UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA THE NEMATODES AND CERTAIN OTHER PARASITES OF SHEEP STANLEY B. FREEBORN AND MORRIS A. STEWART BULLETIN 603 JANUARY, 1937 UNIVERSITY OF CALIFORNIA BERKELEY, CALIFORNIA CONTENTS PAGE Introduction 3 Diagnosis 5 Post-mortem technique 8 Prevention and sanitation 12 Treatment 13 Medications mentioned in the text 16 Arsenic trisulfide 16 Beechwood creosote 16 Benzene 16 Carbon tetrachloride 16 Oil of chenopodium 18 Chloroform 18 Copper sulfate 18 Cunic mixture 19 Ficus laurifolia 20 "Flukoids" 20 Government wireworm remedy (G.W.W.R.) 20 Hexylresorcinol 20 Kamala (glandulae rottlerae) 21 Magdala rose (Sudan red, rose naphthyla- mine) 21 Male fern (aspidium) 21 "Nema" 22 Nicotine sulfate (Black Leaf 40) 22 Picric acid (trinitrophenol) 22 Tetrachlorethylene ("Nema") 22 Summary 23 Technique of administering treatment 23 Nematodes 24 Ascaris lumbricoides L. 1758 27 The pin worm, Skrjabinema ovis (Skrjabin 1915) 28 Strongyloides papillosus (Wedl 1856) 28 The nodular worms 30 Oesophagostomum columbianum (Curtice 1890) 32 Oesophagostomum venulosum (Rudolphi 1809) 33 Oesophagostomum radiatum (Rudolphi 1803) 34 Chabertia ovina (Fabricius 1788) 34 Hookworms 35 Bunostomum trigonocephalum (Rudolphi 1808) 36 Bunostomum phlebotomum (Railliet 1900) 38 Key to the family Trichostrongylidae 38 The eastern stomach worm, Haemonchus contortus (Rudolphi 1803) 39 The Ostertagia stomach worms 41 Key to species of Ostertagia 42 Ostertagia circumcincta (Stadelmann 1894) 44 Ostertagia marshalli Ransom 1907 44 Nematodes, continued The Ostertagia stomach worms, continued Ostertagia ostertagi (Stiles 1892) 44 Ostertagia occidentalis Ransom 1907 44 Ostertagia bullosa Ransom and Hall 1912. 45 Ostertagia trifurcata Ransom 1907 45 Ostertagia mentulata Railliet and Henry 1909 45 Ostertagia tricuspis Marotel 1912 45 Ostertagia turkestanica Petrov and Schachowzewa 1926 46 ( 'ooperia worms 46 Cooperia curticii (Giles 1892) 47 Cooperia oncophora (Railliet 1898) 47 The trichostrongyles 47 Key to the species of Trichostrongylus. ... 49 Trichostrongylus colubriformis (Gilesl892) 49 Trichostrongylus axei (Cobbold 1879) 50 Trichostrongylus vitrinus Loos 1905 50 Trichostrongylus capricola Ransom 1907. . 51 Trichostrongylus probolurus (Raillietl896) 51 Trichostrongylus rugatus Monnig 1925. . . 51 Trichostrongylus falculatus Ransom 1911. 51 The thread-necked strongyles 52 Key to the species of Nematodirus 53 Nematodirus fillicollis (Rudolphi 1802) .... 53 Nematodirus spathiger (Railliet 1896) 53 Nematodirus abnormalis May 1920 54 Nematodirus f urcatus May 1920 54 Mecistocirrus digitatus (Linstow 1906) .... 54 Gongylonema worms 55 Gongylonema pulchrum Molin 1857 56 Gongylonema verrucosum (Giles 1892). ... 57 Gongylonema monnigi Bay lis 1926 57 Setaria worms 57 The trichina worm, Trichinella spiralis (Owen 1835) 57 The whipworm, Trichuris ovis (Abildgaard 1755) 58 The Capillaria worms 59 Capillaria brevipes Ransom 1911 60 Capillaria longipes Ransom 1911 60 The lungworms, family Strongylidae 60 Key to genera of lungworms found in sheep 61 Dictyocaulus filaria (Rudolphi 1809) 61 Metastrongylus apri (Gmelin 1790) 63 Protostrongylus rufescens (Leuckart 1865) 64 Muellerius capillaris (Muller 188?) 65 Trematodes 65 The liver fluke, Fasciola hepatica L. 1758. . . 66 Cestodes 72 Moniezia expansa (Rudolphi 1805) 73 Thysanosoma actinoides Diesing 1835 75 THE NEMATODES AND CERTAIN OTHER PARASITES OF SHEEP 12 STANLEY B. FREEBORN 3 and MORRIS A. STEWART 4 INTRODUCTION The object of this paper is to place in the hands of the practical sheep- man an up-to-date compilation of what is known concerning the life his- tories and control of the various nematode (roundworm) parasites in- fecting sheep. We hope also to include enough data to enable the veterina- rian, or interested layman, to determine the species of parasite involved. The species included are not limited to California records alone for two reasons : in the first place, too little work has been done to determine with any degree of accuracy the entire list of the parasite population in this state ; secondly, we hope to have the information before our readers in such a fashion that if parasites not hitherto recorded from Calfornia are encountered they will be recognized and reported. In this way an accurate list of parasites may eventually be compiled. In some instances where several species are involved, the accurate separation by descrip- tion of differences becomes too verbose for inclusion in the reading mat- ter, and in these cases keys have been included. An earnest effort has been made to illustrate the terms used in the keys and descriptions. Illus- trations have been added to aid in identification where differences are relative. In addition to the consideration of roundworm parasites we have in- cluded consideration of the liver fluke and two tapeworms, none of which is a nematode. Their depredations, however, are considered in the same category by sheepmen as those of the nematodes. No attempt has been made, as in the case of the nematodes, to include all of the allied trema- todes and cestodes that have been reported from sheep, for this is beyond the scope of the present paper. The metric system of measurement is used from necessity because the small differences involved are unintelligible when expressed in fractions of an inch. For the general reader it is recommended that material in reduced type be ignored, since this is designed for specialists or laymen 1 Received for publication July 17, 1936. 2 The authors gratefully acknowledge the criticism, advice, and collaboration of the late Dr. John A. Howarth, Associate in Veterinary Science, and of Mr. Lester J. Berry, Assistant in Agricultural Extension, on certain sections of this bulletin. 3 Professor of Entomology and Entomologist in the Experiment Station. 4 Assistant Professor of Entomology and Assistant Entomologist in the Experi- ment Station. [3] 4 University of California — Experiment Station who are more than casually interested in the determination of the species concerned. Successful sheep husbandry is dependent on the efficient control of parasites. No domesticated animal suffers so severely from parasitic invasions as do sheep. True, cattle are hosts to over fifty different species of roundworms representing thirtj r genera, while some fifty species of roundworms representing thirty genera are all that are recorded from sheep. In spite of this apparent equality, severe parasitism in cattle is rare and localized, whereas parasitism in sheep is universal and consti- tutes an ever-present menace. Reasons for the difference may be found in the close browsing of the sheep, which facilitates the ingestion of myriads of eggs or larval worms that would not be eaten by the cattle. Their gregariousness may be another factor. Whatever the explanation, the fact remains that if cattle and sheep are pastured on the same ground and a parasite attacking both hosts is present, the number of adult worms infecting a calf will be nominal, whereas the number recovered from a lamb will be countless. The end result is a toleration by the calf but death for the lamb. However, the importance of parasites may easily be overemphasized on account of the absence among sheep of any of the important death- dealing plagues, such as tuberculosis, hog cholera, etc., which tend by their absence to accentuate the losses and difficulties attendant to para- sitism. The increase in the parasitism of sheep under modern conditions is in part real and in part merely apparent. In the main, there is definite evi- dence that losses caused by parasitism are multiplying. But part of the increase in parasitism reported is caused by a growing tendency of sheep- men to make autopsies of dead or sacrificed animals in order to ascertain the cause of trouble. And, secondly, after making this autopsy, he is prone to overemphasize the importance of the parasites that he may find because these are visible causes of trouble, easier to find than a more cryptic condition that might require the use of culture media and micro- scopic examinations. The increase in parasitism is no doubt real, at least in the actual number of parasitic individuals concerned, but probably the number of kinds of parasites involved has not materially changed during modern times. The parasites produce enough offspring to counterbalance the enormous mortality that these offspring, either as eggs or larvae, must undergo in nature while awaiting the arrival of a new host. Under nat- ural or even pioneer conditions, where free range made it possible to pass a flock of sheep over a given area for only one or two days a year, Bul. 603] Parasites of Sheep 5 the chances for worm eggs voided in the feces of an infected sheep to go through an incubation period and then to reach the food of a second animal at the right time to accomplish an infestation were very slight. Consequently, Nature endowed the worms with the ability to deposit, say, ten millions of eggs each, in the expectation that perhaps two would find a suitable host and develop. This undoubtedly occurred, for the species of worms persisted, but each host animal probably harbored a minimum number of parasites. Today, with the worms still producing eggs at their original rate, sheep are being confined to smaller and smaller pastures or even feed lots where there is every chance that a large por- tion of these millions of eggs that Nature intended for sacrifice will be eaten and will develop in these confined sheep. If the infestation is too heavy, however, the host animal dies and with it there also die countless thousands of parasites, which cuts off a still further increase. In addition, there is considerable evidence to the effect that early invasions of parasitic worms, particularly moderately heavy invasions, build up an immunity or a resistance in the host to the attack of this particular worm. After the establishment of this resist- ance, the ingestion of the infectious stages of the parasites results in the death of many of the parasites, or in the retardation of their development and reproduction. In this way the older animals that have survived parasitic invasions in their early life act as biological "vacuum cleaners" in diminishing the actual numbers of parasites able to reach maturity. DIAGNOSIS There are no cardinal symptoms for parasitism that may not be dupli- cated by any number of extraneous causes. Emaciation, anemia, lame- ness, diarrhea, bottle jaw, and other edemas are all indicatory but not necessarily diagnostic of internal parasitism. The presence of the actual worms themselves or their eggs or larvae in the feces is an indication, of course, but its severity can be judged accurately only by post-mortem examinations of dead or sacrificed animals. Fecal examinations for worm eggs or larvae are not at all difficult if a microscope is available. The simplest manner of making this examination is by the so-called "smear" method, wherein a small portion of feces is picked up on the point of a toothpick and placed on a microscope slide, diluted with enough water to spread it out in a thin film, and covered with a cover slip, after which it is ready for examination. At the Experiment Station our routine procedure is a modification of the Stoll method, wherein we take a portion of feces the size of a pea (2 grams) and macerate it in a 15-cc centrifuge tube in 4 cc of antiformin solution (30 per cent), allowing it 6 University of California — Experiment Station to stand with frequent stirring for an hour to dissolve organic material. Ten cubic centimeters of sodium bichromate solution (sp. gr. 1.35) is then added and the whole centrifuged for 2 minutes at 2,500 r.p.m. This causes the worm eggs and coccidia to rise to the top layer, from which they are removed with a piece of glass tubing flared out at the bottom. A drop is placed on the slide for examination. The sodium bichro- mate makes a pale-yellow background, while the eggs and cysts of coccidia remain white and easily distinguishable from all extraneous material. Adult worms appear white or opaque and featureless when examined under a microscope unless they are properly prepared for examination. There are countless elaborate methods published for "clearing" and preserving worm specimens for study. Most of these, however, are too elaborate and time-consuming for the worker who is more interested in diagnosis than in the intricacies of worm morphology. We have been very successful in the use of Lamiman's modification of the Berlese medium, particularly with the less delicate types. This material consists of a mixture of : Distilled water 10 cc Gum arabic 8 grams Chloral hydrate 53 grams Glycerine 6 cc Iodine crystals to sherry color The gum arabic should be hand-picked, avoiding pieces containing impurities, and then ground to a fine powder. It may then be dissolved in the water by heat and the other ingredients added. A drop of this material is placed on a slide. The worms, washed in water and drained, may be placed directly in the drop of material and covered with a cover slip. They are ready for examination almost immediately since clearing proceeds rapidly. The addition of iodine stains the specimens slightly and prevents them from becoming entirely transparent. When the material has hardened, the slips may be ringed with Brunswick black or they may be left almost indefinitely without further treatment. Measurements of portions of the specimens may be made by the use of an ocular micrometer. This is a circular piece of glass which fits into the eyepiece of the micro- scope. It is etched with a graduated scale. Any optical company can supply these with a table of factors for transposing the scale readings into millimeters for the various combinations of oculars and objectives in common use. Table 1 gives the length and maximum width of the eggs of each known species of nematodes, arranged according to average length. It is often helpful in making a preliminary diagnosis of species when certain forms are suspected but may be eliminated by egg sizes. However, it should not be used for a final diagnosis because the overlapping of size and the lack of other diagnostic characters make this procedure haz- ardous. Many investigators utilize a culture method in which the feces to be examined are packed to half -fill a fruit jar, so that a crater exists in the middle ; sufficient moisture is added, if necessary, to prevent drying out, and the cover closed to prevent evaporation. The jars may be kept at room temperature, but a constant temperature between 75° and 80° F seems Bul. 603] Parasites of Sheep TABLE 1 Dimensions of Ova of Nematodes Attacking Sheep (Nematodes in order of mean length of ova in millimeters) Name Length and width in mm Remarks Trichinella spiralis 0.040X0.030 Ova never present in feces Capillaria longipes . 045-0 . 050X0 022-0 025 Shell 0.0015-0.0020 mm thick; "plugs" present in both ends Gongylonema verrucosum 045-0 055X0 025-0 032 Strongyloides papillosus 040-0 060X0 020-0 025 Generally larvae in feces ; eggs only found in cases of severe diarrhea Capillaria brevipes 050X0 025 Shell 0.003-0 004 mm thick; "plug" pres- ent in both ends Skrjabinema ovis 054-0. 057X0. 032-0 034 Slightly flattened on one side Gongylonema pulchrum 055-0.070X0.025-0 037 Egg shells thick and transparent; em- bryonated when deposited Ascaris lumbricoides 050-0 070X0 040-0 050 Irregular, viscous covering, stained brownish-yellow Gongylonema monnigi ' 060-0 0625 X0 . 035-0 0375 Cooperia curticii 063-0 070X0 030-0 032 Eggs in morula stage when laid Cooperia oncophora 060-0 080X0 030 065-0.075X0 040-0 045 Oesophagostomum columbianum . Eggs segmenting when deposited Ostertagia ostertagi 0.065-0 080X0 030-0 040 Trichuris ovis 070-0 080X0 030-0 042 Eggs dark brown, lemon-shaped; "plugs" present in both ends Trichostrongylus axei 100-0.112X0.063 0.076-0 080X0 043-0 046 065-0 093X0.035-0:065 Trichostrongylus probolurus Bunostomum trigonocephalum. . . Eggs ellipsoidal; segmented when de- posited Haemonchus contortus 066-0.095X0.040-0 050 Eggs segmenting when deposited Oesophagostomum radiatum 0.075-0 085X0 040-0 045 Eggs segmenting when deposited Trichostrongylus colubr if ormis . . . 073-0 090X0 040-0 046 075-0.095X0.035-0.045 085X0.066 Trichostrongylus capricola Ostertagia bullosa Trichostrongylus vitrinus 084-0 090X0.046-0.050 075-0 100X0.035-0 050 085-0.090X0 040-0 056 Ostertagia circumcincta Ostertagia trifurcata Bunostomum phlebotomum 075-0.098X0.040-0 060 Eggs ellipsoidal; segmented when de- posited Oesophagostomum venulosum. . . . 085-0.100X0.045-0 055 Eggs segmenting when deposited Chabertia ovina 0.090-0 110X0 050 Eggs ellipsoidal ; segmented when de- posited Mecistocirrus digitatus 095-0.120X0.046-0 060 0.105-0. 120X0.050-0 056 Gaiqeria pachyscelis Very thin-shelled Nem todirus filicollis 130-0.200X0.070-0. 100 Eggs oval Ostertagia marshalli 0.160-0 200X0 075-0 100 0.150-0 220X0.080-0.110 Nematodirus spathiger Eggs ovoid-oblong in shape; shells thin, a little thickened at one pole; segmenting when deposited Nematodirus abnormalis 160-0 230X0.085-0 115 Unknown Unknown Unknown Unknown Trichostrongylus rugatus Ostertagia mentulata Ostertagia occidentalis Ostertagia tricuspis Ostertagia turkestanica Unknown Unknown Nematodirus furcatus 8 University of California — Experiment Station TABLE 1— (Continued) Name Length and width in mm Remarks Dictyocaulus filaria Only larvae found in feces Larvae 0.500-0.580 mmXO.025 mm; but- ton-like projection on head; tail blunt; heavily granulated except anterior end Metastrongylus apri Only larvae found in feces Larvae0.250-O.3O0mmX0.010mm;heavily granulated ; posterior end bent sharply ; tail pointed but not drawn out Proto8trongylv,8 rufeacens Only larvae found in feces Larvae 0.250-0.270 mmX0.015-0.020 mm; posterior end bears curved or straight projection Protostrongylus ocreatus Only larvae found in feces Protostrongylus unciphorus Only larvae found in feces Protostrongylus linearis Only larvae found in feces Muellerius capillaris Only larvae found in feces Larvae 0.230-0.300 mmX0.020-0.023 mm; posterior end coiled tightly, bears a sharp spike to be optimum for general culture work. The eggs hatch in the case of the strongylid worms and after molting the larvae start migrating up the moist sides of the jars from which they may be captured for identifica- tion. For those interested Monnig 5 has given a table for the identifi- cation of some of these infective larval forms. Needless to say this procedure is useless for those forms whose eggs do not hatch in the feces but await ingestion by an intermediary or pri- mary host. Another method that is sometimes utilized for the detection of lung- worm larvae is to wash off the fecal pellets that are freshly expelled or taken from the rectum, with distilled water. If living larvae are found in the wash water immediately, it is almost diagnostic of Dictyocaulus larvae, the thread lungworm. If, however, the larvae are present in the wash water only after standing in it for a period of an hour or two, they may be the larvae of the hair lungworm, Protostrongylus, or they may be the larvae of Strongyloides or possibly late arrivals of Dictyocaulus. POST-MORTEM TECHNIQUE One of the most satisfactory ways to assure a correct diagnosis of para- sitism in sheep is to kill an affected animal and search the organs thor- oughly for parasites. Some knowledge of the general parts is a necessary preliminary to a post-mortem. The animal to be autopsied should be killed as humanely as possible and bled out by sticking, according to the method used in slaughterhouses. Carefully bled carcasses will exhibit parasites much more readily, and 5 Monnig, H. O. Veterinary helminthology and entomology, p. 167. Wm. Wood & Co., Baltimore. 1934. Bul. 603] Parasites of Sheep will not handicap the operator by having the different organs contin- ually smeared and discolored by blood. The next step is to cut the legs loose from the body, allowing them to lie in the position shown in figure 1. The skin and abdominal muscles are cut forward from between the hind legs to the sternum. The best pro- cedure is to make a small incision through the abdominal muscles after the skin over the ventral portion of the body has been laid back. Then Fig. 1. — The first step in the autopsy. the first two fingers of the left hand are inserted into the opening made in the abdominal wall (fig. 2) ; the knife is held in the right hand in such a manner as to avoid cutting the intestines and thus allowing the escape of fecal matter into the abdominal cavity. Then a heavy knife or a saw is used to cut forward through the sternum, and the ribs are broken back to expose the thoracic cavity. An excessive amount of a straw-colored or reddish-yellow fluid found in the thoracic or abdominal cavities suggests parasitism. From here on, a more or less systematic procedure should be followed (fig. 3). Consolidated portions of the lungs should be cut into, and the part pressed between the hands. Lungworms, if present, will be forced Fig. 2. — After dividing the hide along the median line and stripping it back, an incision through the body wall is made in this fashion to prevent puncturing the internal organs. A DIAPHRAGM LIVEB CECUM SMALL INTESTINES LARGE INTESTINES LUNGS HEART RETICULUM OMASUM RUMEN ABOMASUM (FOURTH v STOMACH) DUODENUM Fig. 3. — The body cavity opened, with the internal organs exposed for examination. Bul. 603] Parasites of Sheep 11 out of the bronchi in some cases. Opening a few of the bronchi with knife or scissors will reveal them lying free in the air passages. The heart should be incised and examined for tapeworm cysts, commonly called measly mutton ; this condition may be found in the muscles of other parts of the body. The liver should next be removed and examined for enlarged and thickened bile ducts, which, if infested, will be found filled with mature OESOPHAGUS ^RETICULUM - OMASUM -FOURTH STOMACH (ABOMASUM) — DUODENUM -DORSAL SAC OF RUMEN CENTRAL SAC OF RUMEN Fig. 4. — The four stomachs of a sheep. flukes ; occasionally the liver will be rough and discolored, exhibiting ad- hesions to the diaphragm, caused by immature flukes. Tapeworms may also be found in the larger ducts of the liver. The intestinal tract is the next portion to be examined. The stomach of the sheep is very large, filling the greater part of the left half of the abdominal cavity and part of the right half. It consists of four parts: rumen (or paunch), reti- culum (or honeycomb), omasum (or manyplies), and abomasum (or fourth stomach) (fig. 4). The fourth portion (abomasum) is the main habitat of the group commonly called stomach worms. The method for isolating these parasites is described in the section on Hacmonchus con- fort us, page 39. 12 University of California — Experiment Station The small intestine is approximately 80 feet long and about 1 inch in diameter ; it is held partly in suspension by an attachment to the sublum- bar region by the mesentery. Running posteriorly from the stomach are three main divisions of the small intestine — namely, the duodenum, jejunum, and ileum ; but no definite demarcation is visible to the naked eye. The cecum (or blind gut) is about 12 inches long and 2 inches in diameter. The large intestine (or colon) is about 15 feet long. It is about 2 inches in diameter but gradually decreases to the same diameter as the small intestine. A thorough examination can be made if the digestive system is re- moved from the abdominal cavity and slit open lengthwise with either a small sharp knife or a pair of scissors. Some investigators prefer to spread the slit intestines on old newspapers. The outer surface adheres to the newspapers and presents a flat surface to the investigator, who is able to observe the surface carefully and make the necessary scrapings of any unusual areas which should be examined microscopically for the presence of eggs or minute worms. A table describing the parasites of the intestinal tract will be found on pages 26-27. PREVENTION AND SANITATION Intelligent prevention of parasitic invasions is a problem of management based on the known facts of the life history of the individual parasites. Each case requires that the grower should have available the known facts concerning the life history of the parasite involved. When he has these facts, he may adapt his scheme of management to incorporate the best preventive methods capable of practical application. In general, it is almost a universal fact that all the nematode (round- worm) parasites of sheep whose life history is known fully, require a wet or, at least, moist habitat for the development of their free-living stages or for the survival of their intermediary hosts. The avoidance of wet, marshy areas thus always returns dividends in the form of dimin- ished parasitism. The value of this precaution must be balanced by the sheepman against costs in fencing, feed, and sanitary drinking troughs. It may be pertinent to include here a statement concerning watering troughs. The old-time trough supplied with constant running water which drained over the side to make an artificial marsh of permanent character about the trough as a center is far worse than the natural streams as a source of infection. It not only provides a permanent breed- ing place for all the parasitic nematodes, but it acts as a lode-stone for concentrating all the sheep on the particular pasture at daily or more frequent intervals for their supply of water and parasites. Arrange- Bul. 603] Parasites of Sheep 13 merits should always be made by subirrigation or a deep pit filled with stories for the sanitary disposal of the overflow water without the pro- duction of a marsh. Well-nourished animals are much more resistant to parasitic invasions than are animals in poor condition, and even if worms do establish them- selves, their effects are always less noticeable. Of course, if the pasture is heavily infected, even well-fed sheep may accumulate a worm burden too severe to overcome without the aid of medication. If animals are treated regularly so as to be kept free of the most harm- ful worms, they will be able to overcome the less harmful ones them- selves. This measure has been exceptionally successful where it has been practiced. Sheep should be freed of all worms as far as possible during the dry season, at which time the pastures may be sterilized to a consid- able extent by climatic conditions. Overstocking should be avoided since it concentrates worm infection. As lambs are more susceptible to worms than adults, they should be sep- arated from the ewes as soon as possible and allowed to graze in clean pastures. In the main, the preventive features of the problems are self -appar- ent when the life history of the parasite is known and, in general, will not be discussed in the individual parasites except where a specialized technique has been developed. TREATMENT The average grower is generally apprehensive about any parasite for which he knows no specific cure, but once this is made known to him, he is extremely apt to ignore both preventive and therapeutic agencies until the time when the situation becomes economically acute. In some cases where the life history is unknown or where prevention is too costly under the existing setup, it may become necessary or more economical to wait until the sheep are infected and then treat them rather than to spend the energy and money in preventive measures. The use of internal medications for the control of the various para- sites is predicated on the assumption that the treatment is more toxic to Unless the grower has had considerable experience, it is generally money well invested to engage a veterinarian for diagnosis and to at least instruct the grower in the manner and technique of treatment. In many sections de- voted to sheep in California this is a costly procedure on account of the distances involved. Wherever it is at all feasible, however, it is decidedly advantageous. 14 University of California — Experiment Station the parasite than to the sheep. The margin of safety in some cases is slight, and the search for and preparation of safer materials has now enlisted the aid of the chemists. The modern tendency is well illustrated in the march of development from chloroform, which is a good anthel- mintic (worm remedy) but deadly to sheep, through carbon tetra- chloride, equally efficacious for worms (specific for liver flukes) but still dangerous to sheep with a low calcium reserve, to tetrachlorethylene, which is particularly effective against many worms and comparatively harmless to sheep. Despite the fact that worms were the first recognized parasitic organ- isms of both man and his domestic animals, medication for them pro- gressed very slowly until within the past few years. The oldest known anthelmintic in present-day use, as far as can be determined historically, is male fern, which was known to the ancient Greeks. Chenopodium and spigelia are said to have been employed by American Indians at the time of Columbus' discovery of the New World, and kamala has been used since ancient times by the natives of India. Chloroform was first used as an anthelmintic in 1897, and the foundation was thereby laid for the development of carbon tetrachloride and tetrachlorethylene as efficient drugs for the treatment of certain worm infections. Hall (1921)° as a result of his critical tests on dogs of the anthelmintic properties of chloroform, in w T hich he determined that its anthelmintic value was ap- parently correlated with its chlorine content, proposed carbon tetrachlo- ride for the removal of hookworms. Pursuing the same reasoning a little further, Hall and Shillinger (1925) 7 found tetrachlorethylene appar- ently still more effective against hookworms, after having first found dichlorethylene less effective. Reasoning from the series dichlorethylene (C 2 H 4 C1 2 ), chloroform (CHCL), and carbon tetrachloride (CC1J, one might conclude that the anthelmintic efficiency increases in direct pro- portion to the chlorine content of the compound. As Hall has pointed out, however, a complication enters at this point which indicates that chemical composition is not the whole story, since tetrachlorethylene (C 2 C1 4 ) appears to be even more effective than carbon tetrachloride (for nematodes), although the chlorine content of the two drugs is the same and the proportion by comparison with the other constituent, carbon, is even less. Furthermore, Hall and Cram (1925) 8 found that carbon tri- a Hall, M. C. Carbon tetrachloride for the removal of parasitic worms, especially hookworms. Jour. Agr. Eesearch 21:157-75. 1921. 7 Hall, M. C, and J. E. Shillinger. Tetrachlorethylene, a new anthelmintic. Amer. Jour. Trop. Med. 5:229-37. 1925. 8 Hall, M. C, and E. B. Cram. Carbon trichloride as an anthelmintic and the rela- tion of its solubility to anthelmintic efficiency. Jour. Agr. Research 30(10) :949-53. May, 1925. Bul. 603] Parasites of Sheep 15 chloride or hexachlorethane (C 2 C1 6 ), despite its high chlorine content, is entirely ineffective in the treatment of hookworms. The total failure of hexachlorethane is due apparently to the fact that it is exceedingly insoluble and passes through the digestive tract with no appreciable loss or change and without affecting either the host or the parasite. Prob- ably the relative anthelmintic values of tetrachlorethylene, carbon tetra- chloride, and chloroform are similarly correlated with their solubility in digestive juices and water, the optimum solubility being close to that of tetrachlorethylene and carbon tetrachloride. Anthelmintics are, at least to some extent, selective in their action upon the different parasites. Therefore fairly accurate knowledge of the parasite present and its biology determines the choice of a drug to be employed. In general, it is inadvisable to dissolve in alcohol drugs which are to be employed in the treatment of intestinal worms unless the active prin- ciple is to be absorbed and thus reach the blood stream. In view of the fact that the diluent may determine the rate of absorption, it is neces- sary to select the vehicle for the drug carefully. Olive oil increases the solubility and consequently the toxicity of chenopodium, whereas castor oil distributes it throughout the intestine and does not increase its toxic- ity. Male fern is much more toxic to the host without castor oil than with it; probably because the purgation prevents absorption. Carbon tetrachloride must never be administered in an easily absorbed oil and even oily food must be withheld for 24 hours before and after treatment. When a purge is a necessary part of the treatment in order to hasten the passage of the drug, it need not be delayed after giving the anthelmintic since absorption occurs more easily in the absence of purgation. In some treatments adequate starvation before dosing is recommended, and food should be withheld for several hours after treatment. The stom- ach contents not only dilute such drugs but stimulate absorption by the host. The ejection of worms after administering an anthelmintic does not indicate that all the parasites have been eliminated. It may merely point toward the continuance of the treatment. Severe worm infections lower the resistance of the host and thereby increase its susceptibility to the drug. Therefore, such animals should be given small, repeated doses rather than single, massive doses. Almost all anthelmintics are apt to be dangerous in very young and very old animals ; also in cases of fever, toxaemia, gastroenteritis, and constipation. Male fern, chenopodium, or thymol should not be administered to pregnant animals. The treatment of animals heavily infested witli blood-sucking and tissue-feeding stom- 16 University of California — Experiment Station ach and intestinal worms — such as Trichostrongylus, for example — with certain anthelmintics is unwise because the irritation of the stomach and intestinal walls resulting from the attack of the parasites permits rapid absorption of the drug. Arsenical drugs should not be used in the treat- ment of such cases and even less-toxic drugs may produce severe intoxi- cation. Fluids and powders, when administered in small quantities to sheep, apparently pass rapidly to the abomasum if the animal is ruminating at the time of treatment. Capsules invariably pass to the rumen, giving the same result as if a stomach tube were used. In such cases as Oesoph- agostomum infection, treatment by mouth is frequently not successful because the adult worm is located in the colon and the drug is diluted and may be absorbed before it reaches the colon. Drastic purges are not satisfactory. Therefore, it may be necessary to resort to enemas. In order to do this most effectively sheep may be fed succulent green food in order to purge the colon. The enema is given through a funnel and a piece of rubber tubing about 3 feet long, which is passed as far as possible into the colon while holding the sheep up by its hind legs. MEDICATIONS MENTIONED IN THE TEXT Arsenic Trisulfidc- — Gordon 9 claims that a single dose of 0.5 gram of natural arsenic trisulfide is 100 per cent effective in the treatment of Moniezia infestation in adult sheep. It may be administered either as a powder or suspended in a 2 per cent solution of copper sulfate. If, how- ever, this compound is prepared synthetically by fusing equal parts of arsenic trioxide and sulfur, a highly poisonous product results because a large amount of the acid is not decomposed. Beechwood Creosote. — One part of beechwood creosote in 10 parts glycerine has been recommended for intratracheal injection in the treat- ment of Dictyocaidus infection. The fluid must be injected slowly and during the act of inhalation in doses of from 2 to 4 cc. The treatment must be repeated two or three times at intervals of about three days. Only mediocre results are obtained. Benzene. — This chemical has been tried as an anthelmintic against a number of parasites. Its most successful use has been as an enema, 1 cc in 1 to 2 quarts of water, after a purgative has been given to empty the colon, to remove Trichuris. It is not always successful, however. Carbon Tetrachloride. — Carbon tetrachloride is a widely used an- thelmintic. As pointed out in a previous paragraph, it is very closely "Gordon, H. McL. A note on the treatment of tapeworm (Moniezia sr>p.) infes- tation of sheep. Indian Jour. Vet. Sci. and Anim. Husb. 5(2) : 195-98. 1935. Bul. 603] Parasites of Sheep 17 related to chloroform. Its first medical use was as a general anesthetic, but it is more toxic than chloroform and the anesthesia produced by it is not so satisfactory. Therefore, it was dropped from the field of medi- cine and did not reappear until Hall introduced it as an anthelmintic in 1921. Something of its chemical nature was described in the historical discussion of anthelmintics. The chief anthelmintic role of carbon tetra- chloride, resulting from the investigations of Montgomerie in Wales in 1926, is the treatment of liver fluke in sheep. The pure drug should be used. It is not necessary to starve the animals or keep them from water, but they should not receive food which contains much protein or fat. Carbohydrates, however, appear to have a favorable influence on the reaction of the host to the drug. It is desirable to keep the sheep on the feed to which they have been accustomed, furnishing extra carbohy- drates and bonemeal mixed with the food when there is a deficiency of calcium. The sheep should not be treated in hot weather and should be handled quietly. A dose of 1 cc is administered, preferably in a soft gela- tine capsule by means of a capsule "gun" or long forceps, but it may be given by means of a syringe, which is introduced into the mouth against the cheek on one side. These prepared capsules may be purchased from veterinary supply houses, or the chemically pure drug may be purchased and the capsules filled on the ranch. When the drug is administered as a drench, it is diluted w T ith livestock paraffin oil at the rate of 1 part of carbon tetrachloride to 4 parts of oil. The dosage of the mixture, there- fore, becomes 5 cc. The young flukes in the liver tissue or body cavity are not killed; consequently, the treatment must be repeated after 4 to 6 weeks in some cases. Carbon tetrachloride is well tolerated by animals with a short intes- tinal tract but is somewhat dangerous for ruminants, especially cattle ; it should never be administered to cattle unless absolutely necessary and then only after calcium in some form, such as marl, has been fed for at least 2 weeks previous to treatment. The injurious effects sometimes re- sulting from carbon-tetrachloride administration arise from liver in- jury, which causes bile pigments to be liberated into the blood stream ; these in turn give rise to metabolic disturbances that reduce the supply of blood calcium and result in hemorrhages in the serous and mucous membranes and sometimes convulsions and death. The feeding of cal- cium tends to counteract such biochemical upsets. Animals poisoned with carbon tetrachloride may manifest nervous symptoms such as a violent twitching of the nose, body tremors, and gastro-intestinal disturbances, followed later by a comatose condition and death. They may be treated by the prompt and cautious intravenous injection of a small amount of 18 University of California— Experiment Station calcium lactate or some other soluble calcium salt, repeating the injec- tion at intervals if indicated. Carbon tetrachloride should not, in gen- eral, be administered in cases of unusual fatness in the animal, high protein and fat diets, or lactation ; or, as a drench, in cold or wet weather. It is generally regarded to be safe for pregnant animals. Oil of Chenopodium. — Chenopodium has long been known to possess anthelmintic properties. The Indians of South America made infusions from the leaves and seeds of American wormseed (Chenopodium anthel- minticum) . It has little or no effect upon tapeworms. The active princi- ple is known as ascaridol. In sheep a dose of 0.091 cc per pound of body weight is emulsified in 5 ounces of milk and administered as a drench. However, since commercial samples vary in their ascaridol content from 45 to 70 per cent, accurate dosage is very difficult. Excessive doses result in general gastro-intestinal irritation, and since it is absorbed to some extent, dizziness, deafness, and drowsiness may follow. Poorly fed ani- mals are more susceptible to the toxic effects than are well-nourished ones. A diet rich in carbohydrates before treatment is beneficial. Since oil of chenopodium causes constipation in the host and paralyzes rather than kills the parasite, it must be followed with a purgative — preferably castor oil. It is often administered in conjunction with carbon tetra- chloride. Chloroform. — Chloroform should not he used in any form for internal medication in sheep. Copper Sulfate. — (See also "Cunic Mixture," and "Government Wire- worm Remedy.") Copper sulfate is widely used as an anthelmintic against nematodes infesting the gastro-intestinal tract of sheep and cat- tle. It is effective in the treatment of Haemonchus infections but is not efficient against Ostertagia in either pure or mixed infections. A 1 per cent solution of copper sulfate (bluestone) in water (% pound to 3 gal- lons) administered as a drench in doses of 100 cc (approximately 3 fluid ounces) to yearlings and older sheep and 50 cc (1% fluid ounces) to lambs over three months of age forms a very satisfactory treatment. In heavily infested territory this must be repeated every month as long as the mean temperature remains above 50° F. Use only bright blue crys- tals, discarding any that have turned white. Crush these and add to some of the water that has been heated. When completely dissolved, add the remainder of the water. Do not used exposed-metal containers. Allow 3 gallons of the solution for each hundred adult sheep. Copper sulfate if taken in excessive quantity gives rise to severe poi- soning, resulting in death. Fatal accidents may occur if the solution gets into the trachea during drenching. Animals which have been shipped Bi-l. 603] Parasites of Sheep 19 some distance and starved en route should he fed the night before treat- ment to prevent too great absorption of the anthelmintic. Cunic Mixture. — Clinic mixture is a mixture of copper sulfate and Black Leaf 40. It is effective not only against Ostertagia and other stomach worms but also against tapeworms. Nicotine was used in New England a hundred years ago for the treatment of sheep infested with roundworms. Tobacco stems were soaked in salt water and put in the feed troughs. The use of a combination of copper sulfate and nicotine sulfate for tapeworm treatment is evidently traceable to Dr. Cooper Curtice of the United States Bureau of Animal Industry. This combination, which Dr. Curtice called "cunic mixture," consists of water to which is added 1 per cent by weight of copper sulfate and 1 per cent by volume of nicotine sulfate (Black Leaf 40) . In order to make such a mixture : 1. Make a stock solution of 2 pounds of copper sulfate in 1 gallon of water in a wooden or earthenware container. 2. Take 1 pint of the above solution and add 11 V2 quarts of water, to make 3 gallons. 3. To this 3 gallons of copper sulfate solution add 4 fluid ounces of Black Leaf 40. 4. Steps 2 and 3 may be repeated as needed. This is a better procedure than mixing the entire quantity at once as the completed mixture de- teriorates on standing. The dosage for a full-grown ewe is 4 fluid ounces, graduated to 2 ounces for lambs three months old. Warning: Mix carefully and accurately. If mixed properly and ad- ministered in the proper doses, it is perfectly safe. Overdosage is dis- astrous, however. Freeborn and Berry 10 have shown that the anthelmintic efficiency of this drug is probably due to the combination of the copper with the im- purities in Black Leaf 40. It is recommended that the animals be treated in the morning without feeding or watering and starved for another 2 hours. In heavily infected areas the animals should be treated every 3 weeks from the time they are 3 weeks old. If administered in excessive dosages, fatal poisoning may result. Animals which have been shipped some distance and starved en route should be fed the night before treatment to prevent too great ab- sorption of the anthelmintic. Care must be taken during drenching to prevent the solution from getting into the trachea. 10 Freeborn, Stanley B., and Lester J. Berry. Observations on the sheep tapeworm, Moniezia expansa, in California. Jour. Amer. Vet. Med. Assoc, n.s. 38(5) :611-16. 1934. 20 University of California — Experiment Station Ficus Lauri folia. — The latex of the South American fig (Ficus lauri- folia) has definite anthelmintic properties. It contains, other than rubber and resinous substances, an albumin and a substance of fixed composition which readily yields ammonia. It is thought that the active principle is the ammoniacal substance. It is widely used in Brazil and Colombia against Trichuris in man, but dosages for sheep have not as yet been worked out. This drug is not entirely nontoxic or safe. It may cause colic, convulsions, and other symptoms of poisoning. "Flukoids."—See "Carbon Tetrachloride," p. 16. Government Wireworm Remedy (G. W. W.R.). — Government wire- worm remedy, which is a mixture of 4 parts copper sulfate (partly dehy- drated) and 1 part of sodium arsenite, is widely employed in South Africa, where it was developed, and in some other countries for the treat- ment of stomach worms. It is usually administered in powdered form to sheep by placing it well back on the tongue with a teaspoon. This permits rapid treatment of large numbers of animals and avoids the danger of getting it into the trachea. The recommended dosage table is as follows : for lambs two to four months old, 0.20 gram of the mixture ; from four to six months, 0.25 gram ; six months to a year, 0.50 gram ; yearlings and over, 0.625 gram. In South Africa, where this method is used extensively, measuring ladles for the different dosages are available. The liquid form of the drug is made by mixing a liter (2.11 pints) of soft water, 15 cc concentrated hydrochloric acid, and 62.5 grams of the powder. Ten cc of the solution corresponds to the powder dose for an adult sheep and is administered as a drench. For use as an enema I2V2 gallons of water, 3% pounds of bicarbonate of soda, and 1% pints of liquid wireworm remedy are mixed and admin- istered through a rubber tube. The dosage varies with the size of the animal from a pint to a quart of the mixture. It is dangerous to treat constipated sheep. Previous feeding on succulent food to produce purg- ing is highly desirable where treatment is by enema. Government wireworm remedy is dangerous to use in heavy infesta- tions of Trichostrongylus. Smaller doses than those recommended above are indicated when the sheep are in poor condition, when they are not accustomed to this treatment, and when they are grazing on succulent feed. All animals must be kept from water for at least 7 hours before and after treatment, in order to avoid rapid absorption of the drug and consequent arsenical poisoning. The writers do not recommend this treat- ment because of the small margin of safety due to the arsenic content of the mixture. Hexylresorcinol. — This is a recently introduced drug of very great Bul. 603 J Parasites of Sheep 21 anthelmintic promise. It is said to have little, of any, toxic effect upon the host and to be highly efficient against ascarids and whipworms. Hexylresorcinol is a coal-tar product and is somewhat irritating to the mucosa of the stomach and intestine. Proper starvation must precede the administration of the drug and food should be withheld for 3 or 4 hours after treatment. Very little has been done thus far with this anthelmintic in veterinary medicine. Hexylresorcinol is given as a 2% to 5 per cent solution in olive oil, dose by mouth being y 2 to 1 ounce. The crystals are too irritating to be administered as such. A similar preparation, heptyl- resorcinol, has been proposed under the name, "Dihydranol." Kamala (Glandulae Bottler ae.) — This drug consists of minute red glands and hair of the fruit of an evergreen shrub (Mallotus philippinen- sis) which belongs to the spurge (Euphorbiaeceae) family. It is widely distributed throughout the tropical portions of Asia and Australia. The Arabian physicians called it wuras or wars and were familiar with its anthelmintic properties as early as the tenth century. It was introduced into Europe only about seventy years ago and at one time held a con- siderable reputation as a general anthelmintic. It is effective only in the treatment of tapeworm and liver-fluke infestations, particularly in the former. However, we have better anthelmintics for both these parasites, and its use is included here only on account of the general interest ; we do not recommend it because of its bad effects on the sheep. For liver- fluke infestation it has been recommended that the crude drug be given in two doses of 7.5 grams (2 drams) each at 12- to 24-hour intervals to yearlings and older sheep. A single dose of 15 grams may be given to a good strong animal and in the case of a weak animal five doses of 3 grams each may be administered. After treatment sheep are dull for from 3 to 5 days. They eat little, or may stop eating entirely for a day or two, lie down a great deal, and have diarrhea. It is reported that the liver flukes die in from 3 to 8 days. For the expulsion of tapeworms in sheep a dose of from 45 grains to 1% drachms is administered in water or thin syrup. This dose is repeated in 4 hours. If symptoms of poisoning occur, a saline purgation should be administered. Magdala Rose (Sudan Bed, Bose Naphthylamine) . — Lievre" has rec- ommended magdala rose as an excellent anthelmintic against liver fluke. A 1 per cent solution is injected intravenously. It is excreted rapidly, and apparently exclusively, in the bile. Male Fern (Aspidium) . — The powdered rhizome of filix mas (male fern) is one of the oldest drugs known ; as mentioned in an earlier para- 11 Lievre, H. Donnees experimentales sur les agents Therapeutiques de la distoma- tose a Fasciola hepatica. Ann. Parasit. Humaine et Comparee. 12(6) :511-20. 1934. 22 University of California — Experiment Station graph, its anthelmintic properties were well known to such early Greeks as Pliny and Galen. Then it seems to have been forgotten until the eighteenth century. In 1764, Valmont de Bomare redescribed its anthel- mintic properties. In 1884, Grassi and Calandruccio reported favorably on its use in the treatment of sheep infested with liver flukes. Within a few years patent preparations of male fern appeared in many European countries under trade names and since that time the literature is filled with references to male-fern treatment under the proprietary names of "Filmaron," "Fasciolin," "Avisciolina," "Danistol," and "Distol"— all male-fern extractions containing approximately 22 to 26 per cent filicine, the active agent in the male-fern preparations. Male fern is effective against adult liver flukes and affords an adequate treatment where infestation is not too heavy. In such cases death is some- times caused in lambs by hordes of immature flukes too small to be reached by the treatment. The recommended treatment is to administer 4 grams (1 teaspoon ful) of extract of male fern containing 25 per cent filicine in 10 cc (2% teaspoonfuls) of nonpurgative oil on five successive mornings at least 2 hours before the animal is allowed to feed. Male fern, however, is a very toxic substance and should not be ad- ministered to animals of low vitality. It should not be given in preg- nancy. The treatment should probably not be repeated within 7 to 10 days if the first treatment has been unsuccessful. "Nema." — See " T ctrachlor ethylene." Nicotine Sulfate (Black Leaf 40) . — See "Clinic Mixture." Picric Acid (Trinitrophenol) . — According to Magens 12 infections of lungworms are reported to have been effectively treated by means of in- tratracheal injections of a 0.2 per cent aqueous solution of picric acid in a dose ranging from 2 to 5 cc. The treatment is repeated in 3 or 4 days. In toxic quantities, picric acid destroys the red corpuscles. . T ctrachlor ethylene ("Nema") . — This drug, as previously described, is closely related to carbon tetrachloride and chloroform and it has gained very wide and popular anthelmintic use, largely replacing carbon tetra- chloride in the treatment of intestinal worms during the past ten years. Tetrachlorethylene is administered in soft gelatin capsules in doses of 0.091 cc per pound of body weight without purgation. Care must be taken not to break the capsule in the mouth and thereby cause inhalation - intoxication. It has no appreciable effect on the liver, but dizziness and incoordination may occasionally follow treatment ; probably because of excessive fatty food. It is not dangerous in cases of calcium deficiency. 12 Magens, H. J. Pulmonary strongylosis of the small ruminants. Vet. Med. 29: 316-19. 1934. Bul. 603] Parasites of Sheep 23 Tetrachlorethylene should be avoided under the same conditions as carbon tetrachloride but the harmful effects are not so pronounced as in the case of the latter. Summary. — The fact remains, however, that until a material is dis- covered which cannot escape the alimentary canal of the host, but which can penetrate and kill the worms lying therein, the existing anthelmin- tics must be used with great caution. In addition to any toxic effects that a chemical may exercise on the treated animals, the mere excitement and nervousness caused by the handling has a detrimental effect on the animals. Consequently, the grower should be sure that his flock needs treatment before he subjects them to the shock of treatment and han- dling. TECHNIQUE OF ADMINISTERING TREATMENT In general, soft gelatin capsules are best administered by means of re- curved forceps which release the capsule upon pressure on the handles. The forceps are inserted at the side of the mouth, then between the jaws behind the teeth and well down into the throat, thus making sure that the capsule will be swallowed. A capsule released too far forward on the tongue is apt to be broken between the animal's jaws, and the drug in- haled. After the forceps have been withdrawn, the grasping of the muzzle and lower jaw with slight pressure facilitates swallowing. In order to avoid unnecessary handling and excitement of the animals during "pill- ing," a chute is used and the sheep crowded into it rather closely. The operator, carrying the pills in a suitable pouch or his pocket, works from the lower to the upper end of the chute treating each animal as he ap- proaches it from the rear. In this manner and particularly if a narrow chute is used, the treated animals are always behind the operator and the mixing of treated with nontreated sheep is prevented. If such a chute is not available, any small corral or enclosure such as a marking corral can be used. In this case, however, one or two men are employed to catch the lambs, carry them to the operator, hold them while he treats them, and then place them in another corral. Where mature sheep or large yearlings are to be treated, the animals can be crowded against the fence and held by the operator's knee during the treatment. By using either of these methods, and after a small amount of practice, from 50 to 70 sheep can be "pilled" in an hour. When the medication is to be administered in a liquid form by means of the oral drench, a 4-ounce (120-cc) metal dosage syringe with a 3-inch curved delivery tube is used. A syringe employing a leather plunger rather than a metal plunger is advisable because the corrosive action of the salt solutions, particularly of copper salts, soon renders the metal 24 University of California — Experiment Station plunger inefficient for use. A 4-ounce (liquid measure) syringe is rec- ommended since that amount is the commonest dose administered. By marking the plunger shaft, the syringe can be calibrated to deliver any desired amount up to 4 ounces. In "drenching," a chute is advantageous and the operator proceeds as described for "pilling." The sheep are crowded into the chute and the operator approaches the animal from the rear, grasps the head of the animal, and holds it against his thigh, but takes care not to raise the animal's head much higher than is normal. The delivery tube is inserted well back between the jaws but not down the throat, and the liquid is slowly forced into the animal's mouth as it swallows. A gentle rotating of the syringe induces swallowing. The liquid should not be forced into the mouth at such a rate as to cause the animal to choke or spill it. Where a large number of animals are to be treated, it is recommended that the solution be mixed and kept in enamel buckets. The use of two syringes with a man to keep them filled for the operator greatly speeds up the procedure. A skillful operator can drench from 30 to 40 animals an hour. The importance of careful and quiet handling of sheep at all times cannot be overemphasized. Indeed, many of the severe reactions to medi- cations arise from the excitement and nervousness caused by rough, care- less, and unskillful handling during the treatment. If the animals are handled carefully and removed as little as possible from their normal positions during treatment, many of the severe reactions sometimes at- tendant upon such treatment will be materially reduced. Considerable debate lias been recorded regarding the immediate fate of medications administered when the animals were standing on their feet or placed on their haunches at the time of treatment. Trials have indicated that regardless of position, the medication is received in the rumen, and its passage along the tract is governed by its own form — liquid, powder, or capsule — and by the rapidity of food movement. NEMATODES Nematodes are the roundworms as distinguished from the tapeworms (Cestodes) and the flukes (Trematodes). They are characterized by be- ing cylindrical, unsegmented, but with a flexible "skin" and without a proboscis. Included in the group are both free-living and parasitic forms. Of the parasitic forms found in sheep, the size ranges from 6 mm in the case of Strongyloides to 20 cm in the large intestinal worm, Ascaris lumbricoides, which sheep share with man and hogs. Bul. 603J Parasites of Sheep 25 In most species the males and females occur as separate individuals although hermaphroditism and parthenogenesis do occur among the nematodes. The males are generally much smaller than the females and are frequently overlooked or considered as immature females. They are of considerable importance in classifying the species, however, on account of the presence of external characters specific for the species concerned (fig. 5). In the males the genital and alimentary systems open to the exterior at the posterior end of the body through a single opening or cloaca. In most forms chitinoid strips called spicules protrude from this cloaca as accessory copula- Spicules GuBERNACULuM Telamon Ventral SYSTEM Ventro-ventral RAY Latero-Ventoal RAY Antero- lateral ray Medio lateral RAY Post ero- Lateral «av Fig. 5 — The posterior end of a bursate male nematode, illustrating the various structures used in classification. tory structures. When the dorsal wall of the cloaca is chitinized as a guide, the single or double structure formed is called a gubernaculum or accessory piece. In case the ventral wall is similarly thickened, it is called a telamon. In addition to these struc- tures, many species of worms have flaring, bell-shaped flaps of membranous tissue surrounding the posterior end of the body at the opening of the genital system. When these flaps are supported by thickened ribs or rays, the whole structure is known as a bursa. In the females the opening of the genital system may be practically anywhere in the body from the anterior third to the posterior end, but the anus is toward the pos- terior end of the body. The anterior opening of the alimentary canal in both males and females is the mouth, which may be surrounded by lips or the lips may be replaced by specialized structures. The terms buccal capsule and pharynx are used loosely in the literature. Both of these terms refer to a special cavity with thickened cuticular or chitinoid walls, which leads into the alimentary canal. When the cuticular wall is without muscular investment it is called the buccal capsule. When the lumen is more narrowed and the wall is enclosed in muscles as the result of a more intimate connection with the esophagus, it is termed the pharynx. The esophagus is a muscular tube extending posteriorly from the mouth and may terminate in a bulb. 26 University of California — Experiment Station In some cases the cuticle or skin of the worm is extended from the body in the shape of a wing or fin. These are termed alae and are designated as cephalic alae if they occur at the anterior end of the body or caudal alae if associated with the posterior end. The cervical papillae, which are used as distinguishing characters in some cases, are tiny, pointed structures protruding from the cuticle in the esophageal portion of the worm. Nematodes as a rule deposite eggs containing a formless mass of undifferentiated material. In some cases the mass has begun to divide into cells when they are said to be "segmented." In a few species the embryos emerge from the egg in the maternal body. For convenience, we are listing the portion of the host's body where the parasites are most generally found. This is, of necessity, inexact, since the larval forms often migrate and even the adults are frequently found in unusual situations far removed from their place of normal habitation. LUNGS Thread lungworms Dictyocaulus 1 Whitish forms, diameter of thick linen thread, with brown Metastrongylus { lines; male, 1.2-10.0 cm x 4 mm. Hair lungworms Protostrongylus ) If it • ( Reddish worms, hairlike in thickness; 2.5-3.5 cm x 0.17 mm. ESOPHAGUS Gongylonema : Burrowing in the lining ; with oval bosses on the cuticle. RUMEN OR PAUNCH Gongylonema : Free in the lumen or burrowing in the lining ; with oval bosses on the cuticle. ABOMASUM OR FOURTH STOMACH Females over 12 mm long: Oesophagostomum : Female 14-22 x 0.3-0.5 mm; with a shallow buccal capsule and crown of oral teeth. Haemonchus: Female 18-30x0.4—0.5 mm; without a buccal capsule; male bursa asymetrical. Mecisto circus: Female 24-29 x 0.5-0.6 mm; without a buccal capsule; male bursa symetrical. Females under 12 mm long : Ostertagia: Female 9-12 x 0.10-0.16 mm; cervical papillae present. Trichostrongylus : Female 4.6-6.8 x 0.05-0.13 mm; cervical papillae absent; acces- sory piece present. Cooperia: Female 5.8-8 x 0.07-0.19 mm; cervical papillae absent; accessory piece absent. SMALL INTESTINE Females over 9 mm long : Ascaris: Over 2 mm in thickness; large worm frequently approaching the size of a lead pencil. Mecistocirrus : 24-29x0.5-0.6 mm; no buccal capsule; symmetrical bursal lobes. Bul. 603] Parasites of Sheep 27 Nematodirus: 12-23 x 0.15-0.225 mm; posterior part of body abruptly wider than anterior part. Ostertagia: 9-12 x 0.10-0.16 mm; 2 spicules, eggs without plugs. Bunostomum: 19-28 x 0.50-0.75 mm; bucal capsule present; no intestinal nodules. Haemonchus: 18-30 x 0.4—0.5 mm ; no buccal capsule; asymmetrical bursa. Capillaria : 12-20 x 0.08 mm ; single spicule ; eggs with plugs. Oesophagostomum : 14—22 x 0.3-0.5 mm; shallow buccal capsule present; intesti- nal nodules for larvae. Females less than 9 mm long : Trichostrongylus : 4.6—8.0x0.05-0.13 mm; spicules of male with accessory piece. Trichinella : 3-4 x 0.06 mm; seldom found in the lumen; esophagus surrounded by chain of pearllike cells ; not tapered appreciably. Strongyloides : 3.5-6.0 x 0.05-0.06 mm; extremely small clear worms; all females;, with 12-15 eggs only. LARGE INTESTINE Oesophagostomum : 14-22 x 0.3-0.5 mm; with buccal capsule; mouth opening ter- minal. Chabertia ovina: 17—20x0.5 mm; with buccal capsule; mouth opening obliquely to the side and always filled with fecal material. Trichuris ovis: 35-70 mm long; without buccal capsule, anterior end hairlike, gradually expanding posteriorly. Slcrjabinema ovis: 7.6-8.0x0.26-0.57 mm; without a buccal capsule; esophagus terminating in a bulb. ASCARIS LUMBRICOIDES L. 1758 Asearis lumbricoides L. 1758 Fusaria lumbricoides L. 1758 Stomachida pereboomii Goeze 1782 Fusaria lumbricoides (L.) Zeder 1800 Lumbricoides vulgaris Merat 1821 Asearis suum Goeze 1782 Asearis suilla Dujardin 1845 Asearis ovis Eudolphi 1819 Asearis vitulorum Goeze 1782 Asearis vituli Goeze 1790 Asearis lumbricoides is the intestinal roundworm of man, swine, sheep, and probably cattle (the form described as vitulorum) . It is sel- dom found in range sheep. In barnyard flocks or in lambs that have been taken into headquarters for nursing and subsequently been allowed to associate with other farm animals, the infestation is sometimes found, although never in numbers sufficient to warrant treatment. It is included here on account of the curiosity its presence always causes at autopsy. Description. — The adult worms are pinkish yellow, cylindrical and wiry, and in sheep the females measure 10-18 cm in length and about 3 mm in thickness. The specimens found in sheep seldom attain the size that the same species reaches in man or swine. The males are slightly 28 University of California — Experiment Station smaller than the females with the posterior end of the body rolled into a tight curl. Two short spicules emerge from the cloaca within the curl. The mouth opening is guarded by three. lips which may be noted without magnification. Life History. — The eggs, which may be distinguished from all other nematode eggs in the feces by their rough shell and yellowish pigmenta- tion, are passed from the body in the feces in an unsegmented condition. In the presence of moisture (just enough to prevent desiccation of the egg) , development takes place, and in from 10 days to 2 weeks an embryo has matured within the egg and molted once. If the egg is then swallowed by a susceptible animal, the larva emerges from the egg, penetrates the wall of the alimentary canal, enters the blood stream, and is thus car- ried to the lungs; there it burrows into the air spaces, moves up the trachea, is swallowed, and eventually arrives back in the small intestine, where it grows to maturity. Treatment. — Seldom necessary since infestations are never heavy. Hosts. — Man, swine, sheep, cattle. Habitat. — Small intestine. Distribution. — Cosmopolitan. THE PIN WORM, SKRJABINEMA OVIS (SKRJABIN 1915) Oxyuris ovis Skrjabin 1915 STcrjabinema ovis (Skrjabin 1915) Vereschagin 1926 Skrjabinema ovis is the only pin worm reported from sheep, and thus far it has been found only in Russia and Germany in sheep and goats. Any small worm approaching its size (7.6-8.0 x 0.26-0.57 mm) that is found in the large intestine should be examined for a bulbar termination of the esophagus. In addition, the cuticle of the anterior end of the body is inflated, the inflation being followed by a pair of lateral wings or alae. Nothing is reported concerning its life history, but it is assumed to be direct without the aid of an intermediary host. This worm is apparently not pathogenic. Hosts. — Sheep, goats. Habitat. — Large intestine. Distribution. — Russia and Germany. STRONGYLOSES PAPILLOSUS (WEDL 1856) Trichosoma papillosum Wedl 1856 Bhabdonema longus Grassi and Segre 1887 Strongyloides longus (Grassi and Segre 1887) Rovelli 1888 Strongyloides suis Lutz 1894 Strongyloides papillosus (Wedl 1856) Ransom 1911 Strongyloides papillosus (3.5 x 0.05-0.06 mm) sometimes invades the small intestine in enormous numbers and burrows into the mucosa. No Bul. 603] Parasites of Sheep 29 males are present in the parasitic generation. The eggs are produced in small numbers by these parasitic females, only 12 to 15 being present in each worm at one time. These eggs hatch in the intestine, pass from the host with the feces as larval worms and develop in the moist manure. From this point on the embryos may develop into a free-living generation of parasitic larvae or they may develop directly into infectious larvae without the interruption of the free-living generation. In either case all the infectious larvae capable of invading another vertebrate host are ap- parently females. They may burrow directly through the skin, in which case they are carried by the blood to the lungs and thence follow the routine outlined for the large roundworm, Ascaris. This is the usual procedure for Strongyloides stercoralis, which parasitizes man, but 8. papillosus apparently invades the animals principally through the oral route and there is no evidence that it passes through the lungs. Pathogenicity. -^There is little information on pathogenicity. Cases seen by us were discovered only as a result of routine autopsies where the presence of the parasites had not been suspected previously. Other investigators have reported them as the causative agents of extreme diar- rhea. No mention has been made of any clinical manifestation of their passage through the lungs as larvae nor has such a migration ever been demonstrated for the forms parasitic in sheep. Reference has been made to the fact that infestations were very apt to be self -limited, cures ap- pearing spontaneously. This may be the usual procedure, but on the other hand, it might be caused by a lack of continuous infestation or by an infestation of a physiological strain of the parasite not adapted to the specific host. In reference to the last theory, it is frequently possible to infest animals experimentally with species of Strongyloides not natur- ally parasitic in the particular host, but the infestation persists for only a short time. Treatment. — There is apparently no specific treatment that is very efficient on account of the fact that the adults are buried in the mucosa. Carbon tetrachloride and tetrachlorethylene have been used with vary- ing success. According to Faust, 13 gentian violet appears to be effective against Strongyloides and should be tried on domestic animals. Hexylre- sorcinol also may be useful. Hosts. — Sheep, cattle, goats, swine, rabbits, mice. Habitat. — Small intestine. Distribution. — North America, Europe. 13 Faust, E. C. The symptomatology, diagnosis and treatment of Strongyloides infection. Jour. Amer. Med. Assoc. 98(26) :2276-2277. 1932. 30 University of California — Experiment Station THE NODULAR WORMS Three species of nodular worms belonging to the genus Oesophago- stomum are reported from sheep — columbianum primarily from sheep, venulosum from deer, and radiatum from cattle. The species infesting deer, Oesophagostomum venulosum, is the most commonly encountered in California sheep. Life History. — These worms hatch rapidly from the eggs that are ex- pelled in the feces and after molting twice without shedding their skins climb up blades of grass that are moistened with rain or dew and retreat to the soil as the moisture fails. When they are eaten, they pass through the stomach to the intestine, where they emerge from the sheath of cast skins and immediately burrow into the lining of the intestine and pene- trate to the surface of the muscular layer. This is accomplished in a few hours. The body reacts to the presence of the worm by forming whitish cysts 1 to 2 mm in diameter, which sometimes coalesce to form single nodules the size of a pea. Sometimes several worms are included in a single cyst. Growth takes place within the cyst, which eventually opens to the inside and becomes indurated and filled with a yellowish or green- ish caseous material surrounding the larval worms. In lambs, the larval worms leave the cysts at times varying from one to three months after infection, but in adult sheep the larval worms may persist in the nodules for six months or sometimes even longer. As soon as the larvae leave the cyst, the normal process of repair is for the cyst to subside and to become infiltrated and calcareous. With heavily para- sitized animals, however, their weakened condition allows a secondary bacterial infection to become initiated in these open lesions and if severe enough, the animal may die from a septicemic infection. The larval worms reach maturity in the lumen of the intestine, after which they may persist for nearly two years, at least in experimental cases. Lambs seem to be a much more suitable host for nodular worms than adult sheep, to judge from the rapidity with which the worms de- velop in them and the facility with which adult sheep succeed in elimi- nating fourth-stage and adult worms from the intestine. Apparently there is little resistance on the part of sheep or lambs to the cysts for- mation by the invading larvae, but when the parasites emerge from the cysts to take up their adult life in the lumen, they are swept out of the body in large numbers in diarrheal attacks. It is not uncommon to find adult sheep with cysts that have recently been inhabited by larval worms and open cysts still harboring worms but without a single worm free in Bul. 603] Parasites of Sheep 31 the lumen. In these cases the fourth-stage and adult worms apparently have been voided with the feces as soon as they venture out of the pro- tection of the cyst. Symptoms. — In serious cases the cysts may perforate the intestine and cause a peritonitis, which is frequently fatal. In addition to the damage caused by the cyst formation and its consequent tissue destruc- tion, there is a definite poisoning that follows the emergence of the worms from the cysts. This generally occurs about three months after the in- gestion of the infectious worms took place. It is apparently caused by the toxin secreted by the worms and in severe cases in addition to emacia- tion, and anemia, there is often a paresis of the hind legs or sometimes of all four legs. The diarrhea accompanying attacks of oesophagostomiasis is apparently beneficial rather than harmful, since it is a natural method of eliminating the fourth-stage and adult worms from the intestines. Although nodule formation has been emphasized, in cases of initial infection of lambs, the rapid growth of the larvae and their emergence from the cysts causes these to become indistinguishable almost immedi- ately. Thus we often have the anachronism of nodular worms without apparent nodules. This condition is particularly apparent in California, where the nodular worm of the deer is encountered in sheep most fre- quently. Treatment. — There is no adequate treatment that will give consistent results and even the most promising fail to reach the encysted larval worms and must be repeated at monthly intervals. Carbon tetrachloride and tetrachlorethylene will remove varying numbers of worms. Monnig 1 * in reporting upon recent preliminary tests of treatments for esophagostomiasis in sheep indicates that the problem can only be solved when a method is devised for dosing directly into the fourth stomach. He obtained best results when relatively insoluble drugs were used since these reach the colon unchanged. Of seventy-two differ- ent drugs used experimentally, arsenious sulfide and sodium fluosilicate were the most promising. Later 15 he recommended enemas of from 1 to 2 pints of liquid government wireworm remedy, the dose depending on the size of the sheep. Veglia recommends the use of a mixture of copper sulfate and sodium arsenite, the so-called government wireworm remedy of South Africa. The cunic mixture has also been recommended, as has a lick composed of tobacco powder moistened with saturated salt solu- tion. Brumpt obtained satisfactory results with enemas of 1 gram of 14 Monnig, H. O. The chemotherapy of oesophagostomiasis in sheep. Onderstepoort Jour. Vet. Sci. and Anim. Indus. l(l):67-76. 1933. 15 Monnig, H. O. Veterinary helminthology and entomology, p. 165. Win. Wood and Co., Baltimore. 1934. 32 University of California — Experiment Station powdered thymol in a liter of acacia gum solution. Croton oil adminis- tered with castor oil at the rate of 3 cc per animal in 17 cc of the latter gave some relief through a purely mechanical action of purgation. Hex- ylresorcinol may be very useful in enemas. Hexylmeta-cresol, however, does not have the bad irritating qualities of hexylresorcinol. Prevention. — The habit of the infectious larvae of migrating up and down moist plants and their habit of protecting themselves in the soil during unfavorable times makes this worm less dependent on moisture conditions than those that require permanent moisture. However, pro- tracted dry seasons such as occur in California tend to minimize the damage from this type of worm invasion, for all stages of development from the egg up to the infective larval stage succumb immediately to desiccation. The infective larvae, however, are able to withstand three months of drying under ordinary room conditions without protection and have been known to persist for from two to three months in tap- water. The infections found in California sheep are what one might call "single-brooded" in that all the individuals present are generally of about the same approximate size and maturity. This is particularly true of the early spring cases in lambs and yearlings resulting from an in- fection contracted at the time of the early rains. If lambs are confined to bare feed lots with sanitary drinking troughs, little or no infection results. Animals on dry upland pastures are less heavily parasitized than those having access to low swampy swales or poorly drained lowlands. The nodular-disease problem is not at all serious in California, the true nodular worm of sheep, Oesophagostomum (Proteracrum) colum- bianum being almost entirely replaced by the species common to deer, Oesophagostomum venulosum, which never produces as serious results in sheep as the former. OESOPHAGOSTOMUM COLUMBIANUM (CUETICE 1890) Oesophagostoma columbianum Curtice 1890 Hypostomum columbiana (Curtice 1890) Stewart 1898 Oesophagostomum columbianum (Curtice 1890) Stossich 1899 Oesophagostomum (Proteracrum) columbianum (Curtice 1890) Railliet and Henry 1913 Oesophagostomum columbianum, the typical nodular worm of eastern sheep, is differentiated from Oe. venulosum, the nodular worm of deer, which is most commonly found in western sheep, by the fact that its cervical papillae appear within the length of its esophagus (fig. 6, A), whereas in venulosum they appear below the esophagus (fig. 6, C). It is separated from radiatum (fig. 6, B) , the nodular worm of cattle, by hav- Bul. 603] Parasites of Sheep 33 ing a hemispherical mouth collar and by lacking- the inflated cuticle in the head region. Measurements. — Females 12-16 x 0.35 mm and males 14-18 x 0.40 mm. Hosts. — Sheep, goats. Habitat. — Principally large intestine but occasionally in small intestine or even fourth stomach. Distribution. — North America, Africa, Australia. Fig. 6. — The anterior ends of nodular worms: A, Oesophagostomum columbianum ; B, Oe. radiatum; C, Oe. venulosum. OESOPHAGOSTOMUM VENULOSUM (EUDOLPHI 1809) Strongylus venulosus Eud. 1809 Strongylus radiatus Eud. 1803 in Dujardin 1845 (partim) Strongylus contortus Eud. 1803 in Diesing 1851 (misdetermination) Strongylus ammonis Eud. 1819 in Molin 1861 Oesophagostomum acutum Molin 1861 Oesophagostomum inflatum ovis Carita 1887 Hysteracrum venulosum (Eud. 1809) Eailliet 1896. Strongylus follicularis Ostertag in Olt 1898 Oesophagostomum venulosum is the species most commonly encoun- tered in California sheep but the infestations are seldom heavy or serious. 34 University of California — Experiment Station It is differentiated from the other members of the genus by the char- acters mentioned in the discussion of Oe. columbianum above. Measurements. — Females 13-24 x 0.4-0.5 mm; males, 12-16 x 0.3-0.4 mm. Hosts. — Sheep, goats, elk, deer. Habitat. — Large intestine and occasionally small intestine and fourth stomach. Distribution. — North America, Europe. OESOPHAGOSTOMUM RADIATUM (RUDOLPHI 1803) Strongylus radiatus Rud. 1803 Strongylus inflatus Schneider 1886 (nee Molin 1861) Strongylus diliatus Railliet 1884 (S. inflatus Schneider 1866 renamed) Oesophagostoma inflatum (Schneider 1866) Eailliet 1896 Oesophagostomum dilatatum (Eailliet 1884) Eailliet 1896 Oesophagostomum radiatum (Eud. 1803) Eailliet 1898 Oesophagostomum vesiculosum Eatz 1898 Oesophagostomum bovis Schnyder 1906 Oesophagostomum biramosum Cuille, Marotel, and Panisset 1911 Oesophagostomum (Proteracrum) radiatum (Eud. 1803) Eailliet and Henry 1913 Oesophagostomum radiatum var. trifurcatum Lane 1917 Oesophagostomum radiatum is the typical species found in cattle, but in cases where the pasturage is shared with sheep, the latter frequently become infected. It differs from Oe. venulosum by having the cervical papillae within the length of the esophagus and from Oe. columbianum by having the cuticle at the anterior end swollen (fig. 6, B) . It also differs from the other two species by confining its nodule formation largely to the small intestine. Measurements. — Female, 16-22x0.3-0.4 mm; male, 14-17x0.3-0.4 mm. Hosts. — Cattle, sheep, zebra ( ? ) . Habitat. — Small intestine. Distribution. — North America, Europe, Australia, Africa (Sudan). CHABERTIA OVINA (FABRICIUS 1788) Strongylus ovinus Fabricius 1788 Strongylus contortus Rudolphi 1802 (partim) Strongylus ventricosus Rud. 1809 (partim) Strongylus hypostomus Rud. 1819 Strongylus cernuus Creplin 1829 (partim) Sclerostoma hypostomum (Rud. 1819) Dujardin 1845 Dochmius hypostom,us (Rud. 1819) Diesing 1851 (partim) Sclerostomum hypostomum (Rud. 1819) Leuckart 1867 Sclerostomum ovinum Stossich 1899 Chabertia ovina (Fab. 1788) Railliet and Henry 1909 Chabertia ovina is a very common inhabitant of the large intestine of sheep. It is shining white, relatively thick, and wirelike. When removed from the contents of the canal, it almost invariably has a mouthful of food material which comes away with the worm, giving it the appearance Bul. 603] Parasites of Sheep 35 Fig. 7.— The an- terior end of Chab- ertia ovina. of having a brown cap on its anterior end. When this food material is removed, it is noted that the opening of the mouth cavity is not terminal but opens obliquely (fig. 7). Formerly it was considered as a harmless scavenger, but recently sev- eral epidemics have been recorded in which it was apparently the cause, when present in large numbers, of extreme diarrhea with blood and mucus, emaciation, and a colitis that was pronounced the cause of death. It has been ac- cused by some investigators of being a blood sucker. Life History. — The egg develops in moist locations after passage from the host in the feces. It hatches and the young free-living larva molts before it is in- fectious. There is little accurate knowledge of how the process proceeds from this point, but the general as- sumption is that this infectious larval stage is ingested with food or water and the infection established in the large intestine without further complications. Treatment. — Treatment is not often necessary. Tetrachlorethylene removes a large percentage of the worms, but their position in the large intestine makes any treatment difficult. Measurements. — Female, 17-20x0.5 mm; male, 13-14x0.3 mm. Hosts. — Sheep, cattle, goats, deer, gazelle, stag, and others. Distribution. — North and South America, Europe, Asia, and Australia. Habitat. — Large intestine. HOOKWORMS Two species of hookworms are parasitic in the small intestine of sheep. They are approximately an inch long, threadlike, reddish, and with the "neck" bent so that the mouth is directed at an angle. Like the related worms that infect man, these worms are very serious parasites when they are abundant. Fortunately, in California dry summers evidently keep these enemies in bounds and there is no serious trouble with them except that they are encountered from time to time to perplex the discoverer. Life History. — In the presence of moisture, the eggs, which are voided from the body with the feces, hatch, and the free-living larva molts its skin and becomes encased in the shed skin. In this condition it is ex- tremely resistant to changes in temperature and for a short time to desiccation. Although these worms are closely related to the human hookworms, they apparently lack the ability of these relatives to bore through the unabrased skin. Apparently the infective larvae are swal- lowed with the food and water. Although older references imply that 36 University of California — Experiment Station they may burrow through the skin, these complications were based on assumptions, and later work by Schwartz and Cameron indicates that the infective larvae are unable to pierce the skin. Symptoms. — These worms are blood suckers and as such cause more damage per individual than those that merely live in the lumen or bur- row in the mucosa. They secrete a fluid to prevent the blood from coagu- lating, which together with the actual loss of blood tends to produce a severe anemia. Their habit of changing their point of attachment at fre- quent intervals leaves many tiny bleeding spots on the intestinal wall, which increase the loss of blood and provide an entry for bacterial in- vaders. The end result of the anemia is a pronounced edema, manifested by the pendulous bottle jaw and belly ; the mucous membranes are pale, the skin parchmentlike, and the wool dry. It must be borne in mind that these symptoms are almost universal for nematode parasites of sheep, but they are produced so constantly by only moderate infestations of hookworms that they are noted here especially. The identical symptoms are manifested for severe infestations of stomach worms, trichostron- gyles, and the late stages of liver-fluke disease ; and the only differen- tiation is by autopsy and the identification of the worms involved. Treatment. — Sheep hookworms yield very readily to tetrachlorethy- lene, carbon tetrachloride, oil of chenopodium, and less readily to the routine stomach worm treatment with cunic mixture. BUNOSTOMUM TRIGONOCEPHALUM (RUDOLPHI 1808) Strongylus trigonocephalies Rud. 1808 Sclerostoma hypostomum (Rud. 1809) Dujardin 1845 (partim) Strongylus cernuus Creplin 1829 (partim) Dochmius hypostomus (Rud. 1819) Diesing 1851 (partim) Monodontus wedlii Molin 1861 Dochmius cernuus (Creplin 1829) Railliet 1868 (partim) Uncinaria cernua (Creplin 1829) Railliet 1885 Strongylus (Monodontus) cernuus (Crep. 1829) Railliet 1900 Uncinaria (Monodontus) cernua (Crep. 1829) Railliet 1900 Monodontus trigonocephalus (Rud. 1808) Railliet 1900 Bunostomum trigonocephalum (Rud. 1808) Railliet 1902 Bunostomum hashinathi Lane 1917 Bunostomum trigonocephalum is the primary hookworm of sheep. From B. phlebotomum, which is primarily a parasite of cattle, but oc- casionally occurs in sheep, it is differentiated by having but three hooks in the mouth cavity — a large dorsal one and two ventral ones (fig. 8, A) , while B. phlebotomum has a small dorsal one and two ventral and two subventral ones that are leaflike (fig. 8, B). These hooks are difficult to discern and somewhat variable, but the species are easily differentiated Bul. 603] Parasites of Sheep 37 A Fig. 8. — The anterior ends of sheep hookworms: A, Bunostomum trigonocephalum ; B, B. phlebotomum. Fig. 9. — The posterior ends of the males of the sheep hookworms A, Bunostomum trigonocephalum ; B, B. phlebotomum. 38 University of California — Experiment Station by the males ; the spicules of the male are very short and pointed, in trigonocephalum, not reaching the bursa (fig. 9, A), while in phleboto- mum they are spatulate and extend through and beyond the tip of the bursa for at least a quarter of their length (fig. 9, B) . Bunostomum trigonocephalum is common throughout the southern states but does not thrive (although it does occur) north of the hard- frost belt. It has been taken in California sheep. Measurements. — Female, 19-25x0.50-0.75 mm; male, 12-16x0.50 mm. Hosts. — Sheep, goats, cattle. Distribution. — North America, Europe, Africa, and India. Habitat. — Small intestine. BUNOSTOMUM PHLEBOTOMUM (EAILLIET 1900) Strongylus radiatus Rudolphi 1803 (partim) in Schneider 1866 Uncinaria radiata (Rud. 1803) Railliet 1885 (partim) Dochmius radiatus (Rud. 1803) Leuckart 1868 Ankylostoma bovis Strose 1894 Monodontus phlebotomus Railliet 1900 Bunostomum phlebotomum Railliet 1902 (Strongylus radiatus Rud. in Schneider 1866 renamed) Bunostomum radiatum (Rud. in Schneider 1866) Linstow 1906 Uncinaria radiata (Rud. 1803) Bustomum phlebotomum (Railliet 1900) Lane 1917 Bunostomum phlebotomum is the cattle hookworm, which is a serious parasite of these animals in some of the southern states. It has been re- ported from sheep, but although the writers have taken it from cattle in California, it has never been recovered from sheep in this state. It is differentiated from the sheep hookworm as outlined on pages 36-38. Measurements. — Female, 16-19x0.50-0.55 mm; male, 10-12x0.45-0.50 mm. Hosts. — Cattle, sheep. Distribution. — North and South America, Europe, India, Sumatra. Habitat. — Small intestine. KEY TO THE FAMILY TRICHOSTRONGYLIDAE 1. Dorsal lobe of bursa asymmetrical (fig. 10, B) Haemonchus Dorsal lobe of bursa symmetrical 2 2. Spicules short and thick with knobs, indentations, or spikes (fig. 11, B; 12) 3 Spicules ribbonlike, long and slender 5 3. Median accessory bursal membrane with two divergent ribs lying within the bursa (fig. 12, A ) Ostertagia Without this accessory membrane 4 4. Anterior end with striking transverse stripes Cooperia Anterior end without striking transverse stripes Tricho strongylus 5. Body abruptly narrowed behind with the vulva ; anterior end slightly swollen and transversely striped; no cervical papillae. . Nematodirus Body evenly tapered; anterior end not swollen or transversely striped; cervical papillae present Mecistocirrus Bul. 603] Parasites of Sheep 39 THE EASTERN STOMACH WORM, HAEMONCHUS CONTORTUS (RUDOLPHI 1803) Strongylus contortus Rud. 1803 Strongylus fillicollis Molin 1861 (partim) Abomesi ovis Simmonds 1881 Strongylus placei Place 1893 Haemonchus contortus (Rud. 1803) Cobb 1898 Haemonchus fuhrmanni Kamensky 1929 Haemonchus atectus Lebedef 1929 Haemonchus pseudocontortus Lebedef 1929 Haemonchus contortus is the stomach worm, twisted wireworm, or wireworm of eastern sheep, which is becoming a disturbing factor in California animals. Up to comparatively recent years but little impor- tance was placed on this worm in California although it is perhaps the worst parasitic enemy of sheep in the eastern and southern sections of the country. Authorities considered that west of the Sierra its place was taken by the so-called "western stomach worm," Ostertagia spp. Re- cently, however, the increasing occurrence under California conditions has pointed to its importance. Whether this is caused by an increased accuracy in determinations of species or whether it is actually increasing in numbers is problematical, but within the last two years reports of its occurrence in serious infestations have come from both the southern and northern sections of the state, particularly from the high, well- watered valleys and irrigated pastures. These worms are primarily parasitic in the fourth stomach, although they may be found in the small intestine. They are not readily detected when present in small numbers on account of their small size. For field autopsies a slit is made in the fourth stomach, and without spilling its liquid contents, both sides of the slit are grasped in order to peer into the contents. A wavy motion in the liquid indicates the presence of a worm, which may be captured for identification. In heavy infestations the entire surface of the fourth stomach may be carpeted with a network of worms which are, of course, very evident. Scraping the mucosa will demonstrate the worms in lesser infections. The true stomach worm or Haemonchus may be differentiated from Ostertagia worms by the greater thickness of the former. Furthermore, it is distinctly reddish. Microscopically, a tiny tooth may be discerned in its mouth opening (fig. 10, A) and the left side of the bursa of the male has an accessory lobe that is not duplicated on the other side, thus giving it an asymmetrical appearance (fig. 10, B) . Life History. — The egg is segmenting when laid and hatches in a few 40 University op California — Experiment Station hours into a free-living larva which molts twice but retains its cast skins as protection. It has the ability to withstand drying in this stage for as long as four and one-half months, although the actively motile larvae make an effort to migrate with the moisture. This migratory habit is advantageous to the larvae up to a certain point, but it eventually saps their reserve strength and shortens their life. In soil watered without Fig. 10. — Haemonchus contortus, the eastern stomach worm: A, anterior end ; B, posterior end of male. baking the surface crust Monnig 16 succeeded in keeping the infective larvae alive and infective for nine and one-half months in a clay soil. Under natural conditions, however, they lived only about three months in the soil. In tap water the infective larvae exist in an infective stage for from two to three months, apparently wearing themselves out by consuming their reserve energy. Infection is by swallowing the infective larvae ; there is no indication that the larvae can penetrate the skin. Symptoms. — The group of symptoms described for nodular worms will fit the picture of Haemonchus infections adequately. Lambs are much more seriously affected than older animals, for they not only har- bor larger numbers of parasites, but the effect on growth is naturally more important with them than in the older animals. In areas where climatic conditions, such as continued warmth and abundant moisture, are favorable, the lambs pick up infective larvae in cumulative doses, and in order to prevent death monthly treatments must be given during the time that they are picking up the infection. 16 Monnig, H. O. Studies on the bionomics of the free-living stages of Tricho- strongylus spp. and other parasitic nematodes. Union So. Africa Dept. Agr. Kept. Div. Vet. Serv. and Anim. Indus. 16:175-98. 1930. Bul. 603] Parasites of Sheep 41 Treatment. — The standard treatment for stomach worms is a 1 per cent copper sulfate solution, but inasmuch as there is every possibility of other .worms such as Ostertagia or tapeworms being involved, it is ad- visable to use the cunic mixture which includes 1 per cent "Black Leaf 40" in the copper sulfate. In some cases where prolonged treatment is indicated, it is sometimes wiser to alternate the treatments of cunic mixture with other anthelmintics as, for example, the government wire- worm remedy of South Africa or tetrachlorethylene. Prevention. — Since under favorable conditions the infective stage of the larva is reached within 72 hours of its appearance in feces, pasture rotation cannot be looked upon as a method of eradication. However, a susceptible lamb will of course pick up twice as many parasites on a pasture where infected sheep have been grazed for two months as on one where they have been held for only one month, other factors being the same. High, dry pastures facilitate the desiccation of the feces between the time the egg is passed from the host and the time it reaches the infective stage. This period of 72 hours is apparently the deciding factor which determines whether the infection is to become endemic or not ; for after the infective stage is reached considerable dryness can be tolerated. Standing water, if it receives the runoff from moist valleys or seepage areas, is dangerous as a carrier of infective larvae. As a breeding medium for larvae, however, it is negligible, because eggs deposited directly in water of appreciable depth sink to the bottom and fail to hatch. Measurements. — Female, 18-30 x 0.4-0.5 mm; male, 10-20 x 0.25-0.40 mm. Hosts. — Cattle, sheep, goats, man. Distribution. — Cosmopolitan. Habitat. — Fourth stomach and sometimes small intestine. THE OSTERTAGIA STOMACH WORMS Nine species of stomach worms belonging to the genus Ostertagia have been reported from sheep, six of which are reported from North Amer- ica. Three of these have been taken from California sheep and others may, of course, be present. The life history of one of these, Ostertagia circumcincta, which is by far the most important species to sheep in California, has been reported by Threlkeld. Life History. — The eggs are segmenting when deposited with the feces. The larvae hatch from the eggs in 24 hours and in the following 5 or 6 days molt twice to become infective. Two days after ingestion the larvae are found in the rumen and reticulum but have not reached the fourth stomach. By the fourth day, however, all the larvae reach the fourth 42 University of California — Experiment Station stomach and burrow into the mucosa, which causes hemorrhages and some nodule formation. On the ninth day adult form is approached and the worms are attached to but not coiled in the mucosa, and by the fif- teenth day the worms are fully matured. Threlkeld recovered eggs from an artificially infected animal 17 days after oral infection with larvae. Although experiments are being carried on to determine the resistance of these worms to various environmental conditions, there are as yet few significant data concerning this point. Of all the nematodes that have been adequately studied, the larvae of Trichostrongylus appear to be the most resistant to desiccation. The fact that under dry California condi- tions the Ostertagia worms rival the trichostrongyles in numbers would seem to indicate that they too are extremely resistant to drying. Symptoms. — Wherever the infestations are comparable in numbers, the results of an invasion of Ostertagia stomach worms are as dangerous as with Haemonchus and the symptoms are similar. Although California sheep sometimes contract enormous numbers of these parasites, they ap- parently do so only during the late fall, winter, or early spring. Summer infestations are not the rule in California except on well-watered ranges, a fact which allows lambs to mature without the burden of a cumulative summer infection. Treatment. — The cunic mixture is practically specific for these worms, but the straight copper sulfate treatment or a tobacco treatment is never satisfactory. Tetrachlorethylene is more expensive than the cunic mix- ture and no more effective. The species are exceedingly difficult to separate, but the following key, based almost wholly on male characters, may be helpful. KEY TO SPECIES OF OSTEKTAGIA 1. Males more than 9 mm long 2 Males less than 9 mm long 6 2. Spicules more than 0.25 mm long 4 Spicules less than 0.25 mm long 3 3. Gubernaculum lacking tricuspis Gubernaculum present (fig. 11, A) ostertagi 4. Spicules with no gubernaculum marshalli Spicules with gubernaculum 5 5. Spicules long (0.4 mm) and divided at the posterior sixth turJcestanica Spicules shorter (0.29-0.32 mm) and divided for nearly half the length . occidentalis 6. Spicules bifurcate and over 0.25 mm long (fig. 11, B) 7 Spicules single or trif urcate and less than 0.25 mm long 8 7. Male spicules 0.28-0.32 mm long; females with an annulated band at tip of body circumcincta Male spicules 0.5-0.7 mm; females without above band mentulata 8. Spicules unf orked, gubernaculum colorless bullosa Spicules trifurcate, gubernaculum chitinoid (fig. 12, B) trifurcata Bul. 603] Parasites of Sheep 43 Fig. 11. — A, Ostertagia ostertagi, male spicule and gubemaculum ; B, 0. circumcincta, male spicule and guber- naculum. Fig. 12. — Ostertagia trifurcata: A, bursa of the male; B, one spicule and the gubemaculum. 44 University of California — Experiment Station OSTERTAGIA CIRCUMCINCTA (STADELMANN 1894) Strongylus vicarius Stadelmann 1893 ("possibly identical with 0. circumcincta" Ransom 1911) Strongylus instabilis Railliet 1893 (partim) Strongylus circumcincta Stadel. 1894 Strongylus cervicornis MacFadyean 1897 Ostertagia circumcincta (Stad. 1894) Ransom 1907 Ostertagia circumcincta (fig. 11, B) is by far the commonest Ostertagia to be found in California sheep. Measurements. — Female, 10-12 x 0.10-0.16 mm. Hosts. — Sheep, goats. Distribution. — Cosmopolitan. Habitat. — Fourth stomach and sometimes small intestine. OSTERTAGIA MARSHALLI RANSOM 1907 Ostertagia marshalli is consistently present in connection with infec- tions of O. circumcincta in California sheep. The large size of its egg (table 1, p. 7) is a striking feature noticed in fecal examinations. Measurements. — Female, 12-30x0.20-0.26 mm; male, 10-13x0.16-0.20 mm. Hosts. — Sheep and goats. Distribution. — North America (Wyoming, Utah, Montana, and California). Habitat. — Fourth stomach and sometimes small intestine. OSTERTAGIA OSTERTAGI (STILES 1892) Strongylus convolutus Ostertag 1890 (nee S. convolutus Kuhn 1829) Strongylus ostertagi Stiles 1892 (S. convolutus Ostertag 1890 renamed) Strongylus cervicornis MacFadyean 1897 (partim) Strongylus harTceri Stoedler 1901 (partim) Ostertagia ostertagi (Stiles 1892) Ransom 1907 Ostertagia ostertagi (fig. 11,-4.) is the predominant form found in cattle, in which it produces serious symptoms that are mistaken clini- cally for Johne's disease until an autopsy reveals the presence of the worms. It is found rather frequently in sheep, particularly where they are pastured with or have followed cattle on the range. Measurements. — Females, 8-9x0.12-0.16 mm; male, 6.5-7.5x0.14-0.16 mm. Hosts. — Cattle, sheep, deer. Distribution. — North America, Europe, Australia. Habitat. — Fourth stomach, frequently with nodule formation. OSTERTAGIA OCCIDENTALIS RANSOM 1907 Ostertagia occidentalis Ransom 1907 Ostertagia trifida Cuille, Marotel, and Penisset 1911 Ostertagia occidentalis is thus far restricted to Rocky Mountain ani- mals. It has always been found associated with O. marshalli and hence the female has never been isolated. Bul. 603] Parasites of Sheep 45 Measurements. — Male, 12-16 x 0.2-0.4 mm. Hosts. — Sheep. Distribution. — North America (Rocky Mountain area). Habitat. — Fourth stomach and sometimes small intestine. OSTERTAGIA BULLOSA RANSOM AND HALL 1912 Ostertagia bullosa is a Rocky Mountain form, having been taken from Colorado and Montana sheep. It is close to 0. trifurcata but differs in several characters. A swelling of the cuticle on the ventral surface just anterior to the genital opening in the male is diagnostic of this species. Measurements. — Female, 8.8-9.8 x 0.13 mm; male, 7.3 x 0.13 mm. Hosts. — Sheep. Distribution. — North America (Montana and Colorado). Habitat. — Fourth stomach. OSTERTAGIA TRIFURCATA RANSOM 1907 Ostertagia trifurcata (fig. 12) has been found at many points in the eastern United States, but always in company with O. circumcincta. Thus far it has not been encountered in a separate infection, and the female is therefore unidentified. Measurements. — Male, 6.5-7.0 x 0.08-0.10 mm. Hosts. — Sheep and goats. Distribution. — Eastern North America. Habitat. — Fourth stomach, sometimes small intestine. OSTERTAGIA MENTULATA RAILLIET AND HENRY 1909 Ostertagia mentulata was originally described from the camel, but later a decidedly similar worm was taken from sheep in southern France and from goats in Turkestan. The spicules are strikingly cross-striped and long (0.70 mm in the camel parasites and 0.58 mm in the sheep and goat form). OSTERTAGIA TRICUSPIS MAROTEL 1912 Ostertagia tricuspis, reported from central France, is very similar to O. marshalli but differs sufficiently to justify its specific position. In the key (p. 42) it is separated from O. marshalli on the length of spicules. As in the latter, the gubernaculum is lacking, but there occurs a placque- like thickening of the cuticle that may be a telamon, but it is not sclerotic and chitinoid as in the true gubernacula. Measurements. — Female, 15-16 mm; male, 10-12 mm. Hosts. — Sheep. Distribution. — Central France. Habitat. — Fourth stomach. 46 University of California — Experiment Station OSTEETAGIA TURKESTANICA PETEOV AND SCHACHOWZEWA 1926 Ostertagia turkestanica is a recently described form from Turkestan which resembles 0. marshalli but has abnormally long spicules (0.409- 0.421mm). Measurements. — Female, 12.5-13.5 mm; male, 9.8-10.6 mm. Hosts. — Sheep and goats. Distribution. — Turkestan. Habitat. — Fourth stomach. COOPERIA WORMS These tiny worms (approximately Vi inch in length) are seldom re- ported, for they are generally mistaken and discarded as immature stomach or wireworms in a hasty autopsy. Their normal habitat is in the small intestine, but they are also found in the fourth stomach. In both places they may form nodules in the mucosa. They are separated micro- scopically from the other intestinal worms by having longitudinal ridges the length of the body, which appear raised and pitted with holes as one looks directly down on the ridge or striated as one looks through a ridge from the side. The head end is transversely furrowed. Eansom erected the genus for four species, curticii, punctata, onchophora, and pectinata. Since then numerous species have been added and Schwartz in 1928 lists four more species that may definitely be added to the original group and includes a key for the separation of these and other species that have been added to the genus on questionable grounds. The additional species include none that is reported from sheep. In 1931 Monnig experimentally transferred two new species of Cooperia which he described as C. serrata and C. antidorca from the spring buck to domestic sheep. The former is close to C. nodulosa Schwartz and the latter seems to be nearest to C. curticii Giles. Hung described C. fuelleborni from the water buck, together with a form with longer spicules which he names as a variety, C. fuelleborni hungi. He was also able to transmit both of these to lambs by feeding infective larvae. Both because of their doubtful taxonomic position and the fact that they were artificially fed to sheep, we have not considered them further. Of the existing species curticii is primarily a sheep parasite and onchophora is found in cattle but is also reported from sheep. Life History. — The life history of these worms has not been worked out definitely, but it is assumed that they pass through the normal free- living stage as first and second-stage sheathed larvae after the eggs are expelled with the feces in moist locations, and that these infective larvae are ingested with the food or water. Some cases are reported of pure in- fections of this worm where they have done considerable damage, but they are generally associated with other worms so that the amount of damage that they are capable of causing is obscured. Treatment. — Treatment with tetrachlorethylene has been observed to remove large numbers of these worms and in the absence of more accur- Bul. 603] Parasites of Sheep 47 ate information it is assumed that this is the treatment to be used. In the case of extensive nodule formation, however, it is doubtful if any chemical treatment would be more than partially effective. General prophylactic measures will do much to control an infection. COOPERIA CURTICII (GILES 1892) Strongylus ventricosus Rudolphi 1809 in Curtis 1890 Strongylus curticii Giles 1892 Strongylus curticei Railliet 1893 Cooperia curticii (Giles 1892) Ransom 1907 Cooperia curticei (Railliet 1893) Railliet and Henry 1909 Cooperia fuelleborni Hung 1926 Cooperia curticii is the one most commonly found in sheep. It is sepa- rated from oncophora by male characters. The spicules are less than 0.2 mm long, ranging from 0.135 to 0.145 mm, and the dorsal rib of the bursa (the median one whether a ventral or dorsal aspect is presented) is lyre-shaped, forked at the end, and with a pair of offshoots at right angles to the main branches at their bases. Measurements. — Female, 5.8-6.2x0.075-1.00 mm; male, 4.6-5.4x0.75-0.80 mm. Hosts. — Sheep, goats, water buck. Distribution. — North America, Europe, South Africa. Habitat. — Small instestine, sometimes fourth stomach. COOPERIA ONCOPHORA (RAILLIET 1898) Strongylus radiat us Rudolphi 1803 (partim) Strongylus ventricosus Rud. 1809 in Schneider 1866 (partim) Strongylus oncophorus Railliet 1898 (renaming S. ventricosus Rud. in Schneider) Strongylus curticei in Schnyder 1906 Cooperia oncophora (Railliet 1898) Ransom 1907 Cooperia oncophora is commonly found in cattle as well as sheep but the fact that it also occurs in mountain sheep may indicate a closer con- nection with sheep ; or this fact may be merely accidental. It is differen- tiated from the foregoing species by the fact that the male spicules are over 0.2 mm long, ranging from 0.23 to 0.30 mm, and the dorsal ray is U-shaped with the ventral branches well out on the arms rather than lyre-shaped with the branches at the bases of the forks. Measurements. — Female, 6-8x0.12-0.19 mm; male, 5.5-9.0 x 0.15-0.25 mm. Hosts. — Cattle, sheep, mountain sheep (Otis canadensis). Distribution. — North America, Europe. Habitat. — Small intestine, sometimes fourth stomach. THE TRICHOSTRONGYLES The trichostrongyles vie with the Ostertagia worms in the minds of many sheepmen for the doubtful honor of being the most commonly encoun- tered roundworms of California sheep. Their pathogenicity is unques- 48 University of California — Experiment Station tioned, and the fact that infections are generally overwhelming in numbers of individuals increases their importance as parasites. Infes- tations are generally sporadic, and while the immediate results may be disastrous with relatively high mortality, cessation is generally early and abrupt. Life History. — The eggs, already segmenting, are deposited with the feces of the sheep, and in the presence of slightly moist and warm condi- tions these develop a full-grown embryo within the eggs in approximately 19 hours. At this stage Monnig 17 has shown that they are resistant to com- plete drying for months and even years. This is a characteristic that is found in very few nematodes and explains to some extent perhaps the unusual abundance of these species under dry California conditions. If, however, moisture is still available when the embryo reaches this stage, hatching takes place. The larva molts once at the end of 1 day and again about 19 hours later, at which time it reaches the so-called infective larva" stage. In this stage, also, it is extremely resistant to dryness although not to the same extent as in the fully matured egg. Monnig reports that these infective larvae may be dried on a glass slide for eight and a half months or frozen for 10 days without losing their infectivity. They lived in tap water for seven months and in carefully subirrigated pots of clay soil for eight and a half months, but under natural soil conditions life is shortened to slightly over three months. This discrepancy is doubtless caused by the exhaustion of the larva occasioned by constant movement and the fact that it loses its sheath of cast skins when migrating in soil. Koino, who worked with a human trichostrongyle, Trichostrongylns orientalis, reported that the infective larvae could penetrate the un- abraded skin, but all attempts to make those parasitic in sheep perform in this manner have failed. Apparently infection is by mouth. Symptoms. — The picture of general parasitism is all that can be offered along the line of symptoms, and the identification by fecal ex- amination or autopsy is necessary for diagnosis. It is not uncommon to find these worms so plentiful as to form a hairy mat on the surface of the mucosa in the small intestine or fourth stomach. Lameness and frac- tures caused by faulty bone formation have been observed in heavily infested flocks. There is considerable evidence that calcium and phos- phorus metabolism is seriously disturbed in infested lambs. Treatment. — The cunic mixture gives excellent results under Cali- fornia conditions. 17 Monnig, H. O. Studies on the bionomics of the free-living stages of Tricho- strongylus spp. and other parasitic nematodes. Union So. Africa Dept. Agr. Rept. Div. Vet. Serv. and Anim. Indus. 16:175-98. 1932. Bul. 603] Parasites of Sheep 49 Prevention. — A synopsis of the life history emphasizes how difficult prophylaxis against this parasite really is. If the feces remain in a semi- moist condition for approximately 60 hours during warm weather, in- fective larvae are found which remain infective for months. If on the other hand, the feces only remain moist for 19 hours and then dry, a mature egg is formed which remains viable for months until moistened again, when approximately 40 hours of moisture will produce infective larvae. Thus eggs deposited in the dry summer months would have a very good chance of maturing to the embryonated egg stage in the feces before drying killed them, and could then remain in a viable and resis- tant condition until irrigation or early rains supplied the necessary 40 hours of moisture for them to progress from the resistant egg stage to the resistant "infective larva" stage. As several species of the genus that are parasitic in sheep have also been reported from man (although never in the United States), those who handle sheep should be careful of their sources of drinking water and wash their hands well before eating. The species are separated by the males. The following keys, adapted from Bay lis, 18 will serve to separate the species reported from sheep. KEY TO THE SPECIES OF TRICHOSTRONGYLUS 1. Spicules unequal in size 2 Spicules equal in size 3 2. Long spicule 0.11-0.12 mm; both spicules with slender pointed process mid- way axei Long spicule 0.141-0.152 mm; both spicules with irregular ridges and a barb near the tip rugatus 3. Spicules 0.16-0.17 mm long; without barbs vitrinus Spicules less than 0.15 mm long 4 4. Spicules without angular projections or barbs capricola Spicules with barbs 5 5. Spicules slender, over 0.135 mm long; slight barb (fig. 13) colubriformis Spicules less than 0.135 mm long; barbs pronounced 6 6. Spicules thick, 0.126-0.134 mm long; with two terminal barbs, one behind the other probolurus Spicules 0.10 mm long falculatus TRICHOSTRONGYLUS COLUBRIFORMIS (GILES 1892) Strongylus colubriformis Giles 1892 Strongylus instabilis Railliet 1893 Strongylus retortaeformis Railliet 1898 (nee Zedar 1800) Strongylus subtilis Loos 1895 Trichostrongylus colubriformis (Giles 1892) Ransom 1911 Trichostrongylus slcrjabini Kalantarjan 1928 18 Baylis, H. A. A manual of helminthology medical and veterinary, p. 179-180. Bailliere, Tindall and Cox, London. 1929. > 50 University of California — Experiment Station Trichostrongylus colubrif ormis (fig. 13) is probably the commonest form found in the United States, at least in the small intestine of sheep. It is referred to in many of the older publications as T. instabilis because colubrif ormis was reported from India and not well described, and Rail- liet's report of instabilis was from European material and well de- scribed. His name found its way into the literature and was maintained until a comparison of the two species showed them to be identical, and the older name, colu- brif ormis, was made applicable. Measurements. — Female, 5-8 x 0.13 mm; male, 4-6 x 0.08- 0.13 mm. Hosts. — Sheep, goats, man, gazelle, camel, prong-horned an- telope, deer. Distribution. — Asia, Africa, North America. Habitat. — Almost always small intestine but occasionally in fourth stomach. Fig. 13.— Trich- ostrongylus colu- brif ormis, male spicule and guber- naculum. TRICHOSTRONGYLUS AXEI (COBBOLD 1879) Strongylus axel Cobbold 1879 Strongylus tcnuissimus Mazzanti 1891 Strongylus gracilis MacFadyean 1896 (nee Leuckart 1842) Strongylus extenuatus Railliet 1898 Trichostrongylus axei (Cobbold 1879) Railliet and Henry 1909 The name Trichostrongylus axei applies to the trichostrongyle of horses, asses, and mules in most lists, while T. extenuatus is used for the form from sheep. However, the distinction between the forms is too weak to justify separation, and axei, as the older name, takes precedence. This form is found primarily in the fourth stomach although it is more apt to occur in the small intestine than the species colubrif ormis (pri- marily occurring in the small intestine) is to occur in the fourth stom- ach. Recently we have found this form in large numbers in company with Ostertagia sp. in the stomachs of buffaloes held under range condi- tions in California. It is the only member of the genus Trichostrongylus reported from the United States that has spicules of unequal length. Measurements. — Female, 4.6-5.5 x 0.055-0.0700 mm; male, 3.4-4.4 x 0.05-0.06 mm. Distribution. — North America, Europe, Australia. Hosts. — Cattle, sheep, goats, horses, mules, asses, bison (buffalo), Mexican moun- tain sheep. Habitat. — Fourth stomach and sometimes small intestine. TRICHOSTRONGYLUS VITRINUS LOOS 1905 Trichostrongylus vitrinus apparently never occurs in large numbers. We have specimens in the teaching collection without collection data but Bul. 603] Parasites of Sheep 51 apparently from California material. It does not seem to be of serious importance. Measurements. — Female, 5.0-6.5x0.084-0.092 mm; male, 4.0-5.5x0.085 mm. Distribution. — North America, Europe, Africa. Hosts. — Sheep, goats, camels, man. Habitat. — Small intestine, sometimes fourth stomach. TRICHOSTRONGYLUS CAPEICOLA RANSOM 1907 Trichostrongylas capricola is the common trichostrongyle of goats but is also reported from sheep in the United States. It has not been reported from California. Measurements. — Female, 5.8-6.8x0.075-0.080 mm; male, 4.3-4.9x0.09 mm. Distribution. — North America, Europe. Hosts. — Sheep, goats, prong-horned antelope. Habitat. — Small intestine and fourth stomach. , TRICHOSTRONGYLUS PROBOLURUS (RAILLIET 1896) Strongylus probolurus Railliet 1896 Trichostrongylus probolurus (Railliet 1896) Loos 1905 Trichostrongylus probolurus has been reported only once in the United States and on that occasion from a bactrian camel that died in the Na- tional Zoological Park, Washington. Measurements. — Female, 4.5-6.0 x 0.08 mm; male, 4.5-5.5 x 0.08 mm. Hosts. — Sheep, gazelle, camel, man. Distribution. — North America (introduced?), Europe, North Africa. Habitat. — Small intestine. TRICHOSTRONGYLUS RUGATUS MoNNIG 1925 Trichostrongylus rugatus has been reported from South Africa. This and T. axei are the only members of the genus reported from sheep that have unequal spicules. Those of rugatus are ridged on the inner side with a barb near the tip, while axei is smooth with a slender backward projecting spine midway. Measurements. — Female, 5.8-7.3 mm; male, 4.5-6.6 mm. Hosts. — Sheep. Distribution. — South Africa. Habitat. — Small intestine and fourth stomach. TRICHOSTRONGYLUS FALCULATUS RANSOM 1911 This is a little known species reported from sheep and goats in South Africa. The female is unknown. Measurements. — Male, 4.6 x 0.08 mm. Hosts. — Sheep, goats. Distribution. — South Africa. Habitat. — Small intestine. 52 University of California — Experiment Station THE THREAD-NECKED STRONGYLES The thread-necked strongyles, small worms approximately an inch in length, get their common name from and are most easily recognized by the fact that there is a marked and abrupt thickening of the body of the females at the vulva or opening of the genital system. In all the forms infecting sheep this is located at a point approximately separating the anterior third of the body from the posterior two-thirds. Life History. — The eggs, which are unusually large for so small a worm, serve as a shelter for the larval worm to reach the infective stage before hatching. Where the other strongyles emerge from the e^g into a free-living existence, after which they molt twice to reach the infective stage, the larvae of Nematodirus remain within the eggshell for this period and upon hatching have already molted twice as larvae and are ready to be ingested by the sheep. Hatching of the infective larva is ap- parently accomplished by either continued hot weather (75°-90° F) or alternate drying and moistening at lower temperatures. After hatching the larva migrates up blades of grass where it awaits ingestion ; or it may be washed by rains into bodies of standing water, where it may remain alive and infective for nearly a year. This ability to adapt itself to varying climatic conditions, coupled with the added protection it gets from its habit of reaching the infective stage while still within the shelter of the egg, makes the thread-necked strongyle particularly troublesome even in the drier sections. Symptoms. — The thread-necked strongyles, at least in California, are looked upon as secondary invaders which complicate and aggravate the primary parasitism of other species. Occasionally we have found un- complicated invasions of these parasites in numbers sufficient to produce a typical parasitic anemia that could be differentiated from other para- sitic difficulties only by autopsy. They are generally found, however, associated with other parasites, such as Ostertagia worms or tricho- strongyles. Treatment. — These worms do not react to treatment as well as might be expected from their exposed position in the small intestine. Tetra- chlorethylene produces the best results, however. Prevention. — Although their method of resisting unfavorable cli- matic conditions is different from that of the trichostrongyles, the end results are much the same and their prevention seems just about as hopeless. Four species have been described from sheep and are separated by Bul. 603] Parasites of Sheep 53 male characters. The esophagus is apparently eversible and carries a series of outpointing- hooklets, one of which is plainly evident in cleared preparations. Occasionally specimens are seen with this protruding eso- phagus. This sometimes causes confusion, and the presence of the mouth hook causes the beginner to confuse them with Haemonchus and Me- cistocirrus, which both have somewhat similar hooks. Again, there is a definite cross-striation of the anterior end of the body and an inflation, which, together with longitudinal body ridges, causes confusion with Cooperia until size, shape, and the male characters settle the diagnosis. KEY TO THE SPECIES OF NEMATODIRUS 1. Spicules united distally within a membrane 2 Spicules separated and distinct distally furcatus 2. Spicules of equal length 3 Spicules of unequal length abnormalis 3. Spicules ending in sharp pointed membrane, hook-shaped as seen from the side fillieollis Spicules ending in a blunt, spatulate membrane spathiger NEMATODIEUS FILLICOLLIS (RUDOLPHI 1802) Ascaris fillieollis Rud. 1802 Fusaria fillieollis (Rud. 1802) Zeder 1803 Strongylus fillieollis (Rud. 1802) Rud. 1803 Nematodirus fillieollis (Rud. 1802) Ransom 1907 Nematodirus fillieollis is the earliest member of the genus to be de- scribed. After Railliet had described N. spathiger from a bactrian camel in France as distinct from N. fillieollis, which he restricted to sheep, Ransom followed his lead in his classical Bulletin 127 of the United States Department of Agriculture Bureau of Animal Industry. How- ever, he figured as fillieollis, the male of spathiger. This has lead to con- siderable confusion, but both fillieollis and spathiger are now recognized as parasitic in sheep and present in practically every sheep district of the United States. They often occur together in the same host animal but are easily distinguished by the characteristic spicules of the males. Measurements. — Female, 15-21x0.15-0.225 mm; male, 10-15x0.12-0.15 mm. Hosts. — Sheep, goats, cattle. Distribution. — United States and Europe. Habitat. — Small intestine. NEMATODIRUS SPATHIGER (RAILLIET 1896) Strongylus spathiger Railliet 1896 Nematodirus spathiger (Railliet 1896) Railliet and Henry 1909 As mentioned under the preceding species, Nematodirus spathiger was originally described from a camel, and routine workers have been 54 University of California — Experiment Station prone to name as N. ftllicollis any species found in sheep, which may account for the limited recorded distribution of this species as compared with N. fillicollis. Under California conditions N. spathiger is more com- monly encountered than fillicollis, from which it may be separated as n ~>ted in the key and the discussion in the preceding section. Measurements. — Female, 15-23x0.14-0.20 mm; male, 10-15x0.12-0.17 mm. Hosts. — Sheep, cattle, deer, goats, rodents, camels. Distribution. — Practically cosmopolitan. Habitat. — Small intestine. NEMATODIBUS ABNORMALIS MAY 1920 Nematodirus abnormalis was described from museum material taken from sheep and Maltese goats. It is similar to N. fillicollis but larger, and the male spicules are slightly unequal in length, giving the filaments at their distal end an asymmetrical appearance. Measurements. — Female, 18-25 X 0.15-0.20 mm ; male, 11-17 mm. He ts. — Sheep, goats. Dis'ribution. — Eastern United States. Ha) itat. — Small intestine. NEMATODIBUS FURCATUS MAY 1920 Nen atodirus furcatus was described from Michigan sheep. It is an extren 3ly small species, the females of which have never been isolated. It is re aarkable in that the spicules are separated for their distal third rather than confined in a membrane as are the spicules of the other species' Measurements. — Male, 6.0-6.4x0.065-0.070 mm. Hosts. — Sheep. Distribution. — United States (Michigan). Habitat. —Small intestine. MECISTOCIRRUS DIGITATUS (LINSTOW 1906) Strongyt is digitatus Linstow 1906 Strongylus fordii Daniels 1908 Strongylus gibsoni Stephenson 1909 Nematodirus digitatus (Linstow 1906) Railliet and Henry 1909 Mecistocirrus digitatus (Linstow 1906) Railliet and Henry 1912 Mecistocirrus tagumai Morishita 1922 Mecistocirrus digitatus was at one time considered as a species of the foregoing genus, Nematodirus, and in the light of recent work probably should be returned to that genus. It was separated when the anterior position of the vulva was considered to be a generic character, but as new species of Nematodirus have been described, the position of this organ has been found to vary. The fact that the vulva occurs at the pos- Bul. 603] Parasites of Sheep 55 terior end of the body in Mecisto cirrus is no longer a bar to its inclusion in the older genus. However, it does have well-defined cervical papillae, which are not apparent in Nematodirus, and is larger and has very much longer spicules (3.8-6.0 mm long) . Measurements. — Female, 24-29x0.5-0.6 mm; male, 23-24x0.35-0.40 mm. Hosts. — Sheep, cattle, swine, man. Distribution. — South Asia. Habitat. — Rumen, fourth stomach, and small intestine. GONGYLONEMA WORMS All the worms belonging to the order Filarioidea whose life histories have been worked out have intermediary hosts that harbor the larval stages of the parasites. The Gongylonema worms are primarily parasitic in the lining of the esophagus, but in ruminants they are generally found in the rumen. They are of threadlike thickness, but some females approximate 6 inches in length. The anterior end of the body and the male bursa are ornamented with oval or rectangular blisters or farts that are known technically as bosses or scutes. -w-r • Life History. — The eggs when deposited with the feces alread con- tain a formed larva, which, however, does not emerge from the eg until it is eaten by a suitable intermediary host. Dung beetles belonging to the genera Aphodius, Onthophagns, Caccobius, and Oniticellas,, is well as the German cockroach Blattella germanica have all been exp rimen- tally infected with Gongylonema pulchrum, the commonest form found in sheep. After hatching, the young larva bores through the wall of the insect's alimentary canal and encysts in the body cavity, wher,3 it lies until the host is eaten by the primary host. It then bores into the w T all of the stomach or duodenum and begins a migration through sinuous tun- nels that it forms. In human cases the oral cavity is generally reached, but with sheep the esophagus is generally the most distant point attained. Symptoms. — The first indication of infection is generally a* autopsy, for the symptoms of irritation and nervousness ascribed to human cases are difficult to note in sheep. No cases have been reported where it was thought that the infection was of primary importance. Treatment and Prevention. — None. Species. — The differentiation of the different species of the genus Gongylonema is in chaotic condition. Literally dozens of species have been described for different host animals, these have been maintained by some and submerged as synonyms by others. The three generally rec- ognized forms parasitic in sheep are separated by the characters given for each species below. ( 56 University of California — Experiment Station GONGYLONEMA PULCHRUM MOLIN 1857 Gongylonema pulchrum Molin 1857 Gongylonema spirale Molin 1857 Filaria labialis Pane 1864 Spiroptera scutata Miiller 1869 Filaria scutata Leuckart 1873 Myzomimus scutatus (Miiller 1869) Stiles 1892 Gongylonema scutatum (Miiller 1869) Railliet 1892 Gongylonema confusum Sonsino 1896 Gongylonema subtile Allesandrini 1914 Gongylonema hominis Stiles 1921 Gongylonema ransomi Chapin 1922 Gongylonema pulchrum is the form most commonly found in sheep and the form whose life history is outlined above with reference to the Fig. 14. — Anterior ends of Gongylonema worms ; A, G. pulchrum; B, G. verrucosum. specific intermediary hosts. It is differentiated from G. verrucosum and G. mbnnigi by its simple, unfestooned alae or fins on both right and left side of the head end of the body (fig. 14, A) . Measurements. — Female, 145x0.5 mm; male, 62x0.15-0.30 mm. Hosts. — Sheep, cattle, goats, horses, asses, swine, deer, man, and experimentally in rats. Distribution. — Cosmopolitan. Habitat. — Esophagus and rumen. Bul. 603] Parasites of Sheep 57 GONGYLONEMA VERRUCOSUM (GILES 1892) Trichosoma verrucosa Giles 1892 Spiroptera verrucosa (Giles 1892) Giles 1892 (nee Spiroptera verrucosa Molin 1860) Gongylonema verrucosum (Giles 1892) Neumann 1894 Gongylonema crenatum Railliet 1898 [G. verrucosum (Giles 1892) renamed] This form has not as yet been reported from the United States. It is separated from the other forms by having the ala or fin on the left side only and with a festooned edge (fig. 14, B). The bosses are confined to this side also. Measurements. — Female, 70-95x0.42-0.46 mm; male, 32-41x0.25-0.30 mm. Hosts. — Sheep, cattle, zebras. Distribution. — India and South Africa. Habitat. — Rumen. GONGYLONEMA MoNNIGI BAYLIS 1926 This is a South African form not reported elsewhere. It is distinguished from the other species by having a single ala as in verrucosum, but this is not festooned and the bosses are not restricted to the left side. Measurements. — Female, 102-113 x 0.43-0.45 mm ; male, 42 x 0.30 mm. Hosts. — Sheep and goats. Distribution. — South Africa. Habitat. — Rumen. SETARIA WORMS The long, sinuous, white, threadworms found in the peritoneal cavity of horses and cattle are common curiosities at autopsies, but they had never been taken from sheep until Monnig reported the presence of Setaria hornbyi Boulenger 1921 in sheep autopsied in South Africa. This worm was originally described from an African antelope, Hippotragus niger, which is probably its normal host. These parasites are never of economic importance. They are probably transmitted by blood-sucking insects or ticks, since their larvae are found in the circulating blood of the host. THE TRICHINA WORM, TRICHINELLA SPIRALIS (OWEN 1835) Trichina spiralis Owen 1835 Trichina circumflexa Polonio 1860 Trichinella spiralis (Owen 1835) Railliet 1895 The presence of trichinella infection in sheep must be of necessity wholly accidental and is exceedingly rare ; for an animal, in order to be- come infected, must become a meat-eater in order to consume the infective larval worms which are encysted in the muscles. Larval worms ingested with infested muscle tissue come to maturity rapidly in the alimentary canal and copulate, the males dying immediately thereafter. The females burrow into the crypts of the small intestine, and deposit their eggs in 58 University of California — Experiment Station the lymph spaces. The larval worms hatching from these eggs are carried by the blood to the muscle tissue, which is invaded by the worms. The body of the host reacts to their presence and builds a capsule around them in which they await the time that they are eaten by another suscep- tible host or are destroyed by calcification of the cyst. At the time of infection an extreme diarrhea is sometimes present, and later the animal shows evidence of considerable pain and paralysis caused by the migrating larvae. No treatment is of avail after symptoms appear, and the chances for sheep to become infected are so slight that no precautions need be exer- cised in connection with this parasite. The few cases that have been re- ported were probably the result of perverted appetites occasioned by mineral deficiencies. Measurements. — Female, 3—4 x 0.06 mm; male, 1.4—1.6 x 0.04 mm. Hosts. — Swine, rats, mice, man, cats, dogs, sheep, fox, rabbits, horses, cattle, chick- ens, and others. Distribution. — Cosmopolitan. Habitat. — Small intestine, larvae in muscles. THE WHIPWORM, TRICHURIS OVIS (ABILDGAARD 1755) Trichocephalus ovis Abildgaard 1755 Trichocephalus affinis Eudolphi 1802 Mastigodes affinis (Bud. 1802) Zeder 1803 Trichuris ovis (Abild. 1755) Smith 1908 The common name of these worms is more explanatory than the techni- cal one ; for the latter, Trichuris, means "hair tail," which is confusing in that the hairlike portion of the worm is the anterior or "head" end. They are easily distinguished from all other intestinal worms by this long, attenuated, anterior portion of the body and the swollen posterior por- tion which make up respectively the "lash" and the "whipstock." The swollen posterior portion is found at autopsy in the lumen of the large intestine. It is easily seen, since it may be an inch in length, but when one attempts to remove it, the slender anterior portion, from twice to three times as long as the easily visible portion, will be found to be sewed into the lining of the intestine and removed with difficulty. The male is distinguished from the female microscopically by having the posterior end of the body rolled in a tight curl, inside of which there extrudes a single spicule from within a sheath. Life History. — The infection with this worm has been generally assumed to be direct and without an intermediary host. Further work is apt to demonstrate, however, that an intermediary host may play a part. In the absence of definite assurance, it is well to follow the general Bul. 603] Parasites of Sheep 59 procedure outlined for direct-infection cases as with the stomach worms. Symptoms. — No diagnostic symptoms are available other than those generally ascribed to parasitism. Autopsy shows inflamed, hemorrhagic areas where the whipworms are attached. We have seen severe infesta- tions where the numbers of worms present must have produced a severe colitis, to judge from the inflamed condition of the intestine. The eggs, which are lemon-shaped and fitted with hyaline "plugs" at each end, are easily distinguished in fecal examinations. (See "The Capillaria Worms," p. 59, however.) Treatment. — No treatment in general use today w T ill produce results efficient enough to justify the cost. The fact that the parasites are local- ized in the cecum and large intestine in itself makes treatment difficult. However, the chief obstacle is undoubtedly the passive attachment that the worm has to the mucosa which allows it, even though overcome by an anthelmintic, to be held in position until the drug has passed by and recovery is permitted for the parasite. Benzene enemas and the latex of Fie ks laurifolia have been recommended. Measurements. — Female, 35—70 mm; male, 50-80 mm. Hosts. — Sheep, goats, deer, cattle, caribou, antelope, camel, giraffe, chamois, moose, gazelle, and llama. Distribution. — North and South America, Europe, Africa, Asia, Australia. Habitat. — Large intestine and cecum. THE CAPILLARIA WORMS Although these worms may approximate % inch i n length, their slender- ness makes them exceedingly difficult to detect. The routine of their discovery is generally that the catarrhal condition of the small intestine incites the examiner's interest, and a smear made from the scrapings show r s numerous characteristic eggs with translucent "portholes," or "plugs," at each end. This signifies the presence of Capillaria worms (see "The Whipworm," above, however) . A careful scraping of the thick- ened mucosa with frequent lifting of the scalpel generally discloses hair- like objects which appear as mucous strands, but which on closer exam- ination prove to be the adult worms in question. The male is smaller than the female and has at its posterior end, a small bursa supported by a single ray and a membranous crumpled spicule-sheath through which the single spicule may be exerted. The eggs have two "plugs" situated one at each end of the egg as in the whipworms, but are much smaller (not over 0.050 mm as contrasted with 0.070 mm in the latter) and are more rounded and less lemon- shaped. In addition the "plugs" do not protrude as markedly from the end outline of the egg as in whipworm. 60 University of California — Experiment Station Life History. — Infection is probably direct through ingestion of the eggs deposited in feces. Symptoms. — The symptoms are those of general parasitism although the writers have never seen a severe case. At autopsy the small intestine or patches of it have a thickened, "furry" appearance, which may or may not be hemorrhagic. There is an unusual secretion of mucus, which causes a catarrhal condition. Treatment. — Tetrachlorethylene will remove large numbers judging from the decrease, following treatment, of the numbers of Capillaria eggs in the feces. Prevention. — Prevention is the same as for any direct infection of parasites. Species. — Two species of this genus of worms have been taken from sheep. They are separated largely on size characters as mentioned below. CAPILLARIA BREVIPES RANSOM 1911 Capillaria brevipes is the smaller of the two species reported from sheep : the adult female is approximately 12 mm long and the male spicule 0.9 mm long, as contrasted with corresponding measurements 20 mm and 1.2 mm in the larger species, longipes. Measurements. — Female, 12 x 0.06 mm ; male, 8—9 x 0.05 mm. Hosts. — Sheep. Distribution. — United States. Habitat. — Small intestine. CAPILLARIA LONGIPES RANSOM 1911 Capillaria longipes, the larger species, may be distinguished from C. orevipes by measurements given under that species. The thickness of the eggshell is also diagnostic, that of C. longipes measuring 0.0015- 0.0020 mm and that of C. brevipes 0.0030-0.0040 mm. Measurements. — Female, 20 x 0.08 mm; male, 11-13 x 0.05-0.06 mm. Hosts. — Sheep, prong-horned antelope. Distribution. — United States. Habitat. — Small intestine. THE LUNGWORMS, FAMILY STRONGYLIDAE The family Strongylidae includes a group of worms parasitic in the lungs, circulatory system, and head cavities of vertebrates. Only the forms that pass their adult life in the lungs are known to occur in sheep. Lungworms, as a rule, are serious parasites of sheep only when other conditions such as poor management, scanty feed, or serious infection with other parasites or diseases aggravate the picture. In heavy infes- Bul. 603] Parasites of Sheep 61 tations, a mechanical blocking of portions of the lungs takes place which causes a collapse of the affected area and furnishes an ideal focus for other pathogenic organisms to start an invasion that may culminate fatally. For practical purposes it is possible to divide the lungworms into two groups, known as the hair lungworms for the very slender forms and the thread lungworms for the form approaching the thickness of a heavy linen thread. The latter are yellowish white with a well- marked, spiral, brown stripe, which indicates the outline of the sinuous intestine. These forms are found coiled in knots in the larger bronchi and in the windpipe. The hair lungworms, besides being much shorter and more slender, are reddish in color and found in the smaller bronchioles and even in the lung tissue. The four genera of lungworms infecting sheep, three of which are represented by single species as far as sheep are concerned, may be separated by the following key. The genera Dictyocaulus and Meta- strongylus fall in the group known as thread lungworms, while Mueller- ins and Protostrongylus, which are much thinner, are known as hair lungworms. KEY TO GENERA OF LUNGWORMS FOUND IN SHEEP 1. Males with caudal bursa 2 Males without caudal bursa Muellerius Cameron 1927 ; one species, capillaris 2. Dorsal ray of bursa divided to its base forming two parallel rays ; threadlike thickness 3 Dorsal ray broad and undivided except at distal end; hairlike thickness Protostrongylus Kamensky 1905 (= Synthetocaulus R. & H. 1907) 3. Spicules short and pointed ; vulva at middle of the body Dictyocaulus Railliet and Henry 1907; one species, filaria Spicules long, slender and with distal hooks ; vulva near anus at posterior end of body Metastrongylus Molin 1845 ; one species, apri DICTYOCAULUS FILARIA (RUDOLPHI 1809) Strongylus filaria Rud. 1809 Dictyocaulus filaria (Rud. 1809) Railliet and Henry 1907 Life History. — Dictyocaulus filaria, lying in the larger air passages of the lungs, deposits eggs which are raised with the mucus and swal- lowed. The egg contains a motile embryo when deposited, which hatches at the slightest pressure after deposition. Although we have recovered unhatched eggs in the rumen of infected animals, we have never found such unhatched eggs posterior to this point. The newly hatched larvae, after a period of development in moist earth or water, are capable of 62 University of California— Experiment Station infecting- a susceptible animal if ingested with the food or water. The invading larva penetrates the walls of the small or large intestine to the mesenteric lymph nodes, where it develops still further. It is next carried to the lungs, where it bores through the walls of the air spaces and develops to an adult condition. No intermediate host is necessary. Symptoms. — Continual coughing, with a lowered head, staggering gait, and loss of weight and appetite are all indicative of an invasion of the common lungworm. The diagnosis of verminous bronchitis is nearly always referable to this worm in California. Prevention and Treatment. — The use of nasal injections of chloro- form has been widely recommended for lungworms, and although this treatment was developed at this station, it was never recommended for sheep. Goats, calves, and hogs may be treated with safety by injecting enough chloroform into the nostrils with an eye-dropper to make the animal groggy, but if sheep are treated by this method, the operator must anticipate a mortality of at least 50 per cent among the treated animals, for they are particularly susceptible to chloroform. Among sheepmen there is a fairly widespread use of manganese diox- ide. Crystals of this are placed in the bottom of a fruit jar and a few drops of concentrated sulfuric acid are added. As this fumes, the open end of the jar is placed over the sheep's muzzle for a second or two until the animal coughs once, "but not twice." This is a standard remedy among some sheepmen, and although we have used it with no bad effects on the sheep, we are not in a position to state that it had any effect on the lungworm population. Intratracheal injections of a 0.2 per cent aqueous solution of picric acid in doses of 2 to 5 cc have been recommended by Magens. Cures from lungworm invasion often appear spontaneously, and the credit that should be attributed to management, the weather, or better range conditions, is credited to some chemical treatment. Animals with adequate food and shelter frequently harbor many lungworms, but they seldom show any symptoms of this parasitism until their general re- sistance is lowered by other causes. The avoidance of permanently moist or swampy swales, the establish- ment of sanitary drinking troughs, and the practice of the best manage- ment in general will definitely cut down the difficulty from lungworms. In connection with lungworm invasions in California, it has been noted repeatedly that the infections occur most often where sheep share the range with deer, for these animals are heavily infested, particularly in years when climatic conditions make it difficult for them to secure abun- dant food. Bul. 603] Parasites op Sheep 63 In cases where sheep and cattle shared the same pasturage, we have never taken the cattle lungworm, Diet y oca ulus viviparus, from sheep, but we have repeatedly taken D. filar in, the hmgworm of sheep and deer, from calves. Measurements. — Female, 50-100 x 0.5-0.6 mm; male, 30-80 x 0.5 mm. Hosts. — Sheep, deer, calves. Distribution. — Cosmopolitan. Habitat. — Bronchi. METASTEONGYLUS APEI (GMELIN 1790) Ascaris apri Gmelin 1790 (partim) Strongylus suis Eudolphi 1809 (partim) Strongylus paradoxus Mehlis 1831 (partim) Strongylus elongatus Dujardin 1845 Strongylus longevaginatus Diesing 1851 Metastrongylus paradoxus (Mehlis 1831) Molin 1860 Metastrongylus apri (Gmelin 1790) Eailliet and Henry 1907 Metastrongylus elongatus (Dujardin 1845) Eailliet and Henry 1911 Metastrongylus apri is normally a parasite of swine. Its occurrence in sheep, even though this has been noted repeatedly must, nevertheless, be considered as purely accidental. Life History. — Various investigators have worked with this lung- worm and propounded many different theories concerning its develop- ment, but that of the Hobmaiers seems the most logical. They note that the eggs hatch in the lungs of the primary host, and the larvae are pres- ent in the mucus, which is coughed up and swallowed, the larvae passing through the* alimentary canal and leaving the host's body with the feces. In successful cases these larval lungworms penetrate the body of earth- worms, where they develop to the infectious state and await the time when this intermediary host is eaten by the primary host. The larvae then penetrate the alimentary canal and are transported by the blood to the lungs, where they establish their adult existence. It is easy to see that this is a normal and logical development for the parasite of swine, but it is difficult to see how sheep, man, or cattle, which are all reported as hosts, could become infected if the earthworm route were the only means of transmission. It is barely possible that the earthworm may act, as in the case of gapeworms of chickens, as a passive shelter for the larval worms to protect them from desiccation, but not as an essential or obliga- tory host ; the worm may be able to exist in a free-living condition until eaten by another primary host. This would explain the cases in the hosts that do not eat earthworms, but such cases should not be advanced as a proof of the above hypothesis, for there are many instances of wide- 64 University of California — Experiment Station spread perversions of appetite to account for the occurrence of the para- site in seemingly impossible circumstances. Measurements. — Female, 12-58x0.40-0.45 mm; male, 11-25x0.16-0.225 mm. Hosts. — Hogs, cattle, sheep, goat, deer, and rarely man. Distribution. — Cosmopolitan. Habitat. — Bronchi and trachea. PROTOSTRONGYLUS RUFESCENS (LEUCKART 1865) Strongylus retortaeformis Rudolphi 1819 (partim) Strongylus commutatus Diesing 1815 (partim) Strongylus rufescens Leuckart 1865 Strongylus minutissimus Megnin 1878 Pseudostrongylus ovis pulmonalis A. Koch 1883 (partim) Strongylus sagittatus Miiller 1891 Strongylus capillarus Schlegel 1899 Protostrongylus rufescens (Leuckart 1865) Kamensky 1905 Synthetocaulus rufescens (Leuckart 1865) Railliet and Henry 1907 Protostrongylus rufescens produces extensive lung lesions and is one of the most important lungworms. Life History. — The Hobmaiers 19 have determined that the embryo Protostrongylus rufescens invade dry geophilus snails, while the inter- mediate hosts of Muellerius capillaris are snails which prefer a shaded or partly shaded habitat. The species of snails from which larvae have been secured are Helicella ericetorum, H. obvia, and H. bolli. The embryo worm enters the snail through the mucous glands of the foot. Larval development, involving two molts, is completed in from 12 to 14 days after the embryo enters the snail. The development in the mammalian host is the same as that of Metastrongylus apri. The embryo is rapidly killed by complete desiccation, but in clear water it has been observed to remain alive for more than a year. In artificial cultures rotifers readily destroy the embryos. Prevention. — If possible, sheep should be kept off pastures in which Helicella are found. Measurements. — Female, 25-35x0.17 mm; male, 16-28x0.15 mm. Hosts. — Sheep, goats, deer, rabbits (?), hares (?). Distribution. — Europe, Africa, Australia, North America. Habitat. — Small bronchioles. Other Species Attacking Sheep. — Other species of this genus which have been found in sheep are Protostrongylus ocreatus (Railliet and Henry, 1907) in North Africa, P. unciphorus (Railliet and Henry, 1907) in Europe, and P. linearis (Marotel, 1913) in southern France. It is 19 Hobmaier, A., and M. Hobmaier. Life history of Protostrongylus (Syntheto- caulus) rufescens. Proc. Soc. Exp. Biol, and Med. 28(2):156-58. 1930. Bul. 603] Parasites of Sheep 65 possible that P. ocreatus and P. unciphorus are synonymous with P. commutatus (Diesing, 1851). However, this latter species has only been reported from rabbits, never from sheep. MUELLEEIUS CAPILLAEIS (MtiLLER 1889) Pseudalius capillaris Muller 1889 Synthetocaulus capillaris (Muller 1889) Eailliet and Henry 1907 Muellerius capillaris (Muller 1889) Cameron 1927 Muellerius capillaris is the most common lung parasite of sheep in Europe and is also found in the United States. It occurs more commonly in sheep than in lambs, but has been found in animals less than six months of age. Life History. — Like the three lungworms just mentioned, Muellerius capillaris requires an intermediate host, into which it may penetrate through the foot or be swallowed. The following species have been dem- onstrated to be suitable intermediate hosts : the slugs Agriolimax agres- tes, A. reticularis, Limax cinereus, L. flavus, Arion subfucus, A. horten- sis, A. circumscriptus, A. empiricorum, and the snails Succinea putris, 8. pfeifferi, Fruticicola hispida, Monacha umbrosa, M. cidens, Cephea hortensis, Helix pomatia, Cingulifera planospira, and Arianta arbus- torum. The development in the intermediate host and in the sheep is very similar to that of Protostrongylus rufescens. The embryos are able to resist a fair amount of desiccation and are most active at temperatures of from 62.6°-80.6° F. They are not killed by freezing. The infective larvae can live as long as a week after the death of the intermediate host. Prevention. — Where the extermination of the intermediate host, fol- lowing the directions given for the control of the intermediate host of the liver fluke, is possible, this should be carried out. Measurements. — Female, 19-23 x 0.04 mm; male, 12-14 x 0.06 mm. Hosts. — Sheep, goat, and chamois. Distribution. — United States and Europe. Habitat. — Small bronchioles. TREMATODES These are the flukes, which are characteristically flat, leaf -shaped worms without a body cavity (fig. 15) . They are, as a rule, hermaphroditic. The development may or may not require passage through one or two inter- mediate hosts. When there are two, the first intermediate host is a mol- lusk in all known cases. As mentioned in an introductory paragraph, only the liver fluke will be discussed in this paper. 66 University of California — Experiment Station THE LIVER FLUKE, FASCIOLA HEPATICA L. 1758 Fasciola hepatica L. 1758 Bistoma hepaticum Ratzius 1786 Fasciola humana Gmelin 1790 Planaria latiuscula Goezc 1782 Bistoma caviae Sonsino 1890 Cladocoelium hepaticum (Linnaeus, 1758) Stossich 1892 Liver fluke (fig. 15) of sheep and cattle constitutes an important prob- lem in California. This disease is variously known as "leaches," "liver ~4K a c Fig. 15. — a, Adult liver fluke enlarged five times, ventral view ; o, actual size of the fluke shown in a, dorsal view; c, adult fluke cleared and prepared for microscopical study, showing internal anatomy, (x 5.) (From Agr. Ext. Cir. 17.) rot," "rotten liver," "flukes," "hepatic distomiasis," and "fascioliasis." The causative organism, Fasciola hepatica, is a small brownish-gray fluke about 1 inch in length. The severity of the disease depends on the condition of the infested animal and the number of flukes that it is harboring. One rancher on the Pacific Coast is reported to have lost 1,500 animals in a single year (1927). Even though the economic loss from death may be great, it is J ii-L. 603] Parasites of Sheep 67 but a part of the total. Animals that are only moderately infested fail to gain weight properly, are poor mothers, and fall easy prey to diseases such as pneumonia, hemorrhagic septicemia* and lungworms. *34-o a X54-0 XZ5o X 11& AMS x8o Fig. 16. — Developmental stages of the liver fluke that take place outside the body of the sheep : a, egg shortly after being voided from the sheep's body with the feces ; b, egg ready to hatch, containing the fully formed miracidium ; c, miracidium attack- ing the body wall of a snail ; d, sporocyst which has developed from the miracidium in the pulmonary chamber of the snail and contains developing rediae ; e, redia from the liver of the snail containing developing cercariae ; /, free-swimming cercaria which has emerged from the snail's body. (Redrawn in part from Thomas.) (From Agr. Ext. Cir. 17.) Life History. — The life history is diagramed in figure 16. The adult flukes which are located in the bile passages of the liver give rise to tre- mendous numbers of eggs which are carried into the small intestine with 68 University of California — Experiment Station the bile and are voided with the feces of the infested animals. The eggs are yellowish and thin-walled, contain numerous embryonic cells, and possess anteriorly an operculum or cap, which facilitates hatching. The embryo matures very rapidly in warm moist surroundings and in the presence of moisture escapes from the egg as a young fluke, which is known as a miracidium. The development of the egg is stopped at tem- peratures below 50° F, but it remains viable for several months. There- fore, eggs accumulate in mild winters and hatch in the spring. At about Fig. 17. — Galba bulimoides, the principal snail carrier of liver fluke on the Pacific Coast, (x 8.) 80° F eggs hatch in 9 days; lower temperatures lengthen the period. Light stimulates hatching. Copper sulfate apparently has no effect on the egg. The miracidia are microscopic in size, a little more than twice as long as wide, and clothed with cilia or hairlike structures that help them to swim about in the water. The minute organisms swim about in search of their next host, which is one of the following snails : Lymnaea trunca- tula in Europe and North Asia ; Galba bulimoides (fig. 17) on the Pacific Coast of North America from Vancouver Island to southern California ; G. bulimoides techella in the southern United States from Kansas, Mis- souri, and Colorado to southern Texas and from Alabama westward to southern California and northern Mexico ; G. ferruginea in Oregon, Washington, and California; G. cubensis in southern North America (Florida, Georgia, Louisiana, Texas), the West Indies, Mexico, Guate- mala, and northern Venezuela ; and Pseudosuccinea columella in North America (Nova Scotia west to Minnesota, eastern Kansas, and central Bul. 603] Parasites of Sheep 69 Texas; Manitoba and Quebec south to Texas and Florida). As will be observed from this list, the most common intermediate hosts are snails belonging to genera recognized by a cornucopia shape and by having the opening to the right as one faces the opening. The miracidium penetrates actively into the body of the snail, casting off its covering of cilia, and settles down, usually in the pulmonary cham- ber or lymph channels. If many miracidia enter, the snail dies. The parasite now becomes encysted and saclike, and its contents divide and subdivide until the sac or sporocyst contains from three to eight separate cylindrical organisms known as rediae. By the end of 8 days they have escaped from the sporocyst. The rediae now migrate to some other organ in the snail's body, usually the liver. When the temperatures are low, but still above 50° F, daughter rediae are produced parthenogenetically. When the temperatures are higher, each redia, and if daughter rediae have been produced, each daughter redia gives birth to from eight to ten immature, tailed flukes known as cercariae. These cercariae (approximately 300 for each original miracidium that entered) leave the body of the snail, swim about in the water, and eventually work their way up on various meadow and swamp grasses and water plants, such as cress. Here they encyst just below the water level in the form of small white spherules by the activity of certain cells on the surface of the body. These cells produce a tough, parchmentlike material which covers the cercaria and glues it to the surface of the vegetation. This encystment usually takes place within 2 hours after escaping from the snail, but in some cases it may not take place for as long as 24 hours. The cercariae usually encyst near the snail, and a few may encyst on the snail or even on the surface of the water. In the latter case they sink to the bottom when disturbed. Cysts may remain alive for a considerable time, even over winter. They can successfully resist mild desiccation and low temperatures; high temperatures, however, are rapidly fatal. They are able to exist on dry hay for a few weeks, and if it is not properly dried, they may remain infective on it for a year or more. When the vegetation upon which cercariae are encysted is eaten by a primary host, such as sheep, cattle, goats, hogs, rabbits, hares, mules, or even man, the larvae (adolescariae) escape from the cysts in the duodenum and burrow through the intestinal mucosa. After this, they wander about in the body cavity for a time — sometimes occurring in tre- mendous numbers — and finally in the majority of cases reach the liver. Upon reaching the liver from the body cavity, the young fluke burrows 70 University of 1 California — Experiment Station through the capsule and wanders through the liver tissue for about a month or more, reaching the minute bile capillaries down which they migrate to the bile ducts, where they reach maturity. Maturity is reached two or three months after infection, and the adult liberates eggs over long periods of time — variously estimated at from six to twelve months — after which, its function in life accomplished, it flows into the duodenum with the bile and is voided from the body of its victim in a partly di- gested condition. Pathogenicity. — After gaining entrance to the liver, it is very prob- able that the small flukes excrete a definite toxin, which destroys the active liver cells. As the cells break down, areas of dead cells often be- come cavities, and then, at first minute, gradually become extended un- til the blood vessels are tapped and more or less serious hemorrhages are produced. Sometimes these areas may progress to the surface of the organ and by draining into the body cavity produce acute peritonitis. If the condition does not become serious enough to produce death, a chronic state of inflammation is set up. Scar tissue then forms in much greater profusion than is needed for actual repair, with the result that the bile ducts become greatly enlarged. The abnormal growth of this tissue in the supporting framework of the liver causes a condition known as cirrho- sis. Because of their large size the worms sometimes block the bile ducts, causing a bile stasis which may result in jaundice and, together with the sloughed epithelium, may lead to the formation of gallstones, since the epithelial debris may serve as nuclei about which the stones are formed. At autopsy, the first point that will be noticed is the swollen condition of the bile ducts, which often stand out like rope swellings on the surface of the liver. These will be found plugged in many cases by cheesy masses of semisolid bile. When the bile ducts are found in this swollen condition, it is usually possible to find adult flukes present also, but in recovered or convalescent cases all the flukes may have disappeared. In severe cases the liver tissue has the appearance of being decomposed, which gives the name u liver rot." This condition may have progressed from merely slight discolored areas to the almost complete supplanting of normal liver tissues by masses of blood in various stages of coagulation and de- composition. A serious condition known as "parasitic anaphylaxis" is often attrib- uted to fluke infestation in yearlings and aged ewes. The affected animals drop out of the flock suddenly and stand with lowered head. The respira- tion increases rapidly, diarrhea is present, the temperature becomes sub- normal, and within a few hours the animal dies in a short convulsion. On post-mortem examination no abnormal conditions will be found Bul. 603] Parasites of Sheep 71 except the presence of minute flukes, scarcely % to % inch in length, in the liver and old healed scars of a previous infestation of flukes. It is believed that the shock producing death is caused by the introduction into the blood stream of toxin produced by the young flukes and its com- bination with or reaction to some substance formed by the previous in- festation of flukes. This condition is rare. Symptoms. — The first indication of infection usually manifests itself about a month after the invasion of the cercariae. A tendency to lag behind the flock, a paling of the mucous membranes, and a slight edema (or watery swelling) beneath the jaw and under the eyes, are all that may be noted at this time. The animal gains weight during this period ; this' may be explained by the increasing flow of bile caused by the inva- sion of the parasites, which facilitates the digestion and assimilation of fats, or by a decrease in fat combustion caused by the anemia. Shortly after this preliminary manifestation, the length of time de- pending on the severity of the infestation, the gain in weight stops and loss is noticeable. The animal becomes more languid, the watery swelling under the jaw becomes more pronounced and pendulous and may be accompanied by an extensive edema under the eyes and along the belly. The so-called "black" diarrhea may be present or the animal may be constipated. The animal entirely loses its appetite. The skin becomes dry and the wool is dry and brittle, falling out in patches, probably as a result of fever. Fatal cases terminate apparently in exhaustion. The duration of the disease is exceedingly variable, but very rarely exceeds six months, death or recovery having ensued by that time. Treatment. — Numerous treatments for liver-fluke infestation have been advocated. Among them are extract of male fern, kamala, and car- bon tetrachloride. The latter drug administered in 1-cc doses is the one most commonly and successfully used against this worm. In treating sheep with carbon tetrachloride, if they have not had access to pasturage or feed containing legumes, such as bur clover, or other source of calcium, it is well to make a preliminary treatment, under the observations of a veterinarian, of a few trial animals. Treatment, however, should not be given shortly after a change of feed. The intravenous injection of a 1 per cent solution of magdala rose has been recommended by Lievre. Prevention. — With the present practice of small permanent ranges, which are often overstocked, the infective forms of the parasite become concentrated in relatively small areas, and it is almost impossible to avoid infestation of sheep. Infestation probably occurs throughout the year in California, although early winter seems to be the commonest time. Infested animals should be treated at regular intervals. Wet pas- 72 University of California — Experiment Station tures should be avoided and drained wherever practicable. Some ranch- ers have decreased the amount of infestation remarkably on relatively dry ranges by fencing off the marshy areas and supplying water in ele- vated troughs. As mentioned in an introductory paragraph, wherever this procedure is practical, it pays large dividends, because not only fluke but also stomach-worm, lungworm, and intestinal-worm infesta- tions have their origin in marshy areas and stagnant pools. Infected pas- tures should not be used for making hay. The destruction of snails capable of serving as hosts for flukes by the application of copper sulfate (bluestone) is important. A solution of 1 part copper sulfate in 5,000,000 parts water is usually sufficient to kill the snails if there is very little or no decayed organic material in the water ; a solution of this strength will not injure stock, but it may kill fish. The strength of the copper sulfate solution used depends upon the amount of decayed organic material present. In California it is usually employed in standing water at the rate of 1 part of the copper salt to 1,000,000 parts of water (1 ounce to 7,800 gallons) and is repeated at the end of a month to kill those snails that have hatched in the interval. In the case of pools, a rough estimate of the volume of water is made, and the required amount of copper sulfate is added after it has been dis- solved in a little water. Where a stream is to be treated, an appropriate vessel containing a strong solution of copper sulfate, which drips out through a hole in the bottom at a suitable rate, is suspended above the stream at its source. Another method of handling the same situation is to suspend small bags of the chemical in the water. In either case the poison is applied to the stream until there are no more live snails. Where moist pastures are to be treated, the copper sulfate is best ap- plied as a powder mixed with from 4 to 8 parts of sand or road dust. From 10 to 30 pounds of this mixture are broadcast or dusted to the acre, ac- cording to the amount of surface water present. Measurements. — 18-51 x 4-13 mm. Hosts. — Sheep, cattle, goat, camel, llama, elephant, horse, ass, rabbit, guinea pig, squirrel, beaver, deer, roe deer, antelope, kangaroo, monkey, man. Distribution. — Cosmopolitan. Habitat. — Liver and rarely in blood vessels, lungs, subcutaneous abscesses, ven- tricles of brain, eye, pharynx. CESTODES The class Cestoda includes all of the tapeworms. These parasitic worms are characterized by having an elongate flat body (with the exception of a few types) and are without a body cavity. The head (scolex) usualhy possesses suckers or hooks or both and in most cases is connected to the Bul. 603 J Parasites of Sheep 73 body by a neck. The body (stobila) is composed of a number of segments (proglottides) . Tapeworms possess no alimentary tract and each pro- glottis contains one or two complete sets of male and female reproductive organs. MONIEZIA EXPANSA (RUDOLPHI 1805) Taenia ovina Goeze 1782 (partim) Taenia vasi nutriis distinctis Block 1782 (partim) Taenia capreoli Viborg 1795 (partim) Halysis ovina (Goeze 1782) Zeder 1802 (partim) Taenia expansa Bud. 1805 Alyselminthus expansus (Bud. 1805) Blainville 1828 Taenia denticulata Mayer 1837 (nee Bud. 1804) Moniezia expansa (Bud. 1805) Blanchard 1891 Moniezia nullicollis (Moniez 1891) Blanchard 1891 Moniezia trigonophora Stiles and Hassall in Stiles 1892 Moniezia oolongiceps Stiles and Hassall 1893 Moniezia minima Marotel 1912 Considerable concern has been felt regarding the common sheep tape- worm, Moniezia expansa, in California during the past few years. This parasite is found almost universally in California sheep, but the number of worms found in an individual sheep is small, an average infestation comprising but three or four worms. However, an occasional animal will harbor more, although never in the enormous numbers reported from Australian sheep. Life History. — Very little is known of the life history of Moniezia expansa. After the so-called "eggs" of a segment have been fertilized and start to develop, the "ripe" proglottis breaks off from the rest of the body and is expelled in the feces. New segments are constantly being formed at the anterior end of the body. The "eggs" escape from the seg- ments thus expelled and the embryos within the "eggs" develop two long- arms. From this stage of development on, nothing definite is known. It is thought that this tapeworm, unlike nearly all others, may possibly not require an intermediate host. Sinitsin 20 has stated a belief that under opti- mum conditions the embryos continue to develop outside the body of the host and that the two elongate arms become coiled about each other in such a way that they "unwind" in the presence of a moist membrane and become attached or invade the tissue when the capsule is ruptured in the nasal passages, the mouth, or throat. Although we have observed thousands of these embryos under varying conditions of moisture and dryness and have noted the lengthening of the arms and other manif es- 20 Sinitsin, D. F. A glimpse into the life history of the tapeworm of sheep, Moniezia expansa. Jour. Parasitol. 17:223-27. 1931. 74 University of California — Experiment Station tations reported by Sinitsin, we have never seen the complicated ar- rangement for the provision of motive power proposed by this author. Monnig 21 has rather definitely shown that moist conditions are neces- sary for the infection of lambs. Freeborn and Berry" found in the lumen of the jejunum of a single lamb, which with others had been fed "eggs," an interesting cysticercoid larva. These authors state : This larva had the general shape of a liver fluke but the leaflike sac was swollen with a clear fluid to a thickness equal to half its width. The scolex end was roughly spherical and showed a wide transverse slit, which opened and closed in salt solution, disclosing a rounded structure within, which moved forward as the lips of the slit opened. No attempt was made to dissect out what was undoubtedly the scolex, as it was thought best to preserve the specimen entire and depend on clearing to differen- tiate the enclosed structure. The sac cleared very nicely, but all attempts to clear the scolex portion were in vain, and we have been able to discern only the rough outline of an enclosed scolex without any details. The attached sac was leaflike, 15 mm long and 6 mm wide, tapering to a point behind and swollen to a thickness of 3 mm by a clear fluid. The walls were thin, membranous, and the entire surface marked with minute transverse striations. No hooklets were present in the sac. In the absence of any anoplocephalid (family to which Moniezia be- longs) larvae, the authors did not feel justified in claiming this larva to be that of Moniezia expansa. They suggest that whatever it was, it was a chance infestation brought into the stall on bedding or on the feet of attendants. If, however, this larva was actually that of M. expansa, this demonstrates that the parasite is capable of utilizing the lamb's intestine for that stage of its development for which nearly all other tapeworms require a separate intermediary host. These authors suggest, as a con- sequence of their failure to infect lambs by direct feeding of "eggs," coupled with the above observation, that possibly the embryo must be conditioned by passage through the alimentary tract of an invertebrate before becoming infective. Pathogenicity. — Moniezia expansa does not appear to cause marked effects in the infected animals, and they may lose but a negligible amount of weight, but it does make them less valuable to the buyer because they become "coarse" and less economical for slaughter. The relatively slight infestations of California sheep (as compared with Australian conditions) apparently produce a degree of immunity or resistance capable of preventing superinfestation. Such immunity, however, is of only a few months' duration after the original infestation has been eliminated. 21 Monnig, H. O. Investigations into the life-history of the tapeworm, Moniezia expansa. Union So. Africa Dept. Agr. Eept. Div. Vet. Services 15:317-27. 1929. 22 Freeborn, Stanley B., and Lester J. Berry. Observations on the sheep tapeworm, Moniezia expansa, in California. Jour. Amer. Vet. Med. Assoc, n.s. 38(5) :611-16. 1934. Bul. 603] Parasites of Sheep 75 Treatment. — Clinic mixture, administered as a drench, gives perfect control of this parasite. Arsenic trisulfide administered in a single dose of 0.5 gram is claimed to be equally effective. Measurements. — 600 X 1.6 mm • scolex, 0.36-0.80 mm wide with prominent suckers. Hosts. — Sheep, goat, cattle, deer, roe deer. Distribution. — Cosmopolitan. Habitat. — Small intestine. THYSANOSOMA ACTINOIDES DIESING 1835 Thysanosoma actinoides Dies. 1835 Taenia fimbriata Dies. 1850 Thysanosoma actinoides is known as the fringed tapeworm. Its pro- glottids are much broader than long and the worm is easily distinguished from Moniezia expansa by the possession on the posterior margins of the segments of long fringes. It is a very frequent parasite of range sheep in the western United States but is not particularly common in California. Life History. — The life history is not known, but it is presumed that this tapeworm requires an intermediary invertebrate host. Pathogenicity. — The fringed tapeworm is frequently found in the gall ducts, gall bladder, biliary canals of the liver, and in the duct of the pancreas as well as in the small intestine. It occasionally causes an obstruction of the bile ducts and pancreatic ducts and derangement of the liver, all of which results in impaired digestion, loss of flesh, and poor quality of flesh and wool. Such affected sheep may die. The animals may show symptoms of calcium tetany when the bile ducts are invaded. However, the seriousness of its infections has been frequently overesti- mated. Treatment. — The worms located in the small intestine may be success- fully treated by following the same directions as given for Moniezia expansa, but there is no known remedy for those in the bile and pan- creatic ducts. Measurements. — 15-30 x 0.8 cm; scolex, 1.2 mm wide. Hosts. — Sheep, cattle, deer, roe deer. Distribution. — Africa, North America (especially North and South Dakota, Ne- braska, Kansas, Oklahoma, Texas, and states west of these). Habitat. — Small intestine, gall ducts, gall bladder, biliary canals of liver, and ducts of pancreas. 12//(-l,'3T