due to the filterable virus. Engorged with blood. Capsule peels easily. Petechiae distributed as already described. Tend- ency toward more and larger hemorrhages. Changes usually due to filterable virus. Bact. suisepticum or B, cholera suis may be secondary invaders. Very light in color, '^cooked kidney.'' Capsule peels easily. Marked evidences of degeneration. (Cloudy swelling and granular degeneration.) Petechiae distributed as already described. All changes probably due to filterable virus. Very light in color. Capsule peels easily. No petechiae. Seen most frequently in chronic hog cholera. Changes often due to filterable virus, but not characteristic of it. Very light in color. Capsule peels mth diffi- culty, may be thickened. Evidences of degenera- tion followed by increase in interstitial tissue, and chronic nephritis. Primary degeneration prob- ably due to filterable virus. Nephritis due to sec- ondary causes. All of these dianges of little diagnostic significance. Considered in general, these petechial hemor- rhages in the kidney are rarely due to influences other than hog cholera virus. Exceptionally they may be due to Bact. suisepticum, acting either as SYMPTOMS AND LESIONS 53 a primary or secondary influence. There is a tendency by no means constant, and of little diag- nostic significance, for larger and less well defined hemorrhages to appear under the influence of Bact. siiisepticum. There is also some evidence, as yet poorly substantiated, that very exception- ally Bact. necrophorus produces petechias in the kidneys of hogs. This should be regarded as a remote possibility occurring only in association with extensive necrotic lesions in other organs. Bladder. Sometimes normal. Mucosa slightly congested, due to hog cholera virus or other causes. Mucosa dotted with petechiae, due usu- ally to hog cholera virus. Sheath. Often normal. Sometimes distended with foul smelling, discolored urine. Catarrhal inflammation of mucosa. Condition not charac- teristic of hog cholera. Found in other diseases, especially those resembling rheumatism. Lymph glands. Sometimes normal. Typical filterable virus lesion consists of congestion or hemorrhage which appears first in the cortex of the gland, and which may later involve the entire structure giving it a uniform dark color on section. Petechiae are rarely present. Edema frequently pronounced. Permanent enlargement and casea- tion occur in chronic hog cholera. Rare for all glands to show macroscopic changes. Glands 54 HOG CHOLERA most frequently affected are the gastrics, hepatics, superficial inguinals, lumbars, submaxillaries and mediastinals. Plate 6, Lymph glands of pig showing hemorrhages caused by acute hog cholera. Left, darkened surfaces of glands. Above, sectioned surface showing hemorrhages around the periphery and in the sinuses. Eight, darkened gland with small section cut away to show peripheral hemorrhages Skin. Often normal. Typical filterable virus lesions consist of purplish discoloration, repre- senting marked congestion or diffuse hemor- SYMPTOMS AND LESIONS 55 rhage. Ecchymoses more rarely visible. Ulcers, apparently originating in these ecchymoses some- times occur on throat and between forelegs. (In hot weather purple discoloration appears a few hours after death in hogs, especially fat ones, dead from any cause.) The pathology and microscopic tissue changes produced by hog cholera virus are not well worked out, but nevertheless the relation between primary filterable virus lesions and secondary changes due to other causes is fairly well understood. Let us consider, for instance, lesions of the digestive mu- cosa. Congestion appears first. It will disap- pear or terminate in hemorrhage. Follomng hemorrhage, regenerative or degenerative pro- cesses will occur. The degenerative processes may result in destruction and excoriation of the epithelial cells, leaving an unprotected surface in contact with the intestinal contents. Individual resistance and the bacterial flora of the intestine will determine future developments. Regenera- tion will rule, or secondary infection will take place. If Bad, necropJiorus is present in suffi- cient numbers, necrotic enteritis will be produced. If B. suipestifer exists in overpowering numbers, the familiar ^^ button ulcer'' may develop. In the intestine, we find the primary lesions due to the filterable virus most frequently in the cae- 56 HOG CHOLERA cum and upper colon, and as would be expected, we find the secondary lesions distributed in pre- cisely the same manner. If we examine a hog dead of cholera after a short sickness we encoun- ter intestinal lesions in which congestion, hemor- rhages and early evidences of degeneration pre- dominate. In hogs that have been sick longer, autopsies often reveal a surprising variety of le- sions which collectively encompass effects of the struggle between degenerative and regenerative forces, and which reach their most typical form in the ^ ' button ulcer. ' ' In considering thoracic lesions, the same general principles apply. If we inject a pig with filtered hog cholera virus, and kill it about seven days later, the lungs, if affected, will show petechiae and ecchymoses, most likely appearing on the cephalic and cardiac lobes, but not always confined to these parts. There may also be congestion of the mucosa of the air passages. Both changes are due to the filterable virus. What result would we expect if a secondary invader, capable of producing inflammatory changes, should find its way into lesions thus prepared? Obviously we would expect to find bronchopneumonia, occurring most regularly in the cephalic and cardiac lobes but not always thus limited. It is significant that this is the exact picture presented when secondary infection with Bad. suisepticum takes place. SYMPTOMS AND LESIONS 57 The urine of hogs suffering with cholera often contains albumin in excessive amounts, and the chlorids frequently are diminished in quantity, or present only in traces. Contrary to what might be expected, blood and hemoglobin are absent, al- most without exception. CHAPTER VI DIAGNOSIS, DIFFERENTIAL DIAGNOSIS, PROGNOSIS Early and correct diagnosis of hog cholera is essential in coping with the disease effectively. Often an entire herd is in jeopardy, and if hog cholera is present prompt preventive measures must be taken to save it. The diagnosis involves no great difficulties when many hogs are sick, but in the early days of an outbreak when peracute or otherwise atypical cases are likely to occur, puzzling situations arise which sometimes cause costly delay. Thus in exceptional cases we are justified in making a provisional diagnosis of hog cholera, and in handling the herd in exactly the same manner as we would were a positive diagno- sis possible. Experience has taught that we should not be too conservative in regard to taking such a course when the history suggests the dis- ease and when valuable animals are at stake. In seeking to determine the presence of hog cholera we depend on four considerations: 1. History of the outbreak. 2. Symptoms. 3. Lesions. 58 DIAGNOSIS, DIFFERENTIAL DIAGNOSIS, PROGNOSIS 59 4. Animal Inoculation (rarely applicable). History. Securing the history of an outbreak of suspected hog cholera is simply applying knowl- edge of the ways in which the virus spreads. Usually we find that a hog has died of an unknoAvn cause and a few days later sickness has appeared among its associates. Careful inquiry should be made regarding recent introduction of hogs into the herd, existence of swine disease in the vicinity, adjacent arteries of traffic and source of feed and water supply. Stockyard hogs and others intro- duced without clear history of previous health should remain under suspicion. Even though they do not themselves contract the disease they may act as intermediate carriers. There is no evidence that hog cholera virus travels through the air but a road or railroad right-of-way may be contaminated by the drip from infected wagons or cars. If the herd is subsisting on garbage and is not immune the circumstances suggest hog chol- era. If kitchen swill is being fed inquiry should be made as to whether the kitchen is supplied with market pork.^ In general the facts brought out by the history of an outbreak simply constitute supplementary ^ In one instance that came under our observation an outbreak of hog cholera was traced to meat trimmings that were placed in a poultry house. Two small pigs formed the habit of escajDing from the pen and eating freely of these trimmings. Both devel- oped hog cholera simultaneously, and later transmitted it to their associates. 60 HOG CHOLERA evidence tending either to affirm or deny the pres- ence of hog cholera. Unless there is a definite history of direct exposure the history in itself is not conclusive. Symptoms. Unless several animals are sick it is seldom possible to make a positive diagnosis based on symptoms alone, but the experienced ob- server is usually fairly certain of his ground. It is essential to remember that early in an out- break we do not observe the greatly emaciated hog with arched back, straight tail and drooping ears which has been so frequently described and photographed, and which is the product of long- sickness. It should also be kept in mind that many of the symptoms observed in acute hog cholera are present in other diseases, and that all of the symptoms that characterize the disease, do not often appear in one animal. Special consid- eration must be given to a restricted number of the more characteristic symptoms. In examining a herd for suspected hog cholera one should first see it unaffected by artificial ex- citement, taking care to observe a tendency in individuals to chill and crawl beneath the litter. Then the animals may be tempted from the nest with feed, observation being made for any that are reluctant to move, or that stagger or weave in the hind quarters. The animals that come greedily to the trough but leave for the nest in advance of DIAGNOSIS, DIFFERENTIAL DIAGNOSIS, PROGNOSIS 61 their associates, dropping slowly to sternal recum- bency with their snouts half buried in the litter should be regarded as probable cases of hog chol- era, especially when intermittent attacks of chill- ing are observed. Temperature is an important guide, but great care must be taken in securing and interpreting readings. Normal temperatures of hogs vary be- tween 101° and 104° F. and independent of dis- ease, excitement or exertion causes a more rapid temperature elevation in swine than in other ani- mals. Docile adult breeding animals in medium flesh are inclined to show readings near 101° F., while those of young pigs and fat hogs tend to ap- proach 104° F. In taking temperatures of pigs, the thermometer, preferably one with pear or globe-shaped bulb and at least five inches long, should be inserted almost full length. Otherwise many inaccuracies (readings too low) will occur, because a pig, especially if held by the hind legs, will often relax the rectum as long as the ther- mometer remains in position. Chasing pigs to catch them often elevates their temperatures rapidly, and should be avoided. It is important to keep in mind the usual hog cholera temperature curve. In the typical case of the acute form of the disease the curve rises rapidly at the onset of the attack and reaches an elevation between 106° and 107° F. in less than 62 HOG CHOLERA forty-eiglit hours. This level is maintained for about four days and is followed by a sharp decline which may bring it near normal for a few hours. Then there is an upward trend which carries it near the former high level in which position it may be maintained, or it may fluctuate somewhat violently from day to day. Sometimes it remains elevated until death takes place, but usually it sinks below normal a short time before the pig dies. Thus it is always well to secure temperatures of hogs recently affected, and to be cautious in regard to making a negative diagnosis on the strength of a limited number of temperatures near normal. Several readings near or above 106° F., supported by other suspicious symptoms and a history that indicates hog cholera, may rightly form the basis for a provisional diagnosis. On the other hand, a considerable number of tempera- tures below 104° F. in sick hogs, strongly suggests some other disease. Between these extremes the readings are less conclusive. In this country, and in others where swine ery- sipelas is not prevalent, the characteristic diffuse purplish discoloration which appears on the belly, ears and snout is pathognomonic of hog cholera, but it is observed in relatively few cases. If this discoloration is not observed before death it is of no significance, for it may occur as a post-mor- DIAGNOSIS, DIFFEKENTIAL DIAGNOSIS, PROGNOSIS 63 tern change in swine dead from any cause, es- pecially fat hogs that have died in hot weather. Other less characteristic symptoms add evi- dence, but most of them may result from causes other than hog cholera, and it is unsafe to give them too much weight in their relation to diagno- sis. Lesions. Lesions constitute our most accurate guide in diagnosing hog cholera, for it is not often that a conclusion can be reached without consider- ing them. Hogs sometimes die of the disease without showing any characteristic macroscopic tissue changes, so if no cause for death is found, additional autopsies should be performed. In case it is necessary to kill a pig for this purpose, it is best to select one that has been sick several days, but not a chronic case. Petechiae and ec- chymoses are the chief changes which character- ize hog cholera, but it is important to remember that in cases of long standing, and in those in which secondary invasion has taken place these primary filterable virus lesions may be so changed in character that they are difficult to identify. Assuming that we have before us a carcass, and that hog cholera is suspected, the autopsy will in- clude special examination of the skin, kidneys, bladder, lymph glands, spleen, heart, lungs and laryngeal mucosa, as well as the serous membranes readily accessible, and the digestive tract. The 64 HOG CHOLEKA changes which appear in these various parts have already been discussed, so for our present purpose we will consider chiefly those which are of primary importance in their relation to diagnosis. The skin is examined for ecchymoses and yel- lowish-brown ulcers which sometimes appear on the throat and other ventral surfaces. If there is a purplish discoloration, inquiry should be made as to whether it was noticed before death took place. An affirmative reply suggests hog cholera, while a negative one practically dismisses the le- sion from consideration. Changes in the skin are frequently absent. As we open the thoracic and abdominal cavi- ties petechiae and ecchymoses are sometimes ob- served in or immediately beneath the serous sur- faces thus exposed. They appear infrequently in the parietal pleura and parietal peritoneum and are somewhat more common in the serous coat of the intestine, especially that of the cecum and colon. The kidney lesions are highly characteristic of hog cholera, and they occur in nearly all cases. They consist of petechiae which are distributed on the surface, as well as in the deeper structures. These are dark red in color and sharply defined, often giving the organ the 'Hurkey egg^' appear- ance. Sometimes they are so few in number that the capsule must be removed in order to see them, DIAGNOSIS, DIFFEEENTIAL DIAGNOSIS, PROGNOSIS 65 care being taken to make the examination in a strong light. Infrequently other causes produce petechige in the kidneys of swine, but in this coun- try, unless another cause is apparent, either by virtue of the history or accessory lesions, we are safe in attributing them to hog cholera. Petechi^e in the mucosa of the bladder occur in most cases of hog cholera, and they do not often result from other causes. The serous surface is practically always normal. Some of the lymph glands are usually involved, and to the experienced observer the changes in them aid greatly in making a diagnosis. On the surface the gland is very dark red, almost black. On section the periphery is similar in color, while the deeper structures may remain unchanged. It is important to bear in mind that any inflamma- tory process may aif ect adjacent lymph nodes, and to make allowance for this fact, but marked per- ipheral congestion or hemorrhage, when observed in several glands widely separated, in the absence of apparent inflammation in adjacent structures, strongly indicates hog cholera. The spleen reveals characteristic hog cholera le- sions only in the dark, swollen circumscribed hem- orrhages, usually less than 1 centimeter in diam- eter, which appear along the border. In field cases that have died of hog cholera these lesions are not often observed, because secondary invad- 66 HOG CHOLERA ers have so enlarged and darkened the entire or- gan as to render them invisible, and because post- mortem changes take place rapidly. The enlarged, dark, pulpy spleen which is often encountered in hog cholera outbreaks is of little significance in diagnosis, because it is so frequently the result of other causes. The heart reveals no macroscopic lesions in the vast majority of cases, but the petechise which are sometimes visible on the left auricle, less fre- quently on the right, and rarely involve the ven- tricles, are usually caused by hog cholera virus. The lungs are often normal. If the surfaces are dotted with ecchymoses, the fact suggests hog cholera quite strongly, but occasionally these le- sions are due to other causes. The laryngeal mucosa is often the seat of pete- chiae, which are characteristic of hog cholera. Examination of the intestinal mucosa often aids in making a diagnosis, but the lesions encountered are often difficult to interpret. Certain irritants cause changes which may be confused with those due to hog cholera, and secondary invasion tends rapidly to modify filterable virus lesions so that they are difficult to identify. Ecchymoses and larger hemorrhages, as well as ulcers of recent origin, when distributed near the ileocecal valve and elsewhere in the mucosa of the caecum and upper colon, may be accepted as supplementary DIAGNOSIS, DIFFERENTIAL DIAGNOSIS, PROGNOSIS 67 evidence of acute hog cholera. The ^^ button ulcer*' is usually associated with the chronic form, but agents other than the filterable virus may be instrumental in producing it. All these hog cholera lesions will not often be found in one animal, but if two or more organs are involved this fact, supported by a history that does not positively deny the presence of the disease, may be accepted as ground for a diagnosis. If more organs are involved the evi- dence is more conclusive. AnimaJ inoculation. This' method is rarely applicable in actual practice, because it is expen- sive and requires too much time. In very excep- tional outbreaks which present atypical features, and in cases involving litigation it may be useful. The essentials of a conclusive experiment may be summarized thus: 1. Blood should be drawn from a hog which has been sick for only a short time, and which carries a temperature near 106° F. 2. The blood should be diluted with sterile water and passed through a filter which retains all microscopic organisms. 3. Enough of the filtrate to represent at least 1 mil of the undiluted blood should be injected into a susceptible pig, preferably one weighing between forty and one hundred pounds. 4. Twelve days previous and subsequent to the 68 HOG CHOLERA date of injection the pig should be protected from extraneous hog cholera infection; all receptacles and instruments used in making the injections should be sterilized. 5. Symptoms of hog cholera should appear in less than eight days following the injection. 6. The pig should die in less than seven days following the appearance of symptoms, or at the end of that time, providing it is still sick, it should be killed. 7. Autopsy should reveal typical hog cholera lesions in at least two organs. 8. In negative experiments the susceptibility of the experimental pig should be proved by a subse- quent injection with at least 1 mil of virulent hog cholera blood. Differential Diagnosis Peculiar difficulties are met in the differential diagnosis. Clinical examination of the individ- ual is subject to limitations which are not encoun- tered in dealing with larger animals, and some of the maladies which we seek to differentiate from hog cholera occur so frequently in combination with that disease that we do not always have well defined features upon which to base our conclu- sions. Thus under certain circumstances we have not only to decide whether a given outbreak is hog cholera or swine plague, but we must also DIAGNOSIS, DIFFERENTIAL DIAGNOSIS, PROGNOSIS 69 ask ourselves whether the two diseases exist in combination. Laboratory examinations may dem- onstrate the presence of a bipolar organism, but they cannot in the course of a few hours deny the presence of the hog cholera virus, and thus they are often dangerously misleading. Return mail diagnoses of '^ swine plague" or ' 4iemorrhagic septicemia" are without value because they ignore consideration of hog cholera virus, which in this country is present in most outbreaks of rapidly transmissible swine disease. Among the diseases from which hog cholera must be differentiated are uncomplicated swine plague, pneumonias due to a variety of causes, sep- ticemias, tuberculosis, anthrax, so-called ''flu," various parasitisms, soap poisoning, brine poison- ing, and sudden deaths from such causes as heat- stroke and lightning-stroke. Rouget and rinder- pest are also to be considered in countries in which they are prevalent. The differential diagnosis cannot be made by rule of thumb, nor is it possible to summarize or tabulate the determining features of these va- rious maladies, so that the inexperienced observer can distinguish among them. Armed mth defi- nite knowledge of the diseases with which he is dealing the diagnostician usually reaches his con- clusions rapidly and accurately. In the absence of such knowledge, a few rules do not suffice. 70 HOG CHOLEKA Having already dealt with the distinguishing fea- tures of hog cholera we will confine our remarks chiefly to characteristics which suggest the pres- ence of these other diseases. Swine plague. Swine plague rarely occurs in pure form, it affects only a portion of the animals in a herd, and there are frequent spontaneous re- coveries. There is often a history of recent ship- ping. The incubation period is short (1 to 3 days), acute dyspnea and thumping are prominent symp- toms, and the hogs show more distress than is observed in hog cholera attacks. High tempera- tures are not the rule except during the first few hours of sickness. The characteristic ** swine plague pneumonia,^' if present in several autop- sies, speaks for the existence of swine plague, but the absence of the filterable hog cholera virus must be clearly established before a diagnosis of pure swine plague is justified. None of the pneumonias, with the exception of that associated with swine plague, are accom- panied by the lesions in other organs which char- acterize hog cholera. Usually they occur where pigs are kept in very dusty quarters, or where the floors are cold and damp and no dry litter is provided. Recent shipping is a predisposing fac- tor, and lung worm and ascarid infestations play an important part in their development. They are sporadic or only slowly transmissible. High DIAGNOSIS, DIFFERENTIAL DIAGNOSIS, PROGNOSIS 71 temperatures are not common, and the prominent symptoms grow out of the pneumonia itself. Exceptionally septicemia due to nonspecific or- ganisms may occur, but its features are not well defined. In differentiating we must therefore de- pend on the more definite manifestations of hog cholera. Tuberculosis may only rarely be confused with chronic hog cholera. Hogs following tuberculous cattle and those fed infected creamery by-prod- ucts are most commonly affected. The history of the case should be considered and if doubt remains the intradermal tuberculin test may be applied. If material for autopsies is available, the differ- entiation presents no great difficulties. Anthrax and the peracute form of hog cholera are not always easy to differentiate. If the for- mer disease has existed previously in the locality ; if other classes of live stock are affected; if the hogs show swelling of the throat or froth mixed with blood coming from the mouth or nostrils ; if the blood is black and incoagulable, anthrax should be suspected, and a microscopical examination made. A malady known as ** state fair disease" or **flu** has in recent years been recognized in the central states. It is often associated with a his- tory of recent shipping, respiratory symptoms and lesions predominate, and recovery is the rule. 72 HOG CHOLERA This latter fact alone will distinguisli it from hog* cholera, when it occurs in pure form. Ascaris infestation and hog cholera sometimes exist in the same herd. As a result of the diar- rhea incident to the latter disease ascarids are frequently evacuated in the feces, and the entire train of symptoms, as well as the deaths, is attrib- uted to the parasites alone. Even though the parasites are present in large numbers, if deaths are numerous, further examination should be made for evidence of hog cholera. Lung worms cause cough, emaciation and other symptoms which resemble those observed in chronic hog cholera. The history of the outbreak, supplemented if necessary by an autopsy, will be sufficient to determine its cause. Chronic hog cholera is usually a sequel of the acute form. Lung worms are often associated with pneumonia, causing death most frequently in young pigs. Unless great care is used these parasites may be overlooked. The smaller air passages should be laid open mth sharp shears and the examination made in a strong light. Considered collectively, the various drug and food poisonings differ from hog cholera in that several animals often are affected at the same time, the s^nnptoms as a rule are more violent, vomiting is more common, and temperatures are not so high. The history may reveal the source DIAGNOSIS, DIFFERENTIAL DIAGNOSIS, PROGNOSIS 73 of the particular poison, and some of the drug poisonings (strychnin, belladonna, lead) are in themselves characteristic. Poisoning with the al- kaloids produces no lesions, and no poison, so far as we know, is responsible for changes which are observed in hog cholera. Common salt (sodium chlorid) is especially poisonous for hogs that are not accustomed to it, causing intense inflammatory changes in the digestive mucosa, and congestion of the meninges. Long continued feeding with material containing soap and lye will produce disease resembling chronic hog cholera. How- ever, our task is usually to differentiate between, poisonings and acute hog cholera, and this pre- sents no great difficulties if we resort to autopsies, for none of the poisons produce lesions w^hich re- semble those observed in acute hog cholera. In suspected heat-stroke and lightning-stroke, the history is. an important guide. Heat-stroke occurs most frequently in fat hogs deprived of shade or water in hot weather, and in those shipped in overcrowded stock cars, or subjected to excitement or violent exertion during the sum- mer months. The hair of hogs dead of lightning- stroke may be seared, there may be arborescent congestion or hemorrhage in and beneath the skin at the point where the current entered the body, and sometimes there are lacerations of the inter- nal organs. Rigor mortis is not pronounced. 74 HOG CHOLERA Rouget or swine erysipelas does not exist in the United States. The septicemic form of the disease resembles hog cholera very closely. It has a shorter incubation period than the latter disease, but resort must often made to microscop- ical examination, in order to distinguish between them. Rinderpest does not occur in the United States, and in countries in which it is prevalent, swine do not contract it readily. For this reason it is not well characterized, but in case of necessity it may be distinguished from hog cholera by filtration experiments in which cattle are used as test ani- mals. Both viruses are filterable, but that of rinderpest is the only of the two which affects bovines. Prognosis In the individual, hog cholera runs a rapid and fatal course, and even when recoveries occur, they may be slow and incomplete. Therefore in all hogs visibly sick the prognosis is bad, but it is the herd as a unit which we must consider, for we are frequently called on to estimate the salvage which may be expected. The ability to do this Avith a reasonable degree of accuracy is acquired only by experience, and it is a great asset to one who han- dles hog cholera in the field. We can indicate only the guiding principles upon which the progno- sis depends. DIAGNOSIS, DIFFEEENTIAL DIAGNOSIS, PROGNOSIS 75 The number of animals dead and visibly sick at the time of serum treatment forms our chief basis of estimate. Assuming that a herd is kept under average farm conditions, and that there is no evidence of complications, as a very general rule we expect to save about as many hogs as are eating greedily and are free from abnormal tem- peratures on the date of serum administration. Some of those that show no fever will die, and a few of those that show fever will recover, one class approximately compensating the other. In herds in which it is not possible to secure reliable temperature readings, the prognosis must be more guarded. In general, during the early days of an outbreak, we expect about as many deaths to follow serum treatment as the combined sum of the hogs that have previously died and those visibly sick when serum is administered. If fifty per cent of the animals in a herd are dead or visibly sick we expect the salvage to offset the cost of serum treatment, and leave something to spare, but we cannot promise much in such a herd. Evidence of secondary infection, coexisting par- asitisms, improper feeding and housing, a history of recent shipping or other weakening influences all call for a guarded prognosis. If the hogs have not been confined closely, or if they are in several pens some of which remain uninfected, the prog- nosis is relatively more favorable. CHAPTER VII PEEPARATION OF ANTI-HOG-CHOLERA SEEUM AND HOG CHOLERA VIRUS We are indebted to Dr. Marion Dorset and Dr. W. B. Mies of the United States Bureau of Ani- mal Industry for developing our present method of preparing anti-hog-cholera serum. The dis- covery that hog cholera is caused by a filterable virus dismissed further efforts to immunize against it with products of various bacteria, but it suggested hope for a protective serum analo- gous to that used against rinderpest, a filterable virus disease of cattle. That hope was realized in 1908 when Dorset announced his discovery, and although the immediate control of hog cholera which some predicted did not materialize, the ob- stacles encountered have not been due to any fun- damental defect in the serum itself. When prop- erly prepared and used it is one of the most effec- tive biologies knoAvn to preventive medicine. Anti-hog-cholera serum production is highly or- ganized and carefully controlled in the United States and many laboratories are in operation which are models for convenience, cleanliness and 76 S o o -(-I ci ^ o '■+2 c3 be « Oh 77 78 HOG CHOLEKA sanitation. All laboratories which make inter- state shipments must secure licenses from the fed- eral government and submit to regulations which have been formulated to protect those who use the products. The laboratories must meet certain well-defined requirements before they are allowed to operate, and thus despite great deviation in de- tail, the same fundamental processes are used in all of them. AVe will consider tirst the essential requirements for preparing the protective defib- rinated blood, which has been called anti-hog-chol- era serum, and which forms the basis of all the more or less refined products used to prevent hog cholera in the field. Buildings. The buildings should be suited to the conditions under which the laboratory is to operate. These conditions vary so Avidely that uniformity is neither to be expected nor desired, but certain governing principles should be ob- served in all construction. In general, simplicity, convenience in operation, and provisions for clean- liness are the primary considerations. Future up- keep costs should also be reduced to a minimum in the original construction. Under most condi- tions concrete is the best material to use. The walls, ceiling and floors should be fin- ished so that water will not injure them. The floors should be drained in a sanitary manner. Steam or hot water heat should be provided, the 3 > a o o S I5 S ^ 3 o S^ ii a> "a ^ V^ bJDO o O O Oh 79 80 HOG CHOLERA building should be plumbed for hot and cold water, and all outside doors should be screened in summer. Ample light and ventilation are re- quired. The minimum requirements for reasonable con- venience and cleanliness in a serum laboratory consist of preparation room, bleeding room, serum laboratory proper, office, dressing room and lava- tories, store room and refrigerator room, as well as furnace room and coal bins so situated that dust from them will not contaminate other parts of the building. Quarters for the hogs should be suited to local requirements. In any event they should be at least seventy-five feet from the laboratory build- ing, and even a greater distance is desirable. The floors should be of concrete, w^ell drained, and ample light and ventilation should be pro- vided. Room for exercise on the ground is desir- able, and pasture for hogs that are to be kept for several weeks is a great asset. Provision should be made for sanitary disposal of manure, and other waste from the laboratory and hog quarters. In general, convenience for those who care for the animals, and cleanliness and comfort for the animals themselves are the chief consid- erations. The equipment of the laboratory is likewise governed by individual needs. Too much equip- PREPARATION OF ANTI-HOG-CHOLERA SERUM 81 ment is a detriment, as methods are constantly changing and improving and each mmecessary fix- ture takes up room and must be kept clean. Es- sential major equipment includes facilities for washing, sterilizing and storing all instruments and containers used, vacuum and pressure tanks connected with motor driven pumps, portable crates for tail bleeding and hypering, portable or stationary tables or stocks for bleeding serum hogs and virus pigs from the throat, scales,^ motor driven shaker, serum mixer and office equipment including forms for keeping records. Minor equipment includes bleeding and hyper- ing units, tail shears, clamps, hypodermic syringes and needles, wax heater, cannulas and sticking knives, scalpels, instrument trays, antiseptic con- tainers, funnels, graduates, pipettes, detibrinating forks, porcelain containers for serum and virus blood, apparatus for separating out fibrin and clot, and bottles for storing and shipping. Grouped around this essential unit may be a multitude of accessories, or the unit itself may be multiplied so as to provide for production on a large scale. Facilities for butchering, for cooling carcasses, for rendering virus pig carcasses, for handling virus in separate rooms, for keeping susceptible pigs isolated, for dipping and isolating new arrivals, for bacteriological work, for packing and mailing products, and for exposing serum and 82 HOG CHOLERA virus pigs to calves so as to guard against foot- and-mouth disease, are just a few of the acces- sories that circumstance must include or elimin- ate. Further detail in regard to equipment cannot be profitably discussed here. In all these things sim- plicity, cleanliness, convenience and low upkeep cost are the chief considerations. Good equip- ment invites clean operations, but in the last anal- ysis the quality of the finished product is not de- termined by equipment. A careless operator Avill contaminate serum in spite of every convenience ; a careful one will produce clean products under adverse working conditions. Principle governing serum production. When a hog contracts cholera and recovers, or when it receives simultaneously hog cholera virus and protective serum, it is thereafter immune to the disease. The body cells, in self-defense, have elab- orated substances, termed antibodies, which neu- tralize the effects of all hog cholera virus subse- quently introduced into the system. In the ordi- nary immune hog these antibodies protect against any quantity of cholera virus to which the animal may be exposed, but they do not exist in sufficient concentration so that the blood may be used to protect other animals. Antibody elaboration must be further stimulated, and this is done by giving the immune an enormous intravenous dose PEEPAKATION OF ANTI-HOG-CHOLEEA SERUM 83 of virulent hog cholera blood. A slight reaction follows, and in the course of a few days the im- mune becomes a hyperimmune and comparatively small doses of its blood will protect other hogs ex- posed to cholera. We are now ready to consider in some detail the various steps required in preparing anti-hog-chol- era serum. In all these it is a principle that the operating room shall be clean and free from dust, that the floor shall be dampened, that the operator shall wear clean clothing and that his hands shall be scrupulously clean. The hands must not touch the serum or virus blood, and all instruments and containers with which the blood comes in contact must be sterilized before use. Antiseptic solution should be applied by means of a gravity irrigator or some other device which prevents the hands from passing alternately between operating field and antiseptic container. Exact records of each operation must be kept, and each hog used must be identified with a number tag. Immunizing. Requirements. Two hypodermic syringes, one ten mil capacity or less, for virus, the other twenty mil capacity or more, for serum ; scrub-brush and antiseptic solution, also anti-hog- cholera serum and hog cholera virus each in a separate, covered receptacle. The pig is held by an assistant and the skin covering both armpits (or the inner region of both 84 HOG CHOLERA hams) is tliorouglily scrubbed mth antiseptic so- lution. Then two mils of virus are injected into one armpit, and the required quantity of serum (about 35 mils for a 100 pound pig) is injected into the other. Deep injections are desirable. Following this treatment the pig undergoes a reaction beginning in about five days and lasting about a week, during which time a permanent im- munity to hog cholera is established. It is de- sirable to immunize prospective hypers as com- paratively young shoats and to delay h^^ering until they have attained a weight of at least two hundred pounds, as a long interval between the date of immunizing and that of hypering favors potent serum. In no instance should this interval be less than sixty days. The Virus Pig In order that the immune may receive addi- tional virus and become a hyper, a supply of virus must be procured. This is done by injecting sus- ceptible shoats with lethal doses of hog cholera virus and collecting their blood after they sicken with the disease. A virus pig should be in thrifty condition, weighing near one hundred pounds. It should not be heavily infested ^vith parasites. The dose of virus (about 2 mils) is injected in the same manner as has already been described, but no protective serum is given. PREPARATION OF ANTI-HOG-CHOLERA SERUM 85 Four or five days subsequent to injection the pig should show a temperature near 106° F., and a day or two later marked symptoms of hog chol- era should appear. As a very general guide it may be said that a virus pig is ready to bleed when it has carried a high temperature for about three days and when it has shown severe symptoms of hog cholera for about two days. A good strain of virus will bring this about in approximately seven days subsequent to the date of injection. The time required may be extended in certain individ- uals, but a virus that regularly requires more than eight days in which to ^ ' ripen '^ pigs for bleeding is not desirable for hypering. Bleeding the virus pig. When the sick pig is ready to bleed for virus it is taken to the labora- tory. In the preparation room the entire body is washed, and the animal is secured to a tilting operating table, revolving door or other device for securing it by the hind legs and suspending it head downward. The front legs are secured well apart and the snout tied backward, stretching the skin covering the throat. The throat and sternal region are then thoroughly lathered (an antiseptic soap is desirable), carefully shaved and rinsed, and an antiseptic solution is applied. If it is a male pig a clamp is attached to the prepuce to prevent dribbling of urine. Finally the entire body is covered with a cloth, previously dampened 86 HOG CHOLERA ^ in antiseptic solution, leaving only the throat ex- posed, and all is ready to draw the blood. An ordinary two-quart fruit jar, previously sterilized, is a good receptacle. The sticking may be done with a large cannula designed especially for the purpose, or with a narrow bladed knife. In case a knife is used the hand should be held low on the throat so that the blade passes directly upward, the back against the dorsal surface of the sternum. The blade should not leave the median line, but should be forced upward until it severs a carotid or the anterior aorta near the bifurcation. A free clean incision made in withdrawing the knife facilitates rapid and complete bleeding. A pig weighing one hundred pounds should yield about one thousand mils of blood. If pigs are killed too late, after they are very weak, the yield is greatly reduced. Handling the virus blood. Immediately after the blood is drawn it is defibrinated. This is done by closing the receptacle tightly and shaking it vigorously for a few moments. It is then marked for identification and placed in ice-water pending the time when the pig that yielded the blood can be autopsied. Assuming that the autopsy, which will be considered later, has been satisfactory, the next step is to separate out the fluid part of the blood, leaving the clot and fibrin behind. This is accomplished in various ways. Some use a cen- PREPARATION OF ANTI-HOG-CHOLERA SERUM 87 trifuge of which the essential part is an enclosed, revolving, perforated cylinder; others pour the contents of the jars directly into funnels into which one or more thicknesses of sterile gauze have been placed ; still others empty the jars into perforated funnels which fit into the tops of tall re- ceptacles into which the fluid drains, and near the bottom of which is a turncock for drawing it off. Formerly clot presses were used universally as a final means of extracting the last drop of blood from the fibrin and clot, but this practice is gradu- ally being abandoned. It increases the yield but little, and adds unnecessary debris to the blood, whether it is serum or virus. In all methods of handling the final act is to strain the blood through gauze, after which it is placed in storage bottles and refrigerated pending the time when it is re- quired for Iwpering. The blood of several virus pigs is mixed after autopsies have confirmed its fitness for use. This ^^hypering virus'' may be kept forty-eight hours or even longer, but it is best to use it after it has been refrigerated about one day. It is well to strain it a second time just before it is to be in- jected. Preservative is never added to hypering virus. The autopsy. The two essential requirements for a virus pig are that it shall show complete evi- dence that it was suffering mth acute hog cholera 88 HOG CHOLERA at the time it was killed, and that it shall be free of other infectious diseases which may be trans- mitted through its blood. The clinical history of the pig, and more especially the autopsy, enables us to select on this basis. If in addition to a clini- Plate 9. Post-mortem room where autopsies on virus pigs are held. Each pig must show marked lesions of acute hog cholera, and must be free from other infectious diseases. (Courtesy Pitman-Moore Biological Laboratories) cal history suggesting hog cholera a pig shows characteristic lesions of the disease, slight or se- vere, in two or more organs, we consider the first requirement satisfied. Generalized tuberculosis disqualifies, but slight and localized tubercular le- PREPARATION OF ANTI-HOG-CHOLERA SERUM 89 sions do not cause rejection. Here, we believe, a very rigid interpretation is advisable, and in all cases which admit doubt the pigs should be re- jected. Pigs that show enormously enlarged, dark, pulpy spleens as well as those that bleed scantily and yield very dark blood do not produce satisfac- tory virus. The tendency in both cases is for the blood to defibrinate imperfectly and when it is mixed with good virus the entire lot may be ruined. In the routine autopsy the skin, and all of the thoracic and abdominal viscera are examined, as well as the submaxillary and superficial inguinal lymph glands. In case of doubt, due to slight le- sions, the mucosa of the larynx and popliteal lymph nodes should be included. Disposal of carcass. Virus pig carcasses may be burned or rendered as circumstances direct. The Hyperimmune The immunes which are to be hyperimmunized and later yield serum should be carefully selected. The longer they have been immune to hog cholera, the better. They should be hearty feeders, in moderate flesh, and always strong and active. The ears should be moderately large, but thin and well veined, and the tail at least of average length so as to permit the required number of bleedings. 90 HOG CHOLEBA A weight near two hundred pounds is desirable. The intradermal tuberculin test should be applied to prospective hypers, and all reactors rejected. Hypering. The immune is confined in a port- able crate and the snout is secured firmly, drawing the head to one side. Its weight is then obtained and recorded, and it is wheeled to the preparation room in the laboratory. The entire body is wet thoroughly and a cloth dampened in antiseptic so- lution is thrown over it, leaving only the head ex- posed. One of the ears is lathered, shaved, rinsed and washed in antiseptic solution and the hog, thus prepared, is wheeled to the hypering room to receive the required dose of virus. The hypering operation consists of injecting into an ear vein five mils of virus blood for each pound the hog weighs. The virus is placed in a graduated bottle which is closed mth a rubber stopper, perforated in two places. Through one opening is passed a curved nickeled tube which, ex- tending to the bottom of the bottle, serves as an outlet for the virus when air pressure is applied ; through the other is passed a shorter tube extend- ing just through the stopper and through which air is pumped to produce pressure. Both are ex- tended with rubber tubing, the intake being thus connected with a tank containing compressed air, and the outlet terminating in a slip fitting for the hypodermic needle which is to be introduced into PKEPARATION OF ANTI-HOG-CHOLERA SERUM 91 the ear vein. On this outlet tube is a pinch-cock to control the flow of virus. The bottle is filled mth virus, the stopper is forced down tightly with Plate 10. A close view showing the hypering process. A 200 pound cholera immune hog receives 1000 mils of virus in the ear vein. In ten days the animal is ready to bleed for protective serum. New York State Veterinary College at Cornell University 92 HOG CHOLERA a screw clamp, enough virus is passed tlirough the system to ehminate danger from air bubbles, the pinch-cock is closed, and all is ready to make the injection. The vein into which the needle must be intro- duced usually conforms roughly to the contour of the outer margin of the ear, and is about one inch removed from it. A spring clamp is ap- plied near the base of the ear, thus compressing this vein and rendering it plainly visible. The ear is drawn taut with the left hand, and with the right the needle is thrust quickly into the vein, passed rapidly along its course about two inches, and secured in position with the clamp which is no longer needed to compress the vein at the base of the ear. If the needle is properly in place there will be a backward flow of blood through it. With- out a moment's delay it is now necessary to con- nect the needle with the supply of virus under pressure, and to open the pinch-clock allomng the virus to flow into the circulation. Otherwise the hog's blood may clot in the needle rendering the injection impossible. When the flow of virus is established, one must see that the needle is re- tained in place until the required quantity, al- ready determined, has been injected. This will require from four to thirty minutes, the time be- ing governed by the degree of pressure applied, by the size of the needle and the accuracy with PREPARATION OF ANTI-HOG-CHOLERA SERUM 93 which it has been placed in the vein, as well as by individual differences in hogs that are not well understood. When the required quantity of virus has been injected, the pinch-cock is closed, the needle is withdrawn, and the hog is wheeled away and released. This describes the hypering operation in its simplest form with everything favoring the oper- ator. Volumes could be written about the at- tempts that end in failure. Practice is important, but a natural surgical touch amounting almost to instinct is required of the expert operator, and even he may experience unexplainable lapses in the execution of his technique. However, most of the annoyances experienced may be overcome, and it seems desirable to include a few suggestions which may aid the beginner in his work. At first select hypers with ear veins straight and prominent; later it will be possible to hyper practically all subjects : begin the operation soon after the ear has been shaved ; otherwise the vein may recede and be very difficult to distend so that the needle may enter it : use a needle with a per- fect point ; a dull one will roll the vein under it : Hold the ear out straight ; otherwise the skin will be relaxed and the vein will be unnecessarily tor- tuous : after the needle has entered the vein do not release it until it is clamped firmly in position; the nub may drop carrying the point upward and 94 HOG CHOLERA causing it to prick through the wall so that virus will escape from the vein and accumulate in the surrounding tissues when it is applied under pres- sure : if the needle tends to pucker the skin at the point of entrance, dampen both needle and skin (an atomizer containing alcohol is convenient for this purpose). In inserting the needle hold the index finger of the right hand well toward the point, between the ear and the needle; it is im- possible to guide a needle when it is grasped at the nub only: if when pressure is applied virus is seen to escape from the vein and accumulate in the surrounding tissues, release the pressure at once ; otherwise all chance of entering the vein in subsequent trials Avill be destroyed. Before inserting the needle some operators connect it directly to the rubber tubing containing the virus under pressure, thus obviating annoy- ance incident to blood clotting in the needle or to accidental breaks in the slip connection due to struggling on the part of the hog. When this technique is employed one must depend largely on his sense of touch to determine when the needle is in position, for backward flow of blood cannot be observed. In case of doubt as to whether the needle has entered the vein, one may compress the tubing between the pinch-cock and the needle, at the same time observing whether the virus thus PREPARATION OF ANTI-HOG-CHOLERA SERUM 95 forced out follows the course of the vein or is dis- tributed in adjacent tissues. Occasionally one encounters a fleshy-eared hog exhibiting no ear vein which is visible to the naked eye in ordinary light. Subjects of this kind may usually be hypered by darkening the room and holding an electric light bulb directly under the ear. Small, deeply covered veins are thus ren- dered plainly visible, and hypering is accom- plished with surprising ease. Dangers and accidents due to hypering. The ordinary immune hog will tolerate, without inci- dent, intravenous injection of five mils of virus per pound body weight. Usually there is no evi- dence of pain or distress, and the animal lies quietly while the dose is being administered. In exceptional cases, however, sudden death occurs. It is a curious fact that if distress is to appear, it becomes evident before the first half of the dose enters the circulation. Thus it is not quantity alone that kills. Other factors may contribute, but the principal one seems to be failure of nerv- ous control over capillary contraction. The capillary walls fail to adjust themselves to the increased pressure, and as a consequence distend and rupture. Usually the lungs alone bear evi- dence of this fact, as they contain the first set of capillaries through which the foreign blood must 96 HOG CHOLERA pass, but occasionally the effect is observed in the skin. Severe and general congestion, interspersed with areas revealing slight or extensive hemor- rhage, are the usual changes observed in the lungs. Prevention of sudden death resulting from hy- pering is not always possible. Fatalities occur much less frequently if the virus used is first thoroughly cooled. Even ordinary refrigerator temperatures are not objectionable. As a second precaution a close watch should be kept on the hog during the process of hj^pering, though it is not always possible to distinguish between struggles due to fright and perversity and those due to genuine distress. Real danger is marked by a sudden inspiratory gasp or rapidly developing dyspnea, especially when these symptoms are ac- companied by violent struggling and nervous symptoms such as twitching of the snout or eye- lids and protrusion or shuttling of the eyeballs. If distress is not severe the flow of virus may be checked momentarily and then allowed to con- tinue slow^ly, but as a rule it is best to release the hog and take no further chances. Usually in sub- sequent trials these hogs will tolerate h^^ering without incident. Sometimes it is not until the hog is released from the crate that we observe symptoms. Vomit- ing occurs somewhat frequently at this time but PREPARATION OF ANTI-HOG-CHOLERA SERUM 97 it is of no particular consequence. Great prostra- tion and severe dyspnea are the symptoms which suggest impending death, especially when foam colored with blood exudes from the mouth or nos- trils. Hogs suffering thus should be kept cool, their heads should be elevated, and they should not be subjected to unnecessary handling. Some will recover spontaneously. In fatal cases coma and shallow breathing precede death. We have tried hypodermic doses of strychnin under such conditions, but while temporary relief is afforded the treatment seems merely to delay death rather than to prevent it. Fatalities sometimes occur w^hen air is pumped into the vein. These may be avoided by forcing the outlet tube completely to the bottom of the bottle, and by allowing, previous to each opera- tion, a quantity of virus to pass through the out- let sufficient to carrj^ away bubbles that may be accumulated in the rubber tube. Air in the vein does not always cause death, but the risk is great, and avoidable. Deaths from hog cholera as a result of hypering are practically unknown, except in hogs that have been purchased without a clear history of having been properly immunized. During the interval between the date of hyper- ing and that of the first bleeding for serum, about ten days, careful observations of the hyper are 98 HOG CHOLERA necessary. The points to be determined are whether the hog has been vigorous and healthy, and whether this condition still prevails at bleed- ing time. Temperature readings, clinical obser- vations and comparative weights are the sources of information, each being employed as circum- stances direct. The average hjiper shows a mod- erate and transitory fluctuation of temperature immediately following the dose of virus, and he may eat indifferently for a day or two, but as a rule his appetite is unimpaired, and he continues to gain in weight about a pound per day. If a hog's appetite has been greedy during the last seven days preceding the date of bleeding ; if there has been no loss in weight or outward evidence of sickness ; and if the temperature is normal when bleeding time arrives, we consider the animal a fit subject to produce serum. Bleeding for serum. The hog is confined in a portable crate and wheeled to the preparation room. Bleeding is to take place from the tail which now requires thorough mechanical cleans- ing. Warm water and antiseptic soap are applied freely and a stiff scrub-brush is used to work up a lather. After several minutes of scrubbing, the tail, and a circular area surrounding its attach- ment, are carefully shaved. The body of the ani- mal is then wet to settle dust that may be con- tained in its coat, and a cloth dampened in anti- Plate 11. Bleeding unit, and hog prepared for bleeding, but still uncovered. The fruit jar and breeding horn are clamped together and sterilized as a unit. The rubber cap is removed from the mouth of the horn immediately before the latter is applied to the hog's tail. New York State Veterinary College at Cornell University 99 100 HOG CHOLERA septic solution and containing a hole through which the tail protrudes, is thrown over the body. Thus prepared, the animal is ready for the bleed- ing room. Bleeding is accomplished with vacuum which hastens the process and retards coagulation. The essential bleeding unit consists of a curved metal horn, one end armed with a fitting which receives the mouth of a two-quart fruit jar, forming an air tight joint, and the other consisting of a round or oval-shaped opening presenting a moderately broad surface to be pressed firmly against the skin surrounding the tail, which member the horn en- closes. Communicating with the interior of the unit is a tube which, continued with rubber tubing, connects with a pipe leading to a vacuum tank. Somewhere in the line is a turncock so situated that vacuum may be employed or released at will, and between this and the bleeding unit is an intake valve fitted with a small cup containing carbolized cotton through Avhich air must pass to release the vacuum remaining in the unit when bleeding is completed and the turncock is closed, severing connection with the vacuum tank. A vacuum indi- cator is inserted in the line between the tank and the turncock. The operator grasps the tail, disinfects it thor- oughly, and dries it with alcohol. Then with shears designed especially for the purpose an inch Plate 12. Bleeding for F'^riim. Vacuum is applied through the rubber tube, and the blood flows into the jar, 1000 mils of blood can be drawn in about 8 minutes. New York State Veterinary College at Cornell University 101 102 HOG CHOLERA or more is clipped off the end, and the part re- maining is guided into the bleeding horn, which is forced tightly against the body. When vacuum is applied the contact is rendered air-tight, and blood streams rapidly from the severed tail. Moderate and uniform traction should be applied during the process of bleeding. When the desired quantity of blood has been drawn, the turncock is closed, the vacuum remaining in the unit is re- leased through the intake valve already described, and the tail is ligated near the end or the raw sur- face is seared to prevent further hemorrhage. It is well to cover all the shaved surfaces with ointment thus preventing chapping of the skin which may render subsequent bleedings difficult. Bleeding technique is a determining factor as far as cleanliness of the serum is concerned, and too much importance cannot be attached to it. Thorough mechanical cleansing of the tail and surrounding parts is a first essential. Before the razor is used, warm water and soap should be applied vigorously for some time, thus softening the hair and removing all scurf. Disinfecting the tail previous to bleeding should never be alloAved to degenerate into a mere perfunctory process. During the bleeding operation every effort should be made to prevent the vacuum from being broken, for this admits a stream of air which may be con- PREPARATION OF ANTI-HOG-CHOLERA SERUM 103 taminated, and which, in any event, is sure to hasten coagulation of the blood. We have not found dehbrinating during the bleeding process either necessary or desirable. If it is done by shaking the jar into which the blood is flowing, it causes the hog to struggle, thus re- tarding the bleeding process and rendering break- ing of the vacuum imminent ; and if it is done by any device which renders shaking unnecessary during the time the blood is being drawn, com- plete defibrination can be brought about only by shaking the jar after bleeding is discontinued. On the other hand, if the hog is allowed to lie per- fectly quiet, and if moderate and steady traction is applied after the vacuum is established, bleed- ing takes place rapidly, and almost without excep- tion perfect defibrination will be secured if the blood is shaken immediately after bleeding is com- pleted. Individuals differ, but the average hog bleeds best under about fifteen inches of vacuum. Contrary to what might be expected, a more per- fect vacuum than this usually tends to retard bleeding rather than to hasten it. Each hyper is bled once each week during a series of from two to four bleedings, after which it may be rehypered at any time. In rehypering only 21/2 Mills of virus per pound body weight are required. Following this second dose of virus a 104 HOG CHOLEKA like series of bleedings takes place, the first oc- curring from seven to ten days subsequent to re- hypering. The final bleeding takes place from the throat in exactly the same manner in which virus pigs are bled, except that the blood is usually drawn into a deep porcelain receptacle, and de- fibrinated by whipping it with a large fork. If inspection does not disqualify, the blood of the hyper, which has been kept separate throughout the two series of bleedings, is admitted to test, and the carcass is placed on the market. Handling serum blood. Immediately after the bleeding process is completed the jar containing the blood is sealed, and then shaken for a few moments to whip out the fibrin. When this proc- ess is completed the jar is placed in ice-water. Later, the fibrin is separated from the fluid by exactly the same process that is employed mth virus blood. Here again, the clot-press is detri- mental because it adds superfluous debris to the serum and causes it to be exposed to the air un- necessarily. After the defibrinated blood is strained there is added to it, as a preservative, 10 mils of 5 per cent aqueous solution of carbolic acid for each 90 mils of blood. The product is then placed in storage bottles, labeled, and re- frigerated pending the time when enough has accumulated for a test. In laboratories which do not clarify the serum, « PREPAEATION OF ANTI-HOG-CHOLERA SERUM 105 the blood of each hyper is stored separately so that if the animal should show on autopsy general- ized tuberculosis or other disqualifying disease, the blood may be discarded. Local conditions must govern these details. In our own laboratory where it is possible to purchase hypers which have not followed cattle and have not been fed raw creamery products, we always mix bleedings, in spite of the fact that we do not clarify the serum. We have never had a hyper show generalized tuberculosis, and in the few instances in which we have found the disease localized, we have used a guinea-pig test to determine the fitness of the serum for market. We believe this test has a wider application than is now accorded it. FINAL PROCESSES IN SERUM PRODUCTION Testing". Irrespective of detail in preparation, the final requirement is that the finished product shall pass a test proving its protective potency under carefully controlled conditions. For this purpose there is drawn a sample from a mixed lot consisting usually of about 100,000 mils of serum. Seven pigs weighing between 45 and 90 pounds each are selected for the official Bureau of Animal Industry test. Temperatures must be normal and all pigs in good physical condition at the time the test begins. Each pig is given 2 mils of hog cholera virus, five of them receiving in addition, 106 HOG CHOLERA and at the same time, 20 mils each of the sample of serum to be tested. The other two receive no serum, but are employed as controls to determine the virulence of the virus. Daily observations are made and temperatures are recorded as required, preferably once a day. The essential require- ments for a satisfactory test are that both pigs which receive virus only shall sicken during the test period (21 days) and that at least one of them shall sicken between the fourth and seventh days subsequent to injection, and shall before the fif- teenth day suffer from hog cholera in a degree sufficient to cause death. As an additional con- dition, no more than one of the pigs that receive serum and virus shall show visible illness, and in case one should sicken it must be completely re- covered before the twenty-first day following the beginning of the test. Bureau of Animal Industry regulations govern- ing the interpretation of tests will be found in the Appendix. In general, tests are classified accord- ing to results as * ^ satisfactory, ' ' *^ unsatisfac- tory^' or *^no test,'' the latter giving indefinite results. The satisfactory test has already been described; the unsatisfactory test is usually re- ferred to impotent or contaminated serum; re- tests are indicated when the serum-treated pigs or more than one of the virus pigs sicken before the fourth day, when the control pigs do not sicken m <1) 1 a ^ ^ C3 s c3 +J J^ CIJ 4^ t: o 50 o o QJ be Ph H 0) > ■-3 CO Oi ^1 ^^ .G (Ti OJ • fH -t^ o > -1-3 CO o o 3 f^ ^ c b£ o CO O c/i -G O Qj 3 o O -M I.S ? -^^ o .f^ rG ^ '^ ^ -M c ^ 3 a> _ fcJD bJD •5 -p. CP c Co' fl ^ '^' --H S a ni ^ C3 fi H C3 -tJ IX< 1-1 Oh 107 108 HOG CHOLERA as is required in a satisfactory test, or when inter- current disease or accident intervenes. Too much stress cannot be placed on the test, for it is here that all technique leading up to com- pletion of the finished product receives its final confirmation. Careful observations are necessary as well as strict interpretations which mthhold from use all doubtful serum. Regulations are a valuable guide, but they themselves require skill- ful interpretation, and no exact rules can be laid do\^^i which ^^ill serve their intended purpose under all circumstances. Is the serum highly po- tent? Is it free from organisms that will injure hogs into w^hich it is injected? When test con- ditions answer both questions definitely in the affirmative, the serum is fit for use. If doubt re- mains it may be retested, and if it has failed to protect healthy pigs in average condition it should be discarded. In our own work we greatly prefer an eight pig test in which two of the serum pigs receive 10 mils each of serum, two 15 mils each, and two others 20 mils each. We believe that these low doses give much more complete information re- garding the potency of the product, thus allomng a greater margin of safety and adding to the con- fidence mth which it may be used in the field. Out of the last 45 tests conducted in this manner 37 have passed without incident, intercurrent dis- PEEPAKATION" OF ANTI-HOG-CHOLERA SERUM 109 ease (heavy ascaris infestation) necessitated three retests which were satisfactory, one 10 mil serum pig died in each of two, one 15 mil pig died in one, and two were wholly unsatisfactory due to low potency. The test pigs ranged in weight be- tween 27 and 105 pounds, the average being 59. It is of advantage to select test pigs from herds in which no immunizing has been done and in which hog cholera has not appeared in recent years. It is well if all pigs in a single test can be litter mates. The pigs should not be subjected to long hauls just before they go on test, and dur- ing the test great care is necessary to prevent overfeeding of the serum pigs at the time when their reaction begins, which is about the time the virus pigs refuse feed entirely. As a routine measure it is a good plan to reduce the feed one- third or one-half on the morning of the fourth day of test, and to feed subsequently so that the serum pigs are kept just a little hungry. It is interesting and highly instructive to ob- serve the progress of a series of tests, and we know that some field workers would be more cau- tious in their vaccinating if this experience could be theirs. It is in this manner that we see results of the battle between protective and destructive forces, and are brought to realize how easy it is for some disturbing factor to turn the tide in favor of destruction. The virus pigs usually show 110 HOG CHOLERA a temperature near 106° F. on the fourth or fifth day of the test, and this high level is maintained several days. Other symptoms of hog cholera ap- pear a day or two after the temperature curve starts upward. The pigs which receive protective serum in addition to virus also undergo a reaction, which is slightly delayed and very mild as com- pared to that observed in the virus pigs. In some instances no temperature reaction is discernible, but usually readings reach a point between 104° and 105° F., considerable fluctuation between nor- mal and this level being observed. As a rule the casual observer would detect no evidence of a physical reaction, but not infrequently the appe- tite lags just perceptibly for two or three days and in white pigs a slight flush may be observed in the skin. On the whole, all evidence of reaction has usually disappeared from the serum pigs be- fore the tenth day of the test. According to Bureau of Animal Industry regu- lations, serum which protects in doses required in their official test is suitable for use in the field under a dosage label as follows : Sucking pigs 20 mils Pigs, 20 to 40 pounds 30 mils Pigs, 40 to 90 pounds 35 mils Pigs, 90 to 120 pounds 45 mils Pigs, 120 to 150 pounds 55 mils Hogs, 150 to 180 pounds 65 mils Hogs, 180 pounds and over 75 mils PREPARATION OF ANTI-HOG-CHOLERA SERUM 111 Bottling and labeling. After a lot of serum has passed a satisfactory test it remains to place it in bottles of suitable size for shipping. In large laboratories this is done with machines de- sigTied especially for the purpose ; in smaller ones it is done by placing the serum in a large covered container drained by a tubular outlet on which is fitted a few inches of rubber tubing. This tubing terminates in a small umbrella-shaped aluminum device, the serum flowing through the part repre- senting the handle, and the bottle being protected from dust during the filling process by the part representing the cover. All bottles intended for shipping are sealed and placed in the refrigerator until they are needed. A label should be placed on every bottle of se- rum shipped, and should include : 1. Release tag and license number if the labora- tory is being operated under federal license. 2. Name and address of manufacturing firm or institution. 3. Dosage table. 4. Identification mark, which will enable the •manufacturer to trace the exact history of any bottle of serum. 5. Return date, or latest date on which the se- rum may safely be used. 6. Brief directions for use and caution regard- ing methods of preservation. 112 HOG CHOLERA The finished product. It has already been shoAvii that all serum sent out is, or should be, subjected to carefully controlled tests in which it is required to protect laboratory pigs in much smaller doses than would be administered to like animals in the field. The protective defibrinated blood, called anti-hog-cholera serum, is the basic preparation from which all the more or less re- fined products now on the market take origin, and when it is prepared with careful technique it is in the original state a highly effective and safe im- munizing agent. It may or may not be sterile. Clear serum is ''bloody serum ^' minus blood corpuscles. It is prepared from the protective defibrinated blood by various combinations of processes which, individually considered, include precipitation of the red blood corpuscles with navy bean extract, centrifuging, and filtering through various materials. Heat, 60° C, for one- half hour, is applied, which kills some contaminat- ing organisms that may be present. An impres- sion seems to prevail that all clear serum is sterile, but this is not true, for it is not necessarily sub- jected to temperatures or other treatment which' will kill or remove all living bacteria. The comparative merits of clear and "bloody*' serum are the subject of much controversy, but as is true of other things of like nature, individual methods are the deciding factor. Clear serum, PREPAKATIOISr OF ANTI-HOG-CHOLERA SERUM 113 if not subsequently diluted may be administered in somewhat smaller doses than can ^^ bloody'' serum, it is free from extraneous matter which has no immunizing value, and all other things being equal it is more likely to be sterile. On the other hand it usually becomes cloudy on standing, its keeping qualities and continued potency after heating, so often emphasized, are yet to be fully established, and it is more expensive than the ^'bloody" serum. ^'Bloody" serum contains cor- puscles which are of no value in immunizing, and, like the clear serum, if it is not carefully prepared it may also contain excessive numbers of bac- teria. On the other hand it is not subjected to complicated processes which invite error in tech- nique, and it can be prepared much more cheaply, per immunizing unit, than clear serum. Disregarding entirely the form of the finished product, the test, conscientiously applied and skillfully interpreted, is the swine breeder's guar- antee of safety to his herd. Thus either clear or ^'bloody" serum, carefully prepared, is a safe and effective immunizing agent; neither, carelessly prepared, will produce the results the breeder and his veterinarian have a right to expect. The relative merits of tail-bled and carotid-bled serum have also been the subject of much absurd controversy, for no scientific evidence has ever been submitted to prove one product different 114 HOG CHOLERA from, or superior to, the other. Carotid-bled se- rum is a mere ^^ talking point.'' Some laborato- ries situated near stockyards can produce it more cheaply than they can produce the tail-bled prod- uct, and this fact, rather than considerations based on the quality of the product, explains their preference for carotid-bled serum. Both products pass like tests before being released for use. The keeping qualities of anti-hog-cholera semm vary with different lots, and with various methods of preparing and storing. Bureau of Animal Industry regulations place the expiration date at two years from the time the first bleeding in a particular lot takes place, and subject to satis- factory retest at the end of two years, another year may be added. Our own preference is for a shorter period, for in one or two instances we have knoAvn serum to fall away in potency before it was two years old. Serum should always be stored in a dark, cool place. According to a limited number of tests conducted by Kernkampf, freezing does not in- jure it, but temperatures below the freezing point are not desirable. A temperature between 40° and 55° F. seems to be most favorable. After the seal on a bottle has been broken and a portion of the serum removed, the remainder should be used in the course of a few days, or discarded. It is always well to open the bottle out of doors, if all PREPARATION OF ANTI-HOG-CHOLERA SERUM 115 the serum contained in it is not required for im- mediate use. The scope and purpose of this book do not allow further detail which might profitably be included in a more inclusive text. In leaving the subject of serum production, let us emphasize again a few essentials which make for clean, potent serum. These include strong vigorous hypers that have been immune to hog cholera a long time before being hypered; a highly virulent strain of virus that will ^' ripen'' pigs to kill in seven days, or less; scrupulous cleanliness and strict antisepsis in all operations; rapid cooling of all blood im- mediately after it is drawn ; no unnecessary han- dling or exposure of serum during the process of defibrinating and straining; and finally, careful observation of tests, with positive exclusion of doubtful serum. Hog Cholera Virus Hog cholera virus, called by the trade ** simul- taneous virus'' because it is used in the field in conjunction with protective serum, is produced by giving shoats doses of virus (usually 2 mils each), allomng them to sicken, and drawing their blood while the disease is at its height. This blood is handled in exactly the same manner as hyper- ing virus, differing from this latter product only in that there is added to it as a preservative, 5 116 HOG CHOLERA mils of 5 per cent aqueous solution of carbolic acid for each 95 mils of blood. The pigs used to pro- duce simultaneous virus must meet the same es- sential requirements as are met by those used to produce hypering virus; that is, they must show ample evidence that they are suffering with acute hog cholera at the time they are bled, and they must be free of all other infectious diseases trans- missible through their blood. Hog cholera virus is sometimes heated at 50° C. for twelve hours before being sent out, in which case a virulence test is necessary before it can be released for field use. In our own work we greatly prefer unheated virus. Keeping qualities. Like protective serum, hog cholera virus must be kept in a dark, cool place. Bureau of Animal Industry regulations allow it to be used not more than sixty days subsequent to the date of dramng, but wherever a thirty-day limit is practicable, we believe it is safer. There are times when an inactive virus may result in as heavy losses as are sometimes charged to impo- tent serum. Labeling". The virus label should include: 1. Release tag and license number if the labora- tory is operated under federal license. 2. Name and address of manufacturing firm or institution. 3. Dosage table. PREPARATION OF ANTI-HOG-CHOLERA SERUM 117 4. Identification mark, enabling the manufac- turer to trace the exact history of any bottle of virus. 5. Eeturn date, or latest date on which the virus may safely be used. 6. Directions for storing. 7. Brief directions for using, and cautions to be observed in destroying unused virus. Hog cholera virus is dangerous material. One- half mil or even less will readily kill an ordinary susceptible hog if protective serum is not admin- istered in conjunction with it. Thus hogs given simultaneous treatment in the field actually re- ceive, as a routine measure, a lethal dose of virus. It is really remarkable that this practice results in so little trouble, but potential danger, slight though it is, exists whenever virus is used, and this fact should be well understood both by the veterinarian and his client. Under no circum- stances should virus be used by untrained men. CHAPTER VIII METHODS OF USING ANTI-HOG-CHOLEKA SEKUM Confining the animals. We will consider first methods of confining the animals to be treated. To one unaccustomed to handling hogs the task of confining and vaccinating a large herd of swine seems formidable, and not infrequently the diffi- culties presented, although largely imaginary, have led to costly neglect or procrastination. Chasing hogs to catch them is usually futile, it is time consuming, and if double treatment is to be applied, or if the animals are fat, the practice is positively dangerous. Ingenuity is required, and the veterinarian who can use the help and ma- terials at hand to best advantage, enabling him to vaccinate a herd quietly and rapidly, and without exciting the animals, gains much in the confidence of his clients. If the time that vaccinating is to be done is ] knoAvn to veterinarian and client the latter should i tempt the animals into pens or small enclosures with feed and fasten them in securely. Bedding should be provided so that the hogs will be clean and dry. In cases of emergency, where this ad- 118 METHODS OF USING ANTI-HOG-CHOLERA SERUM 119 vance knowledge is lacking hurdles should be used to crowd the animals into the corner of a yard or Plate 14. Injecting anti-hog-cholera serum in the ham pasture. In all cases in which fences are insecure it is important to mark each animal at the time it is vaccinated, so that if treated and untreated ones 120 HOG CHOLERA should accidentally get together identification will still be possible. Paint, chalk, bluing or tincture of iodin are convenient for this purpose, or if a Plate 15. Method of holding shoat for injecting serum in axillary space permanent mark is desired, the ear may be notched. Assuming that the animals are fastened in small pens when the veterinarian arrives, confinement of the individual during the process of immuniza- METHODS OF USING ANTI-HOG-CHOLERA SERUM 121 tion is the next step. As a site of injection, one may select the armpit, medial surface of the thigh, or the area immediately behind the ear. The site I'late 16. An improvised method of holding shoats for immunizing. Injecting serum in axillary space chosen, the size of the animal and individual pref- erences determine the method of holding. If the site is to be the medial surface of the thigh, any 122 HOG CHOLERA pig weighing less than sixty pounds may be seized by the hind legs and held with the head suspended, belly toward the operator. If the armpit is chosen the pig is suspended by the front legs which are drawn well apart. Shoats weighing more than sixty pounds are confined in a variety of ways. Sometimes they are thrown and held on their backs; sometimes two men suspend them by their hind legs ; at other times it is convenient to incline a V-shaped hog trough against a fence so that it forms an angle of about 45 degrees with the ground. Into this the shoats are placed on their backs, heads do^\mward, and their snouts are allowed to slide under a cleat which extends across it. Perhaps the most serv- iceable method of handling animals of this size is to seize them by the front legs and set them on their haunches with their backs drawn firmly against the legs and body of the man holding them. In this position they are quite helpless and they are easily held as their weight rests entirely on the ground. Shoats thus confined are injected in the armpit. In throwing larger hogs that are to be held on their backs for treatment it is well to seize them by the front leg on the nearest side. A common mistake is to reach under them for the off foreleg. Another convenient and surprisingly easy method of throwing is to seize the tail with the right hand METHODS OF USING ANTI-HOG-CHOLERA SERUM 123 and the left hind leg with the left, pulling down- ward and to the right on the tail, upward and to the left on the leg. Like the double half -hitch in throwing a bull, this method of throwing hogs is effective, but its manner of action is a mystery. Large hogs are seldom thrown but are confined either by means of a noosed rope which is placed well back in the mouth and tightened around the snout, or with one of the many types of hog-hold- Plate 17, Convenient hog holder made from i/o inch gas pipe and flexible clothes wire. It may be disjointed in the middle for convenience in carrying ers. In case a snout-rope is used it should be either i/4 or % inches in diameter, and about fif- teen feet long. An eye about % inches in diame- ter is braided in one end, and through this the other end of the rope is passed to make a running noose. Directly around the rope forming the noose is braided a jerk-rope about a foot long. This device renders it possible to release a hog instantly, and saves time, for if it is not used re- leasing the animal sometimes is as difficult as confining it. A large rope tied in any manner to 124 HOG CHOLEKA form a running noose is clumsy to liandle, and allows a great many animals to escape. There is a great knack in noosing the snout of a large hog. Assuming that a person is right- 1 Plate IS. Method of preparing snout rope for confin- ing large hogs. The short ''jerk-rope" renders it possible to release the hog instantljv ^/i or % inch Manila rope is used handed he should stand near the center of the pen and start the animal moving around it to the left, at the same time seeking a position at the hog's left shoulder. Holding in readiness a short sec- tion of the noose, and at the same time crowding METHODS OF USING ANTI-HOG-CHOLERA SERUM 125 the hog suddenly and forcibly against the side of the pen with the right leg, one takes advantage of the fact that the animal opens its mouth to squeal or champ its teeth when its progress is thus momentarily arrested. The noose is slipped into the mouth, drawn backward quickly, and tightened 1^^^^. ^ i. ^^^gp^^^^ ■^^Jl .^/ 1 ■wT " \ Plate 19. Method of noosing the snout of hog. The animal is forced suddenly against the gate with the right knee, the noose is thrust into the mouth, drawn behind the canine teeth and tightened around the snout. The free end of the rope is then secured and the animal is tapped on the snout to make it pull backward, for a hog mil not stand quietly unless the rope is tight. In this position the site of injection behind the ear is readily available. When a sow and sucking pigs are to 126 HOG CHOLERA be immunized, the sow should be tied and injected first, and released only after the pigs have been vaccinated. Another method of confining large hogs is to connect two pens with a narrow, low chute, which can be closed at both ends. Into this a limited number of hogs are crowded tightly as they pass from one pen to the other, and the operator may reach over the side of the chute and inject the animals behind the ear. This involves some labor in preparation, but it is a rapid method of han- dling, and may be serviceable when a large num- ber of hogs are to be immunized. Quiet hogs may sometimes be injected without resorting to noose or holder as the operation is by no means painful. Methods of Using Serum Preventive vaccination against hog cholera in- volves the use of just two materials; anti-hog- cholera serum, which is protective in nature, and which is prepared from the blood of hogs that are hyperimmune to cholera; and hog cholera virus which is the defibrinated and preserved blood of pigs that are suffering with hog cholera at the time bleeding takes place. With these two ma- terials three methods of immunizing have been developed; serum alone, simultaneous (double, or serum-virus), and follow-up, which is a combina- tion of the two first-named methods. 1 I METHODS OF USING ANTI-HOG-CHOLERA SERUM 127 The practicing veterinarian is regularly re- quired to select the method best suited to the conditions he encounters, and he can handle hog cholera with maximum efficiency only when he judiciously chooses and employs the particular method indicated. The selection is based entirely on the effects produced by each method, just as we choose drugs on the basis of their action. When once these effects are well understood, the choice involves no great difficulties. Serum alone method. This consists of deep injection of the required quantity of serum. If the animals thus treated are not infected ^ with hog cholera immediately before or during the four weeks following serum administration the immu- nity conferred may, with rare exceptions, be de- pended on four weeks. In many individuals it lasts much longer. Swine more than twelve weeks old that receive serum alone and are infected with cholera immediately before immunization, or dur- ing the three or four weeks following, are there- after permanently immune. The effect on pigs less than twelve weeks old is still a matter of con- troversy, but at present we are not safe in depend- ^ Much misunderstanding has arisen because of the loose use of the terms ''infected" and ''exposed." The first term implies that hog cholera virus sufficient to produce the disease has actually entered the system ; the second implies that the animal has been in close contact with virus from any source, but infection may or may not have taken place. Hogs given serum alone and in- fected with hog cholera acquire a permanent immunity; if they are exposed but not actually infected the immunity is temporary. 128 HOG CHOLEKA ing on serum alone plus natural infection to pro- tect young pigs more than four weks. Technique of serum administration. Require- ments. Serum in covered container, or in a bottle fitted with cannula through which it may be dra^vn ; hypodermic needles, and syringe, the lat- ter preferably one of 30 or 40 mil capacity ; anti- septic solution in large container, and scrub-brush, for disinfecting site of injection; antiseptic solu- tion in small container for disinfecting needles and syringe. In field work these are placed conven- iently upon an improvised table consisting usually of a box covered with a clean toAvel or oilcloth. The pig is confined in the manner already de- scribed, and the site of injection is thoroughly cleansed with the scrub-brush dampened in anti- septic. If syringe and needles have not been pre- viously sterilized, they should now be thoroughly disinfected, after which the required quantity of serum is drawn into the syringe and injected deeply into the tissues. As the needle is with- drawn it is well to pinch the skin to prevent back- ward flow of serum. Massage is now applied if required, the site of injection is again dampened in antiseptic, and the pig is released. Choice of the site of injection is governed by the size, condition and intended use of the animal, by the method of confining, and by individual preferences. All other things being equal we pre- METHODS OF USING ANTI-HOG-CHOLERA SERUM 129 fer the armpit because the skin covering it is usually clean, the serum enters the tissues freely, and with each step the animal takes, massage is automatically applied. Very young pigs are most Plate 20. Injecting serum behind the ear. The needle is thrust deeply into the loose areolar tissues, and very little force is required to expel its contents conveniently confined for injecting in the ham. Heavy hogs, especially pregnant sows, are almost always injected behind the ear, because it is safer and more convenient to confine them standing. Hogs nearly ready for market should not be in- 130 HOG CHOLERA jected in the ham, and young pigs and shoats are not injected behind the ear. Sometimes serum is administered in the flank, or in the loose tissues immediately back of the elbow, but we believe neither practice has much to recommend it. Rapid and complete absorption of serum is greatly to be desired, because it gives the highest and most prompt immunizing effect, and tends to prevent abscess formation. Some will inject no more than 20 mils of serum in a place, believing that a greater quantity will be absorbed but slowly, but it is the placing and distribution of the dose, much more than its size, that govern ab- sorption. In real small pigs it is well to divide the dose, and whenever possible the practice may be followed in older animals. In injecting young pigs the parts that receive the serum should be kneaded gently after the needle is withdrawn; in larger animals the needle should be thrust deeply into the loose tissues immediately behind the ear, and after the injection is completed the ear should be drawn forward and vigorous massage applied in order to distribute the dose. Serum injected immediately beneath the skin, forming a distinct welt, absorbs but slowly, and when it fails to spread in the deeper tissues, as evidenced by un- due pressure required in making the injection, rapid absorption cannot be expected. A syringe METHODS OF USING ANTI-HOG-CHOLERA SEEUM 131 which operates easily and requires uniform pres- sure on the plunger should always be selected. Cleaning and disinfecting the site of injection are processes frequently neglected, because the hog is proverbially difficult to infect. He can be infected though, as some have found to their sor- row. If hogs are at pasture or in clean, dry, well- bedded pens, cleaning is not difficult. Some sim- ply paint the skin with tincture of iodin, and this answers well when the site of injection is both dry and clean, but tincture of iodin is not suitable for use on wet surfaces. We have found nothing better than a good coal-tar disinfectant applied with a stiff scrub-brush, for this removes all dirt and scurf, in addition to furnishing the desired antiseptic action. If pigs are unusually dirty the site of injection should first be cleaned with warm soapsuds. Good technique includes thorough me- chanical cleansing, and nothing else will take its place. Dosage of serum. The best rule is to give at least as much serum as the label requires. Serum varies widely in immunizing units per mil, and although the margin of safety — the increase of the field dose over the laboratory test dose — ob- served in individual laboratories is not the same, doses recommended in any particular laboratory are, in a very general way, determined by its indi- 132 HOG CHOLERA vidual methods of preparing and testing. Dosage is based on weight, and one not accustomed to estimating weights of hogs should weigh one or more before beginning work, for a common and disastrous error is to estimate far too low, and to give correspondingly small doses of serum. Not infrequently we have known weights to be estimated at less than half what they actually were. We believe a common error in dosing, and one for which labels are frequently responsible, consists of giving all hogs above a certain weight a fixed quantity of serum. Thus on one label we read: ^'Hogs 180 pounds and over, 75 mils." A hog weighing 180 pounds may properly receive 75 mils of average serum, but one weighing 500 pounds will not be adequately protected by that quantity. Under all conditions under which it is known or suspected that the hogs have resistance below the average, it is a wise precaution to in- crease the dose measurably. In badly infected herds it should be doubled. If serum is carefully administered, with due precautions regarding rapid absorption, it is prac- tically impossible to overdose, and there is no dis- ease or condition of swine, so far as we know, that even an unnecessarily large dose of serum alone will affect unfavorably. Thus in case of suspected hog cholera, in which the diagnosis cannot be clearly established, it may, and should be, admin- METHODS OF trSING ANTI-HOG-CHOLERA SERUM 133 istered ; and in case deviation from the dose table seems desirable, a quantity unnecessarily large is preferable to one dangerously small. Therapeutic value of serum alone. Serum is employed almost entirely as a preventive of bog cholera, but it possesses some therapeutic value when used in generous doses early in the course of the disease. Herein lies the reason for in- creased doses in badly infected herds — ^many ani- mals apparently well are really in the first stages of hog cholera. Ordinarily we do not regard treating hogs visibly sick with cholera as a profit- able venture, but when the disease appears in mild form, or when the animals are adults or of excep- tional value, we are more than repaid for our efforts to save them. Double doses of serum are recommended under such circumstances, and or- dinary doses may follow at intervals of from three to seven days, as the condition of the animal re- quires. Good nursing as an adjunct to serum treatment is of the utmost value. A plentiful supply of fresh water should be furnished, to which may be added a saline purgative when there is constipation. The diet should be severely restricted, and under no circumstances should unconsumed food be kept before the animal. Warm milk alone is an excel- lent diet for hogs suffering with cholera. Dangers and after-effects of serum alone im- 134 HOG CHOLERA munization. Occasionally rough handling during the process of vaccinating will injure an animal, but this is not to be charged to the effect of serum. Sometimes, especially in very young pigs, a tem- porary stiffness or lameness exists for a day or two following treatment, but this is exceptional, and usually it is of little consequence. Large quantities of cold serum, especially when the dose is not well distributed, sometimes cause this trouble in an aggravated form. The obvious pre- cautions are to use due care in injecting, and to warm serum that is to be administered to young pigs in cold weather. A temperature approaching blood heat is desirable, and may be secured by placing the bottles in warm water. Very exceptionally there is observed, immedi- ately following serum administration, a rapidly spreading local infection often involving an entire quarter and encroaching on other parts. There is acute lameness in the atfected quarter. The area involved is either doughy in consistency, or else gas formation is evident, and under both con- ditions there is pronounced edema. The skin usually assumes a purple hue. As a rule, animals thus affected die in a short time. We have seen but a limited number of such cases, and with one exception, all could be traced to gross carelessness in technique, or to working conditions which ren- dered even average technique impossible. We METHODS OF USING ANTI-HOG-CHOLEEA SEKUM 135 have never seen a considerable number of animals in one herd thus affected. Abscesses follow serum administration infre- quently, and like the rapidly terminating type of infection just described, they are usually asso- ciated with faulty technique or conditions below the average as far as sanitary surroundings of the animals are concerned. They occur most fre- quently in poorly nourished, weak animals, but are not always thus limited, nor is it possible in all cases to ascribe them to bad technique. The bacterial flora of the particular surroundings in which the immunizing is done seems to play an im- portant part, but even this factor may be con- trolled to a great extent by the free use of disin- fectant. Dust contamination of serum and instru- ments also favors abscess formation, and for this reason one should work out of doors whenever possible. Failure to distribute the dose of serum thoroughly sometimes results in local inflamma- tion, leading to abscess formation. Abscesses are rare when the serum is not contaminated, when care is used in administering it, and when the treated animals are in reasonably clean quarters. Vaccination abscesses usually encapsulate and form slowly, and although they sometimes reach a considerable size and retard the growth of the animal to some extent, they rarely threaten its life or cause general symptoms of disease. If 136 HOG CHOLERA they occur in the hams of hogs ready for market they are highly objectionable, as they cause con- demnation of the entire quarter in which they are located. The handling of vaccination abscesses consists of opening them when the first evidence of fluctuation appears, pressing out the thick, greenish-yellow pus which they usually contain, and irrigating the sac with weak antiseptic solu- tion. In opening, the incision should be made with due regard for continuous drainage. Considerable space has been devoted to these untoward results which sometimes follow serum administration, but on the whole they are uncom- mon when reasonably good technique is employed. One who is careful will immunize hundreds and even thousands of hogs mthout encountering difficulties of this kind, but it is well to know that they sometimes occur, and to understand the im- portance of seemingly trifling influences that operate to cause or prevent them. Summary of action of serum alone. 1. Produces in hogs not infected with cholera near the time of its administration a passive im- munity lasting about four weeks. 2. Produces active and permanent immunity in swine more than twelve weeks old that are defi- nitely infected mth cholera immediately before immunization, or during the three or four weeks following it. METHODS OF USING ANTI-HOG-CHOLEEA SERUM 137 3. Produces an active and permanent immunity in many pigs less than twelve weeks old which are definitely infected with cholera near the time of treatment, but cannot be depended on to produce permanent immunity in all young pigs. 4. Does not affect other diseases unfavorably, and if it is carefully administered, untoward re- sults following its use are practically negligible. Indications for serum alone. 1. In seemingly well and exposed animals in in- fected herds. 2. In all cases in which a four-week immunity will meet the requirements. (Show hogs under some circumstances, those near the end of the fattening period, breeding animals crated for shipping.) 3. In all cases in which immediate protection is required and simultaneous treatment cannot be safely administered. (Sows near farrowing time, weak unthrifty animals temporarily threatened with hog cholera.) See also follow-up treatment. Contra-indications for serum alone. Serum alone is contra-indicated when the following con- ditions coexist in the same herd or animal. 1. A permanent immunity is desired. 2. Hog cholera infection does not exist. 3. Simultaneous treatment may safely be ad- ministered. Simultaneous or double treatment. This 138 HOG CHOLERA method consists of giving serum in exactly the same manner as has already been described, and of administering at the same time, and wdth a separate syringe, the required dose of hog cholera virus. Usually the dose of serum is given in one of the sites of injection already mentioned, and the virus at the corresponding point on the oppo- site side. The technique of administering virus does not differ from that employed with serum, except that special care is required in disinfecting the site of injection after the needle is removed. Also the dose of virus is so small that massage is not required. No virus should be allowed to drop on the ground, and all that is not used should be burned. Simultaneous treatment possesses the great ad- vantage of producing a permanent immunity in all swine that are more than twelve weeks old, and in many of those that are younger. On the other hand it involves the use of a lethal dose of hog cholera virus, thus producing certain sequelae and adding specific dangers that are not associated with serum alone treatment. Dosage of serum and virus. The same princi- ples that apply to dosage of serum administered alone, apply when it is given with virus. We give at least as much serum as the label indicates, in- creasing the dose when we are compelled to ad- minister simultaneous treatment to hogs below METHODS OF USING ANTI-HOG-CHOLEEA SERUM 139 average in resistance. In using virus the label is likewise our guide. Although in giving simultane- ous treatment to hogs we regularly administer a lethal dose of virus, we should not let that fact tempt us to decrease the quantity. Too much stress has been laid on carefully graded doses of virus and on the necessity for balancing virus and serum doses. One mil of virus will kill almost as regularly and quickly as three, and an ordinary dose of serum will protect against either quantity. The dose of serum is not governed by the quantity of virus, but by the potency of the serum, which is reflected on the label, and by the size and con- dition of the hog. Thus, if circumstances compel us to give simultaneous treatment to hogs below average in resistance, we increase the dose of serum, but leave the virus dose unchanged. The primary aim is to give enough virus to infect, and enough serum to protect against an infecting dose. In our own field work we never give less than one mil of virus nor more than two mils, our prefer- ence being for a dose approaching the latter figure in all swine weighing more than seventy-five pounds. After-effects and dangers of simultaneous treat- ment. A reaction, very slight in the vast ma- jority of cases, but severe in others, usually follows simultaneous treatment. In effect, the animals go through an attack of hog cholera which 140 HOG CHOLEEA is SO light that symptoms do not appear, but if temperatures are recorded the curve will usually show slight elevation and more or less fluctuation between the fifth and twelfth days following immu- nization. Under unfavorable conditions the reac- tion becomes relatively more severe, and symp- toms of hog cholera may appear. If these are slight, complete recovery will take place; if they are severe, they threaten the life of the animal; and if it dies its death is due to hog cholera just as truly as it would be if no serum were adminis- tered. Sickness and deaths due to hog cholera following simultaneous treatment are termed ^'breaks'' or ^^vaccination cholera.'' If the trou- ble appears during the first three weeks foUomng treatment it is called a ^ ' serum break ' ' the suppo- sition being that the serum is impotent and allows the virus to kill the animal; if it appears after a longer time it is termed a ^' virus break,'' the effect being ascribed to the fact that inert virus has been administered and the serum produces only a tem- porary immunity, which, as it disappears, leaves the herd again susceptible. In reality, ^* serum breaks" are due to a variety of causes, among which are impotent serum, faulty technique in vaccinating, insufficient doses of serum, and, in addition, any influence whatso- ever that temporarily lowers the resistance of the animals during the two or three weeks subsequent METHODS OF USING ANTI-HOG-CHOLERA SERUM 141 to vaccination. Most important among these may be mentioned shipping, weaning, castrating, heavy ascaris infestation in which the gall ducts are tilled with the parasites, overheating incident to handling during immunization, severe exposure in cold rains during the reaction period, injudicious feeding during that time, and general unthrifti- ness due to any cause. These are not imaginary influences that may cause ^'breaks,'' but are real influences that do cause them, and while they may be repeatedly ignored without dire consequences, the tendency is to ignore them once too often. The practicing veterinarian is helpless in re- gard to the potency of the serum he uses. He has no opportunity to test it, and must therefore ac- cept it on faith. His safest plan is to secure it only from the most reliable sources. Of course if the virus used is up to standard, and the serum is impotent the hogs that receive the two simultane- ously will probably die, and no veterinarian who has had this result follow his work will soon for- get it. It is well to remember, though, that impo- tent serum is just one of many causes of so-called ** serum breaks'' and that the remainder of these causes are for the most part controlled by the practitioner or breeder. There is a triple respon- sibility associated with all simultaneous treat- ment, and neither serum producer, -veterinarian 142 HOG CHOLERA nor breeder should throw stones until he is sure he is not living in a glass house. Shipping hogs immediately after simultaneous treatment has been administered, or worse still, holding them three or four days and then shipping them so that they will be on the road at the time the reaction following treatment is in progress, is a fruitful cause of serum ''breaks/' We are aware that this practice is stoutly defended by many, principally by those who administer the treatment in stockyards, see the hogs loaded in cars, and never see them again. The practice is not defended by veterinarians who are on the re- ceiving end of the line, for it is a well-known fact that ' ' serum breaks ' ' often occur soon after these hogs reach the farms on which they are to be fattened, and it is fortunate indeed if hog cholera is not thus transmitted to other herds in the vi- cinity. This method of handling hogs may be necessary under present conditions, even if it must carry with it the risks we have mentioned, but granting that it is necessary, let us at least recog- nize the dangers in their true proportions, and work toward a better method of handling feeding hogs. Lowered resistance due to shipping accounts for many of these ''breaks,'' yet the tendency is to charge them to impotent serum. The best se- rum that can be manufactured will not protect all METHODS OF USING ANTI-HOG-CHOLERA SERUM 143 animals thus handled, but the fact that many lots of hogs will endure it, leads some to think that all ought to do so. Individual differences exist, and while they are not always obvious, the lots that ** break '^ more often consist of hogs that have been held in stockj^ards a long time, those badly infested with parasites, or suffering with respira- tory diseases. Distances traveled to and from the stockyards, and the degree of crowding of the cars are also potent factors in determining the hazards of shipping simultaneously treated hogs. Hogs are not fit subjects for simultaneous treat- ment just as they are unloaded from long railway journeys. It is best to give these animals serum alone at this time, and simultaneous treatment two or three weeks later. This is the follow-up treatment w^hich we have already mentioned, and which will be considered separately in this chapter. In farm hogs, weaning, castrating, ringing, and the absurd practice of knocking '^ black teeth '^ out of all pigs may operate individually or collec- tively to lower resistance and render simultaneous treatment dangerous. Due to pressure of other work pigs are frequently neglected several weeks, then suddenly there is a desire to do all of these things, and immunize, at the same time, in order to avoid handling the animals more than once. The wonder is that pigs will frequently, even usu- 144 HOG CHOLEEA ally, survive the ordeal, but exceptions prove the rule — and embarrass the veterinarian. In several instances we have known men to castrate pigs dur- ing the week following simultaneous treatment. In some of these a number of the castrated pigs died, while the female pigs, which remained as checks, survived, thus furnishing excellent but rather involuntary and costly experiments. Pigs are best castrated as sucklings, but in any event, it is well to separate castrating and simultaneous treatment at least two or three weeks. Ascarids may exist in the intestine in large numbers without appreciably lowering the resist- ance of simultaneously treated pigs, but if the parasites enter and occlude the gall duct, the in- fested hog shows a remarkable intolerance for virus. We have observed this intolerance again and again both in test pigs and in the field. Prac- titioners cannot always avoid trouble due to as- carids, for granting that they know the parasites exist in a herd, it is not always possible to deter- mine their location in the individual, and often it is not safe to delay treatment. Severe jaundice in pigs is usually due to ascarids in the gall-duct, and its presence, easily observed in white pigs, should suggest caution. Overfeeding is injurious to pigs passing through the reaction following simultaneous treatment. Any one who has observed serum tests knows m:ethods of using anti-hog-cholera serum 145 that. Often there is no change in the appetite during this time, but if a few animals in a lot eat scantily, the others gorge themselves on the sur- plus thus rendered available, and a period of dis- tress or dullness follows, during which the virus may get in its work. A simple rule is to feed so that the animals remain just a little hungry after each meal, and to be prepared for a slight lagging in appetite between the fifth and twelfth days fol- lowing treatment. Methods of preventing ^* serum breaks'' are ob- vious when the causes of these ^^ breaks" are un- derstood. Full doses of potent serum adminis- tered with due regard for rapid absorption, and proper caution in regard to treating hogs below average in resistance are the two essential con- siderations. Handling *^ serum breaks" involves first of all informing the owner of the animals, before serum is administered, that such ^^ breaks" are possible but by no means probable, and asking him to ob- serve the herd carefully and report any sickness that may appear during the three weeks following treatment. Should a ^' break" occur prompt measures are required. If only two or three hogs out of a herd of considerable size appear dull, and if these have sickened later than the twelfth or fourteenth day following vaccination, it is well to take temperatures on several animals in the herd. 146 HOG CHOLEKA If the temperatures vary between normal and a little above 104° F. and if there is no visible dull- ness, serum alone may be given to the sick ani- mals only; but if sickness appears before the tenth day, if several hogs are dull, or if a number of them show temperatures near 106° F. the entire herd should receive full doses of serum alone without delay. Most * ^breaks," taken in time, can be checked. Abortion in sows has been caused by simultane- ous treatment, but it is rather unusual, and occurs most frequently during ^^ breaks'' due to the causes we have mentioned. Sows near farrowing time certainly should not receive serum and virus, but when they are in the early period of gestation we are frequently compelled to assume the slight risks as a necessary evil. Stunting may result from simultaneous treat- ment, and we are told that one of America's most famous pure-bred breeders had his herd ruined by unthriftiness following vaccination. We do not know the particulars, but we do know that such consequences need not follow simultaneous treat- ment judiciously administered, and we know that hundreds of pure-bred breeders maintain fine herds immune, and are satisfied. We have al- ready enumerated a few of the factors which cause * ^breaks." Any one of these may cause death, or falling just short of such a result, stunt the ani- METHODS OF USING ANTI-HOG-CHOLERA SERUM 147 mal. Thus it is the abuse of simultaneous treat- ment rather than its use which incriminates it. Elimination of hog cholera virus in the excre- tions of simultaneously treated pigs sometimes takes place for a few days during the resulting reaction. There was a time when this fact was denied, but no person experienced in handling hog cholera would seriously question it to-day. Reac- tions vary between one extreme in which no tem- perature elevation is recorded, and the other rather unusual one in which death takes place. In the first instance virus elimination is rare, but as the latter extreme is approached, it is the rule. Most hogs do not eliminate infectious material, but the exceptions to the rule are so numerous that it is not safe to keep susceptible animals with those that receive simultaneous treatment. Because of the danger of virus elimination, a period of quarantine is usually imposed on simul- taneously treated hogs. The duration of this quarantine is prescribed by law in most states, the usual time varying between twenty-one and thirty days, with extension in case ^^vaccination chol- era^' appears. Hogs that have shown no physical evidence of disease are very rarely eliminating •virus at the end of twenty-one days following serum-virQs immunization. ''Virus breaks" are not manifest until several weeks following simultaneous treatment, and they 148 HOG CHOLEEA are due to inert virus, insufficient doses, and, very probably, to giving simultaneous treatment to pigs too young. If virus is inert infection is not produced, active imniunity is not established, and if hogs chance to be exposed to cholera after the passive immunity due to the serum has disap- peared, they readily contract the disease. If a pig more than twelve weeks old receives a full dose of virulent virus as a part of simultaneous treatment and remains well during the following four weeks, his immunity to cholera may be ac- cepted as a fact ; if a herd that is given simultane- ous treatment passes the first four weeks without incident and later *' breaks" with hog cholera, we may safely assume that inert virus was used, or that doses ridiculously low were administered. Sometimes inert virus is sent out with impotent serum that will protect against no other kind; sometimes virus is used too long after being drawn; and if it is heated — we do not believe it should be — there is some danger of killing it. Prevention of ^' virus breaks," when one under- stands their causes, is simple. Provided one treats pigs more than twelve weeks old, a full dose of virulent virus in conjunction with the serum used in simultaneous treatment is all that is re- . quired. A breeder who is familiar with the bene- fits and hazards of simultaneous treatment will not be greatly disturbed if a shoat or two should METHODS OF USING ANTI-HOG-CHOLERA SERUM 149 die of ^^vaccination cholera'^ when he has his herd immunized; he may even view a more serious ^' serum break'' complacently, but if his swine re- ceive simultaneous treatment as shoats and die of hog cholera when they are about ready for market, he has a real grievance, which he will be slow to forget. It is fully as important that virus shall be virulent as it is that serum shall be potent. ** Hemorrhagic septicemia" forms a convenient and altogether too common alibi for both * ^ serum breaks" and ^ Virus breaks." If either occurs (and disease which is really hog cholera is called *' hemorrhagic septicemia"), this automatically absolves from all blame the serum producer who sells impotent serum or inert virus ; it excuses the man who abuses the products in administering them, as well as the breeder who subjects his ani- mals to improper care during the resulting reac- tion. The only defect in such an alibi is that it does not save the hogs or tell us what really kills them. When hogs kept under average farm con- ditions receive simultaneous treatment and any considerable number of them develop febrile dis- ease during the following three weeks, unless a cause other than ^^hemorrhagic septicemia" is obvious the chances are ten to one that the primary cause of the disease is hog cholera virus. Under such conditions no other cause can be accepted unless negative filtration experiments, requiring 150 HOG CHOLERA about ten days, are carried out. The field man who represents a laboratory which sells question- able serum, and who pronounces such ''breaks'^ *^ hemorrhagic septicemia'' on information ob- tained from a few autopsies or a brief bacterio- logical examination, must, in mercy, be called ignorant, or else his honesty must be questioned. Most ^'breaks" can be prevented, but some cannot. Let us prevent those we can, and call the others hog cholera. That is what they are. Under conditions existing in the United States during the last decade simultaneous treatment has been a great boon to the swine industry; it has saved hogs worth millions of dollars ; it has made it possible for any breeder who will, to banish fear that hog cholera will destroy his herd. But in spite of these facts it is not perfect in its opera- tion; it is sometimes instrumental in spreading the disease it is intended to check ; it involves some dangers. These are best avoided when their causes are fully understood ; best combated when they are frankly admitted to exist. Forewarned is forearmed. Any veterinarian who contemplates using simultaneous treatment in a client's herd should tell him that it involves a little danger; that the herd must be carefully handled for about three weeks; that if a ''break" should occur it must be reported promptly, and that under no circumstances are susceptible hogs METHODS OF USING ANTI-HOG-CHOLEKA SERUM 151 to come in contact with vaccinated ones during the four weeks following treatment. It is some- times difficult to mention these things, without causing the dangers to be exaggerated in a client's mind, and some breeders will decide not to take risks which they would readily assume could they know how slight they really are. Nevertheless a veterinarian's first duty is to protect his client, and he must protect himself if he is to remain in practice. The man who glibly advises that there is **no danger'' following his vaccinating is not doing either. Summary of action of simultaneous treatment. 1. Produces an active permanent immunity in all hogs more than twelve weeks of age. 2. Produces active immunity in some suckling pigs, passive immunity in others. 3. Usually produces a very mild reaction begin- ning about five days following treatment, and last- ing less than seven days. 4. In hogs with low resistance,^ sometimes pro- duces a severe reaction which exceptionally ter- minates in death. 5. Causes some hogs to eliminate hog cholera virus in their excretions during the time the reac- tion is in progress. ^ The terms ' ' resistance ' ' and ' ' condition ' ' should not be con- fused. The former, as used here, applies to the state of the ani- mal's natural defenses against disease, and is determined by the history, as well as by the appearance of the animal. "Condition" 152 HOG CHOLEKA 6. May cause abortion in pregnant sows, and may stunt pigs if they are treated while their re- sistance is low. Simultaneous treatment is indicated in herds where hog cholera virus is almost sure to find its way sooner or later, but where actual infection of the herd may be delayed several weeks or months. Such conditions exist : 1. In sound herds on infected farms. 2. In other herds immediately threatened with cholera. 3. In some show hogs. See ^4iandling show hogs'^ in Chapter IX. 4. On farms on which hog cholera has appeared periodically. 5. In very large herds in which there is con- stant exchange of animals. 6. In garbage-fed herds. Simultaneous treatment is contra-indicated: 1. When it cannot be applied by experienced men. 2. When the entire herd cannot be immunized. (Some may, if necessary, receive serum alone, but none must be left susceptible.) applies more specifically to the degree and quality of flesh an animal carries, as well as to the appearance of the coat, and is determined, in hogs, principally by inspection. Fat hogs recently shijjped or fat sows that have recently farrowed, though in good condition, will not tolerate simultaneous treatment nearly as well as ordinary farm hogs in very moderate flesh. The "resistance" of the latter is higher, although their "condition" is lower. METHODS OF USING ANTI-HOG-CHOLERA SERUM 153 3. When the treated herd cannot be properly- segregated. 4. For sucking pigs as a routine measure. (In- formation still incomplete on this point.) 5. For sows about to farrow, or for those nurs- ing young litters. 6. In badly infected herds. 7. In animals with low resistance due to ship- ping, weaning, castrating and other influences. 8. In all circumstances in which serum alone will be equally etfective. FoUow-up treatment. This consists of giving serum alone and following it in a few weeks, usu- ally less than four, with simultaneous treatment. It has been called ^^ double treatment'' by some, but according to usage which has now become fixed, the terms ^^ double treatment'' and ** simul- taneous treatment" are applied interchangeably to serum-virus administration. It therefore seems desirable to apply to serum alone followed by simultaneous treatment, the separate, distinct and self-explanatory term, * ^follow-up treatment." Follow-up vaccination is safer than simultane- ous treatment, it can be applied under circum- stances which practically forbid the use of the latter method, and the final result is the same — a permanent immunity is established. There are those who believe that the passive immunity pro- duced by the dose of serum alone prevents the re- 154 HOG CHOLERA action and consequent permanent immunity due to subsequent serum-virus treatment. The im- pression seems to prevail that there is just one way to immunize a hog permanently, and that is to give him simultaneous treatment as a first and only measure. Various troubles following follow- up treatment have been cited as proof of this theory, but we have never investigated a case in which there was the least evidence that the system was fundamentally at fault. The trouble has been in its application. In applying the follow-up system, there is a marked tendency for the veterinarian to give the dose of serum alone and to neglect for too long a time to follow it ^viih. simultaneous treatment. There is no danger in this unless the pigs happen to be exposed to cholera after the passive immu- nity due to the dose of serum has disappeared, but too often just that very thing takes place. The owner of the animals derives a false sense of se- curity from the fact that serum has been adminis- tered, and hence does not report the sickness as promptly as he otherwise would. The final result is that when hog cholera is well started in the herd, the veterinarian receives an urgent call to give serum and virus as the final installment of the follow-up treatment. Heavy losses inevitably follow, and the entire system is condemned. It should always be remembered that serum alone METHODS OF USING ANTI-HOG-CHOLEKA SEKUM 155 cannot be depended on to protect more than four weeks. *^ Virus breaks^* are no more likely to occur when follow-up treatment is administered than they are following simultaneous treatment, and, as with the latter method, their prevention con- sists wholly of giving full doses of virulent virus, and using due care not to treat pigs too young. When these precautions are observed, we can vouch for the fact that follow-up treatment pro- duces a permanent immunity. We have used it since 1912 in maintaining many immune herds, usually administering the final dose, simultaneous treatment, when the pigs were about twelve weeks old. We have not had a ^* virus break ^' during the nine years the system has been employed; that is, no pigs that survived the immediate reac- tion following the final serum-virus treatment sub- sequently developed hog cholera. It is our custom to select hypers from these herds, and so far none of them have developed hog cholera as a result of hyperimmunization. In the East many veteri- narians use the follow-up system in maintaining herds immune to cholera, and ** virus breaks'' are not common. Experimentally we have tested the effects of giving follow-up t;:eatment using various inter- vals between the time of administering serum alone and that of administering serum and virus. 156 HOG CHOLERA and trying to smother the action of virus by large and repeated doses of serum alone previous to simultaneous treatment. In no case have we ob- tained evidence to justify even a suspicion that follow-up treatment does not produce permanent immunity, and we know of no experimental work that contradicts these results. The factor of greater safety cannot well be questioned, although it is seldom that hogs with average resistance require follow-up treatment. Simultaneous immunization produces the same re- sult, and is cheaper. But if exceedingly valuable animals are to be immunized, one cannot go amiss in giving a dose of serum alone and following it in a week or two with simultaneous treatment. If the first dose of §erum is in the system, already absorbed, when the second dose is given with virus, there can be no question that the hazards are reduced. Exact comparisons of the safety of simultaneous and follow-up treatment are difficult to make, because under ordinary conditions both are nearly 100 per cent effective. We have seen follow-up treatment used in immunizing cattle against rinderpest \vith losses running less than 5 per cent when simultaneous treatment with the same serum and virus caused such heavy losses as to forbid its use altogether. "We do not care to generalize too far on this point, but the princi- ples employed in preparing and using the two se- METHODS OF USING ANTI-HOG-CHOLERA SERUM 157 rums are the same, and we offer the observation for what it is worth. Follow-up treatment is indicated: 1. For very valuable hogs where the greatest possible safety is required. 2. "When the following conditions coexist in the same animal or herd : A. Immediate protection is imperative. B. Ultimate permanent immunity is desired. C. Conditions render immediate simultaneous treatment dangerous. Follow-up treatment is contra-indicated in all cases in which it appears 'that serum alone or si- multaneous treatment will be equally eif ective. It is in immunizing hogs mth resistance obvi- ously below normal, and in maintaining immune herds under somewhat adverse conditions that follow-up treatment renders greatest service. In practice, especially in the East, we constantly en- counter the three conditions we have enumerated above, and follow-up immunization relieves us from the necessity of choosing between serum alone which will not produce a permanent immu- nity, and simultaneous treatment which is posi- tively dangerous at the time when immediate pro- tection is required. In a succeeding chapter the adaptations of follow-up treatment will receive further attention in connection with specific con- ditions which we meet in the field. CHAPTER IX HANDLING HOG CHOLEKA IN THE FIELD Handling hog cholera in the field requires ap- plication of the principles that have been outlined in preceding chapters. In this chapter our plan is to assume the existence of certain actual con- ditions which the practitioner frequently meets in the field, and to suggest methods of hiandling suited to these conditions. We know that in doing this we may invite criticism, for methods of han- dling hogs are so mdely different in various parts of the country that one cannot supply details that will apply everywhere. In some parts of the South, for instance, where hogs are allowed almost unlimited range, where predatory animals are common, where hog cholera is prevalent, and where a few breeders use simul- taneous treatment regularly, others must protect their hogs in the same manner, or lose them. In certain sections of the corn-belt hog cholera is prevalent to such a degree that it is the part of wisdom for practically all breeders to maintain immune herds. In the East, where hogs are rather closely confined, w^here they are raised in limited 158 HANDLING HOG CHOLERA IN THE FIELD 159 numbers, where hog cholera is not common and its spread is not rapid, most herds do not require immunization. Moreover, in the corn-belt where hog raising is a business, methods of swine hus- bandry are relatively much better than they are in sections in which it is a mere adjunct to other farming operations. The average corn-belt breeder has had more or less experience with hog cholera, he knows what it means to have it sweep unchecked through his herd, and he is not in- clined to be dissatisfied with measures that will check it, even though these measures may not always be perfect in their operation. On the other hand, the Eastern breeder whose herd we are called on to handle very often is having his first experience with the disease, he is inclined to be skeptical as to the merits of protective serum, and to doubt its value if he loses a few animals after it has been administered. Frequently also, the herd is found in unthrifty condition due to poor meth- ods of swine husbandry and heavy parasitic in- festation. Virus cannot be used as freely in such surroundings as it can under circumstances where its effects will be more correctly judged. Despite these differences, though, and despite the fact that methods of swine husbandry have a direct and important bearing on the handling of disease, the principle holds that hog cholera is hog cholera the country over, and not, as some 160 HOG CHOLERA would have us believe, different according to the section of the country in which we chance to find it. The differences we observe in various parts of the country are due principally to prevailing sec- ondary invaders, as well as to variation in viru- lence of the hog cholera virus itself, for they are observed also in comparing individual herds or outbreaks in any one section. While we must accept all these variations and allow for them, the underlying principles em- ployed in handling hog cholera remain unchanged, and it is desirable and necessary in a treatise of this kind to suggest definite working plans, leaving the reader to alter or supply detail as individual cases warrant. We are moved to do this because we have seen young graduates of veterinary col- leges who had had good instruction and whose technique in administering serum left little to be desired — we have seen some of these men practi- cally helpless in the presence of outbreaks of cholera which presented disturbing but not un- usual features. Likewise men who are accus- tomed to the routine of vaccinating thousands of stockyard hogs are sometimes confused when they are called on to accept the conditions they meet on the average farm, to prescribe treatment for a mixed lot of swine, and guide the breeder away from future trouble. Mere knowledge of how to vaccinate hogs does not equip one to handle hog HANDLING HOG CHOLEKA IN THE FIELD 161 cholera; diagnosis, when and whether to vacci- nate, the method to use, and the subsequent han- dling of the herd all enter into the problem. Handling the cholera infected herd. Let us assume, as a working basis, that a herd consisting originally of one hundred ordinary shoats, in good condition, is infected with hog cholera; ten have died, ten are visibly sick, and there is no evidence of secondary infection; there are no other hogs on the farm, and the shoats are in a pasture con- taining several acres; the owner has had hog cholera in his herd in previous years, and knows the results that may reasonably be expected from preventive measures. This represents the sim- plest situation we are called on to cope with in handling hog cholera in the field. Three methods of handling are open to us : 1. Give generous doses of serum alone to all animals that are not exceedingly weak. 2. Give simultaneous treatment to all seemingly well animals, and double doses of serum alone to those that are visibly sick, and not obviously near death. 3. Give serum alone in full doses to all ani- mals that are apparently well, in double doses to those that are sick and have a chance to recover, and follow this in three weeks with simultaneous treatment for all animals that were not visibly sick at the time of the first treatment. In other 162 HOG CHOLERA words, give serum alone to the sick animals, fol- low-up treatment to those that are apparently well. Eegardless of the method selected, we must proceed promptly with the one that becomes our final choice, and we must take immediate precau- tions to prevent spread of the disease to other herds. Method mimher one may prove highly satisfac- tory in some cases of this kind, but it is open to the serious objection that it may not produce per- manent immunity in all the animals. In the indi- vidual, serum alone plus hog cholera infection produces permanent immunity, but in a herd of this kind, although all the animals are exposed, some may not become infected in time to secure this result, because hog cholera does not always spread rapidly through herds that are at pasture or in other large runs. Let us select, as an instance, one shoat in the herd and assume that the animal has received serum alone to-day. If in the course of the next three or four weeks — the usual duration of immu- nity due to serum alone — it chances to take up virus sufficient to infect, it will undergo a reaction and thereafter be permanently immune to hog cholera; but if the event of infection is delayed much longer, it will find the animal susceptible to the disease. In other words, if infection takes HANDLING HOG CHOLERA IN THE FIELD 163 place while passive immunity due to serum alone still exists, a permanent immunity is acquired; if it takes place after the passive immunity dis- appears, the animal will readily contract hog cholera; and, except where hogs are quite closely confined, chance alone must decide whether any particular individual will become permanently im- mune, or, failing in this, eventually die of hog cholera. Method number two will produce more reliable results. The sick are distinguished from the well by physical appearance and temperature read- ings. In handling herds in this manner it is our custom to give serum alone to all animals showing temperatures above 104° F., and to all visibly sick, and not at the point of death, regardless of tem- perature reading. If, however, the weather is warm, and if the hogs are excited in handling, most temperatures will rise above this point, and the thermometer gives us very little information. Under such circumstances physical appearance is our only guide. A useful practice, whenever con- ditions are such that it can be employed, is to feed the hogs a little grain and to place those that leave the feed in a few moments among the sick that are to receive serum alone, and those that remain for a longer time and eat greedily, among the well that are to receive serum and virus. Practically all will eat a little, but the infected animals are 164 HOG CHOLERA first to leave their feed. Any method of distin- guishing tlie sick from the well is only approxi- mately correct, but a herd handled in the manner we have outlined mil emerge from the treatment permanently immune to hog cholera. On the whole, this method of handling is quite satisfac- tory, but it is open to the objection that we may introduce a more virulent strain of virus into herds already infected, and we may be. accused of killing animals when we have merely failed to pre- vent their death. This method is practicable only when the owner of the animals fully realizes that some apparently well hogs in infected herds will die following even serum alone administration, and when he is dis- posed to expect like losses following serum-virus treatment. Veterinarians experienced in handling hog cholera dread to use virus in infected herds, but we meet conditions under which it is wise to do so. Method number three is safest, and, as with method number two, the herd emerges with all animals permanently immune to hog cholera. The added expense is the only objection, but in many instances, especially when the animals are above average in value, it is more than justified. There is great satisfaction to the practitioner, as well as to the breeder, in knowing that nothing has been f HANDLING HOG CHOLERA IN THE FIELD 165 done to add fuel to the flames, and in being al- lowed tliree weeks ' respite in which to observe the progress of an outbreak. Irrespective of the plan we choose, if new cases continue to appear later than the sixth or seventh day following treatment, a second dose of serum alone is indicated; and if ^^ breaks'' occur subse- quent to simultaneous treatment, they should be handled in the manner described in the preceding chapter. Under the conditions in which we found this herd of shoats, we explain the situation to the breeder, and recommend method number three as safest, informing him at the same time that method number two is, in the majority of cases, satisfactory. With the facts before him he can then decide for himself. Precautions to prevent spread of hog cholera to neighboring farms include preventing sale or ex- change of sick or well animals from the infected herd, exclusion from the infected pasture of all persons, vehicles, or animals that may later enter non-infected hog quarters, and prompt disposal of carcasses so that they will not attract carrion- eating animals or birds. Burning is by far the best method of destroying carcasses, but burying in quicklime, or rendering, is permissible. In a pasture such as we find this herd of shoats dis- 166 HOG CHOLERA infectants are of little service, and we must de- pend on natural influences (drying and sunlight) to destroy virus which contaminates the soil. Many states have specific regulations governing precautions against interherd spread of hog chol- era, and when these are available and practicable they should be followed. None of the shoats should be removed earlier than thirty days follow- ing disappearance of all sickness from the herd, and previous to their removal, if they are to min- gle with cholera susceptible hogs they should first be dipped or sprayed with 3 per cent compound cresol solution. It is legal in some states, in han- dling a herd of this kind, to remove apparently well animals for immediate slaughter under in- spection, but except in unusual circumstances the practice has little to recommend it. If we go back to our original problem and as- sume alterations in the conditions there outlined, corresponding changes in the plan of handling will suggest themselves, and the reasons for these changes will appear. If hogs are closely confined and the herd is badly infected, serum alone is indi- cated, because natural infection will take place and produce permanent immunity in all that sur- vive ; if they are found under conditions that sug- gest low resistance, if they are of exceptional value, or if the owner is skeptical, nervous, or overcritical, plan number three should be recom- HANDLING HOG CHOLEEA IN THE FIELD 167 mended, special care being taken to build up the resistance of the animals during the interval be- tween serum alone and serum-virus administra- tion. If, as is sometimes the case, we are compelled to make a provisional diagnosis of "hog cholera, we should give serum alone and observe the future development of the disease. Provided it proves to be hog cholera, or if it disappears entirely so that doubt still remains, we may give simultaneous treatment three or four weeks later; if it proves to be some other malady, and if hog cholera is not in the vicinity, simultaneous treatment should not follow unless the OAvner wishes to maintain an im- mune herd. Usually, when there is hog cholera together with some active complication, the im- munity of the herd should be maintained on serum alone until the animals are in fit condition to re- ceive serum-virus treatment. This may require two or more doses of serum at three or four week intervals, but if the complication is of such nature that it cannot be controlled after serum alone is administered, we mil only aggravate it if we give simultaneous treatment. Methods of preventing spread of hog cholera to neighboring herds are also somewhat different when we find the infected animals closely confined. We gain very little by cleaning and disinfecting quarters occupied by hogs sick with cholera, be- 168 HOG CHOLERA cause each time an infected animal urinates, rein- fection of its pen takes place. As long as hog cholera is active in a herd we should devote our attention to elTective quarantine, prompt disposal of carcasses, and the maintenance of ordinary cleanliness that is at all times conducive to the health of the animals. When the disease disap- pears, all contaminated litter should be burned, and the indoor quarters sprayed vdth. 3 per cent lysol or compound cresol solution. Often appli- cation of disinfectant at intervals of several days is advantageous. Hog cholera virus cannot al- ways be killed in outside yards. Spreading a thick layer of straw over the yard and burning it is probably most effective, but this is not always practicable. Plowing and free use of disinfec- tants hasten destruction of the virus, but the lat- ter measure is useful only in small enclosures. Too often directions given for disinfecting quar- ters require more than is possible, and they are not specific. If we are careful not to require unneces- sary and laborious measures we will secure much better cooperation in carrying out those that actu- ally are essential; and if surroundings are such that we find it impossible to give detailed and spe- cific directions for cleaning and disinfecting, we may be sure that the general admonition to ' * clean and disinfect'' will do very little good. We must recognize the fact that some hog quarters cannot HANDLING HOG CHOLERA IN THE FIELD 169 at once be freed of hog cholera virus, at least by methods within reach of the man of average means. Under such circumstances, if hog raising is to be continued, the herd should be maintained immune to hog cholera. We have already said that handling a herd of infected shoats is the veterinarian's simplest duty in dealing with hog cholera. We will now con- sider some of the more complex problems that field work constantly place before us. Let us suppose that in addition to the herd of infected shoats there is on the same farm, some distance away, a number of feeding hogs that have shown no signs of disease. If the animals are to be marketed in less than four weeks they may receive serum alone, and if hog cholera does not appear among them in the course of six or seven days, it is allow- able to kill them under inspection; if marketing must be delayed more than four weeks, simultane- ous treatment is indicated. As far as the effect of treatment itself is concerned, hogs may, if emergency demands it, be killed for food as early as one day following administration of serum alone, but if serum and virus are given, a delay of at least three weeks is desirable. In addition to feeders we encounter on practic- ally every farm a considerable number of breeding stock. A boar, pregnant sows, some just farrow- ing, and others nursing litters make up the repre- 170 HOG CHOLEKA sentative farm herd. A permanent immmiity is desired for all of these, and we follow the general plan of giving simultaneous treatment to all ani- mals in condition to receive it, and protecting the others with serum alone pending the time when they may safely receive serum and virus. Assuming that breeding stock of this character is on the farm with the infected shoats, but that after numerous temperatures have been taken there is no evidence of disease, it may be handled as follows : the boar may be given serum and virus at once, or if he is of exceptional value, follow-up treatment; sows in early pregnancy may be han- dled in the same manner, but always after the breeder has been informed that simultaneous treatment will sometimes produce abortion, and that the slight danger must be accepted as a lesser evil ; sows due to farrow in less than three weeks and those that have pigs a few hours or days old cannot safely receive virus. It is true that the infection on the farm will in most cases ultimately reach them, but our aim should be to delay this as long as possible, and to protect the sows with serum alone in the meantime. Continued isola- tion of the sows is desirable. Two or even three doses of serum alone at three or four- week inter- vals may be required before the time is ripe for the final simultaneous treatment, but the extra ex- pense is greatly to be preferred to the alternative HANDLING HOG CHOLEEA IN THE FIELD 171 — that of using simultaneous treatment so that the sow will be farrowing or nursing a newborn lit- ter at a time when the resulting reaction is in progress. The pigs likewise should be maintained on doses of serum alone at four-week intervals until they are at least nine w^eeks old, preferably twelve, and then they should receive simultaneous treatment. If they are fairly well isolated from the infected animals the first dose of serum alone may be de- layed until they are two or three weeks of age, otherwise it should be given when they are only a few days old.^ ^ The question whether young pigs acquire a permanent immu- nity as a result of simultaneous treatment is yet unanswered. Niles describes experiments indicating that they do, while Cahill on the other hand found that over 50 per cent of several hundred pigs given serum and virus betAveen the ages of two and eight weeks failed to acquire a permanent immunity as a result. Peter- sen found that only fifteen out of one thousand ' ' baby pigs ' ' given simultaneous treatment proved susceptible as old hogs. We have collected very little experimental data on this point, the results agreeing substantially with those of Niles. Our field observations, however, lead us to believe that a per- manent immunity is not always established Avhen serum and virus are given to sucking pigs. In one instance we gave simultaneous treatment to fifty pigs that were about eight Aveeks old. When the animals had reached a weight of about 150 pounds, one of them was brought to us for autopsy and showed undoubted lesions of hog cholera. Three or four of the others developed symptoms of the disease during the following week, so the entire herd was revaccinated. Two of those that sickened died later but we did not have an opportunity to perform autopsies. There is little doubt that they died of hog cholera, but just how many more would have died in the absence of a second injection is a matter of conjecture. In another instance that came under our observa- tion about eighty young pigs were given simultaneous treatment, and when these animals reached a weight of about 180 pounds each, approximately twenty of them died. We performed autop- sies on several, and found unmistakable hog cholera lesions. *1! 172 HOG CHOLERA f i We have been called on repeatedly to handle herds of sows infected mth hog cholera just at farroAving time. Whenever it is possible we dip the animals, segregate them as best we can and administer serum alone, carrying both sows and pigs along mth doses of serum alone at four- week intervals until the latter are weaned and at least nine weeks old, at which time sows and pigs receive simultaneous treatment. In herds in which isolation is impossible, we follow the same course in regard to administering serum, giving the first dose, about 4 mils, when the pigs are a day or two old. It is possible to bring pigs safely These observations do not carry the weight that may be attached to carefully controlled experiments, but they suggest caution in regard to the sweeping conclusion that all young pigs acquire permanent immunity as a result of simultaneous treatment. Closely bound up with this question is the one of the immunity of sucking pigs to hog cholera. Pickens found that 100 per cent of pigs nursed by immune mothers Avere themselves immune, but any person with extensive experience in handling hog cholera knows that we cannot always, or usually, depend on this immunity. We have repeatedly seen pigs born of immune mothers and nursed by them dead with hog cholera before they were four weeks old, but there are others, as Pickens' experiments show, that are immune. Collectively, all experimental work and clinical observations so far recorded point to the conclusion that some pigs of cholera immune mothers are themselves immune, and others are not; some will acquire active immunity as a result of simultaneous treat- ment, others will not. We have no way of knowing whether any particular young pig or litter will acquire permanent immunity if simultaneous treatment is given, so we prefer to maintain the immunity of all young pigs with serum alone, and to finish with simultaneous treatment when the animals are about twelve weeks old. A cheaper plan than this will be available in well-kept herds if the findings of Niles are confirmed ; a more effective one is not likely to be found as long as we use serum and virus as they are now prepared. HANDLING HOG CHOLERA IN THE FIELD 173 through an outbreak even when they are born in pens containing hogs sick with cholera, and this presents no great difficulties when the sows are immune, but when farrowing and recently far- rowed sows are susceptible, they do not tolerate virus well. Despite the fact that they receive serum a few will die, other will fail to nurse their litters, and on the whole results are much less satisfactory than they are when reasonably effec- tive isolation can be practiced. We do not wish to convey the impression that after hog cholera reaches a herd we can prevent, by isolation, ultimate infection of all the animals in it for exactly the reverse is true. The point we emphasize is that when the disease appears among sows that are farrowing, infection of many of them can be delayed by isolation, that they gain valuable time, and they and their litters are in better condition to withstand the effects of the virus when later it reaches them, either by natural means or through simultaneous treatment. A sow undergoing serum-virus reaction when her litter is a day or two old is in some danger of death, and even if she lives lactation may cease and her pigs perish. Delay the event of infection four weeks, and regardless of how it affects the sow the litter can be saved. The theoretical grounds for handling farrowing sows in this man- ner are obvious, but we recommend the plan of 174 HOG CHOLERA isolation only because repeated trials have proved it effective. Establishing and maintaining a hog cholera immune herd. So far we have dealt with hog cholera after it has reached the herd. We are now to consider methods of preventing it from in- fecting the herd, which yield even better results. In their relation to the prevention of hog cholera, most herds fall into three general classes: those from which the virus can be excluded ; those con- stantly threatened with hog cholera; and pure- bred herds from which immune breeding stock is sold. The herds in the tirst class do not require immunization; those in the other two classes are best maintained immune. The first question to be decided when a client consults his veterinarian is whether it is really necessary for the herd to be maintained immune. Is hog cholera prevalent in the vicinity? Has it appeared periodically on the farm in question? Is the herd subsisting partially or wholly on gar- bage ? Is the breeder buying in hogs at frequent intervals! Does he take sows to neighboring farms to be bred, or are sows brought to his farm for the same purpose? Has he an established market for immune breeding stock, or does he wish to estabhsh one? Has the herd access to a stream that may be contaminated mth hog chol- era virus? If all these questions can be answered HANDLING HOG CHOLERA IN THE FIELD 175 in the negative we should advise the breeder not to immunize. It is an unnecessary expense, and when once simultaneous treatment is employed in a herd there is some danger in discontinuing its use. Pigs thus immunized may eliminate vir- us, and this may be on hand to infect susceptible animals that subsequently are added to the herd by birth or purchase. In case it is desired to dis- continue immunization, at least four months, and preferably six, should elapse between the date when simultaneous treatment is last used on the place, and that of the introduction of susceptible recruits into the herd. All of these facts should be perfectly clear to the breeder before virus is used in his herd. When chances of infection with hog cholera are remote, and the breeder is advised against main- taining an immune herd, he should be cautioned against all the practices that may result in the in- fection of his swine. He should also be informed regarding the things that would lead him to sus- pect the presence of hog cholera, and the neces- sity for early reporting of an outbreak, should it occur, must be made plain. When hog cholera threatens ultimately to attack a herd and destroy it we can render the breeder no greater service than in advising him to main- tain it immune to cholera. Much as we dislike the idea, in the abstract, of introducing virus into 176 HOG CHOLERA new territory, our experience in concrete cases is that one untreated cholera infected herd in a neighborhood is more of a menace to adjacent herds than ten properly maintained immune with simultaneous treatment. In the untreated, in- fected herd, there is a great temptation sometimes to sell animals before a diagnosis of cholera is made, some breeders are slow to accept the fact that hog cholera is in their herds, and on the whole the attack comes on unheralded, and much damage is done before its true nature is realized. On the other hand, when we administer simultane- ous treatment to a herd we deliberately establish our defenses against the spread of hog cholera that may possibly result from it, the period of acute danger is quickly passed, and the herd is no longer a menace to others in the vicinity. "When once the breeder decides to maintain his herd immune to cholera, the practice must be faith- fully carried out. Between keeping all animals immune to cholera at all times and declining to use any virus whatever, there is no middle ground. We cannot temporize with a disease like hog chol- era. Like the proverbial nettle, simultaneous treatment incident to maintaining a cholera-im- mune herd must be grasped firmly or avoided alto- gether, for it mil not do to have virus and suscep- tible pigs in the herd at alternate intervals. Sooner or later the two will get together. HANDLING HOG CHOLERA IN THE FIELD 177 Let US suppose that a breeder of pure-bred hogs wishes to establish a trade for immune breeding animals, and has decided to maintain a cholera im- mune herd. His herd consists of two large herd boars, fifty brood sows nursing litters about four weeks old, fifty gilts recently bred and now being sold daily in twos and threes as the trade de- mands, and a herd of one hundred fattening hogs that will be ready for market in six weeks. Hog cholera is not threatening the herd. How is it to be handled with the greatest safety, and with the least expense and inconvenience? The brood sows are not in the best condition to receive simultaneous treatment, the gilts could not be sold and shipped at once if it were given, and the fattening hogs will be sold anyhow in six weeks. If we wait that length of time the gilts also will be sold, the young litters will be weaned, and sows and pigs will be in condition to receive simultaneous treatment. The two boars are thus the only animals in the herd for which the delay of six weeks is not positively indicated, and they can be immunized as well at one time as another. From this concrete example we develop the sim- ple rule that when choice is allowed we begin im- munizing at a time when the herd is at a minimum as far as numbers of adult breeding stock is con- cerned, and when the animals are in condition to receive simultaneous treatment with the least pos- 178 HOG CHOLERA sible risk. In the average farm herd the most opportune time to immunize is three or four weeks after the spring litters are weaned. On the other hand, when the herd is immediately threatened with hog cholera we have no choice but to accept it as it is, and protect it at once. Under such circumstances the plan is to give simultane- ous treatment to all animals in condition to re- ceive it, and serum alone to the remainder. Every four weeks we return and repeat the process, con- fining the treatment to those that received serum alone previously, until the entire herd has received simultaneous treatment, and permanent immunity has thus been established. When once the adult breeding stock is immune, our task is then to immunize the young litters as they come on. This is relatively simple for the veterinarian and inexpensive for the breeder. On farms where methods of swine husbandry are the best, and at times when there appears to be little immediate danger from hog cholera, the best plan is to keep close watch on the pigs until they are about twelve weeks old and then give simul- taneous treatment. In many herds though, es- pecially the large garbage-fed herds in the East, a high percentage of the pigs will, if left unpro- tected, contract hog cholera before they reach an age approaching twelve weeks, and a considerable number that do not actually contract the disease HANDLING HOG CHOLERA IN THE FIELD 179 will fail to develop so as to be fit subjects for simultaneous treatment. In these herds, the only effective plan we know of is to protect the pigs with serum alone until they are old enough and in proper condition to receive serum and virus. Un- der ordinary conditions the pigs receive serum alone when they are between three and six weeks of age, they are weaned when they are about eight weeks old and receive simultaneous treat- ment two to four weeks later. It is best to cas- trate them as sucklings. Under exceptional con- ditions we are compelled to give more than one dose of serum alone before the time is ripe for simultaneous treatment, but an extra dose of se- rum for a small pig is not expensive. We have used this general plan since 1912, starting with several garbage-fed and cholera in- fected herds in quarters that did not permit clean- ing and disinfecting, and protecting all subsequent litters of pigs, year after year, with losses from all causes totaling considerably less than five per cent. We know of several other veterinarians who have obtained like results during a term of years, and we do not know of a single instance where the plan has been followed consistently and found wanting. The preliminary doses of serum alone are not necessary in all herds, but we may resort to them confidently under conditions such as we have described. 180 HOG CHOLERA Several points that contribute to the success of maintaining an immune herd remain to be men- tioned. Especially in large herds it is a good practice to mark each pig at the time it is immun- ized so that it can be positively identified. Other- wise we are likely to miss an occasional pig or lit- ter, and if these untreated animals subsequently contract hog cholera, we are called to account for deaths for which we are in no way responsible. We should also suggest to the breeder the advan- tage of breeding several sows near the same time, so that a considerable number of pigs can be im- munized at one time. In addition to economy in immunizing this practice enables the breeder to provide foster mothers for pigs farrowed by sows which on account of death or disease incident to parturition are unable to nurse their litters. It is important that pigs shall grow steadily and rapidly from birth until the time when simultane- ous treatment is administered. Influences that re- tard growth usually lower resistance as well and we are thus compelled to maintain the immunity of poorly nourished pigs with serum alone much longer than is necessary in handling thrifty pigs. Any suggestions that will aid the breeder to grow pigs rapidly during the first three months of their lives mil be greatly to his advantage. Handling feeding hogs. A common practice on farms in many parts of the country, more par- HANDLING HOG CHOLERA IN THE FIELD 181 ticularly in the corn-belt, is that of purchasing feeding shoats in the fall of the year to consume the season's crop of grain. The general tendency is for these shoats to be raised in regions where land is rather cheap, and fattened in localities where higher-priced land compels a more inten- sive type of farming. Direct communication be- tween the breeders who raise the shoats and the feeders who finish them is not generally main- tained. The breeder seeks a seller's market in cities where there are large stockyards, and the feeder habitually goes to these places to buy. Be- fore the discovery of anti-hog-cholera serum, long years of bitter experience had taught feeders that hogs which pass through large public stockyards very often contract cholera. As soon as the serum was discovered it was eagerly seized on in at- tempts to protect stockyard shoats that subse- quently were to be shipped to other farms to be fattened. The desire was to give these animals permanent immunity to hog cholera, so it grew to be a general practice to administer simultaneous treatment to them in the yards, and ship them in the course of a few days to the feeder's farm. Years of experience prove that this practice, though perhaps an improvement over old meth- ods, is frequently the cause of heavy losses, both in the immediate animals treated and in hogs 182 HOG CHOLERA with which they come in contact after they reach their various destinations. Those who follow the practice are merely lucky if they do not sustain heavy losses because they continually ignore the fact that a reaction nor- mally follows simultaneous treatment, and that shipping lowers the resistance of hogs to such an extent that the reaction may prove fatal. When we add to the effects of shipping and simul- taneous treatment those incident to a brief or prolonged stay in infected yards before the treat- ment is administered, as well as those that grow out of injudicious feeding and watering when the animals reach the end of a journey, fatigued, hun- gry, and thirsty, we have a chain of devitalizing influences that often cause disaster. It is well known also that many swine unloaded at stockyards do not leave home free from dis- ease. Oftentimes a consignment of hogs repre- sents a breeder 's final determination to ^ ' cash in ^ ' on a herd that is badly infested with parasites, that is suffering with some obscure respiratory disease, or one that has recently contracted hog cholera. Despite the fact that apparently well animals are selected from such herds for shipping each animal selected is potentially the source of future trouble. What is one to expect if in pur- chasing hogs for the feed-yard he chances to in- clude even a few individuals of this kind? The HANDLING HOG CHOLERA IN THE FIELD 183 mere fact that many lots of shoats are shipped long distances to stockyards and after receiving simultaneous treatment are at once reconsigned to distant localities which they reach without im- mediate or subsequent mishap has little bearing on the problem as a whole. It is the fact that many lots of hogs will not endure such handling, and that we cannot always distinguish in advance between those that will and those that will not, that still troubles us. This aspect of the subject will receive further attention in the chapter on ^^The Control and Eradication of Hog Cholera.'' Let us assume that a man living in western New York requires two hundred shoats as feeders. His natural purchaser's market is in the stock- yards at Buffalo, or further west in the hog-rais- ing districts of Ohio. He knows that there are certain dangers connected with shipping hogs and he consults his veterinarian in order to learn how they can be avoided. What precautions should he be advised to take? Other things being equal it is best to purchase direct from the farm, for this avoids unloading animals at large stockyards, and it is much easier to determine the true condition of hogs when we examine them in what may be termed their nor- mal habitat than when we inspect them hurriedly during the excitement and confusion that prevails at the average stockyard. If immune feeders can 184 HOG CHOLEKA be purchased from a reliable source on the farm, that is by far the most satisfactory plan. In case that is impossible, our client should be ad- vised to purchase from thrifty farm herds and to assemble the animals on a stated day at a local shipping point. They should then be given serum alone, placed in clean comfortable well-bedded cars, and shipped at once to their destination. Wlien they arrive at the feeder's farm, they should be placed in dry comfortable quarters and fed sparingly on light foods for a few days. After they become accustomed to the change in feed and quarters — say in two or three weeks — they should be given simultaneous treatment. If circumstances compel our client to purchase at the stockyards, he should if possible see the animals unloaded, and in any event he should not select animals that have been in the yards several days. It is best to avoid mixed lots of hogs, and those that contain a considerable number of dead animals when they arrive at the yards, for these often are shipped to market because of disease. Hogs that cough persistently should not be ac- cepted. When once the selection is made the ani- mals should be given serum alone without delay and shipped at once to their destination. When they arrive at the feeder's yards they require han- dling similar to that accorded animals purchased directly from the farm. HANDLING HOG CHOLEKA IN THE FIELD 185 Careful and experienced men can usually select satisfactory feeders in large stockyards, but on the whole there are unavoidable risks associated with the practice. Handling- show hogs. Show hogs constitute a separate problem in themselves, because they are of exceptional value, and because they must necessarily be subjected to handling entirely dif- ferent from that accorded the ordinary farm or market hog. It is not uncommon for show hogs to contract cholera during contact with other swine in the show ring or in transit from fair to fair, and not infrequently they arrive home appar- ently well, and develop symptoms of the disease during the few days following, thus infecting the entire herd which they represent. This experi- ence has been so common that the practice of showing hogs that are not immune to cholera is indefensible. Some fair associations require cer- tificates to the effect that hogs are immune to chol- era before they will admit them to the show ring. The breeder who maintains his herd immune to cholera has no difficulties to face from this quar- ter, for as far as hog cholera is concerned, he* may send his animals out on the fair circuit secure in the knowledge that they will not themselves be- come infected, nor be instrumental in infecting others with which they come in contact. The breeder whose herd is susceptible to cholera 186 HOG CHOLERA must have his show hogs simultaneously treated at least thirty days before they leave for the fairs, or else he must give them serum alone at the time they start, and repeat the treatment at three- week intervals as long as they are on the road. Neither plan is entirely free from objection, but either is far from better than to neglect immun- izing. If simultaneous treatment is given this necessitated the introduction of virus on a farm where there are untreated susceptible hogs, and thus it is applicable only where there are facili- ties for effective segregation of the show hogs. If serum alone is given and the hogs are infected with cholera at the fairs they must pass through the resulting reaction at a time when they are low in resistance, and if the reaction is so severe that it results in virus excretion, there is danger that in returning from the fair circuit the show hogs may infect the home herd. If simultaneous treatment is to be given show animals and the remainder of the herd is to re- main susceptible to cholera, the following plan is safest: isolate the show hogs in quarters that will permit subsequent disinfection and give them serum and virus; if during the next thirty days none of the animals develop visible sickness, dip or spray them thoroughly, using 3 per cent com- pound cresol solution, and send them out on the show circuit; when they return, it is best to dip I HANDLING HOG CHOLERA IN THE FIELD 187 them a second time before they are placed with susceptible hogs, and where there are facilities for isolating them two weeks after they return this should be done as an additional precaution. We must not lose sight of the fact that even an immune hog can become the intermediate carrier of hog cholera virus. Should a '^ break" appear when the show hogs are immunized it should be handled according to the plan previously outlined, and as an addi- tional precaution, the entire herd had best be pro- tected with serum. In any event, w^hen the hogs leave the quarters in which they are placed for simultaneous treatment, the pens should be care- fully disinfected. When no virus is to be used in treating the show animals they require serum alone at the time they leave home, and thereafter every three weeks as long as they are on the road. After they re- turn it is well to isolate them two weeks, after which they may be dipped in antiseptic solution and placed with the remainder of the herd. On the whole, a breeder who habitually places hogs in the show ring should maintain his entire herd immune to hog cholera. Under most cir- cumstances, when this is not done the use of serum alone for temporary protection is indicated, but under exceptional conditions, where perfect seg- regation is possible simultaneous treatment may 188 HOG CHOLEKA be given the show animals. Not infrequently the practitioner has the question of immunization thrust on him as an eleventh-hour consideration just on the eve of the departure of show hogs for the fairs. In this event he has no legitimate choice but to protect the animals with serum alone during the period of probable exposure. ORDERING SERUM Every veterinarian in country practice is likely sooner or later to be called on to immunize swine against hog cholera, and because much immuniz- ing consists of emergency work, serum must be procured without delay. For this reason the vet- erinarian should establish relations with a reput- able laboratory near at hand so that telegraphic orders from him Avill be filled promptly. Because they cannot assume responsibility for products that have been in other hands, most laboratories will not allow credit for returned serum and virus and thus it is desirable to order the exact quanti- ties required. Before ordering serum the veterinarian should ascertain the number of hogs to be vaccinated, and their approximate weights. A representative list would appear thus: 1 boar, weight 600 pounds 8 sows, weight 400 pounds each 65 pigs, weight 20 pounds each 50 shoats, weight 60 pounds each HANDLING HOG CHOLERA IN THE FIELD 189 The common tendency is to estimate weights of swine far too low, and this should be thought of in connection with every serum order. Before the list is completed the final question, **Have you any other hogsT^ should always be asked, for it is very annoying and very common to find, even after we reach a farm to do the immun- izing, that the owner has hogs which he has not mentioned because he *^ hadn't thought of having them immunized. '^ If a simultaneous treatment is to be given to any of the hogs in a herd, the remainder must not go long without some kind of immunization, and lack of sufficient serum to treat an entire herd may often postpone the date of treatment or necessitate a second call. When all of the hogs that are in the herd are listed, the veterinarian can estimate the quantity of serum and virus required, provided he has a dose table from the laboratory he patronizes. Lacking this, he should send in the list and allow the laboratory to make the estimate. Telegrams or letters containing orders such as *^ Serum and virus for 20 swine'' or ^^ Serum to treat a mixed bunch of 100 sows, pigs and shoats" are not sufficient. Every order should state the required quantity of each product, or it should include a list of the number of hogs and their approximate weights. 190 HOG CHOLERA Most field work falls within the scope of the con- crete instances outlined in this chapter, but it is necessary, as we endeavored to make clear in the beginning, for one who handles hog cholera to understand hog cholera. Our aim throughout has been to show why as well as what, but if we have fallen short of this aim we can at least assure our readers that the methods recommended are con- servative and effective, and that they have been developed as a result of years of field and labora- tory experience. One final thought. The beginner in hog cholera work sooner or later finds himself face to face with some baffling situation. A herd seems in need of immediate protection but doubt in regard to diagnosis, doubt as to whether the complete history of the herd has been frankly laid before him, and the question whether complete coopera- tion will be accorded him in the subsequent han- dUng of the herd, render selection of the method of immunizing difficult to make. ''When in doubt and emergency recjuires immediate protection of a herd, use serum alone; then follow with simulta- neous treatment in less than four weeks if subse- quent development of the disease requires it" is the final caution we leave with the beginner. HANDLING HOG CHOLERA IN THE FIELD 191 The Veterinarian's Charge for Serum and Its Administration If a veterinarian expects to remain long in prac- tice he must render service worth much more than the charge he attaches to it, and the benefit derived from his calls must be obvious to his clients. The fact that immunization of hogs, especially large herds in localities where hog cholera is prevalent, results in a great and obvious saving to the breeder has placed this phase of veterinary prac- tice almost in a class by itself. We do not ac- tually render a greater service in checking an out- break of hog cholera than we do in eradicating tuberculosis from a cattle breeder's herd, but hog cholera is an acute and fatal disease and the direct saving due to its control is far more appar- ent to the breeder than some other services, equally as valuable, that we render him. Because of this fact, and because of the great demand that has existed for the services for veterinarians in immunizing swine, certain abuses in regard to charges for serum administration have come to light. Complaints have been leveled at a few shortsighted and greedy individuals, but they have reacted to the dicredit of the profession as a whole. Especially when large numbers of hogs are vaccinated in one day, when charge is made by the head, and a profit greater than is fair is added 192 HOG CHOLERA to the serum used, the veterinarian goes home leaving his client believing that he, and other members of the profession, are shameless prof- iteers. The natural inference is that other pro- fessional charges as well are exorbitant, and this, as all veterinary practitioners know, is not true. When immunization of a herd of hogs is really indicated and when a veterinarian does the work thoroughly and conscientiously, he renders a great and obvious service, and is entitled to a fee con- siderably above that which the average breeder is inclined to regard as fair. The breeder would be surprised if he knew the cost of waste, breakage, and overhead which the veterinarian must pay. We believe though, that instead of courageously charging fees which are actually their due, and which will enable them to use first-class products and do careful work, too many veterinarians have yielded to a temptation to collect their fees, un- known to the breeder, in the form of profit on the serum used. The purchase price of the serum sooner or later comes to light and in the absence of previous explanation, the breeder naturally be- lieves that the difference between the price the veterinarian pays and the price he charges his clients for serum is all profit. Real and imagin- ary abuses in this direction have led to actual and proposed legislation designed, on the one hand, to place vaccination of hogs largely in the hands HANDLING HOG CHOLERA IN THE FIELD 193 of laymen, and on the other hand to fix the margin of profit which the veterinarian may charge, or at least to prevent him from concealing from his client the purchase price of the serum he uses. Legislation of the former type can result only in disaster to the swine industry and harm to the veterinary profession, but we do not believe there are good reasons why the purchase price of serum should not be known to the breeder. Obviously the profession puts itself in a bad light when it opposes legislation of this kind, unless it can justly be opposed on the ground that the handling charge proposed is not sufficient to cover costs of waste and breakage. Such opposition only gives sub- stance to the suspicion that there is something to conceal. It is a principle which should be ob- vious to all that if the veterinary profession is to retain exclusive rights to administer serum and virus it must exercise these rights in a manner to justify this exclusion ; and any legislative attempts to discipline the occasional renegade who habitu- ally reaps an excessive profit on serum should, and we believe will be, welcomed by the better ele- ment in the veterinary profession. The veterinarian's fee for his work is his own private concern, and the compensation he can com- mand depends for the most part on the skill and knowledge which he employs to benefit his client ; but the best interests of the public demand that the 194 HOG CHOLERA use of serum and virus shall be placed exclusively in his hands, and when this is done he has not the same right to fix the selling price of these products that he has to name his o^vn fee. Use of serum and virus is a public trust reposed in him rather than a monopoly given into his hands for private exploitation. His profits should come from his work, not from the serum he uses. Some practitioners charge according to the num- ber of hogs treated, some according to the quantity of serum injected, and others on the basis that they fix fees for other calls. No system is entirely free from objection, but we believe that the most satisfactory and fair plan is for the veterinarian to place a value on his day's work and charge for vaccinating according to the time consumed in doing it. He is entitled to add to this a handling charge on the serum he uses, to compensate for clerical work, express, breakage, and unused prod- ucts that are left on his hands. Under ordinary conditions, if breeders pay cash, an increase of 20 or 25 per cent over the purchase price mil take care of these items, but it will not be sufficient if credit is habitually allowed. A practitioner can lose more on one bad serum bill than he can collect as fees for several days' work. The practice of charging according to the time consumed has obvious advantages if we let our clients know that we are follomng it. It con- HANDLING HOG CHOLERA IN THE FIELD 195 sumes less time to vaccinate a given number of hogs for a client who will have the animals se- curely penned in clean dry quarters, and plenty of help ready for work when the veterinarian ar- rives, than it does to vaccinate one-fourth that number for a man who awaits the veterinarian's arrival and then begins a frantic or leisurely search for gates, lumber, ropes, and other needed paraphernalia. A veterinarian cannot consume several hours in vaccinating a small lot of pigs and at the same time keep his fee at a figure that the breeder can afford to pay. The breeder who provides facilities and help so that the work may be done dexterously and rapidly should profit by his foresight; the one who is neglectful must ex- pect to pay for his negligence. Emergency hog cholera practice, that is, the care of herds already infected, will come regularly to a man who handles it with only a fair degree of effectiveness. Under such circumstances even average veterinary service is far better than none. The same rule does not apply in maintaining im- mune herds, the phase of hog cholera control that offers greatest satisfaction to both practitioner and breeder. If the breeding in a herd is so or- dered that a large number of pigs can be vaccin- ated at one time, if the animals are grown rapidly and conditioned so that they will withstand simul- taneous treatment at an early age, and if the 196 HOG CHOLERA breeder habitually provides facilities that allow vaccinating to be done without loss of time, the cost per head can be kept at a minimum. The veterinarian who so advises his clients as to bring these things about is the only one who can hope to enlarge his swine practice and gain lasting success in hog cholera work. A system of wireless which we do not completely understand, but whicn nevertheless spreads intelligence rapidly and un- erringly in country districts, will, in each veterin- arian's community ultimately convey the news that immunizing pays, or that it does not pay ; and the veterinarian must have it whispered abroad that immunizing their herds pays his clients or he will ^'kill the goose that lays the golden egg.^' CHAPTER X HOG CHOLERA, MEAT INSPECTION AND GARBAGE FEEDING Hog cholera is a widespread disease affecting just one species of animal used solely to produce meat for human food, and its status as far as meat inspection is concerned is necessarily well estab- lished. The following paragraphs from Edel- mann^ set forth the broader principles which gov- ern the formulation of more detailed and specific regulations which are in force in various abattoirs throughout the country: *^ Judgment of the meat in swine erysipelas swine plague and hog cholera. In view of the fact that meat of these diseased animals has frequently been eaten for food without ever having incurred any impairment or injury to man, it can hardly be classed as injurious to health. In individual cases however the following should be considered : **1. The entire carcass is unfit for food as soon as marked substantial changes (congestion of blood, serous infiltration, degeneration, yellow discoloration) of the musculature or fatty tissue are observed or when marked emaciation has occurred. ^Edelman, Meat Hygiene (English translation by Mohler and Eichhorn; 2d edition, 1911). 197 198 HOG CHOLERA ''2. In all other cases, with the exception of the chronic forms of swine plague and the sequelae of this disease and those of hog cholera, the carcass in all of these diseases is to be considered fit for food but subject to certain conditions. For veterinary sanitary reasons, and partly in consideration of the causative agents in the blood of swine erysipelas, swine plague and the acute forms of hog cholera, the meat and fat are to be boiled, steamed (rendered into lard) or pickled. The portions affected by the disease should be condemned. *'3. In case of slow chronic forms of swine plague without disturbance of the general condition, or sequelae of this disease (adhesions, cicatrices, capsulated caseated areas etc.) or of hog cholera (caseation of mesenteric lymph glands, adhesions of intestines, formation of cica- trices in the intestinal mucosa) only the affected portions of the meat are to be condemned and destroyed. The remainder of the carcass is fit for feed without any re- striction. ' ' It will be observed that swine plague and swine erysipelas are governed by the same general con- siderations that apply to hog cholera. In view of the fact that swine plague occurs most frequently as a complication of hog cholera as well as of the fact that rapid differentiation of all three dis- eases based on abattoir examinations alone is not possible, it is fortunate indeed that these diseases run so nearly parallel in their relation to meat inspection. From the excerpt from Edelmann we glean the following essential considerations: first, the fit- ness of the meat for human food is based on patho- HOG CHOLERA AND MEAT INSPECTION" 199 logical changes in the meat itself, and is not deter- mined by the probable presence or absence of the causative agents of hog cholera, swine plague or swine erysipelas ; second, carcasses of hogs which before slaughter were obviously suffering with any one of the three diseases, may, in the absence of extensive pathological changes in the meat it- self be passed for human food, but for veterin- ary sanitary reasons it should be boiled, rendered or pickled in order to destroy causative agents of either of the three animal diseases which it may contain. A review of these facts leads logically to the conclusion that as far as hog cholera is concerned there is, and can be, no sharp line of demarcation between carcasses that are fit for human food and those which are unfit, because it has not been shown that hog cholera virus is injurious to man. The more important phase of meat inspection as it applies to hog cholera centers around the de- cision which determines whether a particular car- cass requires special treatment (boiling, render- ing or pickling), in order that parts of it may not subsequently infect other swine. Edelmann states clearly the need for a distinction between the fit and the unfit based solely on veterinary sanitary reasons, but he is silent as to how this distinc- tion is to be made. The IT. S. Bureau of Animal Industry meat in- 200 HOG CHOLERA spection regulations are much more specific in regard to the manner in which the distinction be- tween the fit and the unfit shall be drawn, but the distinction is based wholly on considerations deal- ing with the fitness of the meat for human food. Veterinary sanitary considerations, which would include atempts to require cooking or rendering of all carcasses which contain hog cholera virus, do not enter in. The parts of these regulations which refer specifically to hog cholera read as fol- lows: ''Reflation 9, section 2, paragraph 2. All hogs plainly showing on ante-mortem inspection that they are affected with either hog cholera or swine plague shall be marked 'U. S. condemned' and disposed of in accordance with section 8 of this regulation. ''Regulation 9, section 2, paragraph 3. If a hog has a temperature of 106° F. or higher, and if it is of a lot in which there are symptoms of either hog cholera or swine plague, in case of doubt as to the cause of the high temperature, after being marked for identification, it may be held for a reasonable time, under supervision of an inspector, for further observation and taking of temperature. Any hog so held shall be reinspected on the day it is slaughtered. If upon such reinspection, or, when not held for further observation and taking of temperature, then on the original inspection, the hog has a temperature of 106° F. or higher, it shall be condemned and disposed of in accordance with section 8 of this regulation. "Regulation 9, section 2, paragraph 6. All animals which, on ante-mortem inspection, do not plainly show, but are suspected of being affected with, any disease or HOG CHOLEEA AND MEAT INSPECTION 201 condition that, under these regulations, may cause con- demnation, in whole or in part, on post-mortem inspec- tion, shall be so marked as to retain their identity as suspects until final post-mortem inspection, when the car- casses shall be marked and disposed of as provided else- where in these regulations, or until disposed of in ac- cordance with section 7 of this regulation. **Eegulation 9, section 4, paragraph 1. All hogs, even though not themselves marked as suspects, which are of lots one or more of which have been condemned or marked as suspects under section 2 of this regulation for either hog cholera or swine plague, shall so far as possible be slaughtered separately and apart from all other animals passed on ante-mortem inspection. *' Regulation 9, section 7, paragraph 3. A hog sus- pected of being affected with hog cholera or swine plague may be set apart and held, under bureau supervision, for treatment with anti-hog-cholera serum. If at the expiration of the treatment period the animal upon examination is found to be free from disease it may be released for any purpose. ''Regulation 9, section 8. Except as hereinafter pro- vided in this section, animals marked 'U. S. condemned' shall be killed by the establishment, if not already dead, and shall not be taken into an establishment to be slaughtered or dressed ; nor shall they be conveyed into any department of the establishment used for edible products; but they shall be disposed of and tanked in the manner provided for condemned carcasses in regula- tion 14. The 'U. S. condemned' tag shall not be re- moved from, but shall remain on, the animal when it goes into the tank. The number of such tag shall be reported to the inspector in charge by the bureau em- ployee who affixed it, and also by the bureau employee who supervises the tanking of the animal, provided, that any animal condemned on account of hog cholera and swine plague, as prescribed in paragraph 1, 2, 202 HOG CHOLEEA or 3 of section 2 of this regulation, may be set apart and held, under bureau supervision, for treatment with anti-hog-cholera serum, the requirement that such ani- mal shall be killed shall be held in abeyance to await the result of the treatment. If at the expiration of the treatment period the animal upon examination is found to be free from disease, the 'U. S. Condemned' tag shall be removed and the animal released for any purpose." Post-mortem inspection. ''Kegulation 11, section 4, paragraph 1. The car- casses of all hogs marked as suspects on ante-mortem inspection shall be given careful post-mortem inspection ; and if it appears that they are affected with either acute hog cholera or swine plague they shall be disposed of in accordance with paragraph 2 of this section. '* Regulation 11, section 4, paragraph 2. Carcasses of hogs that show acute and characteristic lesions of either hog cholera or swine plague in any organ or tissue, other than the kidneys or lymph glands, shall be condemned. Inasmuch as lesions resembling those of hog cholera or swine plague occur in the kidneys and lymph glands of hogs not affected with hog cholera or swine plague, carcasses of hogs in the kidneys or lymph glands of which appear any lesions resembling lesions of hog chol- era or swine plague — shall be carefully further in- spected for corroborative lesions. On such further in- spection — ''(a) If the carcass shows such lesions in the kid- neys, or in the lymph glands or both, accompanied by characteristic lesions in some other organ or tissue, then all lesions shall be regarded as those of hog cholera or swine plague, and the carcass shall be condemned. "(&) If the carcass shows in any organ or tissue, other than the kidneys or lymph glands, lesions of either HOG CHOLEKA AND MEAT INSPECTION 203 hog cholera or swine plague which are slight or limited in extent, it shall be passed for sterilization in accord- ance with regulation 15. ** (c) If the carcass shows no identification of either hog cholera or swine plague in any organ or tissue other than the kidney or lymph glands it shall be passed for food unless some other provision of these regulations requires a different disposal." For years it has been a common practice among swine raisers to consign hogs to market as soon as hog cholera appeared among them, and even at the present day, when an effective preventive of the disease is at hand, the custom still prevails. If an entire herd consists of hogs nearing com- pletion of the fattening period, and if cholera is recognized as soon as it appears, the loss to the feeder is not heavy. He promptly markets all hogs that are apparently well, leaving behind the few that are visibly sick. If, though, a herd in- cludes sows, pigs and shoats which cannot be mar- keted to advantage, or if it consists of pure-bred animals, heavy and unnecessary loss must be ac- cepted in consigning it to market. Unfortunately the loss is not confined to the man who ships the infected hogs. His herd becomes a menace to others in the vicinity as it is driven to the nearest loading station, and it helps to perpetuate the in- fection which, existing in practically all large pub- lic stockyards in the country, threatens all cholera susceptible swine not intended for immediate 204 HOG CHOLERA slaughter. Nor is the danger terminated when the hogs reach the shambles. An impression pre- vails that in establishments where meat inspec- tion regulations are in force, carcasses that con- tain hog cholera virus are condemned, and those that do not contain it are passed for food. This is not the case. Many carcasses that contain the virus readily pass inspection, and although they are perfectly fit for human food, trimmings from them regularly find their way into garbage, and when this is fed to susceptible hogs, they, in turn, contract disease. It is a vicious cycle, and one very difficult to break. When a consignment of hogs from a cholera infected herd reaches an establishment where fed- eral meat inspection regulations are in force it is first subjected to ante-mortem inspection. With respect to hog cholera it may contain five classes of hogs: first, dead hogs; these are condemned and tanked: second, hogs that show undoubted symptoms of cholera; these also are condemned and tanked: third, those that show suspicious symptoms and temperatures below 106° F., these are slaughtered; carcasses that show hog cholera lesions are condemned or passed for sterilization according to the extent of the lesions; those that show no lesions are passed for food : fourth, hogs apparently normal, and those which show suspi- cious symptoms, having temperatures above 106° HOG CHOLERA AND MEAT INSPECTION 205 F. ; these are condemned or isolated for further temperature records; in case further tempera- tures are taken the animals are condemned if the readings are still above 106°; otherwise they fall into class three or class five : fifth, apparently nor- mal hogs that show temperatures below 106°; these pass ante-mortem inspection and post-mor- tem as well if they do not show lesions of hog chol- era in organs other than the kidneys or lymph glands. Let us consider the individual hog. Briefly stated, the requirements in order that it may pass inspection are that it shall not show conclusive symptoms of hog cholera, it shall not show sus- picious symptoms plus hog cholera lesions, it shall not maintain repeated temperature readings above 106° F., and regardless of ante-mortem findings the carcass shall not on post-mortem show hog cholera lesions in organs other than the kidneys or lymph glands. What are the chances for car- casses that contain hog cholera virus to pass in- spection? This question is best answered by considering the average case of hog cholera. Let us suppose that a hog becomes infected to-day. According to Dorset, ^^ Repeated experiments have sho^\^l that the blood of pigs that have previously been in- oculated with the virus of cholera becomes infec- tious for others within twenty-four hours; the 206 HOG CHOLERA urine and feces contain the virus usually in forty- eight hours, and the secretions of the eyes and nose become infectious by the third day follow- ing infection: therefore these experiments show that infected pigs are capable of transmitting the disease before they themselves show any visi- ble illness. '^ ^ Thus the blood and therefore the meat of a hog infected to-day will to-morrow contain hog cholera virus sufficient to infect others, but there will be neither symptoms, temperature readings nor le- sions to cause its condemnation. The same will be true on the second, third and fourth days fol- lowing infection, but from that time on we may at any time expect developments that would cause condemnation. These may, though, be delayed several days longer. There is a time, at least three days on an average, in the lives of practi- cally all hogs affected with acute hog cholera when they ivill pass inspection and when hits of porTc from their carcasses ivill infect other sivine to which they are fed. This interval varies from one or two to several days, and is measured, roughly, by the time required, after the first twenty-four hours following infection, for the temperature to rise to 106° F., or for conclusive symptoms or extensive cholera lesions to appear. ^ Keport of the chief of the U. S. Bureau of Animal Industry for the year ending June 30, 1917, HOG CHOLERA AND MEAT INSPECTION 207 With these facts in mind, let us again consider the farm herd from which cholera infected hogs are shipped. Often a considerable number must die before the owner will admit, even to himself, that he is dealing with hog cholera. Then there is the delay incident to securing transportation, and there are many hours during which infected and sound animals are crowded together in a stock car. Finally, after the hogs reach the yards there is an additional delay of several hours or even several days before they are killed. x\ny person familiar with hog cholera knows that in such a consignment a great majority of the hogs become infected before they are killed and any person familiar with present-day meat inspection regula- tions knows that under such circumstances the vast majority of the infected animals will pass in- spection. The hogs have every chance to become infected but the disease does not have time to develop sufficiently to cause their condemnation. The practice of marketing swine herds as soon as cholera appears is no longer necessary. It rarely profits the man who follows it, and it per- petuates hog cholera, working great harm to the smne industry. Before the discovery of protec- tive serum a herd of hogs once infected with chol- era became a total loss unless some of the animals could be salvaged by slaughter. With the plenti- ful supply of serum now available an infected herd 208 HOG CHOLERA can safely and profitably be kept at home. All that is required is prompt reporting, prompt diag- nosis and prompt serum treatment. With few exceptions serum will, at any given time, save all hogs which are not at that time already danger- ous carriers of hog cholera virus. In the United States, during the decade ending in 1911 approximately 18,000 hogs were condemned annually on account of hog cholera. In 1914 the number reached a total of 116,000; in 1917, 33,000. According to Bureau of Animal Industry estimates, 40 per cent of the pork which is killed and 15 per cent of that which is marketed in the United States is slaughtered on farms or in abat- toirs in which no inspection is maintained. Judg- ing from my study of the situation as a whole, my belief — which I would be reluctant to express in concrete terms if it were not essential to convey at least an approximate idea of existing conditions — is that in the country at large, for each hog which is condemned for cholera, at least three virus-con- taining carcasses pass or evade inspection. What becomes of them subsequently? Each infected carcass possesses almost infinite possibilities in regard to its final distribution. Whether the pork reaches the consumer in the form of hams, shoulders, or bacon, or whether it is fresh, refrigerated or cured, we should not lose sight of the fact that it actually contains unlabeled HOG CHOLERA AND MEAT INSPECTIOTC 209 hog cholera virus, and that uncooked portions of it fed to susceptible hogs will produce cholera. Of the various preserving and preparing proc- esses to which pork is subjected before being sent to the consumer, only one that we know of — cooking — is certain to destroy hog cholera virus which it may contain. According to extensive experiments ^ which we have carried out the virus lives in fresh meat until decomposition sets in, it is not affected by prolonged refrigeration, and a representative sugar curing and smoking process killed it in only 43 per cent of the tests made. So far we have dealt chiefly with the facts sur- rounding hog cholera and meat inspection as they have been determined by exact scientific methods and recorded data. It remains to be added that clinical observations are entirely in accord with these facts. We hear of one outbreak of hog chol- era in Canada, and it is traced to a consignment of infected hams ; we hear of another in a remote lumber camp in the Adirondacks where hogs are kept to consume the kitchen refuse; and of still another on an inaccessible farm in Nevada follow- ing purchases of market pork. These are merely representative instances. At least 90 per cent of the outbreaks we encounter in New York can be traced to no other source than infected pork trim- * Eeport of New York State Veterinary College 1915-1916, page 60. 210 HOG CHOLERA mings in garbage, and in other Eastern states the situation is essentially the same. Torrance ^ reports similar conditions in Canada. In the Southern and central states a much smaller pro- portion of herds become infected through the agency of pork trimmings from carcasses that contain hog cholera virus, but even in these sec- tions there is ample evidence that the first infec- tion in many outbreaks takes origin in this man- ner. Once established in territory that supports a dense swine population, the disease spreads rapidly through many other agencies. Meat inspections in field outbreaks of hog cholera. The practicing veterinarian who is called to handle a farm herd infected with hog cholera very frequently is questioned regarding killing and marketing all animals that remain ap- parently well. How is he to advise his clients? Disregarding, for the moment, legal and sani- tary considerations, and thinking only of the plan that will cause our clients the least immediate financial loss, w^e will find relatively few instances where immediate slaughter can be advised. These occur principally in herds of feeders about ready for market anyhow, and in herds in which the disease has progressed so far that protective serum otfers very little hope. In either case the * * ' Garbage Feeding in Eelation to the Control of Hog Cholera, ' ' Journal of the American Veterinary Medical Association, Octo- ber, 1921, p. 22. HOG CHOLEKA AND MEAT INSPECTION 211 hogs are worth more as pork than they will ever again be worth on foot, but here legal and sanitary considerations enter in, and it is only where the state law provides for slaughter under inspection and where provision can be made to minimize the danger to other herds that may result from mar- keting the pork, that slaughtering is to be ad- vised. New York, for instance, has a law which permits killing under inspection from herds infected with cholera, but it is only at institutions and on farms where the pork will not be placed on the open mar- ket that we have advised such a course. We hab- itually follow the plan of explaining the situation to our client, and informing him that he has a legal right to kill, but that he has at the same time a moral obligation to protect his neighbor. When we offer at the same time the alternative of serum treatment, giving a prognosis as nearly exact as is possible, there are few who will not decide to use serum or who will not profit by doing so. Indeed in just one instance that we recollect has one of our clients elected to take shelter under the law and disregard his neighbor. This man had a herd consisting originally of about four hundred hogs. Cholera appeared, but he refused to accept our diagnosis. Finally when his herd had dwindled to about one hundred and fifty animals, he decided to vaccinate. It was a forlorn hope, but we began 212 HOG CHOLERA taking temperatures, intending to administer se- rum only to those that showed readings below 104"^ F. After numerous trials in which we found but a negligible number of readings below 106° F., we gave up the attempt and returned home. Later we were informed from reliable sources that imme- diately on our departure about seventy-five hogs from the herd were shipped to market and that the majority of them passed federal inspection.^ The man in this instance received more for the hogs than he would have received had he administered serum to all of them as an eleventh-hour mea- sure, but he received infinitely less than would have fallen to his lot had he treated the herd mth protective serum at the time when he was first warned of the danger. In those instances in which the practicing veter- inarian is called to inspect hogs that are being slaughtered from cholera-infected herds, the fed- eral meat inspection regulations ^ should be se- lected as a convenient guide, but unless it is so specified by state law, they are not to be regarded as inflexible or final. The practitioner must * This must not be construed as a criticism of the administration of the federal meat inspection regulations. It is merely a rather striking example of the fact that the regulations, admirably formulated and enforced to protect human health and human life, cannot be relied on to eliminate from our markets swine carcasses that contain hog cholera virus. ^ The paragraphs that relate to hog cholera appear near the beginning of this chapter. HOG CHOLEEA AND MEAT INSPECTION 213 adapt his decisions to the conditions under which he is working. If he knows that the pork is to be sold in the open market where it will become the potential cause of future outbreaks, he cannot be justly criticized if he is relatively severe in his decisions ; on the other hand, if the pork is to be retained at the place where it is killed, as it is on some institution farms, for instance, rather ex- tensive hog cholera lesions should be required in order to condemn. Carcasses that are not deemed fit for pork can be partially salvaged in the form of lard. When slaughter on the farm is decided on, ante-mortem inspection should consist first of ob- serving the hogs before they are disturbed, and re- jecting any that obviously are suffering with hog cholera. Then temperatures may be taken of those that remain and any that show readings above 106° F. should be condemned or put aside for subsequent readings. Later if they show tem- peratures below 106° F. they may be slaughtered and post-mortem findings will determine whether the carcass shall be passed or condemned. In case the weather is very warm, or if it is necessary to excite the animals unduly in taking tempera- tures, one may secure more accurate information by giving them a limited quantity of feed and re- jecting those that do not remain at the trough and eat greedily. Nearly all will come to the trough at 214 HOG CHOLEEA first, but those that are suffering most with chol- era will soon return to the nest. Principles governing post-mortem inspection have already been discussed. Briefly, extensive changes in the meat or fat should cause condemna- tion. Hog cholera lesions in the kidneys and lymph glands do not condemn the carcass, al- though in cholera-infected herds such lesions prac- tically always establish its status as a virus car- rier. Carcasses that show hog cholera lesions in the kidneys, lymph glands and other organs as well are not used for pork, but if the lesions are slight in extent the fat may be rendered into lard. Most hogs that appear well on foot pass post-mortem inspection as well. Garbage Feeding Intimately bound up with meat inspection as it applies to hog cholera is the subject of garbage feeding. As we have already shown this prac- tice is the final link in the chain which is respon- sible for the introduction of cholera into so many herds of hogs. If meat inspection regulations be- come more stringent, garbage feeding becomes less hazardous; if they become less stringent, or if they are neglected altogether the risks from in- fected pork trimmings in garbage increase. In any event, chance alone decides when any partic- HOG CHOLERA AND MEAT INSPECTION 215 ular herd that subsists on garbage will contract hog cholera. The larger the herd, the greater the supply of garbage necessary to maintain it, and the more certain it is to become infected. In earlier years feeding garbage to hogs has produced the most surprising and contrasting re- sults. Its feeding value has long been well known, and men who were tempted to utilize it in feeding hogs usually began the practice on a small scale. If hog cholera did not happen to reach the herd during the first year, the financial returns were usually gratifying beyond expectations, and the hog raiser enthusiastically increased the size of his herd — at the same time multiplying its chances to become infected with cholera. Thus a common experience was for the breeder to have the savings of one or more years invested entirely in hogs when cholera finally reached his herd and de- stroyed it. Various preventives of the disease incident to garbage feeding were advertised, and magic for- mulas were passed around by word of mouth. Perhaps one man fed salt and sulphur to his hogs and did not lose a single one; another neglected to do this and his entire herd was destroyed. Could any proof be more convincing! But the law of chance was still in operation, and hog chol- era was relentlessly striking down one herd after another, including those which received the lauded 216 HOG CHOLERA preventives with those that did not, in a wholly impartial manner. There was a belief that garbage in itself pro- duced the disease, and there was divided opinion as to whether it was dietetic in nature or whether it was really hog cholera. The trouble was thought by some to be due to a variety of causes — as in truth it was to a limited extent — but when anti-hog-cholera serum was brought into use it was found that this product prevented most rap- idly-fatal infectious disease which had formerly plagued the garbage feeder's herd. Also the ad- vent of kitchen sinks and drains eliminated soap poisoning due to dish water which was formerly included in garbage. These two advances have placed garbage feeding on a relatively safe basis. The collection and disposal of city garbage is a complex and exacting process, and staggering sums are paid annually for this service. Disposal plants cost huge sums of money as original invest- ments, and coal, labor and upkeep incident to their operation require a heavy and continuous outlay. One city of 100,000 that we know of — and it is no exception — was until recently incurring the ex- pense of collecting its garbage and hauling it three miles to a disposal plant, and it was also operating the plant at an annual expense of $40,000. The garbage was burned and there was no salvage, as HOG CHOLEKA AND MEAT INSPECTION" 217 there is in some disposal plants, in the form of grease, tankage and bones. Viewing the subject of garbage feeding from the standpoint of the mmiicipality it may be said that in cities of less than 100,000 feeding is by far the most economical plan of disposal, and ex- perience will probably prove that the same rule holds good for larger cities. If provisions are made for feeding, no city of less than 100,000 should find it necessary to pay disposal costs, and many should be able to offset in some degree, collection costs as well. Cities that elect to dis- pose of their garbage by feeding may maintain piggeries as a municipal function, or they may provide by contract for collection and disposal. We believe the most satisfactory plan is for the city to collect the garbage and deliver it to the contractor's piggery or to a specified loading station. Long term contracts with optional renewals on the part of the contractor are the only ones that will prove satisfactory when the plan is to feed the garbage. No man can afford to build adequate quarters for large numbers of hogs unless there is assurance of a constant supply of feed during a term of years. Short term contracts are respon- sible in large measure for the fact that the gar- bage feeder's establishment is so often a public nuisance. He does not have time to organize his 218 HOG CHOLEEA feeding operations, he cannot invest in good equip- ment that will have to be sold at a loss as soon as his contract terminates, and there is not sufficient time for the enterprise itself to yield profits that may be returned to it in the form of equipment. When a city wishes to let its garbage contract to the best advantage it should agree to give the contractor all the municipal garbage, and it should provide ordinances that require its drainage and the exclusion of tin cans, broken bottles and the like. Collections should be required at least once a week in winter and twice in summer. A five- year contract which the contractor can renew at his option if he discharges his obligations, is satis- factory, and will serve to entice reliable con- tractors. Municipal piggeries are successful sometimes, but changing city administrations are not always to their best advantage. Sooner or later self- styled ^'business men" are likely to be charged with their general supervision, and in formulat- ing business rules for their subordinates they themselves are likely to ignore essential natural laws governing swine husbandry and the handling of s^^ine diseases. Business principles must of course be observed, but they must be made to dovetail with principles that conserve the health of the swine and provide each day for their intelli- gent care. I HOG CHOLEEA AND MEAT INSPECTION" 219 Garbage varies greatly in feeding value, but as a very general rule one ton of well drained city garbage which is free from extraneous matter will feed about fifty or sixty fattening hogs^ causing them to gain from % to one pound each. In other words one ton of garbage should produce about fifty pounds of pork. At least 200 pounds of a good grain ration is required to produce the same gains. Thus as far as the public at large is con- cerned dumped or burned garbage represents a great and avoidable waste, and in states with large urban populations this waste assumes huge proportions. Veterinary Supervision of Garbage-Fed Herds Herds of hogs fed on city garbage are con- stantly threatened with cholera, and for this rea- son they sooner or later come under the veteri- narian's care. The dangers nowadays are fre- quently known in advance and hence professional advice is sought before a herd is assembled, but many feeders are still ignorant of the chances they assume, and still others procrastinate in regard to immunizing. When a veterinarian is consulted before a herd is assembled, or before hog cholera appears in it he can render service of a high order if he is fa- miliar with disease prevention and swine hus- bandry methods. He also assumes considerable 220 HOG CHOLEKA responsibility, for, given a clean herd he is sup- posed to know how to keep it clean. The preven- tion or handling of hog cholera in herds fed on garbage is not different in principle from han- dling the disease in other herds, but there are several difficulties peculiar to the garbage-fed herd that must be overcome. These difficulties are so closely linked up mth methods of swine hus- bandry that all must be considered at the same time. Should the garbage feeder raise or purchase feeding hogs? Many considerations enter in, but as a general rule if the herd is to be relatively small, say less than 500, if there is provision for exercise and a little pasture, if warm farrow- ing pens can be provided, and if a supervisor who thoroughly underctands swine breeding can be se- cured, the "'^est plan is to raise the pigs. Under ordinary conditions, as the herd is increased in size, raising the pigs becomes relatively less feas- ible. The question of loroximity to a good mar- ket for good feeding shoats likewise must be con- sidered, and what we have said in a preceding chapter in regard to handling feeder hogs, applies here as well. Shoats that have been immunized on the farm are by far the safest purchase, and susceptible ones that can be purchased from thrifty farm herds may be immunized without much danger. Purchase of stockyard hogs is ad- HOG CHOLERA AND MEAT INSPECTION 221 visable at times, but judicious selection and care- ful handling are essential, and even then the best professional care does not always insure against considerable loss from hog cholera and its com- plications. When it is desirable to purchase feeding shoats to consume garbage, those weighing between 75 and 120 pounds are most desirable. Although it is feasible to raise the very best pigs on garbage alone, the fact remains that often they begin to eat it well and put on rapid gains only after they have attained considerable size. It is likewise true that shoats cannot be put on full feed as rap- idly when garbage is fed as they can when their ration consists of grain, hence it is well to pur- chase rather light shoats so that the loss of time in getting them started can be made up by a rela- tively long fattening period. Except when cholera immune shoats are pur- chased from the farm it is necessary that immu- nizing shall take place before or immediately after they reach the feeder's yards, and thus they must often undergo the resulting reaction before the condition known in the fattening pen as ^'full feed'' is reached. Special care is necessary not to overfeed at this time. Efforts to crowd the animals beyond their capacity may aid in caus- ing ^^ serum breaks," and do injury that will re- quire weeks to overcome. With this one special 222 HOG CHOLERA precaution our readers are referred to the head- ing in the last chapter entitled '^ Handling Feeder Hogs/' It is in raising pigs entirely on garbage that the greatest care is required. Numerous pitfalls are in the path of the beginner, and it is a quite general rule that one serious disaster is necessary to impress him with the necessity for avoiding neglect. The critical period in a pig's life is from weaning time until he reaches a weight near 75 pounds. When garbage is to be the sole feed it is a great mistake, and a common one, for the pigs to be weaned while they are very young. The breeder is anxious that the sow shall produce an- other litter as soon as possible, and thus it is not uncommon for weaning to take place when the pigs are four weeks old, or a trifle more. They are then too young to gain well on garbage alone and they are subject to various dietary troubles that are not often observed in pigs weaned later in life. One good litter a year born quite early in the spring and nursed until the pigs are eight or even twelve weeks of age is more profitable than two litters weaned too young. However when warm farrowing pens are provided it is not neces- sary to choose between one litter a year, and two. The sow can nurse her litter the required time and then be bred at the first period of heat fol- HOG CHOLERA AND MEAT INSPECTION 223 lowing weaning of the pigs regardless of the time of year that farrowing will occur. When the pigs are weaned too young *^ runts'' are common among them, and in waiting for the animals to become of sufficient size to receive si- multaneous treatment it is not uncommon for the breeder to prolong to a dangerous degree the in- terval between serum alone and simultaneous treatments. The passive immunity due to the former partially disappears, and hog cholera, fre- quently of an atypical and subvirulent type, some- times appears among them. Often this type of the disease is not recognized as hog cholera. Pigs in large herds require earlier serum alone treatment and are more likely to require two treatments prior to the final serum-virus administration than are those in smaller herds. This is because of the fact that in large herds the chances for infection are so great that the virus of the disease must be regarded as being continuously present. Pasture and abundant room for exercise are of great benefit to young pigs that subsist on gar- bage. There seems to be a general fear that pigs mil ' ' run all the fat off them ' ' if they are allowed generous room for exercise. We have repeatedly observed the effects of turning pigs from cramped and dirty quarters into pastures or large enclos- ures, and the change has always been in their 224 HOG CHOLERA favor. Granting good weather conditions, very young pigs that become exhausted in attempts to follow the sow, and feeders near completion of the fattening period are the only exceptions to this rule. There is a tradition that hogs grown on garbage from generation to generation become accustomed to it and consume it to better advantage. For- merly we were inclined to regard this belief as being without foundation on fact, but in later years we have seen evidence that causes us to change our views. It is certain that sows pur- chased from grain-fed herds and required to sub- sist on garbage frequently fail to farrow large litters in the spring subsequent to the change, and while this may often be explained on the ground of insufficient exercise and overfat condition, this explanation covers only a portion of the cases. If we were purchasing breeding animals for a garbage feeding establishment we would regard it of considerable advantage to secure them from herds long accustomed to that kind of feed. Pigs must have dry sleeping quarters or they will not thrive. Due to the excessive moisture in garbage, wet quarters are a common and disas- trous cause of unthriftiness among pigs that sub- sist on it. The greater the run allowed the pigs the easier it is to keep them dry. When the quar- ters are of necessity somewhat crowded, special HOG CHOLERA AND MEAT INSPECTION 225 provisions are necessary or all parts of the floor will be clamp. This difficulty can be obviated by constructing overlays consisting of floors of matched material built on two-by-fours laid flat. These are built up around the edges so that in effect they are wide shallow boxes which contain the litter. They should be located as far as pos- sible from the platform where the garbage is fed. What we have said in preceding chapters in regard to maintaining herds immune to hog chol- era applies as well to those that subsist on gar- bage. Young garbage-fed pigs are relatively somewhat slow in getting started, hence they re- quire a little extra care such as we have already outlined. In the absence of this care they are in more or less danger of falling victims to various influences that retard growth, or to ill effects fol- lowing simultaneous treatment administered at a time when they are not in the best condition to withstand it. Grarbage Feeding and Sanitary Considerations We have already described the cycle which enables the practice of garbage feeding to aid in perpetuating hog cholera. The ways in which this cycle can be assailed remain to be considered. Our attacks should include efforts to prevent ship- ment from cholera infected herds, gradual revi- sion of our meat inspection regulations with a 226 HOG CHOLEKA view to reducing the number of virus containing carcasses that are placed on the market, measures to license and control establishments where gar- bage is fed, and educational activities designed to acquaint breeders with the risks they assume when they feed even a limited quantity of garbage. Measures to prevent shipment from cholera- infected herds may take two forms : first, the al- ternative — prompt serum treatment — should be made available to every breeder, and practicing veterinarians will do well to school themselves in handling hog cholera on the farm, so that the folly of marketing infected hogs will be obvious to the breeder ; second, some form of penalty should be attached to the practice. It is obviously impos- sible to reach all offenders but the more flagrant ones could easily be detected, and the effect would be wholesome. When a shipment of smne arrives at the yards containing a considerable number of dead hogs and many others obviously infected with cholera, the chances are that most of the animals in it will produce carcasses which contain the virus. If it could be made compulsory to market such carcasses only in the form of safe but less valuable cooked products, and if the hogs in such a shipment were so tagged and identified that the shipper himself had to accept the conse- quent loss, there would be fewer cholera infected HOG CHOLERA AND MEAT INSPECTION 227 herds marketed, and a higher price for sound ones would prevail. Ante-mortem inspection could at least be made to incriminate an entire shipment containing hogs obviously infected with cholera to the extent of requiring a more severe interpretation of lesions in individuals contained in it. "While it is true that petechia in the kidneys and peripheral hem- orrhages in the lymph glands, for instance, may be due to causes other than cholera, it is likewise true that in shipments such as we have described these lesions are, with negligible exceptions, con- clusive evidence of the disease. License and control of garbage feeding estab- lishments have much to recommend them. Sur- rounding the average city, under present condi- tions, are numerous small herds in which garbage is being fed, and in each one lurks the danger of an outbreak of hog cholera. If a licensing system were in operation, instead of having many un- known sources of infection without any control whatever, we would have a limited number of known sources, in which methods could be so regu- lated as to minimize danger due to spread of the infection. It would be possible to require immu- nization of all hogs fed on garbage — an advantage rather than a burden to the individual feeder — and it would likewise be possible to govern the 228 HOG CHOLERA location of garbage feeding establishments, and to require adequate equipment for their operation. Regulations in Canada require that all men who plan to feed garbage shall first secure licenses, and the plan seems to be working well; princi- pally, we believe, because the sources of danger are limited in number and known. Cooking the garbage is required, but this, in our experience, is a measure of doubtful value. There is no doubt that a boiling temperature will kill the virus, but there is doubt that such a temperature will ac- tually be applied to all garbage fed in any estab- lishment. We have frequently seen neglect of this kind end in disaster. In one instance we were called to handle an outbreak of hog cholera at a large sanitarium where provision had even been made for cooking all garbage under pressure. An unguarded interval during which the apparatus was temporarily out of order was responsible for this outbreak. Immunizing the herd is usually far safer than cooking the garbage on which it is fed, and it has the additional advantage of pro- tecting against all sources of infection. Despite the need for various measures to pro- tect the swine breeder's herd, the fact remains that the measures which he himself can apply will be most effective. He can exclude all pork trim- mings from the kitchen refuse which he feeds, he can discontinue feeding garbage, or he can in co- HOG CHOLEKA AND MEAT INSPECTION 229 operation with his veterinarian keep his herd im- munized. Either measure faithfully carried out will protect his herd from cholera infection di- rectly due to garbage feeding. CHAPTER XI CONTROL AND ERADICATION OF HOG, CHOLERA Control of an infectious disease means that rather definite limits have been placed on its spread. Eradication, as applied to a particular area, implies that all the virus which causes the disease has been killed, and that the malady can no longer exist unless it is introduced from with- out. Naturally, in a country in which an acute and fatal infectious disease such as hog cholera is widely disseminated control is the first con- sideration. But eradication is the distant goal, and while our progress toward this goal must at times yield to expediency, there must be no per- manent or long surrender to methods that con- tribute nothing toward the ultimate purpose. Long acceptance of losses due to hog cholera has given us a fatalistic attitude toward the dis- ease. Like the poor, it is always with us and we habitually expect and tolerate it as we expect and tolerate inclemencies of weather or the infirmi- ties of old age. If a foreign infectious SAvine dis- ease, equally destructive and equally well under- stood, were to appear in this country, even though 230 CONTEOL AND ERADICATION OF HOG CHOLERA 231 it were to gain a firm foothold, those whose inter- ests were threatened would demand its eradica- tion and the veterinary profession in cooperation with many breeders — and in spite of the violent opposition of a few — would eradicate it. The first prerequisite, then, is a change on the part of veterinarians, breeders and the public from a passive to an active attitude toward hog cholera. In expressing this view we must not be understood as declaring our faith in a short and intensified campaign against the disease, for the methods that finally succeed will involve details which must grow out of a continual process of trial and adjustment ; but the start must be made, the goal must be kept clearly in view, and con- stant, active and unyielding pressure must be brought to bear on the most obvious practices that serve to perpetuate the disease. During the last four decades hog cholera has caused in this country annual losses ranging be- tween $13,000,000 and $200,000,000, killing annu- ally an average of 66 out of every 1,000 hogs. About once in each decade the disease becomes greatly intensified and in 1887, 1897 and 1914, respectively, the number of hogs killed by it rose above 10 per cent of the country's entire swine population. These are staggering losses, and when one reflects that they will continue indefi- nitely unless intelligent, organized efforts are 232 " HOG CHOLERA made to check them the advantages of such efforts become self-evident. It is not impossible to eradicate hog cholera. The task presents no such diflficulties as are en- countered in the eradication of bovine tuberculo- sis, for instance. Hog cholera does not exist long unknown to the owner of the herd it infects ; indi- viduals apparently well do not regularly live year after year disseminating the virus ; deaths due to it are rapid and certain and the resulting losses are obvious; it is a foe that strikes in the open. The disease can be stamped out quickly in any herd, and there is an immunizing agent so etfec- tive that prompt reporting is the breeder ^s surest way to avoid loss. When we reflect on the sig- nificance of these facts we may well be led to wonder why the disease does not disappear. The truth is that it does tend to do so, for undoubtedly there are to-day many counties free from the dis- ease that have suifered severely from it in past years, and that will suffer again when the virus once more is introduced from without. When once the virus finds its way into a locality the methods by which it may spread from herd to herd are innumerable but it is time that we direct our attention to the sources of the original infec- tions. We dissipate our energies in trying to con- trol outbreaks of huge proportions instead of concentrating them on the prevention of primary CONTROL AND ERADICATION OF HOG CHOLERA 233 infections. The three most important methods by which hog cholera travels from locality to locality are: 1. Marketing from infected herds. The hogs thus shipped are a menace to others as they are taken to market, they keep stock cars and stock- yards constantly infected, they are sometimes sold from the yards as feeders, and their carcasses are regularly placed on the market in large numbers where they serve to infect many new localities through the medium of garbage feeding. 2. The transportation from public stock- yards of susceptible feeder hogs, and those which receive simultaneous treatment imme- diately prior to shipping. Wlien susceptible feeders are placed in public stockyards they often become infected, and though they leave the yards apparently in good health they soon develop cholera and the farms which receive them become new centers of infection. Feeder hogs that receive simultaneous treatment and which are at once shipped to distant points, frequently ^ 'break" as .a result, and thus introduce hog cholera into new territory. 3. Wide and indiscriminate use of hog cholera virus in immunizing, especially by untrained men. '^ Vaccination cho]er.a" is still too common in farm herds, despite the fact that experienced men know how to avoid most of it. 234 HOG CHOLEEA These three practices have essentially the same relation to hog cholera eradication that the feed- ing of uncooked creamery products has to the eradication of bovine tuberculosis. They furnish obvious and wide-open routes for dissemination of the virus. Are they really necessary evils! Are there no possible ways to avoid them? Let us examine the three practices more in detail. Marketing from infected herds. We have al- ready shown that marketing from infected herds is a common practice, that it serves to spread hog cholera virus as the animals are driven to market and when trimmings from their carcasses later find their way into garbage that is fed to suscep- tible hogs. We have also drawn attention to the fact that feeders selected from these herds and shipped to distant points cause many new out- breaks of hog cholera. For our present purpose it remains to review briefly means by which this endless chain of infection can be severed. The first object should be to keep cholera in- fected herds at home. Good local veterinary serv- ice will do much in this direction for it is the ill- advised breeder who ships his infected hogs to market. On the part of the meat inspection serv- ice, rigid interpretations of lesions in all indi- viduals that come from lots obviously infected with hog cholera at the time they reach the yards ♦ CONTROL AND ERADICATION OF HOG CHOLERA 235 will serve to discourage shipping from infected herds, provided a tagging system is adopted which will place the losses due to condemnations where they belong — on the man who ships the hogs. The second object should be to prevent the sale of carcasses of infected hogs that reach market despite efforts to keep them away. In other words, carcasses that obviously are carriers of hog cholera virus should not be sold except in the form of cooked products, for hog cholera will be with us as long as the practice continues. We have already mentioned the present deficiency of the federal meat inspection regulations as they apply to this particular point. Whether this de- ficiency is due to lack of authority or to failure to use authority already granted, the etfect is the same — many carcasses that show lesions usually considered characteristic of hog cholera are still allowed to pass inspection. It is deceptive to assert, as the regulations do, that these lesions are sometimes due to causes other than hog cholera. Granting, as we freely do, that this is true we still maintain that it is exceptional to such an extent that it should re- ceive scant consideration in the judgment of car- casses that come from lots which contain hogs suffering with cholera w^hen they reach the yards. Hogs that come from infected herds and that show 236 HOG CHOLERA even slight lesions suggestive of cholera mil yield carcasses that contain virus, almost without ex- ception. The third object sought should be that of neu- tralizing the effects of virus-carrying carcasses that pass inspection. To this end it should be made known among swine raisers that danger al- ways lurks in the practice of feeding even small quantities of garbage that contain pork trim- mings. A system of licensing garbage-feeding such as the one that now exists in Canada, is also Avorthy of consideration. Transportation and sale of susceptible feeder hogs and those tvhich receive simidtaneous treat- ment just before shipping. Most public stock- yards are contaminated with hog cholera virus, and eventualh^ it should be so ordered that when susceptible hogs enter, it shall be for immediate slaughter only, and the gates shall close behind them forever. Previously we have drawn atten- tion to the fact that ^' serum breaks" are fre- quently a result of giving hogs simultaneous treat- ment and shipping them immediately afterward. Though this practice is probably the lesser evil as compared to shipping susceptible hogs from the yards without immunization, the fact remains that it is still a potent factor in the dissemination of hog cholera virus. Follow-up treatment as a sub- stitute for simultaneous treatment given immedi- CONTROL AND ERADICATION OF HOG CHOLERA 237 ately before shipping, will do much to minimize this danger, but the ideal will be reached only when feeder hogs are permanently immune to hog cholera before they are shipped long distances. It will take time to provide for an adequate supply of immune feeders so that shipping suscep- tible and recently-immunized hogs from public stockyards will not be necessary, but there are hopeful indications that this will be brought about. Men experienced in the feed-yard even now are eagerly seeking means of avoiding the heavy financial losses associated with ^Vaccination cholera'' immediately following simultaneous treatment and shipping. Among such men there is an active demand for immune feeder shoats, and efforts are being made, though as yet on a limited scale, to supply this demand. The prac- tice of assembling and immunizing feeders, and shipping them only after the resulting reaction is over is already being adopted by some serum companies. This is a step in the right direction, and our belief is that a promising field is open to others who will make a business of supplying the trade with carefully selected cholera - immune feeder shoats. When the supply of these animals is equal to the demand the practice of shipping susceptible and recently-immunized feeders from public stock^^ards will cease. Indiscriminate use of hog cholera virus in im- 238 HOG CHOLERA muyiizing. When the effectiveness of serum-virus immunization was first demonstrated the demand for these products far exceeded the supply, and hasty preparations were made to produce them in enormous quantities. Enthusiasm for immuniza- tion ran high, and it was looked on as the final solution of the hog cholera problem. Men with- out previous experience with disease and with no fundamental knowledge of the processes that produce immunity were drafted into service to produce and use products potentially capable of doing great harm. It was the accepted belief that all hogs should be immunized, that the process of immunization was a simple one requiring only a low grade of mechanical skill, that serum and virus could be administered without a suggestion of danger, and that the hogs receiving them were from the moment the doses were administered permanently immune to hog cholera. It is little wonder that impotent serum was sent out, that potent serum often fell into unskilled hands, and that some of the laboratories that featured *^ virus q. s. with all serum orders'' sometimes sent out quantities that were just a little more than suffi- cient. The Bureau of Animal Industry laboratory in- spection service ^dth the aid of many far-sighted serum companies has done much to correct these initial evils. The sale of impotent serum for use CONTROL AND ERADICATION OF HOG CHOLERA 239 with virus was much more readily prevented than were the disasters growing out of the use of good serum by untrained or indifferent men, and to- day it is to the latter abuse that most outbreaks of hog cholera which originate from laboratory virus must be attributed. The task of reducing '^vaccination cholera'* to a minimum must be referred to a trained and awakened veterinary profession. There is an in- sistent demand that vaccination of hogs shall be placed in the hands of laymen, a policy which, if adopted generally, will be disastrous to the swine industry. Yet this demand will be heard — and heeded — as long as there is territory in which there are not qualified veterinarians to do the work. Reducing the problem of hog cholera control to its simplest terms it may be said that in the indi- vidual animal the disease soon terminates, for the virus will destroy or immunize its host in a few weeks. Likewise in the herd the same principle applies, but if we expand our unit to include county, state or nation the difficulties that present themselves multiply accordingly. The limiting factors in the control of the disease are lack of thoroughly trained men, lack of understanding on the part of the public, and the expense involved. The federal Bureau of Animal Industry has 240 HOG CHOLEKA demonstrated that the disease can be kept down in individual counties, but tlie expense involved was so great as to forbid use of the plan on a large scale. Area work in the eradication of hog chol- era is, we believe, wrong in its conception as long as the virus continually invades the selected terri- tory from without through the three channels that have just been indicated. No successful standardized plan for the control of hog cholera has yet appeared. Killing infected and exposed animals and indemnifying the owners has been tried in England and Canada but results have not been such as to recommend wide applica- tion of the plan. Immunizing all hogs against cholera was once enthusiastically recommended, but we doubt if there can be found to-day an ex- perienced man who considers this method feasible. It would involve the principle of forcing owners to vaccinate, the expense would be prohibitive, and the trained men necessary to carry it out do not exist. In our appraisal of the cooperative forces which can be brought to bear immediately in hog cholera eradication we must include the swine breeder, the practicing veterinarian, the official veterinarian and the serum producer. The breeder should be acquainted with the methods by which hog cholera is spread so as to be able to protect his herd against extraneous CONTROL AND ERADICATION OF HOG CHOLERA 241 infection. He should, with the advice of his veterinarian determine whether his herd is to be maintained immmie to hog cholera, or whether it is to remain susceptible and be kept under obser- vation. In case the former plan is adopted the practice of immunizing should not be allowed to lag, and in case the latter seems advisable he should report promptly any infectious disease that appears. The practicing veterinarian's part consists in snuffing out the outbreaks as fast as they appear, in aiding owners to clean up their herds so that they will not serve to infect others in the vicinity, in doing the vaccinating incident to maintaining immune herds, and in advising his clients relative to methods by which their herds can best be pro- tected. Only when the need for police power ap- pears does the province of the practitioner ter- minate and that of the official veterinarian begin. The official veterinarian's primary duty is to bring pressure to bear on the three principal practices that serve to spread hog cholera from locality to locality. By placing restrictions on the sale of hogs from infected herds and from public stockyards ; by a far more severe interpretation of hog-cholera-like lesions in the administration of meat inspection regulations ; by restricting the use of virus so that only trained men may handle it; and by continued supervision of commercial 242 HOG CHOLEKA serum laboratories the official veterinarian can play an indispensable part in the fight against hog cholera. The serum producer's part is to supply suffi- cient potent serum to immunize all hogs that ac- tually require immunization. Despite notable ex- ceptions it must be said that on the whole the part has been played well, and when breeders, prac- ticing veterinarians and official veterinarians, as classes, meet their obligations as well as the serum producer is meeting his, there will be far less hog cholera in the country. Volumes could be written on the eradication of hog cholera if we were to follow the various rami- fications into which details of the problem lead us. There are the questions of uniform regulations for interstate shipment of swine ; of separate reg- ulations for crated swine; of rules governing the exhibition of hogs at fairs ; and of funds to admin- ister laws and regulations that are already pro- vided. These and many other supplementary problems appear but consideration of them here w^ould only cloud the more important issues. The points we emphasize in closing are that at the present time the obstacles presented in the eradication of hog cholera rest not so much in lack of machinery to do the work as in the manner in which the existing machinery functions; that three well-known wide-open routes for the inter- CONTROL AND ERADICATION OF HOG CHOLERA 243 sectional spread of hog cholera virus still exist and that thej^ must be closed as the first step to- ward substantial progress in eradicating the dis- ease. Only when this is accomplished can we correctly appraise the lesser task that will yet remain. At present the country's attitude toward hog cholera eradication may be likened to that of a farmer who each year sows weed seeds with his grain, and then labors diligently to eradicate the weeds that spring up. Let us stop sowing the seed. References The following references have been selected from the numerous publications on hog cholera because most of them are available to the American veterinarian, and because, as a group, they cover the subject in a fairly complete and satisfactory manner. No attempt has been made to include a complete bibliography. Birch, R. R., **Hog Cholera and Its Prevention," Cor- nell Veterinarian, Hog Cholera Number, May, 1916. Birch, R. R., *' Garbage Feeding and the Care of Gar- bage-fed Swine," Cornell Veterinarian, January, 1918, p. 26. Birch, R. R., "Hog Cholera Transmission Through In- fected Pork," Journal of the Am. Vet. Med. Assn., June, 1917, p. 303. Birch, R. R., "Researches in Regard to Immunizing Young Pigs, ' ' Report of the New York State Veter- inary College at Cornell University, 1918-1919, p. 73. Cahill, E. a., "Hog Cholera Control in the East," Journal of the Am. Vet. Med. Assn., January, 1919, p. 314. 244 HOG CHOLERA Cahill, E. a., ''Relative Potency of Tail-bled and Carotid-bled Anti-hog-cholera Serum," Journal of the Am. Vet. Med. Assn., November, 1919, p. 177. CoNNOWAY, J. W., ' ' Hog Cholera and Immature Corn, ' ' Bulletin No. 74, University of Missouri College of Agriculture. De Schweinitz and Dorset, "A Form of Hog Cholera not Caused by the Hog Cholera Bacillus," Circular No. 41, U. S. Bureau of Animal Industry. DiMOCK, W. W., "Differential Diagnosis of Diseases of the Pig," Journal of the Am. Vet. Med. Assn., Janu- ary, 1919, p. 321. Dorset, Bolton, McBryde, "The Etiology of Hog Cholera," Bulletin No. 72, U.S.Bureau of Animal Industry. Dorset, McBryde, Niles, "Further Experiments Con- cerning the Production of Immunity from Hog Cholera," Bulletin No. 102, U. S. Bureau of Animal Industry. Dorset, M., and Houck, U. G., "Hog Cholera," Farm- ers' Bulletin No. 834, U. S. Department of Agricul- ture. Dorset, M., McBryde, C. N., Niles, W. B., Rietz, J. H., "Studies on H3q3erimmunization against Hog Chol- era," Journal of the Am. Vet. Med. Assn., June, 1919, p. 259. Eichhorn, a., "Present Status of Hog Cholera Con- trol, ' ' J&urnal of the Am. Vet. Med. Assn., October, 1919, p. 51. Prink, W. E., "The Control of Hog Cholera," Cornell Veterinarian, October, 1920, p. 244. HosKiNS, H. Preston, "Notes on the Occurrence of Petechial Hemorrhages in the Larynx and Kidneys in Hog Cholera," Journal of the Am. Vet. Med. Assn., July, 1916, p. 478. Hoskins, H. Preston, "Observations on 2800 Pigs In- oculated with Hog Cholera Virus," Journal of ihe Am. Vet. Med. As^n., September, 1915, p. 817. CONTROL AND ERADICATION OF HOG CHOLERA 245 HoucK, U. G., ''Progress in Hog Cholera Control," Journal of the Am. Vet. Med. Assn., January, 1920, p. 359. Kernkamp, H. C. H., ''The Longevity of the Virus of Hog Cholera," Cornell Veterinarian, January, 1920, p. 1. Kerni^amp, H. C. H., "Results of Experiments to Note the Effects of Freezing on Anti-hog-Cholera Se- rum," Cornell Veterinarian, January, 1918, p. 7. King, W. E., and Hoffman, G. L., "Spiroehifta Suis : Its Significance as a Pathogenic Organism," Journal of Infectious Diseases, Vol. 13, p. 463. King, W. E., Baeslach, F. W., Hoffman, G. L., "Stud- ies on the Virus of Hog Cholera, ' ' Am. Vet. Review, Vol. 44, p. 555. Kinsley, A. T., Swine Practice (Am. Veterinary Pub- lishing Co., Chicago). Lynch, Chas. F., Diseases of Swine (AV. B. Saunders Co., Philadelphia). JMoore, V. A., DiMOCK, W. W., Haring, C. M., Gilli- LAND, S. H., Kinsley, A. T., "Report of the Com- mittee on Diseases," Journal of the Am. Vet. Med. Assn., November, 1915, p. 207. Meyer, "The Filterable Viruses," Am. Vet. Review, Vol. 46, No. 2, p. 132. NiLEs, W. B., "Field Tests with Serum for the Preven- tion of Hog Cholera," Report of the U. S. Bureau of Animal Industry, 1908. NiLES, W. B., RiETZ, J. H., "Immunity of Young Pigs," Journal or the Am. Vet. Med. Assn., May, 1920, p. 176. Palmer, C. B., "The Hog in Relation to Municipal Gar- bage," Journal of the Am. Vet. Med. Assn., 1918, p. 227. Pickens, E. M., Welsh, M. F., Polema, L. J., "The Susceptibility of Young Pigs to Cholera," Journal of the Am. Vet. Med. Assn., October, 1921, p. 22. Records, Edward, ' ' Purification and Concentration of Hog Cholera Serum," Journal of the Am,. Vet. Med. Assn., December, 1919, p. 291. 246 HOG CHOLEKA Stange, C. H., ''Hog Cholera Control," Journal of the Am. Vet Med. Assn., November, 1915, p. 156. Torrance, Frederick, "Garbage Feeding in Relation to the Control of Hog Cholera," Journal of the Am. Vet. Med. Assn., October, 1921, p. 22. APPENDIX B. A. I. Order 265. Issued September 12, 1919. UNITED STATES DEPARTMENT OF AGRICULTURE Bureau of Animal Industry John R. Mohler, Chief of Bureau Regulations Governing the Preparation, Sale, Barter, Exchange, Shipment, and Importation of Viruses, Serums, Toxins, and Analogous Products Intended for Use in the Treatment of Domestic Animals. Effective on and after September 1, 1919 CONTENTS Page. Regulation 1. Definitions 248 Regulation 2. Licenses and inspections 251 Regulation 3. Permits 254 Regulation 4. Suspension or revocation of licenses and permits 256 Regulation 5. Notice to licensees and permittees. . 257 Regulation 6. Assignment of bureau employees. . . 257 Regulation 7. Facilities for inspection 258 Regulation 8. Sanitation 258 Regulation 9. Sterilization 261 Regulation 10. Storage 262 Regulation 11. Records 262 Regulation 12. Labels 263 Regulation 13. Collecting samples 265 Regulation 14. Testing 266 Regulation 15. Retesting 266 247 248 HOG CHOLEKA Page. Regulation 16. Reports 266 Regulation 17. Animals 267 Regulation 18. Hog-cholera virus 274 Regulation 19. Anti-hog-cholera serum 282 Regulation 20. Bacterins, vaccines, toxins, etc. . . . 295 Regulation 21. Admission of viruses, serums, tox- ins, and analogous products 296 The virus-serum-toxin law 296 U. S. Department of Agriculture, Office of the Secretary, Washingto7i, D. C, August 1, 1919. Under authority of the act of Congress approved March 4, 1913, entitled "An act making appropriations for the Department of Agriculture for the fiscal year ending June 30, 1914" (37 Stat., 832), the following regulations are hereby issued for the purpose of en- forcing the provisions of said act governing the prepara- tion, sale, barter, exchange, shipment, and importation of viruses, serums, toxins, and analogous products in- tended for use in the treatment of domestic animals. These regulations, which for the purpose of identification are designated as B. A. I. Order 265, shall become and be effective on and after September 1, 1919, except that stocks of approved labels on hand may be used until December 31, 1920. D. F. Houston, Secretary of Agriculture. EEGULATION 1. — DEFINITIONS Section 1. Paragraph 1. For the purpose of these regulations the following Avords, phrases, names, and terms shall be construed respectively to mean : Paragraph 2. The virus-serum-toxin act of 1913 : *' An act making appropriations for the Department of Agri- APPENDIX 249 culture for the fiscal year ending June 30, 1914," ap- proved March 4, 1913 (37 Stat., 832). Paragraph 3. Viruses, serums, toxins, and analogous products or veterinary biologies: All viruses, serums, toxins, and analogous products, such as antitoxins, vac- cines, tuberculins, malleins, microorganisms, killed micro- organisms, and products of microorganisms which are intended for use in the treatment of domestic ani- mals. Paragraph 4. The department : The United States De- partment of Agriculture. Paragraph 5. The bureau : The Bureau of Animal In- dustry of the IJnited States Department of Agriculture. Paragraph 6. Bureau employee : Any officer, agent, or other individual employed in the Bureau of Animal Industry, who is authorized by the chief of the bureau to do any work or perform any duty in connection with the execution of the provisions of the virus-serum-toxin act of 1913. Paragraph 7. Veterinary inspector: A veterinary in- spector of the Bureau of Animal Industry. Paragraph 8. Licensed establishment : Any establish- ment owned or operated by a person, firm, or corporation holding an unexpired, unsuspended, and unrevoked li- cense issued by the Secretary of Agriculture for the preparation of any virus, serum, toxin, or analogous product. Paragraph 9. Official station: One or more licensed establishments included under a single supervision. Paragraph 10. Inspector in charge : An inspector as- signed to supervise and perform official work at an offi- cial station and who reports directly to the chief of the bureau. Paragraph 11. Person: Natural persons, individuals, firms, partnerships, corporations, companies, societies, and associations and every agent, officer, or employee 250 HOG CHOLERA thereof. This term shall import both the plural and the singular, as the case may be. Paragraph 12. Hog-cholera virus: The clear serum, plasma, or defibrinated blood, derived from hogs sick of hog cholera and free from other communicable disease or diseases. Paragraph 13. Hyperimmunizing virus : Hog-cholera virus prepared for hyperimmunizing hogs which are im- mune to the disease hog cholera. Paragraph 14. Simultaneous virus : Hog-cholera virus prepared for inoculating hogs which are to be injected simultaneously with anti-hog-cholera serum for the im- munization of those animals against the disease hog cholera. Paragraph 15. Anti-hog-cholera serum : The clear serum, plasma, or defibrinated blood, or derivatives there- of, containing the protective principles derived from im- mune hogs which have been hyper-immunized by an in- travenous injection of at least 5 cubic centimeters, per pound body weight, of the virus of hog cholera. Paragraph 16. Immediate or true container: The unit, bottle, vial, ampule, tube, or other receptacle or con- tainer in which any virus, serum, toxin, or analogous product is customarily sold or distributed. Paragraph 17. Serial number : The number given each batch of virus, serum, toxin, or analogous product to identify the said virus, serum, toxin, or analogous prod- uct with the records of preparation thereof. Paragraph 18. Return date: The date placed upon trade labels affixed to or used in connection with imme- diate or true containers of viruses, serums, toxins, and analogous products by producers to indicate the limit of time during which the said products may be expected to retain their full strength or potency. Paragraph 19. U. S. Released: That veterinary bi- ologies so marked have been prepared and tested in ac- APPENDIX 251 cordance with the provisions of these regulations and that when thus prepared, tested, and marked, they were not worthless, contaminated, dangerous, or harmful. REGULATION 2. — LICENSES AND INSPECTIONS Section 1. Every establishment in the United States at which any virus, serum, toxin, or analogous product is prepared for sale, barter, or exchange in the District of Columbia or in any Territory of or place under the jurisdiction of the United States, or for shipment or de- livery for shipment from any State or Territory or the District of Columbia to any other State or Territory or the District of Columbia, shall hold an unexpired, unsus- pended, and unrevoked license, issued by the Secretary of Agriculture, and shall have inspection under these regulations. Section 2. All viruses, serums, toxins, and analogous products produced at licensed establishments shall be prepared, handled, stored, marked, received for trans- portation, and transported as required by these regula- tions. Section 3. Paragraph 1. The proprietor or operator of each establishment of the kind specified in section 1 of this regulation shall make application in writing to the Secretary of Agriculture for a license. When one proprietor conducts more than one establishment, a sep- arate application- shall be made for a license for each establishment. Blank forms of application will be fur- nished upon request addressed to the Bureau of Animal Industry, Washington, D. C. Paragraph 2. Triplicate copies of plans, properly drawn to scale, and of specifications, including plumbing and drainage of establishments, together with triplicate copies of all labels and advertising matter to be used in connection with or relating to all viruses, serums, toxins, and analogous products prepared therein, shall accompany the application for a license, unless these 252 HOG CHOLEKA plans, specifications, labels, and advertising matter have already been approved in writing by the bureau. Paragraph 3. In case of change in ownership or loca- tion while an application is pending, or after a license has been issued, a new application shall be made. Section 4. Paragraph 1. A license will not be issued unless the condition of the establishment and the methods of preparation are such as reasonably to insure that the product will accomplish the object for which it is in- tended and that such product is not worthless, contamin- ated, dangerous, or harmful. Paragraph 2. A license will not be issued unless and until the establishment is prepared to operate under the direct supervision of a competent person trained in bacteriological technique and in the preparation of viruses, serums, toxins, or analogous products named in the application. Paragraph 3. A license will not be issued for the preparation of any virus, serum, toxin, or analogous product if advertised so as to mislead or deceive the pur- chaser, or if the package or container in which the same is intended to be sold, bartered, exchanged, or shipped bears or contains any statement, design, or device which is false or misleading in any particular. Section 5. Paragraph 1. A license will be issued only after inspection of the establishment by a bureau employee has shown that the condition and equipment of the establishment and the methods of preparing, han- dling, and storing are in conformity with these regula- tions. Paragraph 2. Licenses shall be numbered and shall be in the following form : United States Veterinary License No Washington, D. C, 19 . . This is to certify that, pursuant to the terms of the act of Congress approved March 4, 1913 (37 Stat., 832), APPENDIX 253 governing the preparation, sale, barter, exchange, ship- ment, and importation of virnses, serums, toxins, and analogous products intended for use in the treatment of domestic animals, is hereby licensed to maintain at Street, city or town of , State of , an establishment for the preparation of during the calendar year 19. . .. This license is subject to suspension or revocation if the licensee violates or fails to comply with any provision of said act approved March 4, 1913, or of the regulations made thereunder. Secretary of Agriculture. Countersigned : Chief, Bureau of Animal Industry. Two or more licenses may bear the same number when they are issued to firms under the same ownership or control, provided a serial letter is added when necessary, to identify each license. Paragraph 3. Each license shall teminate at the end of the calendar year for which it is issued. Section 6. Paragraph 1. No viruses, serums, toxins, or analogous products shall be prepared in whole or in part in a licensed establishment by any other licensed establishment unless authorized in advance by the chief of bureau. Paragraph 2. Each licensed establishment shall be separate and distinct from any unlicensed establishment in which any virus, serum, toxin, or analogous product is prepared or handled. Paragraph 3. When a license is issued the bureau shall inform the proprietor or operator of the establish- ment of the requirements of these regulations. If the establishment at the time the license is issued contains any viruses, serums, toxins, or analogous products, which 254 HOG CHOLERA have not theretofore been prepared, and of which the containers have not been theretofore marked, in com- pliance with these regulations, the identity of the same shall be maintained and they shall not be shipped or delivered for shipment from any State or Territory or the District of Columbia to any other State or Terri- tory or the District of Columbia, or otherwise dealt with as products prepared under these regulations. The es- tablishment shall adopt and enforce all necessary meas- ures, and shall comply with all such directions as the chief of bureau may prescribe for carrying out the pur- poses of this paragraph. REGULATION 3. — ^PERMITS Section 1. Each importer of viruses, serums, toxins, or analogous products shall hold an unexpired, unsus- pended, and unrevoked permit issued by the Secretary of Agriculture. Section 2. Paragraph 1. Each importer of viruses, serums, toxins, and analogous products shall make appli- cation in writing to the Secretary of Agriculture for a permit. The application shall specify the port or ports of entry at which the imported articles will be cleared through the customs. Blank forms of application will be furnished upon request addressed to the Bureau of Animal Industry, Washington, D. C. Paragraph 2. Each application for a permit shall be accompanied by the affidavit of the actual manufacturer produced before an American consular officer, giving the city or town where the viruses, serums, toxins, or analogous products mentioned therein are prepared, and stating that said products are not worthless, contami- nated, dangerous, or harmful, whether the products were derived from animals, and if so derived, that such ani- mals had not been exposed to any infectious or conta- gious disease, except as may have been essential in the APPENDIX 255 preparation of the products and as specified in the affi- davit. Paragraph 3. Each application for a permit shall be accompanied by the written consent of the actual manu- facturer that properly accredited employees of the de- partment shall have the privilege of inspecting, without previous notification, all parts of the establishment at which such viruses, serums, toxins, or analogous prod- ucts are prepared, and all processes of and all records kept relative to the preparation of such products at such times as may be demanded by the aforesaid em- ployees. Paragraph 4. Each application for permit shall be accompanied by triplicate copies of all labels and adver- tising matter. Section 3. A permit will not be issued for the impor- tation of any viruses, serums, toxins, or analogous prod- ucts if advertised so as to mislead or deceive the pur- chaser, or if the package or container in which the same is intended to be sold, bartered, exchanged, shipped, or imported, bears or contains any statement, design, or device which is false or misleading in any particular. Section 4. Paragraph 1. Permits shall be numbered and shall be in the following form : United States Veterinary Permit No Washington, D. C, , 19 . . . This is to certify that, pursuant to the terms of the act of Congress approved March 4, 1913 (37 Stat., 832), governing the preparation, sale, barter, exchange, ship- ment, and importation of viruses, serums, toxins, and analogous products intended for use in the treatment of domestic animals, , of , State of , is hereby authorized, so far as the jurisdiction of the Department of Agriculture is concerned, to import manufactured by , of , into the United States through the port 256 HOG CHOLERA of during the calendar year 19.... This permit is subject to suspension or revocation if the permittee violates or fails to comply with the pro- visions of the said act approved March 4, 1913, or of the regulations made thereunder. Secretary of Agriculture. Countersigned : Chief, Bureau of Animal Industry. Paragraph 2. Each permit shall terminate at the end of the calendar year for which it is issued. REGULATION 4. — SUSPENSION OR REVOCATION OF LICENSES AND PERMITS Section 1. Licenses or permits may be suspended or revoked after opportunity for hearing has been accorded the licensee or permittee if it appears — (1) That the construction of the establishment in which the viruses, serums, toxins, or analogous products are prepared is defective, or that the establishment is improperl}^ conducted ; (2) That the methods of preparation are faulty, or that the said products contain impurities or lack po- tency ; (3) That the products are labeled so as to mislead or deceive the purchaser in any particular; (4) That the license or permit is used to facilitate or effect the preparation, sale, barter, exchange, shipment, or importation of any worthless, contaminated, danger- ous, or harmful viruses, serums, toxins, or analogous products; or (5) That the licensee or permittee has violated or failed to comply wdtli any provision of the virus-serum- toxin act of 1913, or of the rules and regulations made thereunder. APPENDIX 257 Section 2. All hearings shall be private and at times and places designated by the Secretary of Agriculture. The parties interested may appear in person or by at- torney, and may submit oral or written evidence on the questions involved. Upon request and by paying the cost, the person involved will be furnished with a copy of the transcript of the hearing. REGULATION 5. — NOTICE TO LICENSEES AND PERMITTEES Section 1. If at any time it appears that the prepa- ration, sale, barter, exchange, shipment, or importation of any virus, serum, toxin, or analogous product by any person holding a license or permit may be dangerous in the treatment of domestic animals, the Secretary of Agriculture will so notify the licensee or permittee, and unless and until the Secretary of Agriculture shall oth- erwise direct, no person, so notified, shall thereafter pre- pare, sell, barter, or exchange, nor shall thereafter ship, offer for shipment, or import any of such product. regulation 6. ASSIGNMENT OF BUREAU EMPLOYEES Section 1. Any bureau employee, as defined in these regulations, shall be permitted to enter any establish- ment licensed under these regulations at any hour dur- ing the daytime or nighttime ; and such bureau employee shall be permitted to inspect without previous notifica- tion the entire premises of the establishment, including all buildings, compartments, and other places, and all equipment such as chemicals, instruments, apparatus, and the like, as well as the methods used in the manu- facture of, and all records maintained relative to viruses, serums, toxins, or analogous products. Section 2. Each bureau employee, as defined in these regulations, will be furnished with a numbered official badge, which he shall not allow to leave his possession. This badge shall be sufficient identification to entitle him 258 HOG CHOLERA to admittance at all regular entrances and to all parts of the licensed establishment and premises and to any place at any time for the purpose of making an inspection pursuant to section 1 of this regulation. REGULATION 7. FACILITIES FOR INSPECTION Section 1. When required by the chief of bureau or the inspector in charge, the following facilities, and such others as may be essential to efficient conduct of inspec- tion, shall be furnished by each licensed establishment: {a) Satisfactory pens, equipment, and assistance for conducting tests required in accordance with these regu- lations. (&) Suitable rooms, compartments, or receptacles in such number and places as may be necessary for holding any viruses, serums, toxins, or analogous products for treatment or testing required in accordance with these regulations. Such rooms, compartments, or receptacles shall be equipped for secure locking and shall be held under locks furnished by the department, and the keys of such locks shall not leave the custody of bureau em- ployees. REGULATION 8. — SANITATION Section 1. Paragraph 1. Triplicate copies of plans properly drawn to scale, and of specifications, including plumbing and drainage, for remodeling plants of licensed establishments and for new structures, should be sub- mitted to the chief of bureau in advance of construction. Paragraph 2. Stables or other premises for animals used in the production or testing of viruses, serums, tox- in^, or analogous products shall be properly ventilated and lighted, appropriately drained and guttered, and kept in good sanitary condition. Paragraph 3. Animals infected with or exposed to any infectious, contagious, or communicable disease shall be properly segregated. APPENDIX 259 Paragraph 4. Licensed establishments shall be so lo- cated as to avoid the spread of disease, and suitable arrangements shall be made for the disposal of all refuse. Paragraph 5. Direct communication to licensed es- tablishments shall not be maintained from public stock- yards, abattoir pens, or other places in which animals are received or held for any purpose. Paragraph 6. All viruses, serums, toxins, and analo- gous products shall be prepared, handled, and distrib- uted with due sanitary precautions, and all viruses, serums, toxins, or analogous products shipped or deliv- ered for shipment shall be securely packed. Section 2. Paragraph 1. The floors, walls, ceilings, partitions, posts, doors, and all other parts of all struc- tures at licensed establishments shall be of such material, construction, and finish as can be readily and thoroughly cleaned. Paragraph 2. Separate rooms or compartments shall be provided for preparing, handling, and storing viru- lent or attenuated micro-organisms or toxins. Paragraph 3. All rooms and compartments shall have abundant light and sufficient ventilation to insure sani- tary and hygienic conditions. Section 3. Paragraph 1. Each licensed establish- ment shall have dressing rooms and toilet rooms and urinals sufficient in number, ample in size, conveniently located, properly ventilated, and meeting all require- ments as to sanitary construction and equipment. These shall be separate from rooms and compartments in which any viruses, serums, toxins, or analogous products are prepared, handled, or stored. Paragraph 2. Each licensed establishment shall have modern lavatory accommodations, including running hot and cold water, soap, towels, and the like. These shall be located at such places in establishments as may be 260 HOG CHOLERA essential to assure cleanliness of all persons handling viruses, serums, toxins, or analogous products. Section 4. There shall be an efficient drainage and plumbing system for the establishment and premises, and all drains and gutters shall be properly installed with approved traps and vents. Section 5. The water supply, both hot and cold, shall be ample and clean. Adequate facilities shall be pro- vided for the distribution of water in each establish- ment and for the washing of all equipment, containers, machinery, instruments, other apparatus, and animals used in the preparation, handling, or storing of any viruses, serums, toxins, or analogous products. Section 6. All equipment, containers, instruments, and other apparatus used in the preparation, handling, or storing of any virus, serum, toxin, or analogous prod- uct shall be of such material, construction, and design as can be readily and thoroughly cleaned and sterilized, and such equipment, containers, instruments, and other apparatus shall be handled so as to insure freedom from contamination. Equipment, containers, instruments, and other apparatus used for preparing, handling, or stor- ing virulent or attenuated micro-organisms or toxins shall not be used for handling, preparing, Or storing other forms of biological products. Section 7. All emploj^ees of the establishment who handle viruses, serums, toxins, or analogous products shall keep their hands and clothing clean. The hands of such employees shall not come into contact with any viruses, serums, toxins, or analogous products, or with any part of the equipment, containers, instruments, or other apparatus, which after sterilization may come into contact with any such products. Section 8. Caps, gowns, and other outer clothing worn by persons while handling any viruses, serums, toxins, or analogous products, or by those who enter APPENDIX 261 any room, compartment, or place where any such prod- ucts are being handled, shall be of clean, white material whenever practicable. Section 9. The outer premises of every licensed es- tablishment, embracing docks, driveways, approaches, yards, pens, chutes, and alleys, shall be properly drained and kept in a clean and orderly condition. The accumu- lation on the premises of an establishment of any ma- terial in which flies may breed is forbidden. No nuisance shall be allowed in any licensed establishment or on its premises. Section 10. Every practicable precaution shall be taken to keep establishments free of flies, rats, mice, and other vermin. Section 11. All parts of the carcasses of animals pro- ducing viruses, all dead animals, all refuse, and all worthless, contaminated, dangerous, or harmful viruses, serums, toxins, or analogous products, shall be inciner- ated or otherwise destroyed by establishments in accord- ance with methods approved by the chief bureau. Section 12. All rooms, compartments, and other places used for preparing, handling, or storing viruses, serums, toxins, or analogous products shall be kept clean and sanitary, and all equipment, containers, instruments, and other apparatus used in joreparing, handling, or storing any such products shall be thoroughly cleaned and sterilized before use. Section 13. Smoking or expectorating in any room, compartment, or place in which viruses, toxins, or analo- gous products are prepared, handled, or stored is pro- hibited. regulation 9. — sterilization Section 1. Paragraph 1. All equipment, containers, instruments, and other apparatus, before being used in preparing, handling, or storing viruses, serums, toxins, or other analogous products, except as prescribed in the 262 HOG CHOLERA following paragraph, shall be thoroughly sterilized by live steam at a temperature of at least 120° C. for not less than one-half hour, or, by dry heat at a temperature of at least 160° C. for not less than one hour. If for any reason such methods of sterilization are impracticable, then a process known to be equally efficacious in de- stroying microorganisms and their spores may be sub- stituted after approval by the chief of bureau. Paragraph 2. Instruments used in connection with the bleeding of virus pigs and hyperimmune hogs, and other like equipment, of establishments manufacturing hog-cholera virus and anti-hog-cholera serum, which are found to be damaged by exposure to the degree of heat prescribed in the preceding paragraph, after having been thoroughly cleaned, may be sterilized by boiling for not less than 15 minutes, provided apparatus, satisfactory to the inspector in charge, is furnished for this purpose. REGULATION 10. — STORAGE Section 1. Viruses, serums, toxins, and analogous products which may be injuriously affected by exposure to light or to high temperature shall be stored in a dark, cold chamber or refrigerator at a temperature of not to exceed 55° F. All dealers in the District of Columbia or any Territory or in any place under the jurisdiction of the United States shall keep such products protected from light and under refrigeration until sold or other- wise disposed of. REGULATION 11. — RECORDS Section 1. Paragraph 1. Permanent detailed rec- ords of the sources, of the preparation, of tests for purity and potencj^, and of methods of preservation, of each batch of virus, serum, toxin, and analogous products shall be kept by each licensed establishment and by each APPENDIX 263 manufacturer producing such products for importation into the United States. Paragraph 2. Permanent detailed records, in a form satisfactory to the chief of bureau, shall be maintained by each licensed establishment and by each importer, showing the sale, shipment, or other disposition of the viruses, serums, toxins, and analogous products handled. REGULATION 12. — LABELS Section 1. Paragraph 1. Each immediate or true container of viruses, serums, toxins, or analogous prod- ucts, prepared for sale, barter, exchange, or shipment, by any licensed establishment, or imported into the United States, shall bear a trade label as hereinafter de- scribed. Paragraph 2. No container of virus, serum, toxin, or analogous product shall bear a trade label unless and until the product contained therein shall have been pre- pared in compliance with these regulations and found not to be worthless, contaminated, dangerous, or harm- ful. Paragraph 3. No person shall apply or affix, or cause to be applied or affixed, any trade label, stamp, or mark, to any container of hog-cholera virus, or anti-hog- cholera serum, prepared or received in a licensed estab- lishment except in compliance with these regulations. Suitable tags or labels of a distinct design should be used for identifying all biologies while in course of preparation. Section 2. Paragraph 1. Trade labels shall bear the true name of the product contained in the package, the name and address of the manufacturer except as other- wise provided in paragraph 7 of this section, and the license or permit number assigned by the department. The license number and permit number shall be shown in either of the following forms, respectively: "U. S. 264 HOG CHOLEEA Veterinary License No. ," or ''U. S. Vet. License No. ," and ''U. S. Veterinary Permit No. ," or ''U. S. Vet. Permit No. ." Such labels shall bear all other information required by the chief of bureau and may also bear any other statement not false or mislead- ing and which has been approved by the bureau. Paragraph 2. Each trade label shall bear a serial number, affixed by the manufacturer, by which the prod- uct can be identified with the records of preparation. Paragraph 3. Each trade label shall bear a return date affijxed before the product is removed from the establishment. The date shown shall be a date after which the manufacturer does not guarantee the product to be of full strength or potency. Paragraph 4. All trade labels affixed to or used in connection with each immediate or true container shall bear a dosage table and full instructions governing the use of the product. Paragraph 5. Trade labels affixed to the immediate or true containers of viruses and products prepared from attenuated organisms shall bear, in addition to the statements required by the preceding paragraphs of this section, the following, prominently placed and lettered: ''Caution — Burn this Container and all Unused Contents. ' ' Paragraph 6. When any virus, serum, toxin, or analo- gous product is prepared by a licensed establishment or imported for a person other than the one to whom a license or permit has been issued and the name and ad- dress of the distributor as well as that of the manufac- turer is to appear on the label of the container thereof, a statement shall be made on the label to the effect that the virus, serum, toxin, or analogous product is dis- tributed by such person. The term, ''Distributer/' "Distributers," "Distributed by," or other equivalent terms may be used, if prominently ^placed and lettered APPENDIX 265 in connection with the name and address of the distrib- uting person, provided the same are not used so as to be either false or misleading. Paragraph 7. The name and address of the manufac- turer may be omitted from trade labels when any virus, serum, toxin, or analogous product is to be distributed by a person other than the manufacturer, provided the name and address of the distributor appears on such trade labels in immediate connection with a statement showing the license under which the product was manu- factured. This statement, together with the name and address of the distributor, shall appear in letters of uni- form size and character, and be in the following form: ''Produced under U. S. Veterinary License No, — — . Distributed by (name and address of distributor)." Paragraph 8. Copies of all trade labels before use shall be submitted to the bureau for examination and approval. These labels shall be submitted in triplicate, quadruplicate, or quintuplicate, as may be indicated. Triplicate copies of new trade labels in the form of sketches, proofs, or photographic copies should be sub- mitted, through the inspector in charge, to the bureau for approval. REGULATION 13. — COLLECTING SAMPLES Section 1. Paragraph 1. Samples of viruses, serums, toxins, and analogous products* shall be collected by au- thorized officers, agents, or employees of the department. Paragraph 2. Samples may be purchased in the open market and the marks, brands, or tags upon the package or wrapper thereof shall be noted. The collector shall note the names of the vendor and agent of the vendor who made the sale, together with the date of purchase. The collector shall purchase representative samples. Paragraph 3. All samples or parts of samples shall be sealed by the collector and marked with identifying marks. 266 HlOG CHOLEKA REGULATION 14. — TESTING Section 1. Except as otherwise provided in these regulations, all viruses, serums, toxins, and analogous products shall be prepared, handled, stored, marked, treated, and tested by licensed establishments in accord- ance with methods prescribed by the Chief of the Bu- reau of Animal Industry. regulation 15. — retesting Section 1. Viruses, serums, toxins, and analogous products, the containers of which bear United States veterinary license numbers or United States veterinary permit numbers, or any other mark required by these regulations, shall be subject to inspection at any time or place. If it appears as a result of such inspection that any such product, even though prepared in a licensed establishment or imported under permit issued by the Secretary, is worthless, contaminated, dangerous, or harmful, the Secretary shall give notice thereof to the manufacturer or importer and to any jobbers, dealers, or other persons known to have any of such product in their possession. Unless and until the Secretary shall otherwise direct, no person so notified shall thereafter sell, barter, or exchange in any place under the jurisdic- tion of the United States nor shall thereafter ship or deliver for shipment from any States, Territory, or the District of Columbia to any other State, Territory, or the District of Columbia, any of such product. regulation 16. — REPORTS Section 1. Paragraph 1. Reports of the work of in- spection carried on in every licensed establishment shall be forwarded to the bureau by the inspector in charge in such form and manner as may be specified by the chief of bureau. APPENDIX 267 Paragraph 2. Each licensed establishment shall fur- nish to the bureau employees accurate information as to all matters needed by them for making their reports pursuant to paragraph 1 of this section. REGULATION 17. — ANIMALS Section 1. Paragraph 1. Licensed establishments which procure animals from public stockyards, abattoir pens, or similar places shall afford opportunity for all hogs, cattle, sheep, and goats admitted to the premises of such establishments to range in contact with other animals as prescribed in section 3 of this regulation. Paragi^aph 2. Cattle, sheep, and goats from whatever source, except calves procured under the provisions of section 5 of this regulation and used for testing hog- cholera virus to determine its freedom from foot-and- mouth disease, admitted to the premises of licensed es- tablishments shall be afforded opportunity to range in contact with other animals as prescribed in section 3 of this regulation. Section 2. Paragraph 1. Licensed establishments shall provide suitable pens to be known as '^Receiving pens" through which all hogs, cattle, sheep, and goats shall pass in accordance with the provisions of this regulation before they shall be admitted to any other part of the premises. Paragraph 2. Licensed establishments shall provide healthy calves in thrifty condition and ranging from 3 to 12 months of age for use as contact animals in re- ceiving pens. They shall be referred to as ^'contact calves." Paragraph 3. Each contact calf shall have the left ear thereof pierced with a hole not less than % inch in diameter and to the right ear of each animal shall be attached a serially numbered metal tag. Section 3. Paragraph 1. All hogs susceptible to hog 268 HOG CHOLEKA i cholera which are admitted to the premises of licensed establishments under the provisions of section 1, para- graph 1, of this regulation shall be held in receiving pens for at least 24 hours after admission to the premises and during this time they shall be allowed free range and contact with not less than 4 contact calves for each lot of 200 hogs or less in the receiving pens. Paragraph 2. Hogs which are immune to hog cholera, admitted to the premises of licensed establishments un- der the provisions of section 1, paragraph 1, of this regulation, shall be held in receiving pens with contact calves as prescribed in the preceding paragraph for at least 48 hours. Paragraph 3. All animals covered by section 1, of this regulation, except hogs, shall be held in receiving pens for at least 48 hours as prescribed in paragraph 1, of this section, except that not less than two contact calves shall be used for each lot of 20 animals or less in the same pen. Section 4. Paragraph 1. All surviving contact calves shall be held in the receiving pens of licensed establish- ments for at least one month and not to exceed four months from date of admission to receiving pens as contact calves. Paragraph 2. Kemoval of contact calves from receiv- ing pens shall be so arranged that a rotation will be es- tablished whereby one of the animals will be replaced at intervals of one month and the entire group replaced every four months or less. Paragraph 3. Removal of contact calves from receiv- ing pens shall be accomplished so that the animals last furnished for the purpose may be used for the maximum time permitted by the preceding paragraphs of this section. No contact calf shall be used as such more than once. Paragraph 4. Contact calves shall be carefully ob- APPENDIX 269 served by a veterinary inspector as frequently as may be necessary to detect evidence of disease. Section 5. Establishments licensed to prepare anti- hog-cholera serum or hog-cholera virus which do not procure animals from public stockyards, abattoir pens, or similar places, shall furnish a properly executed cer- tificate according to the following form covering each lot or shipment of animals offered for admission to the premises thereof. These certificates shall be signed by an authorized representative of the licensed establish- ment. ,19--. This is to certify that , / Calves [ '^^i^^^ ^^^ offered for admission to the estab- lishment of the Company, are from the farm or premises of , in the State of , county of , town- ship of , and to the best of our knowledge and belief were on said farm or premises at least 21 days prior to this date, and were not exposed to any infectious, contagious, or communicable disease, and no new stock was brought on to the said farm or premises during that time. The said animals have not been in or transported through any public stockyards, abattoir pens, or similar places, nor have they been exposed to any infectious, contagious, or communicable disease since their removal from said farm or premises. (Signed) Co., Per Section 6. Paragraph 1. All animals presented for admission to the premises of establishments licensed to prepare hog-cholera virus or anti-hog-cholera serum shall be examined by a veterinary inspector as soon as prac- ticable after they are received and before their re- moval from the receiving pens in order to determine 270 HOG CHOLEEA their physical condition. No animal shall be removed from receiving pens without examination by and the permission of a veterinary inspector. Paragraph 2. After examination, if the animals are permitted to remain upon the premises and to gain en- trance to the holding pens of the establishment, they shall be given serially numbered metal tags, either prior to or at the time of inoculation or hyperimmunization. Paragraph 3. All tags used for the identification of animals shall be attached to the ears of the animals in a manner satisfactory to the inspector in charge. The tags so attached shall be the means of assisting in identi- fying the animals so long as they remain on the premises. Paragraph 4. All tags which are used to identify ani- mals shall be furnished and attached by the licensed establishment, and when said tags are not in actual use they shall at all times be held in the custody of a bureau employee. Paragraph 5. When practicable, the left ear of each animal used in testing the purity and potency of viruses, serums, toxins, and analogous products shall be pierced with a hole not less than three-fourths of an inch in diameter. Animals bearing marks of the above-de- scribed character shall not be used more than once by licensed establishments in testing the purity and po- tency of any virus, serum, toxin, or analogous product. Furthermore, animals Avith the left ear removed or mutilated so as to prevent the detection of this identi- fying mark shall not be used in any test. Section 7. Animals used in the production or testing of viruses, serums, toxins, or analogous products shall not be treated with biological products other than those which are incidental to the preparation and testing of the products prepared from or tested upon said animals, except with the approval of and in such manner as may be prescribed by the chief of bureau. APPENDIX 271 Section 8. Paragraph 1. If for any reason hyper- immune hogs are practically the only animals held upon the premises of a licensed establishment, they shall be caused to range in contact with calves in the manner prescribed in section 3 of this regulation for a period of at least 10 days prior to their being subjected to carotid or final bleeding. Paragraph 2. All animals with which hyperimmune hogs have been held in contact as prescribed in this sec- tion, shall be held on the premises of the licensed estab- lishment and under the observation of a bureau employee for at least two weeks after the hyperimmune hogs have been destroyed. Paragraph 3. All hyperimmune hogs which are sub- jected to the tail-bleeding process only, shall be held under the supervision of a bureau employee for at least two weeks after the last tail bleeding has been col- lected. Section 9. Paragraph 1. Establishments licensed to prepare hog-cholera virus and anti-hog-cholera serum shall not remove either hogs or calves from the premises of the establishment without written permission obtained in advance from the inspector in charge. Paragraph 2. Permission for the removal of hogs or calves from the premises of licensed establishments for the purpose of immediate slaughter shall be given by the inspector in charge under the following conditions : {a) Wlien such animals are found not to be affected with any disease or condition that may render them in whole or in part unfit for food purposes. (Z>) When such animals are found to be affected with any disease or condition which maj^ render them unfit for food purposes in whole or in part, provided said animals are slaughtered at an establishment where Fed- eral meat inspection is maintained, and provided fur- ther, that the inspector in charge of meat inspection 272 HOG CHOLERA where said animals are to be slaughtered is given due notice thereof. Paragraph 3. Permission for the removal of hogs or calves from the premises of licensed establishments for purposes other than immediate slaughter shall be given by the inspector in charge under the following condi- tions: {a) Calves may be removed if found to be free from any infectious, contagious, or communicable disease, provided the feet and legs of calves used for testing hog-cholera virus or anti-hog-cholera serum are cleaned and disinfected with a 2 per cent aqueous solution of cresol compound, U. S. P., or a permitted substitute therefor and the animals held in noninfectious pens on the premises of the establishment for at least three hours before being loaded for transportation. (&) Hogs which survive inoculation and exposure for the production of hog-cholera virus, surviving controls from tests of anti-hog-cholera serum, and surviving hogs which have been used for testing hog-cholera virus may be removed from the premises of the establishment not sooner than 15 days subsequent to the day of inocula- tion and exposure, provided they are healthy. It is required, however, that all such hogs before their re- moval from the premises be given the serum-alone treat- ment as prescribed under {a) of paragraph 4 of this section. Hyperimmune hogs and pigs used for testing the purity and potency of anti-hog-cholera serum may be removed from the premises of licensed establishments 21 days subsequent to the day of hyperimmunization or inoculation, provided they exhibit no symptoms of any infectious, contagious, or communicable disease and pro- vided further that they are first disinfected as provided in paragraph 4 of this section. Other hogs shall be removed from the premises of the establishment only after treatment and disinfection as provided in para- APPENDIX 273 graph 4 of this section, except that such hogs need not be held 21 days when treated with serum and virus which have been released for marketing. Paragraph 4. Hogs which require treatment as pro- vided under (&) in paragraph 3 of this section shall be treated and disinfected as follows: {a) Serum-alone method. — The serum used shall have been prepared and released for marketing at an estab- lishment holding a license from the Secretary of Agri- culture and the dose employed shall conform to that re- quired in paragraph 1, section 6, or paragraph 3, sec- tion 10 of Regulation 19. After receiving this treatment they shall be disinfected by dipping in a 2 per cent aqueous solution of cresol compound, U. S. P., or a per- mitted substitute therefor, except when prevailing low temperatures make it impracticable, and be held in non- infectious pens for at least 3 hours before being loaded for transportation. (&) Simiiltaneous-inoculation method. — The serum and virus used shall have been prepared at an establish- ment holding a license from the Secretary of Agriculture and the doses shall be not less than those required in paragraph 1, section 6, or paragraph 3, section 10 of Regulation 19. After receiving this treatment they shall be held under the supervision of a bureau employee for a period of at least 21 days, except when treated with virus and serum released for marketing. If no symp- toms of hog cholera or other infectious, contagious, or communicable disease are exhibited by the animals, they shall be disinfected by dipping in a 2 per cent aqueous solution of cresol compound, U. S. P., or a permitted substitute therefor, except when prevailing low tempera- tures make it impracticable, and held in noninfectious pens for a period of at least 3 hours before being loaded for transportation. Section 10. Except as otherwise provided in these 274 HOG CHOLERA regulations, all animals used by licensed establishments in the preparation or testing of veterinary biologies shall meet such requirements as may be prescribed by the Chief of the Bureau of Animal Industry and deemed by him necessary to prevent the preparation and sale of any worthless, contaminated, dangerous, or harmful viruses, serums, toxins, or analogous products. Section 11. Each licensed establishment shall adopt such measures as the chief of bureau shall from time to time prescribe for carrying out the provisions of this regulation. REGULATION 18. — HOG-CHOLERA VIRUS Section 1. Paragraph 1. All operations incident to the production of hog-cholera virus shall be conducted under the supervision of a bureau employee. Each licensed establishment shall notif}^ the inspector in charge or his assistant a reasonable time in advance when any operations are to be conducted. Paragraph 2. Pigs which are used in the production of hog-cholera virus shall be healthy and the tempera- ture of each animal shall be accurately taken and per- manently recorded by the establishment immediately be- fore inoculation when in the opinion of the inspector in charge this is necessary to determine the health of the animals. Each animal shall be subjected to a careful examination by a veterinary inspector immediately prior to inoculation. Paragraph 3. Temperatures of all pigs used to pro- duce hog-cholera virus shall be correctly taken and re- corded by licensed establishments each day subsequent to the fifth day after inoculation and at such other times as the inspector in charge may deem necessary. The temperature of each pig invariably shall be taken and recorded on each day the animal is found to be visibly sick. APPENDIX 275 Paragraph 4. Pigs which have been inoculated for the production of hog-cholera virus shall be killed for this purpose only after a veterinary inspector has ob- served well-marked symptoms of hog cholera. Paragraph 5. All pigs from which hog-cholera virus is derived shall be subjected to a post-mortem examina- tion by a veterinary inspector. Paragraph 6. Hog-cholera virus derived from pigs which become visibly sick within three days after the time they are admitted to the premises of licensed estab- lishments shall be destroyed as provided in section 11, Regulation 8, under the supervision of a bureau em- ployee. Paragraph 7. Hog-cholera virus derived from pigs which upon post-mortem examination do not show le- sions of acute hog cholera or which are found to be so affected with any infectious, contagious, or communi- cable disease or in such condition as to render the virus contaminated, shall be destroyed as provided in section 11, Regulation 8, under the supervision of a bureau employee. A diagnosis of hog cholera will not be made unless macroscopic lesions of the disease are found in two or more organs or tissues. Paragraph 8. Hog-cholera virus derived from pigs which are found to be affected with tuberculosis shall be destroyed as provided in section 11, Regulation 8, under the supervision of a bureau employee, unless the lesions are slight or are localized, and are calcified or encapsu- lated. Hog-cholera virus derived from pigs so affected may be marketed only when the product is heated as provided in paragraph 6, section 3, of this regulation. Paragraph 9. All records shall indicate clearly the particular animal, or group of animals, from which each batch of hog-cholera virus is derived. The amount col- lected and the total amount after phenolization should be separately recorded. 276 HOG CHOLERA Paragraph 10. Hog-cholera virus shall not be re- moved from the premises of a licensed establishment un- less the virus has been prepared in accordance with the provisions of these regulations. Paragraph 11. No immediate or true container of hog-cholera virus shall be filled in whole or in part, and no trade label shall be affixed to such containers except under the supervision of a bureau employee. Paragraph 12. The following special facilities, and such others as may be required by the chief of bureau, shall be provided by each establishment licensed to pre- pare hog-cholera virus: (a) Separate operating rooms. (6) A separate room in which the animals shall be washed, cleaned, and otherwise prepared before being taken into the operating room. (c) A separate room for conducting autopsies. (cZ) A separate room for the preparation and mixing of virus. (e) A separate room for washing and sterilizing equipment. (/) Clean cloths which shall be kept damp when in use, to be used for covering pigs during all operations incident to the collection of hog-cholera virus. {g) All outside screens, openings, and windows shall be equipped with dust screens. Paragraph 13. All persons, immediately before en- tering the operating or laboratory rooms of an establish- ment licensed to prepare hog-cholera virus, shall change their outer clothing or cover it by the use of clean gowns, or other satisfactory garments. Section 2. Paragraph 1. For use in the production of hyperimmunizing virus, licensed establishments shall inoculate young pigs weighing not more than 145 pounds each with at least 2 cubic centimeters of a virulent strain of hog-cholera virus. APPENDIX 277 Paragraph 2. Hyperimmunizing virus prepared in accordance with sections 1 and 2 of this regulation may be transported from one licensed establishment to an- other under bureau seal, provided the product is prop- erly iced and its transfer is accomplished in such man- ner and by such methods as shall be approved by the chief of bureau. Section 3. Paragraph 1. For use in the production of simultaneous virus, licensed establishments shall in- oculate young pigs weighing not less than 40 pounds, nor more than 100 pounds each with at least two cubic centimeters of a virulent strain of hog-cholera virus. Paragraph 2. Simultaneous virus shall not be col- lected from pigs which become visibly sick on or before the fourth day, or subsequent to the seventh day after the time of inoculation. The physical condition of pigs from which simultaneous virus is collected shall be re- corded daily on and after the fourth day subsequent to inoculation. Paragraph 3. Simultaneous virus shall be collected only from pigs which exhibit visible symptoms of hog cholera within seven days, and are visibly sick of this disease to a degree sufficient to result in death within 15 days after the time of inoculation. Paragraph 4. Pigs which have been inoculated for the production of simultaneous virus shall be killed only after permission has been obtained from an authorized bureau employee. Paragraph 5. Simultaneous virus shall be defibri- nated promptly after collection, and immediately there- after chilled and maintained at a temperature not to exceed 55° F. (12.8° C). Paragraph 6. When simultaneous virus is heated it shall be done under the supervision of a bureau employee and in such manner as to subject the product and the 278 ^ HOG CHOLERA entire container thereof to a temperature ranging from 50° to 50.5° C. for 12 hours. Paragraph 7 . Simultaneous virus which has been heated, as provided in the preceding paragraphs, shall not be handled thereafter in a manner which will ex- pose the product to contamination. Paragraph 8. AVhen simultaneous virus is heated, as described in paragraph 6 of this section, and tested upon pigs, as hereinafter provided, the product need not be tested upon calves. Paragraph 9. When simultaneous virus is heated, each batch shall be tested for virulence by inoculating intra- muscularly, with two cubic centimeters of virus, each of two pigs which are susceptible to hog cholera. Should the pigs thus inoculated exhibit visible symptoms of hog cholera, as required for pigs inoculated to furnish simul- taneous virus, the virus under test may be marketed. Paragraph 10. Pigs selected for testing the virulence of heated simultaneous virus shall be inoculated imme- diately after their admission to the premises. The quar- ters where these pigs are held during the test shall be isolated as completely as feasible from quarters occu- pied by other pigs sick of hog cholera. All reasonable precautions shall be taken to prevent infection of these pigs from sources other than by inoculation. Such pre- cautions shall include a thorough cleaning and disinfec- tion of the pen in which the pigs are held during the test, and a disinfection of these animals after they are placed in a holding pen. The disinfection of these pens and the test pigs shall be accomplished by such methods as shall be approved by the chief of bureau. Section 4. Paragraph 1. Simultaneous virus shall be collected in batches of not to exceed 20,000 cubic centi- meters each and each batch shall be mixed thoroughly in a single container. Paragraph 2. After mixing, but before phenoliza- APPENDIX 279 tion, a representative sample of each batch, consisting of at least 15 cubic centimeters of the mixture, shall be taken by a bureau employee. This sample shall be known as the ' ' Virus-test sample. ' ' Paragraph 3. Simultaneous virus which has been mixed as provided in this section, after withdrawal of the '* Virus-test sample," shall have added to it a suffi- cient quantity of a 5 per cent solution of phenol so that the virus will contain one-half of. 1 per cent phenol by volume. This phenolization must be accomplished Avith accuracy and in a manner which will prevent undesir- able changes in the product. After thorough mixing in a single container, a representative sample, consisting of at least 100 cubic centimeters, collected in three contain- ers, shall be taken by a bureau employee. This sample shall be known as the "Virus-stock samj^le." Paragraph 4. Simultaneous virus which has been mixed and phenolized, as provided in this section, to- gether with the virus-stock sample and the unused resi- due of the virus-test sample, shall be placed under bu- reau lock and held as provided under (5), section 1 of Regulation 7 until su,ch time as the tests have shown the batch of virus to be virulent and free from contami- nation. Paragraph 5. At least one container of the virus-stock sample shall be held unopened under bureau lock, in the manner provided in Regulation 7, for at least three months after the expiration of the latest return date shown upon the trade labels affixed to the immediate or true containers of the product corresponding to the virus-stock sample. Unless the virus is heated as pro- vided in paragraph 6, section 3, of this regulation the virus-test sample described in paragraph 2 of this sec- tion shall be used to determine the freedom from con- tamination of each batch of simultaneous virus. Paragraph 6. Two healthy calves, with mouths free 280 HOG CHOLERA from abrasions, and not less than 3 nor more than 12 months old, shall be furnished by the establishment for the inoculation with the virus-test sample. Paragraph 7. All animals used for the testing of simultaneous virus shall be inoculated only under the supervision of a veterinary inspector, and shall be marked as provided in paragraphs 2, 3, 4, and 5, section 6 of Regulation 17. Paragraph 8. Each of the calves selected for testing the purity of simultaneous virus shall be inoculated by injecting 5 cubic centimeters of the virus-test sample into either the auricular or jugular vein Avithin 24 hours after the virus is collected. Paragraph 9. Calves inoculated for the purpose of determining the purity of simultaneous virus as pro- vided in the preceding paragraph shall be held under the observation of a veterinary inspector for a period of at least 7 days. Should foot-and-mouth disease appear in the United States the said calves shall be held under the observation of a veterinary inspector for 10 days or longer, in the discretion of the inspector in charge. Paragraph 10. Simultaneous virus which has been either heated, as provided in paragraph 6, section 3 of this regulation, or subjected to the test prescribed in paragraph 8, section 4 of this regulation, may be re- leased for marketing, provided the animals treated with the virus remain well and develop no symptoms of any infectious, contagious, or communicable disease. Paragraph 11. Simultaneous virus found to be worth- less or contaminated shall be destroyed as provided in section 11, Regulation 8, under the supervision of a bureau employee. Section 5. Paragraph 1. Each immediate or true container of simultaneous virus which has been tested and found not to be worthless or contaminated shall bear a stamp or mark approved by the department. Such APPENDIX 281 stamp or mark shall bear the phrase ''U, S. Released." Each container of simultaneous virus shall be appropri- ately sealed with a suitable material and the aforesaid stamp or mark securely affixed to the sealing material under the supervision of a bureau employee. Should any difficulty result from the action of moisture upon said stamp or mark, causing it to become detached or illegible, that portion of the container which has been sealed and stamped shall be subjected at once to dipping in hot paraffin or other waterproof material. Paragraph 2. The trade label on each immediate or true container of simultaneous virus shall bear the date of manufacture, which date shall be the day on which the virus is collected. Paragraph 3. The return date placed upon the label of each immediate or true container of simultaneous virus shall be a date within 60 days after the date of manufacture. Paragraph 4. Trade labels affixed to or used in con- nection with the immediate or true containers of hog- cholera virus shall plainly show the amount of the con- tents of said containers. Paragraph 5. Trade labels affixed to or used in con- nection with each immediate or true container of simul- taneous virus shall bear a dosage table in which the doses recommended are not less than those appearing in the following table: Weight. Minimum dose. Pigs weighing 100 pounds or less 1 c. c. Hogs weighing more than 100 pounds. . . 2 c. c. Paragraph 6. No hog-cholera virus shall be released for marketing unless and until all information required by these regulations has been affixed to the containers thereof under the supervision of a bureau employee. 282 HOG CHOLEKA REGULATION 19. ANTI-HOG-CHOLERA SERUM Section 1. All operations incident to the production of anti-hog-cholera serum shall be conducted under the supervision of a bureau employee. Each licensed estab- lishment shall notify the inspector in charge, or an as- sistant, a reasonable time in advance when any opera- tions are to be conducted. Section 2. Paragraph 1. Anti-hog-cholera serum shall be derived only from hyperimmune hogs which have been immune to hog cholera for at least 60 days prior to hyperimmunization. Paragraph 2. Anti-hog-cholera serum shall be derived only from hyperimmune hogs which have been subjected to not more than 4 successive bleedings after each hyper- immunization. The first bleeding shall take place not earlier than 10 daj^s after hyperimmunization, subse- quent bleedings shall not take place more frequently than once in 7 days, and the last bleeding shall be made on a date not later than 38 days after hyperimmuniza- tion. Paragraph 3. Hogs which are used to produce anti- hog-cholera serum shall be healthy at the time of hyper- immunization, this fact to be determined by a careful examination made by a veterinary inspector prior to hyperimmunization. The temperature and weight of each animal shall be accurately obtained and recorded by tlie establishment before hyperimmunization. Paragraph 4. All hogs which are used to produce anti-hog-cholera serum shall receive a single intravenous injection of at least 5 cubic centimeters of hog-cholera virus for each pound of the animal 's weight. Paragraph 5. Temperature of all hogs used to pro- duce anti-hog-cholera serum shall be accurately taken and recorded by licensed establishments, either on the afternoon before or on the day of bleeding, and at such APPENDIX 283 other times as the inspector in charge may deem neces- sary. All temperatures shall be taken under normal conditions so far as possible and in a manner which will expedite the work. Paragraph 6. All hogs which are used to produce anti-hog-cholera serum shall be subjected to a careful examination by a veterinary inspector immediately prior to each bleeding. Only those hogs shall be bled for serum which are found to have a temperature of less than 104° F. and are free from infectious, contagious, or communicable diseases or other harmful conditions. Paragraph 7. All hogs from which anti-hog-cholera serum is derived shall be subjected to a post-mortem ex- amination by a veterinary inspector, except as herein- after provided, and if, as a result of such examination, it is found that any hog is so affected with any infec- tious, contagious, or communicable disease, or is in such condition as to render the serum worthless, contami- nated, dangerous, or harmful, the serum collected from such hogs shall be destroyed by the establishment as pro- vided in section 11, Regulation 8, under the supervision of a bureau employee. Serum derived from hogs which are found to be affected with tuberculosis need not be destroyed, provided the lesions are slight or are localized, and are calcified or encapsulated. Paragraph 8. Anti-hog-cholera serum derived from each hyperimmune hog shall be kept separate and apart from other serum except when heated as prescribed in paragraph 10 of this section, until it has been determined by post-mortem examination that the hog from which the serum is derived is not so affected with any infec- tious, contagious, or communicable disease or is in such condition as to render the serum worthless, contami- nated, dangerous, or harmful. Paragraph 9. When anti-hog-cholera serum is heated as described in the following paragraph, the serum de- 284 HOG CHOLEEA rived from each hyperimmune hog may be appropriately mixed with serum from other hyperimmune hogs imme- diately after collection, provided the final batch or mix- ture is prepared as prescribed in the following para- graphs of this section. Paragraph 10. Heating of anti-hog-cholera serum shall be conducted under the supervision of a bureau employee and in a manner in which the product and the entire container thereof will be subjected to a tempera- ture ranging from 59° to 60° C. for 30 minutes. Paragraph 11. Anti-hog-cholera serum which has been heated as provided in the preceding paragraph shall not be handled thereafter in a manner which will expose the product to contamination. Final mixtures or batches of anti-hog-cholera serum shall contain relative proportions of the several bleedings. Single bleedings from each hog shall not be divided or become a part of two or more batches unless the serum is subjected to heat as described in paragraph 10 of this section. Paragraph 12. Anti-hog-cholera serum which is to constitute a batch or portion thereof may be strained into a single container, after which the amount should be accurately determined. Paragraph 13. Anti-hog-cholera serum shall have added thereto a sufficient quantity of a 5 per cent solu- tion of phenol to make the serum contain one-half of 1 per cent of phenol by volume. Paragraph 14. Phenolization of anti-hog-cholera se- rum must be accomplished with accuracy, and in a man- ner which will prevent the occurrence of undesirable changes in the product. Paragraph 15. All records shall indicate clearly the particular hog or group of hogs from which each batch of serum or portion thereof is derived. The amount prepared for phenolization and the total amount after phenolization shall be separately recorded. APPENDIX 285 Section 3. Paragraph 1. Anti-hog-cholera serum prior to testing shall be collected in batches of not more than 100,000 cubic centimeters each, which shall be thoroughly mixed in a single container. After mixing and phenolizing, a representative sample consisting of at least 375 cubic centimeters collected in three contain- ers of not less than 25 centimeters, each to be known as the '^Serum-test sample," shall be taken and marked with identifying marks by a bureau employee. The se- rum, together with the test sample, shall be placed under bureau lock, as provided under (b) section 1, Regula- tion 7, and so held until such time as the tests required by these regulations have been completed, and have shown that the serum is not worthless, contaminated, dangerous, or harmful. Paragraph 2. If the serum is released, one of the three containers of the test sample thereof shall be held under bureau lock for at least six months after the latest return date shown on the trade labels affixed to the im- mediate or true containers of the serum of which the test sample is a part. Section 4. Paragraph 1. All anti-hog-cholera serum shall be tested for purity and potency by licensed estab- lishments as prescribed by these regulations. Paragraph 2. For use in testing each batch of 100,- 000 cubic centimeters of anti-hog-cholera serum of less, 7 healthy pigs, susceptible to hog cholera and weighing not less than 45 pounds and not more than 90 pounds each, shall be furnished by the establishment. Paragraph 3. Each of the seven pigs furnished for the test shall be injected with 2 cubic centimeters of hog-cholera virus; of these pigs 5 shall receive 20 cubic centimeters of the serum Avhich is to be tested. Two of the pigs shall receive no serum and shall serve as con- trols. The virus and serum injections shall be made simultaneously, the virus being injected into the left and 286 HOG CHOLEEA the serum into tlie right axillary space. The same vims shall be used for the inoculation of all pigs in the test and shall be administered by a veterinary inspector. Paragraph 4. A veterinary inspector shall indicate the pigs which shall receive serum with virus and those which shall receive the virus only in each serum test. Paragraph 5. Pigs which are injected with serum in serum tests shall be held under the observation of a veterinary inspector for a period of 21 days, or as much longer as the inspector in charge may deem necessary to determine the health of the animals and the purity and potency of the serum under test. Paragraph 6. Pigs in serum tests which receive virus only shall be held under the observation of a veterinary inspector and shall not be removed from the test unless and until released by such an inspector who will permit their removal when exhibiting well-marked symptoms of hog cholera, as described in rule D, paragraph 2, sec- tion 5, of this regulation, or after they have served their purpose in the tests. Paragraph 7. The temperature of each pig used in a test of anti-hog-cholera serum shall be taken and re- corded shortly before each test is inaugurated. Paragraph 8. Temperatures of control pigs and sick serum-treated pigs in serum tests shall be procured daily throughout the test period, with the possible exception of Sundays and holidays, and an accurate report of these temperatures rendered by the establishment to the in- spector in charge as he may direct. Paragraph 9. When serum-treated pigs do not ex- hibit symptoms of sickness their temperatures need not be taken except when required by the inspector in charge or his assistants to determine more accurately the true physical condition of the animals under observation. Section 5. Paragraph 1. The following principle APPENDIX 287 and rules are declared for a guide in judging the re- sults of serum tests : Principle : It is practically impossible in many cases accurately to differentiate between hog cholera, pneu- monia, and other conditions affecting hogs, without the aid of an autopsy as well as applied laboratory technique and certain experiments which may be necessary to de- termine the causative agent responsible for the condi- tion. Therefore, when healthy pigs are selected for test- ing- anti-hog-cholera serum any abnormal condition which may arise in the pigs subsequent to their inocula- tion should be regarded as due either to the virus used or, in the case of the serum-treated pigs, to the fact that the serum does not protect, unless the condition is defi- nitely known or can be shown to be due to some other cause. Paragraph 2. The following rules shall be observed in disposing of anti-hog-cholera serum which has been sub- jected to the tests prescribed by this order: Rule A. A serum test shall be declared a *'No test"" if any one of the following conditions obtains : 1. When any of the serum-treated test pigs or both of the control pigs become visibly sick on or before the fourth day after the time of inoculation. 2. When both of the control pigs do not exhibit symp- toms of hog cholera at some time during the test period as described in rule D of this paragraph. 3. When neither of the control pigs exhibits symp- toms of hog cholera subsequent to the fourth day and within 7 days after the time of inoculation as described in rule D of this paragraph. 4. When one or both of the control pigs exhibit sj^mp- toms of hog cholera within 7 days, as prescribed in rule D of this paragraph, but do not become sick to a degree sufficient to result in death within 15 days after the time of inoculation. 288 HOG CHOLERA 5. Wlien the senim-treated test pigs develop during the test period symptoms of any infections, contagions, or communicable disease (other than hog cholera) which is not caused by the serum used. 6. When a condition obtains in any of the test pigs which is not otherwise covered in this section. Rule B. A serum test shall be declared "unsatisfac- tory and the serum contaminated" when the following condition obtains: 1. When during the test period any of the serum- treated test pigs develop symptoms of any infectious, contagious, or communicable disease (other than hog cholera) which is due to the serum used. Rule C. A serum test shall be declared "Unsatisfac- tory" when any one of the following conditions obtains: 1. When both of the control pigs react as described in rule D of this paragraph and one of the serum-treated pigs becomes visibly sick subsequent to the fourth day after the time of inoculation and is found not to have fully recovered before the test animals are released by a veterinary inspector, as provided in paragraph 5, section 4, of this regulation. 2. When both of the control pigs react as described in rule D and two or more of the serum-treated pigs be- come visibly sick after the fourth day after the time of inoculation. 3. When an abscess, which is not definitely known to be due to a cause other than the serum used, develops at the site of the serum inoculations in any of the serum- treated pigs. Rule D. A serum test shall be declared "Satisfac- tory" when the following conditions obtain: 1. When both of the control pigs exhibit visible symp- toms of hog cholera at some time during the test period, one of which becomes visibly sick of this disease subse- quent to the fourth day of this period but within seven APPENDIX 289 days after the test is inaugurated, and is sick to a de- gree sufficient to result in death within 15 days after the time of inoculation, while all of the serum-treated pigs remain well throughout the test or not more than one of these serum-treated pigs become visibly sick subse- qu.ent to the fourth day after the time of inoculation, and fully recovers before the test animals are released by a veterinary inspector as provided in paragraph 5 section 4, of this regulation. Section 6. Paragraph 1. Anti-hog-cholera serum may be released for marketing as hereinafter prescribed when the test required by this regulation is found to be satisfactory as defined in rule D, provided the product is recommended for use in doses not less than those ap- pearing in the following table. This table shall be a part of trade labels, wrappers, and the like, affixed to or used in connection v/ith each immediate or true con- tainer of the product. We ig h t . Minimum D ose. Sucking pigs 20 c. c. Pigs 20 to 40 pounds 30 c. c. Pigs 40 to 90 pounds 35 c. c. Pigs 90 to 120 pounds 45 c. c. Hogs 120 to 150 pounds 55 c. c. Hogs 150 to 180 pounds 65 c. c Hogs 180 pounds and over 75 c. c. Paragraph 2. Anti-hog-cholera serum, the test of which has proved it to be "Unsatisfactory," as defined in rule C of this order, may be tested again as described in sections 4 and 5 of this regulation. Should the sec- ond test prove to be " Satisfactor}^ " as defined in rule D, the serum may be released for marketing under the conditions set forth in paragraph 1 of this section. If the test is again found "Unsatisfactory," as defined in 1 and 2, rule C, paragraph 2, section 5, of this regula- tion, the serum shall not be marketed unless and until 290 HOG CHOLEKA it is either concentrated, refined and tested in a manner approved by the chief of bureau, or mixed with other serum and tested as provided in section 7 of this regu- lation. Section 7. ParagrapJi 1. "When it is desired to mar- ket anti-hog-cholera serum without concentration and re- finement which has been tested with the results indi- cated in paragraph 2, section 6, of this regulation, it shall be mixed with other anti-hog-eholera serum with the view of increasing its potency and the final mixture shall consist of not less than 50 per cent nor more than 60 per cent of the serum of doubtful potency. Paragraph 2. Anti-hog-cholera serum which has been mixed as provided in the preceding paragraph shall be tested as outlined in sections 4 and 5 of this regulation, with the following exceptions: {a) Eleven pigs in lieu of the 7 shall be used, 3 of which shall receive virus only and shall serve as controls. (&) Unless two of the control pigs exhibit visible symptoms of hog cholera subsequent to the fourth day of the test period, but within 7 days after the test is inaugurated and are sick of this disease to a degree suffi- cient to result in death within 15 days after the time of inoculation, ''No test" will be declared. Paragraph 3. A second test conducted in the same manner as before may be made of serum mixed as pro- vided in paragraph 1 of this section should the results of the test of the mixture be declared ''Unsatisfactory" as to potency. Section 8. Paragraph 1. Should abscesses develop at the sites of the serum inoculations in any of the pigs used for testing serum as provided in this regulation, the following rules shall apply : {a) Judgment of the results of tests made on pigs to determine the potency of anti-hog-cholera serum will be APPENDIX 291 rendered irrespective of those conditions found which are regarded as an index to the purity of the product. (h) Should the results of a test of an ti -hog-cholera serum be declared "Satisfactory for purity," and it is found necessary to subject the batch of serum to a re- test to determine its potency, judgment concerning the purity of the product shall be based upon the first test unless evidence is found subsequent to such test which indicates that the serum is in fact contami- nated. (c) Should the results of a test of anti-hog-cholera serum be declared ' ' Satisfactory for potency ' ' but ^ ' Un- satisfactory for purity" the product may again be tested for purity upon the same number of pigs as provided under (a), paragraph 2, section 7, of this regulation provided each pig receives a single injection, in the axillary space, of at least 25 cubic centimeters of the product to be tested. Immune pigs may be used for this test if desired, and they shall be held under the super- vision of a bureau employee for at least 15 days. Paragraph 2. Anti-hog-cholera serum may be released for marketing as prescribed in paragraph 1, section 6, of this regulation, after having been tested, as provided by sections 7 and 8 and found satisfactory for purity and potency. Section 9. Paragraph 1. Anti-hog-cholera serum which has been tested twice with unsatisfactory results as to purity as provided in 3 of rule C of this regulation but satisfactory as to potency may again be tested with the view of ascertaining whether it is in fact contami- nated with pus-producing organisms, by treating 50 hogs on the premises of the manufacturing establish- ment. The serum shall be administered under the super- vision of a bureau employee, and each hog treated shall receive a single injection, in the axillary space, of not 292 HOG CHOLERA less than 25 cubic centimeters of the product to be tested. Paragraph 2. Animals used for testing serum as pre- scribed in paragraph 1 of this section shall be held under the supervision of a bureau employee for at least 15 days, and each animal carefully examined at the sites of the inoculations to determine whether or not the product has caused abscess formation. At the conclu- sion of the test a report shall be submitted to the Wash- ington office by letter concerning the results thereof, after which the bureau will advise the inspector in charge as to what disposition should be made of the serum. Section 10. Paragraph 1. Blood derived from hyper- immune hogs and ordinary defibrinated blood anti-hog- eholera serum may be clarified, or refined and concen- trated by licensed establishments, provided methods used to accomplish this are approved by the chief of bureau. Paragraph 2. When products described in the pre- ceding paragraph which have not been tested or have been tested and found '' Satisfactory" are clarified, or refined and concentrated so that the volume thereof is reduced 20 per cent or more, and it is desired to market the produ.ct in doses smaller than those indicated in paragraph 1, section 6 of this regulation, it shall be tested as provided in sections 4 and 5 of this regulation, except that each pig in the test shall receive 15 cubic centimeters of the product to be tested. Paragraph 3. Should the test required in paragraph 2 of this section be found "Satisfactory," as provided in rule D, paragraph 2, section 5 of this regulation, the product may be marketed, if it is recommended for use in doses not less than those appearing in the following table. This table shall be a part of trade labels, wrap- pers, and the like, affixed to or used in connection with each immediate or true container of the product : APPENDIX 293 Weight. Minimum Dose. Sacking pigs 15 c. c. Pigs 20 to 40 pounds 25 c. c. Pigs 40 to 90 pounds 30 e. c. Pigs 90 to 120 pounds 35 c. c. Hogs 120 to 150 pounds 45 c. c. Hogs 150 to 180 pounds 50 c. c. Hogs 180 pounds and over 60 c. c. Section 11. Paragraph 1. Each immediate or true container of anti-hog-cholera serum which has been tested and found not to be worthless, contaminated, dan- gerous, or harmful shall bear a stamp or mark approved by this department. Such stamp or mark shall bear the phrase ''U. S. Released." Each container of anti-hog- cholera serum shall be appropriately sealed with a suit- able material and the aforesaid stamp or mark shall be affixed securely to the sealing material under the super- vision of a bureau employee. Should any difficulty re- sult from the action of moisture upon said stamp or mark causing it to become detached or illegible, that por- tion of the container which has been sealed and stamped shall be subjected at once to dipping in hot paraffin or other waterproof material. Paragraph 2. The return date placed upon trade labels of anti-hog-cholera serum shall be a date not more than two years after the date of bleeding. The date of bleeding shall be regarded as the date upon which the first serum was collected, which is a part of the batch. Paragraph 3. Should the return date of any batch of anti-hog-cholera serum which has been tested as pro- vided in this regulation expire before the serum is used, this date may be extended one year, provided the serum is retested and found satisfactory as defined in rule D, paragraph 2, section 5, of this regulation. Paragraph 4. Trade labels affixed to or used in con- nection with the immediate or true containers of anti- 294 HOG CHOLERA hog'-cholera serum shall plainly show the quantity of the contents of said containers. Paragraph 5. No immediate or true container of anti- hog-cholera serum shall be filled in whole or in part, and no trade label shall be affixed to such containers, except under the supervision of a bureau employee. Paragraph 6. Anti-hog-cholera serum shall not be removed from the premises of a licensed establishment unless it has been prepared in accordance with the pro- visions of these regulations. Paragraph 7. No anti-hog-cholera serum shall be re- leased for marketing unless and until all of the informa- tion required by those regulations has been affixed to the containers thereof under the supervision of a bureau employee. Section 12. The following special facilities and such others as may be required by the chief of bureau shall be provided by each establishment licensed to prepare anti-hog-cholera serum. (a) Separate operating rooms. (&) A separate room in which the hogs shall be washed, cleaned, and otherwise prepared before being taken into the operating room. (c) A separate room for conducting autopsies. {d) A separate room for the preparation and mixing of serum. (e) A separate room for washing and sterilizing equipment. (/) Clean cloths, which shall be kept damp when in use, to be used for covering hogs during all operations incident to the collection of anti-hog-cholera serum. ig) All outside doors, windows, or other openings shall be equipped with dust screens. Section 13. All persons immediately before entering the operating or laboratory rooms of an establishment, licensed to prepare anti-hog-cholera serum, shall change APPENDIX 295 their outer clothing or effectively cover the same by the use of gowns or other satisfactory garments. REGULATION 20. — BACTERINS, VACCINES, TOXINS, ETC. Section 1. Paragraph 1. Viruses entering into the preparation of bacterins, vaccines, or toxins shall be de- rived from animals which are affected with no disease other than that for which the bacterins, vaccines, or toxins are intended to be used. Paragraph 2. All bacterins, vaccines, and toxins, shall be derived from the specific cause of the diseases for which they are intended to be used, or from the secon- dary invaders of the respective diseases. Section 2. Paragraph 1. The return date on the trade labels of blackleg vaccine prepared from attenu- ated B. gangrcenoi emphysematosoi or blackleg muscle virus, shall be a date not more than 6 months later than the date on which the preparation of the product is completed, without regard to the filling of final con- tainers. Paragraph 2. The return date on the trade labels of anthrax vaccine prepared by the Pasteur method shall be a date not more than 3 months later than that on which the preparation of the product is completed without regard to the filling of final containers. Section 3. The immunity unit for measuring the strength of tetanus antitoxin shall be 10 times the least quantity of antitetanic serum necessary to save the life of a 350-gram guinea pig for 96 hours against the official- test dose of the standard toxin furnished by the Hy- gienic Laboratory of the United States Public Health Service. The number of the immunity units recom- mended for the prevention of tetanus in a horse shall be at least 500 units. 296 HOG CHOLERA REGULATION 21. ADMISSION OF VIRUSES, SERUMS, TOXINS, AND ANALOGOUS PRODUCTS Section 1. No virus, serum, toxin, or analogous prod- uct which has not been prepared, handled, stored, and marketed in accordance with these regulations, and no virus, serum, toxin, or analogous product which is worth- less, contaminated, dangerous, or harmful shall be brought on to the premises of any licensed establish- ment. THE virus-serum-toxin LAW [Extract from "An act making appropriations for the Depart- ment of Agriculture for the fiscal year ending June 30, 1914," approved March 4, 1913 (37 Stat., 832).] That from and after July first, nineteen hundred and thirteen, it shall be unlawful for any person, firm, or corporation to prepare, sell, barter, or exchange in the District of Columbia, or in the Territories, or in any place under the jurisdiction of the United States, or to ship or deliver for shipment from one State or Territory or the District of Columbia to any other State or Terri- tory or the District of Columbia, any worthless, contami- nated, dangerous, or harmful virus, serum, toxin, or analogous product intended for use in the treatment of domestic animals, and no person, firm, or corporation shall prepare, sell, barter, exchange, or ship as aforesaid any virus, serum, toxin, or analogous product manufac- tured within the United States and intended for use in the treatment of domestic animals, unless and until the said virus, serum, toxin, or analogous product shall have been prepared, under and in compliance with regula- tions prescribed by the Secretary of Agriculture, at an establishment -holding an unsuspended and unrevoked license issued by the Secretary of Agriculture as herein- after authorized. That the importation into the United States, without a permit from the Secretary of Agricul- 1 APPENDIX 297 ture, of any virus, serum, toxin, or analogous product for use in the treatment of domestic animals, and the importation of any worthless, contaminated, dangerous, or harmful virus, serum, toxin, or analogous product for use in the treatment of domestic animals, are hereby prohibited. The Secretary of Agriculture is hereby au- thorized to cause the Bureau of Animal Industry to ex- amine and inspect all viruses, serums, toxins, and analo- gous products, for use in the treatment of domestic ani- mals, which are being imported or offered for importa- tion into the United States, to determine whether such viruses, serums, toxins, and analogous products are worthless, contaminated, dangerous, or harmful, and if it shall appear that any such virus, serum, toxin, or analogous product, for use in the treatment of domestic animals, is worthless, contaminated, dangerous, or harm- ful, the same shall be denied entry and shall be destroyed or returned at the expense of the owner or importer. That the Secretary of Agriculture be, and hereby is, authorized to make and promulgate from time to time such rules and regulations as may be necessary to pre- vent the preparation, sale, barter, exchange, or shipment as aforesaid of any worthless, contaminated, dangerous, or harmful virus, serum, toxin, or analogous product for use in the treatment of domestic animals, and to issue, suspend, and revoke licenses for the maintenance of es- tablishments for the preparation of viruses, serums, tox- ins, and analogous products, for use in the treatment of domestic animals, intended for sale, barter, exchange, or shinment as aforesaid. The Secretary of Agriculture is hereby authorized to issue permits for the importation into the United States of viruses, serums, toxins, and analogous products, for use in the treatment of domestic animals, which are not worthless, contaminated, danger- ous, or harmful. All licenses issued under authority of this Act to establishments where such viruses, serums, toxins, or analogous products are prepared for sale, bar- ter, exchange, or shipment as aforesaid, shall be issued on condition that the licensee shall permit the inspection of such establishments and of such products and their 298 HOG CHOLERA preparation ; and the Secretary of Agriculture may sus- pend or revoke any permit or license issued under au- thority of this Act, after opportunity for hearing has been granted the licensee or importer, when the Secre- tary of Agriculture is satisfied that such license or per- mit is being used to facilitate or effect the preparation, sale, barter, exchange, or shipment as aforesaid, or the importation into the United States of any worthless, contaminated, dangerous, or harmful virus, serum, toxin, or analogous product for use in the treatment of domes- tic animals. That any officer, agent, or employee of the Department of Agriculture duly authorized by the Sec- retary of Agriculture for the purpose may, at any hour during the daytime or nighttime, enter and inspect any establishment licensed under this Act where any virus, serum, toxin, or analogous product for use in the treat- ment of domestic animals is prepared for sale, barter, exchange, or shipment as aforesaid. That any person, firm, or corporation who shall violate any of the provi- sions of this Act shall be deemed guilty of a misde- meanor, and shall, upon conviction, be punished by a fine of not exceeding $1,000 or by imprisonment not ex- ceeding one year, or by both such fine and imprisonment, in the discretion of the court. UNITED STATES DEPARTMENT OF AGRICUL- TURE, BUREAU OF ANIMAL INDUSTRY Amendment 1 to B. A. I. Order 265 Regulations Governing the Preparation, Sale, Barter, Exchange, Shipment, and Importation of Viruses, Serums, Toxins, and Analogous Products Intended for Use in the Treatment of Domestic Animals. Effective on and after August 1, 1920 U. S. Department of Agriculture, Office of the Secretary, Washington^ D. C, July 14, 1920. Under authority conferred by law upon the Secretary of Agriculture, paragraph 2, section 3, Regulation 17 of B. A. I. Order 265, dated August 1, 1919, and effective September 1, 1919, is hereby revoked. Section 9, Regulation 17, is amended by adding thereto a paragraph, numbered paragraph 5, reading as herein- after set forth. Paragraphs 2 and 3, section 5, Regulation 2 ; paragraph 7, section 2, Regulation 12 ; paragraph 1, section 3, para- graph 2, section 4, (&) paragraph 3, and {a) and (&) paragraph 4, section 9, Regulation 17 ; paragraph 5, sec- tion 5, Regulation 18; paragraph 2, section 6, (c) para- graph 1, section 8, and paragraph 3, section 11, Regula- tion 19 ; and paragraph 1, section 2, Regulation 20 of B. A. I. Order 265, are hereby amended so as to read as hereinafter set forth. This amendment, for the purpose of identification, is designated Amendment 1 to B. A. I. Order 265, and shall become and be effective on and after August 1, 1920. E. D. Ball, Acting Secretary of Agriculture, 299 300 HOG CHOLERA REGULATION 2. ^LICENSES AND INSPECTIONS Section 5. Paragraph 2. Licenses shall be numbered and shall be in the following form : United States Veterinary License No Washington, D. C, This is to certify that, pursuant to the terms of the act of Congress approved March 4, 1913 (37 Stat., 832), governing the preparation, sale, barter, exchange ship- ment, and importation of viruses, serums, toxins, and analogous products intended for use in the treatment of domestic animals, is hereby licensed to maintain at an establishment for the preparation or : This license is subject to termination as provided in the regulations made under the authority contained in said act approved March 4, 1913, and also to suspension or revocation if the licensee violates or fails to comply with any provision of the said act or the regulations made thereunder. Secretary of Agriculture. Countersigned : Chiefs Bureau of Animal Industry. Section 5. Paragraph 3. Should a licensed establish- ment discontinue the production of any virus, serum, toxin, or analogous product, the license of such establish- ment shall be returned to the bureau for termination and a new license issued covering such products named therein as the establishment shall continue to produce. Should an establishment be engaged in the preparation of various products under a number of licenses issued from time to time by the department, the licenses shall be returned to the bureau at its request for termination and a new license issued covering all of the products i APPENDIX 301 embraced in the returned licenses which the establish- ment shall continue to produce. REGULATION 12. — LABELS Section 2. Paragraph 7. The name and address of the manufacturer may be omitted from trade labels when any virus, serum, toxin, or analogous product is to be distributed by a person other than the manufac- turer, but in such case the distributor must state on the label his or its trade name and address in immediate connection with a statement showing the license under which the product was manufactured. This statement, together with the name and address of the distributor, shall appear in letters of uniform size and character and be in the following form: "Produced under U. S. Veterinary License No. . Distributed by (name and address of distributor)." The name of the dis- tributor shall not appear on the label except in imme- diate connection with the Federal license legend. REGULATION 17. — ANIMALS Section 3. Paragraph 1. All hogs which are admit- ted to the premises of licensed establishments under the provisions of section 1, paragraph 1, of this regulation shall be held in receiving pens for at least 24 hours after admission to the premises, and during this time they shall be allowed free range and contact with not less than 2 contact calves for each lot of 200 hogs or less in the receiving pens. Section 4. Paragraph 2. The removal of contact calves from receiving pens shall be so arranged that a rotation will be established whereby each animal will be replaced at intervals of one month and both animals replaced every two months. Section 9. Paragraph 3 (&). Hogs which survive inoculation and exposure for the production of hog- 302 HOG CHOLERA cholera virus, surviving controls from tests of anti-hog- cholera serum, and surviving hogs which have been used for testing hog-cholera virus may be removed from the premises of the establishment not sooner than 15 days subsequent to the day of inoculation and exposure, pro- vided they are healthy. It is required, however, that all such hogs before their removal from the premises be given the serum-alone treatment as prescribed under (a) of paragTaph 4 of this section, or the simultaneous treatment prescribed under (h) of the same paragraph and section. Hyperimmune hogs and pigs used for test- ing the purity and potency of anti-hog-cholera serum may be removed from the premises of licensed establish- ments 21 days subsequent to the day of hyperimmuniza- tion or inoculation, provided they exhibit no symptoms of any infectious, contagious, or communicable disease, and provided further that they are first disinfected as prescribed in paragraph 5 of this section. Other hogs shall be removed from the premises of the establishment only after treatment and disinfection as provided in paragraph 5 of this section, except that such hogs need not be held 21 days when treated with serum and virus which have been released for marketing. Section 9. Paragraph 4 (a) . Serum-alone method. — The serum used shall have been prepared and released for marketing at an establishment holding a license from the Secretary of Agriculture and the dose employed shall conform to that required in paragraph 1, section 6, or paragraph 3, section 10, of Regulation 19. After receiving this treatment they shall be disinfected as pre- scribed in paragraph 5 of this section. Section 9. Paragraph 4 (h). Simultaneous-inocula- tion method. — The serum and virus used shall have been prepared at an establishment holding a license from the Secretary of Agriculture and the doses shall be not less than those required in paragraph 1, section 6, or para- APPENDIX 303 graph 3, section 10, of Kegnlation 19. After receiving this treatment they shall be held under the supervision of a bureau employee for a period of at least 21 days, except when treated with virus and serum released for marketing. If no symptoms of hog cholera or other in- fectious, contagious, or communicable disease are ex- hibited by the animals, they shall be disinfected as pre- scribed in paragraph 5 of this section. Section 9. Paragraph 5. Before removal from the premises of licensed establishments all hogs shall be dis- infected in a 2 per cent aqueous solution of cresol com- pound, U. S. P., or a permitted substitute therefor, and held in noninfectious pens for a period of at least three hours before being loaded for transportation. When the temperature of the air is below freezing, comfort- able quarters shall be furnished for the disinfected ani- mals until they are dry. REGULATION 18. — HOG- CHOLERA VIRUS Section 5. Paragraph 5. Trade labels affixed to or used in connection with each in^iediate or true con- tainer of simultaneous virus shall bear a dosage table in which the doses recommended are not less than those appearing in the following table: Weight. Minimum Dose. Pigs weighing 45 pounds or less 1 c. c. Hogs weighing more than 45 pounds .... 2 c. c. regulation 19. — ANTI-HOG-CHOLERA SERUM Section 6. Paragraph 2. Anti-hog-cholera serum the test of which has proved it to be ''unsatisfactory," as defined in 1 and 2 of rule C of this regulation, may be tested again as described in sections 4 and 5 of this regulation. Should the second test prove to be ''satis- factory, ' ' as defined in rule D, the serum may be released 304 HOG CHOLERA for marketing under the conditions set forth in para- graph 1 of this section. If the test is again found * * un- satisfactory, " as defined in 1 and 2, rule C, paragraph 2, section 5, of this regulation, the serum shall not be marketed unless and until it is either concentrated, re- fined, and tested in a manner approved by the chief of bureau, or mixed with other serum and tested as pro- vided in section 7 of this regulation. Sections. FaragrapK 1 {c). Anti-hog-cholera serum which has been found ''unsatisfactory for purity" may again be tested for purity upon 8 pigs, provided each pig receives a single injection in the axillary space of at least 20 c. c. of the product to be tested. Immune pigs may be used for testing the purity of anti-hog-cholera serum if desired. The pigs used should be held under the supervision of a bureau employee for at least 15 days. Section 11. Paragraph 3. Should the return date of any batch of anti-hog-cholera serum expire before the serum is used, the serum should be retested, and if found satisfactory as defined in rule D, paragraph 2, section 5, of this regulation, tl^^ return date may be extended one year from the date of retest. ^ REGULATION 20. — BACTERINS, VACCINES, TOXINS, ETC. Section 2. Paragraph 1. The return date on the trade labels of blackleg vaccine prepared from attenu- ated B. chauveaui, or blackleg muscle virus, shall be a date not more than one and one-half years later than the date on which the preparation of the product is completed, without regard to the filling of final con- tainers. UNITED STATES DEPARTMENT OF AGRICUL- TURE, BUREAU OP ANIMAL INDUSTRY Amendment 2 to B. A. I. Order 265 Regulations Governing the Preparation, Sale, Barter, Exchange, Shipment, and Importation of Viruses, Serums, Toxins, and Analogous Products Intended for Use in the Treatment of Domestic Animals. U. S. Department of Agriculture, Office of the Secretary, Washington, D. C, February 15, 1921. Under authority conferred by law upon the Secretary of Agriculture, paragraphs 1 and 6, section 2, Regula- tion 12, of B. A. I. Order 265, dated August 1, 1919, and effective September 1, 1919, are hereby amended to read as hereinafter set forth. Paragraph 7, section 2, Regulation 12, of Amendment 1 to the above order, dated July 14, 1920, and effective on and after August 1, 1920, is hereby revoked ; said rev- ocation, as applied to anti-hog-cholera serum and hog- cholera virus, to be effective on and after May 1, 1921 ; as to other products said revocation to be effective on and after January 1, 1922. Paragraph 8, section 2, Regula- tion 12, of B. A. I. Order 265 will accordingly, on and after January 1, 1922, be designated paragraph 7. Paragraph 1, section 3, Regulation 17, of Amendment 1 of the above order, is hereby amended to read as here- inafter set forth. This amendment, for the purpose of identification, is designated Amendment 2 of B. A. I. Order 265, and shall become and be effective on and after March 1, 1921, except as provided below. E. T. Meredith, Secretary of Agriculture. 305 306. HOG CHOLERA REGULATION 12. LABELS Section 2. Paragraph 1. Trade labels shall bear the true name of the product contained in the package, and this name shall be identical with that given in the license under which the product is prepared. The name shall also be so lettered and placed as to give equal promi- nence to each word composing it. Such labels shall also bear the name and address of the manufacturer, and the license or permit number assigned by the department. The license number and permit number shall be shown in either of the following forms, respectively: "U. S. Veterinary License No. ," or "U. S. Vet. License No. ," and ''U. S. Veterinary Permit No. ," or ''U. S. Vet. Permit No. ." These labels shall bear all other information required by the chief of the bureau, and may also bear any other statement not false or mis- leading, and which has been approved by the bureau. Section 2. Paragraph 6. When any virus, serum, toxin, or analogous product is prepared by a licensed establishment, or imported for a person other than the one to whom a license or permit has been issued, and the name and address of the distributor, as well as that of the manufacturer, is to appear on the trade labels of the containers thereof, a statement shall be made on the labels indicating that the virus, serum, toxin, or analo- gous product is distributed by such person. The name and address of this person shall not appear in any form or manner indicating that the distributor is the pro- ducer of the product, and operating under the license as shown on the label. The terms ''Distributor/' ''Dis- tributors," "Distributed by," or equivalent terms may be used if prominently placed and lettered, in connec- tion with the name and address of the distributing per- son, provided the same are not used so as to be either false or misleading. Eeference to the distributing per- son shall be made by name and address only. APPENDIX 307 The preceding paragraphs 1 and 6, as applied to anti- hog-eholera serum and hog-cholera virus, shall become and be effective on and after May 1, 1921; as to other products they will be effective on and after January 1, 1922. REGULATION 17. — ANIMALS Section 3. Paragraph 1. All hogs which are admit- ted to the premises of licensed establishments under the provisions of section 1, paragraph 1, of this regulation, shall be held in receiving pens for at least 24 hours after admission to the premises, with the exception of pigs which are used in testing the potency and purity of anti-hog-cholera serum, in which case 6 hours will be sufficient ; and during this time all of these animals shall be allowed free range and contact with not less than 2 contact calves for each lot of 200 hogs or less in the receiving pens. UNITED STATES DEPARTMENT OF AGRICUL- TURE, BUREAU OF ANIMAL INDUSTRY Amendment 3 to B. A. I. Order 265 Reflations Governing the Preparation, Sale, Barter, Exchange, Shipment, and Importation of Viruses, Serums, Toxins, and Analogous Products Intended for. Use in the Treatment of Domestic Animals. Effective on and after April 1, 1922 U. S. Department of Agriculture, Office of the Secretary, Washington, D. C, March 13, 1922. Under authority conferred by law upon the Secretary of Agriculture, paragraphs 6, 8, and 9, section 4, Regu- lation 18, of B. A. I. Order 265, dated August 1, 1919, and effective September 1, 1919, are hereby amended so as to provide that three pigs immune to hog cholera may be used in lieu of the two calves prescribed by the afore- mentioned paragraph 6. This amendment, which for the purpose of identifica- tion is designated as Amendment 3 to B. A. I. Order 265, shall become effective on and after April 1, 1922. C. W. PUGSLEY, Acting Secretary of Agriculture. 308 INDEX Abortion, due to simultaneous treatment, 146 Abscesses, following serum injection, 135 Absorption, of injected serum, 130 Ante-mortem inspection, in outbreaks of hog chol- era, 213 Anthrax, differentiating hog cholera from, 71 Animal inoculation, in diag- nosing hog cholera, 67 Ascarids, as a cause of * * serum breaks, ' ' 144 Ascaris infestation, confused with hog cholera, 72 Autopsy, of virus pig, 87 Bact. suisepticum, as a com- plication of hog chol- era, 21, 46, 47, 52 hemorrhages due to, 53, 56 Bladder, hog cholera lesions in, 53 Bleeding, for serum, 98 the virus pig, 85 B. necrophorus, complicating hog cholera, 30, 43, 44, 45, 47 B. pyocyaneus, complicating hog cholera, 27, 47 B. pyogenes suis, lesions pro- duced in swine, 33 * ' Breaks, ' ' following serum- virus treatment, 18, 140, 181, 182 B. suipestifer, ''button ul- cers ' ' due to, 45 complicating hog cholera, 25, 50, 52 relation to hog cholera, 3 Buildings required for serum preparation, 78 Cecum, hog cholera lesions in, 44 Confinement, of hogs for serum treatment, 118 Diagnosis, of hog cholera, 58 Diagnosis, differential, of hog cholera, 68 Disinfectants, as destroyers of hog cholera virus, 12 Dissemination, of hog chol- era, 17 Dosage, of serum, 131 of serum and virus, 138 Dose table, of serum. Bureau of Animal Industry, 110 Equipment, for serum prepa- ration, 80 Feeder hogs, handling to pre- vent hog cholera, 180 relation to hog cholera dis- semination, 236 [Fees, veterinarian 's, for serum administration, 191 Filterable virus, the cause of hog cholera, 4, 8 disinfectants, destroyers of. 12 elimination of, following serum-virus treatment, 147 heat as a destroyer of, 11 putrefaction as a destroyer of, 11 virulence of, 10 "Flu," so-called, differenti- ating from hog cholera, 71 309 310 INDEX Follow-up treatment, 153 Garbage fed swine herds, veterinary supervision of, 219 Garbage feeding, as a means of hog cholera spread, 17, 214 and sanitary considera- tions, 225 licenses for, 227 municipal, 217, 218 Heart, hog cholera lesions in, 47 Heat, as a destroyer of hog cholera virus, 11 Hemorrhagic septicemia, rela- tion to ''serum breaks," 149 History, of outbreak, in rela- tion to hog cholera di- agnosis, 58, 59 Hog cholera, complications, 21 control and eradication of, 230 diagnosis, 58 diagnosis, differential, 68 economic importance, 2 forms of, 35, 36 handling in the field, 158 history of, 1 incubation period of, 35 infected herd, handling, 161 lesions of, 40-56 methods of dissemination, 17 nature and cause, 7 prognosis, 74 relation to garbage feeding, 214 relation to meat inspection, 197 symptoms, 35 Hog holder, 123 Hyperimmune, the, 89 Hypering, dangers due to, 95 technique, 90 Immunity, of young pigs to cholera, 8, 171, 172 establishing herd, 174 Immunity, active, due to fol- low-up treatment, 155 active, due to simultaneous treatment, 138, 151 passive, due to serum alone, 127, 136 Kidney, hog cholera lesions in, 50, 51 Label, features of serum, 111 features of virus, 116 Larynx, hog cholera lesions in, 45 Legislation, regarding use of serum and virus, 192, 193 Lesions, of hog cholera, 40 as an aid in diagnosing hog cholera, 63 Lungs, hog cholera lesions in, 45 Lung worm infestation, con- fused with hog cholera, 72 Lymph glands, hog cholera lesions in, 54 Lysol, as a destroyer of hog cholera virus, 15 Marketing hogs, following serum and virus treat- ment, 169 Meat inspection, in field out- breaks of hog cholera, 210 relation of hog cholera to, 197 Mixed infection, in swine, 33 Mortality, due to hog chol- era, 7 Mouth and pharynx, hog cholera lesions in, 43 Putrefaction, as a destroyer of hog cholera virus, 11 Eeferences, 243 Eegulations, meat inspection. B. A. I. relative to hog cholera, 199, 200 relative to preparation and sale of biologies (B. A. L), 247 INDEX 311 Einderpest, differentiating from hog cholera, 74 Eouget, differentiating from hog cholera, 74 Septicemia, following serum treatment, 134 Serum, anti-hog-cholera, fees for administering, 191 keeping qualities, 114 Serum, anti - hog - cholera, methods of using, 118, 126 follow-up method, descrip- tion, 153 indications and contrain- dications, 157 serum alone, method, 127 dangers due to, 133 indications and contrain- dications, 137 technique of administer- ing, 128 therapeutic value of, 133 simultaneous method, 137 dangers, 139 dosage of serum and virus, 138 indications and contrain- dications, 152 technique of, 138 Serum, anti-hog-cholera, or- dering, 188 anti-hog-cholera, prepara- tion of, 76 anti-hog-cholera, testing, 105 bleeding for, 98 bottling and labeling. 111 B. A. I. Regulations for, 247 clear and ''bloody," 112 principle involved in, 82 tail and carotid bled, 113 Serum ' ' breaks, ' ' preventing and handling, 145 Shipping, as a cause of serum ''breaks," 142, 181, 182 Show hogs, handling to pre- vent hog cholera, 185 Site of injection, choice of, 128 Small intestine, hog cholera lesions in, 44 Spiroeheta hyos, relation to hog cholera, 33 Spleen, hog cholera lesions in, 47 Swine plague, differentiating from hog cholera, 70 in cholera immune herds, 25 Stomach, hog cholera lesions in, 43 Stunting, of pigs, as a result of simultaneous treat- ment, 146 Symptoms of hog cholera, 35 as related to diagnosis, 60 Technique, of serum adminis- tration, 128 Temperature readings, as an aid in diagnosis, 61 Temperatures, low, influence on hog cholera virus, 12 Trachea, hog cholera lesions in, 45 Tuberculosis, differentiating from hog cholera, 71 ' ' Vaccination Cholera, ' ' 18, 140 Virus "breaks," 140, 147 Virus of hog cholera, keeping qualities, 116 labeling, 116 manner of producing, 84, 115 Virus, laboratory, relation to hog cholera spread, 18 Virus pig, the, 84 autopsy of, 87 il LIBRARY OF CONGRESS 002 839 996 '^[^■r^--uu '1 :^i}m a m mM ■■^■Siim ':,'i-: t>ri.j:>t I m?^ ;y.*^«vv M ,vm ^:i^>:. >(^; rfM .0^ S?^ ;i!.:;'M.Vr m>mfi:^m m^i m l^:-iy-^>-^< •>-;P M ;:H ^liii m f<^m ;}Xm 'S'^r^'^ mm m 9!^\