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 E-481 June 1939 
 
 United States Department of Agriculture 
 Bureau of Entomology and Plant Quarantine 
 
 DIPHENYLAMINE AS A WOUND PROTECTOR AGAINST THE 
 SCREWWORM, COCHLIOMYIA AMERICANA C. AND P. 
 
 By Roy Melvin, Henry E. Parish, Edward F. Knipling, 
 
 and Raymond C. Bushland, 
 
 Division of Insects Affecting Man and Animals 
 
 A crystalline chemical substance known as. diphenylamine has been 
 found to be very effective for protecting wounds of livestock from becoming 
 infested with screwworms and for treating wounds infested with these maggots. 
 
 The value of diphenylamine for the control of screwworms was dis- 
 covered after extensive tests had been made with it and a large number of 
 other chemical compounds on several hundred sheep, goats, and cattle under 
 ranch conditions in southwestern Texas. 1/ 
 
 Diphenylamine is not a strong fly repellent and does not entirely 
 prevent flies from laying their eggs on wounds, but it kills the tiny screw- 
 worms hatching from these eggs before they can injure the tissues. It has 
 been shown to be greatly superior to pine tar oil, bone oil, and many other 
 fly-repellent substances commonly used for the prevention of screwworm in- 
 festations. Not only does this material serve to protect wounds against 
 infestation, but it will kill the young worms up to 3 days old that may be 
 present in a wound. It cannot be depended upon, however, to kill screwworms 
 that are more than 3 days old. 2/ 
 
 1/ Circular E-480 , entitled "Results of Studies on Diphenylamine as 
 a Wound Protector against the Screwworm, C ochliomyia americana C. and P.," 
 gives more detailed information on the experimental work leading to the 
 discovery of diphenylamine as a screwworm remedy. 
 
 2/ Experiments carried on by the Bureau of Entomology and Plant 
 Quarantine indicate that there are several other crystalline chemicals which, 
 if used in a similar way, m.ay be even more effective than diphenylamine in 
 the control of screwworm.s. Further investigations of these are being 
 undertaken as rapidly as possible to determine their practical value; how- 
 ever, because diphenylamine has been proved to be so much superior to the screw- 
 worm remedies now in use, it has been decided to release information concern- 
 ing it, even though better chemicals may be found later. 
 
- 2 - 
 
 How to Use Diphenylamine in Treating Wounds 
 of Animals for Screwworm Control 
 
 The following steps are recommended for obtaining the best results 
 with diphenylamine in preventing screwworm infestation in uninfested wounds 
 and for treating animals already infested: 
 
 1. For protecting uninfested wounds against screwworms: 
 
 In wounds freshly made by such operations as castrating, ear marking, 
 docking, and dehorning, in older wounds of this kind, or in those caused by 
 ofher injuries, provided the wounds are not infested with screwworms, enough 
 diphenylamine should be used to cover the injured tissues completely. In 
 the case of castrations it is applied immediately after the removal of the 
 testes, and a little of the material should be pushed into the scrotum. In 
 wounds that are bleeding freely, as is the case in dehorning, it is desirable 
 to take more time for the treatment by putting on small quantities of the 
 chemical at frequent intervals and holding it in place with the hand or ap- 
 plicator far several seconds, until bleeding is reduced and there is no 
 longer danger of most of the chemical being washed away by the flow of blood. 
 In treating docking cases, a handful of the chemical is simply applied 
 to the fresh wound and held in place with the hand for about 30 seconds. 
 Fresh applications of diphenylamine should be made to the wounds every 3 
 days until they heal. 
 
 2. For treating wounds infested with screwworms; 
 
 (a) Swab the wound with clean cotton to remove pus, blood, and serum. 
 Spray a small amount of benzol (commercial 90 percent) into all parts of the 
 wound with a rubber-bulb syringe or similar applicator to stop the flow of 
 blood and serum. 
 
 (b) Add more benzol and plug the opening of the wound with cotton. 
 The excess benzol will be absorbed by the cotton, and the fumes will be con- 
 fined to the cavity of the wound. The fumes of benzol will kill all screw- 
 worms that breathe them, regardless of their age. Leave the cotton plug in 
 the wound for at least 3 minutes; then remove it, and, with a pair of blunt- 
 pointed forceps, pick out most of the larger dead worms, taking care not to 
 induce bleeding. 
 
 (c) Apply diphenylamine freely to the entire wound, making sure that 
 all pockets of the wound are filled and that the entire area is covered, 
 
 (d) Re-treat all wounds at least every third day with diphenylamine 
 until they are healed. Benzol need not be used in re-treating on this 
 schedule, as diphenylamine will kill all worms that have hatched since the 
 previous treatment. If large worms (over 3 days old) are present, they 
 indicate that the animal was overlooked or improperly treated with diphenyla- 
 mine the last time. In such cases the use of benzol will again be necessary 
 to kill the worms. 
 
- 3 - 
 
 Precautions to be Taken in Using Diphenylamine 
 for Screwworm Control 
 
 1. Diphenylamine must be finely ground before it is effective as a 
 screwworm killer and before it will give good results in protecting wounds 
 from infestation. It should be of about the fineness of fine granulated 
 sugar. The condition of diphenylamine as used in the dye industry is much 
 too coarse to be suitable for the treatment of screwv/orm cases, and it must 
 be reground before being applied to wounds. 
 
 Diphenylamine does not repel flies or prevent them from laying eggs on 
 the wound, but by killing the tiny maggots after they hatch it prevents the 
 wound from becoming infested. To accomplish this the particles of the chem- 
 ical have to be very small so that they can be easily devoured by the worms 
 or brought in close contact with them. Some of the manufacturers of di- 
 phenylamine are making arrangements to furnish this material of suitable 
 fineness for use against screwworms. In general, grinding at the factory 
 is superior to home grinding. If the livestock owner does not want to go 
 to the trouble and expense of grinding the material himself he should, when 
 purchasing it, specify that at least 50 percent of it must be fine enough to 
 pass through a screen having 40 meshes to the inch and that at least 90 
 percent must be fine enough to pass through a 20-mesh screen. 
 
 2. Diphenylamine has a tendency to "cake," especially at high tem- 
 peratures, when left standing in containers for any appreciable length of 
 time. In this condition it is not suitable for application to wounds. If 
 it cakes to such an extent that it cannot be readily crushed with the hands, 
 it should be restored to its original fineness by regrinding. Storing the 
 material in a cool place in tight metal or wooden containers and not allowing 
 it to be exposed to the direct rays of the sun will tend to prevent it from 
 excessive caking. 
 
 The Bureau of Entomology and Plant Quarantine is experimenting with 
 methods whereby diphenylamine of a suitable finesess and which will not cake 
 may be produced and be made readily available commercially. It is expected 
 that in a short time the objectionable properties of diphenylamine will be 
 eliminated. 
 
 3. In tests with diphenylamine on a large number of sheep and goats 
 and a few cattle, horses, and hogs, this material has not been found to be 
 harmful to any of these animals. Furthermore, in tests in which Dr. W. C. 
 Mitchell of the Bureau of Animal Industry cooperated and in which large 
 doses of diphenylamine were administered to sheep, goats, hogs, and cattle 
 as a drench, by feeding, and in large fresh wounds, no ill effects v/hatever 
 were observed. 
 
 Despite this evidence of the nonpoisonous nature of diphenylamine, 
 precautions should be taken to avoid its being eaten by man or animals. 
 When handling it in the treatment of animals for the control of screwworms, 
 for any continuous length of time, it is advisable for the operator to wear 
 gloves or to apply it to the wounds with a spoon or other applicator, and 
 to avoid getting the material into the mouth, eyes, or nostrils. 
 
- 4 - 
 
 "fii^H 
 
 Where Diphenylamine may be Obtained 
 
 Diphenylamine is manufactured' in large quantities for use in the dye 
 industry, but its use as an insecticide for the control of screwworms is a 
 new development; consequently livestock owners are not generally informed as 
 to where it may be obtained. For the information of those who desire to 
 purchase it for the control of screwworms there is given below a list of 
 companies which manufacture it and which may be interested in preparing the 
 material in suitable form for this purpose. No claim is made that the list 
 is complete, nor is any guarantee here expressed or implied for the products 
 of the companies listed. 
 
 E. I. Du Pont de Nemours & Company, Inc., Wilmington, Del. 
 Lederle Laboratories, Inc., 30 Rockefeller Plaza, New York, N. Y. 
 Eastman Kodak Company, Chemical Sales Division, Rochester, N. Y. 
 The Dow Chemical Company, Midland, Mich. 
 
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