Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices Sieur ate pitioe sinh B a) : r aur ty t va? ae aGhes Ce ey 4 \ y Lirengt 4 phe a c Ae oe Mieccrales wt: i hi Talk RY Bea ___ a eS 7 j - UNITED STATES DEPARTMENT OF &GAIBOLTORE CIRCULAR No. 148 |. 8, Deparesset af Rarvenl ts Washington, D.C. . November, 1930~ Parasites and Parasitic Diseases of Horses By BENJAMIN SCHWARTZ Senior Zoologist MARION IMES Senior Veterinarian and WILLARD H. WRIGHT Associate Veterinarian Zoological Division, Bureau of Animal Industry ee on CIRCULAR No. 148 NOVEMBER, 1930 UNITED STATES DEPARTMENT OF AGRICULTURE WASHINGTON, D. C. PARASITES AND PARASITIC DISEASES OF HORSES’ By BENJAMIN ScHWARTZ, Senior Zoologist, MARION IMEs, Senior Veterinarian, and WILLARD H. WRIGHT, Associate Veterinarian, Zoological Division, Bureau of Animal Industry CONTENTS Page Page Internal parasites of horses............______ 1 | Internal parasites of horses—Continued. Abundance and location_________________ 1 DisposalrofomantiTe =e a ee 31 Symptoms and damage produced by Summary of control measures____________ 32 DALASILCS eae ee Tad NS thi 1 | External parasites of horses_________________- 34 General control measures________________ 2 FVOFS@ SiGe tee see ek ee ea eee 34 Medicinalbtreatment===—--5- 5 ee 3 Elorse) Manges =. 24 a eed ee 38 IPLOLOZ ON ee ree eee ae ee ne Sl 4 FN CK Sater se ea 45 avons DATASILES Mae ae Saher ee ; Treating horses for external parasites__- 48 ODS Mewes eh BS a ae 2 INTERNAL PARASITES OF HORSES? ABUNDANCE AND LOCATION HE TERM PARASITE as used in this circular refers to forms of animal life which, for the purpose of obtaining food and shelter, live on or in the bodies of other animals which are larger than the parasites and are known as hosts. All classes of domesti- cated animals harbor numerous kinds of parasites, and horses, in particular, are liable to infestation not only with many different kinds but also with very large numbers of these pests. A horse’s stomach may contain hundreds of bots, and the small intestine may be packed with large roundworms. The large intestine of the horse is a location especially preferred by parasites, and very often the colon and cecum are found to be teeming with hundreds or thousands of wriggling, parasitic worms, some free in the lumen and others attached to the walls of the gut. Several kinds of worm parasites present in the gut and elsewhere have previously wandered through various parts of the horse’s body before reaching their final locations. In fact, there is hardly an organ or a tissue in the horse which is absolutely free from possible attacks by mature parasites or by their wandering larval forms. SYMPTOMS AND DAMAGE PRODUCED BY PARASITES Parasitic diseases, unlike diseases caused by bacteria, are seldom spectacular in their onset and symptoms and are marked by a slowly 1 This circular supersedes Farmers’ Bulletin No. 1493, Lice, Mange, and Ticks of Horses. *By Benjamin Schwartz and Willard H. Wright. Many of the illustrations in this section of the circular were drawn by Joseph E, Alicata, junior zoologist. 15390°—30 1 Z CIRCULAR 148, U. S. DEPARTMENT OF AGRICULTURE progressing chain of symptoms which the owner may entirely over- look or confuse with other conditions. The general symptoms of worm infestation in the horse are unthriftiness, weakness, emacia- tion, tucked-up flanks, distended abdomen, rough coat, whitening or bleaching of the mucous membranes (noticed particularly in the mucous lining of the eyelids and mouth), and in some cases frequent eolics and diarrhea. ‘The appetite usually remains good and the ani- mal shows no rise in temperature. Heavily parasitized animals tire quickly and are frequently unable to stand heavy work. Parasites are particularly damaging to young, growing animals. They attack the foal when it should be making its best growth and produce stunting and lack of development. A considerable part of this damage is a result, no doubt,‘of the wanderings of the larval worms through various parts of the body of the host before they ‘reach their preferred location where they develop to maturity. While the death rate from parasitic infestation is not high, never- theless these internal pests cause considerable damage. The loss is represented largely by the poor development and stunting of foals, inability of heavily parasitized horses to do a normal amount of work, added costs of feed and maintenance, and loss of working time from verminous colics. The aggregate loss resulting from these con- citions is sufficient to warrant the attention of horse owners to the subject of parasite control. GENERAL CONTROL MEASURES Most parasites of livestock owe their perpetuation to the fact that domestic animals often take their food from the same places they deposit their fecal matter. The eggs of parasites are passed by horses with the manure in stables and on pastures and then go through various stages of development, after which either the eggs or the larval worms reach the interior of the horse with the food and drinking water. Prevention must be directed toward breaking this cycle. Stables and paddocks should be kept in a sanitary condition by the frequent removal of manure. Concrete standings, although objected to by some horsemen, have the advantage of being easily cleaned and provide a relatively unfavorable medium for the de- velopment of parasites. If wooden standings are used, the timber should be sound. Rotten, moisture-soaked floors are difficult to keep clean, and they provide a favorable medium for the development of parasites. If standings of earth are used, it is advisable to re- move the top layer of soil down to 10 or 12 inches-once or twice a year and replace it with clean, uncontaminated soil. Horses should be fed grain from feed boxes and hay from racks which are sufficiently high above the ground or the floor of the stall to prevent contamination of the feed with manure. Watering troughs should be so constructed as to prevent similar contamination of the drinking water. Horses should not be forced to obtain drink- ing water from pasture or barnyard pools. In general, low, wet pastures are more favorable for the propagation of parasites than are high, well-drained areas. Animals grazed on heavily stocked, permanent pastures have greater opportunity for picking up para- site eggs and larvee than those changed frequently from one pasture to another. For this reason pastures should be changed as often as PARASITES AND PARASITIC DISEASES OF HORSES 3 possible. The common practice of spreading horse manure on pas- ture plots adds to the parasite burden of the pastures. Suitable treatment of manure before spreading, as described in this circular, will prevent this added contamination. MEDICINAL TREATMENT It is not always practicable on the average farm to apply the sanitary measures necessary for the prevention of parasitic infesta- tion in horses. Treatment i is, therefore, an important consideration. Periodic treatment will not ‘only reduce infestation in parasitized horses and render the animals more serviceable but will likewise reduce the output of eggs in the manure, with a resultant decrease in stable and pasture contamination. Prevention of parasites in horses by the application of sanitary measures 1s the business of the horse owner, but the diagnosis and treatment of parasitic diseases are functions of the veterinarian. Different parasites require different and more or less specific treat- ments. Before these treatments can be intelligently applied it is necessary to know which species of parasites are present. The veteri- narian is qualified by training and experience to ascertain this. Drugs used in treatments for horse parasites should be adminis- tered, as a rule, in capsules or by stomach tube, the latter being the preferred method for certain drugs. If capsules containing an 1rr1- tant or volatile drug are broken in the mouth, some of the drug may be drawn into the “windpipe and cause serious consequences. All drugs used in the treatment of horse parasites are poisonous, being intended to poison the parasites, and great care must be used in selecting the dose in accordance with the weight and condition of the animal. Some drugs should not be used in the presence of certain conditions and, if used under such unfavorable circumstances, may cause serious results. Because treatment involves diagnosis and an intimate knowledge of how a drug acts and when to use it or not to use it, it is advisable that all treatments for horse parasites be administered by a veterinarian. The treatments recommended in this circular are, for the most part, those which have been found by experimentation to be the most effective for the parasite or parasites involved. Many drugs, some of them long purported to be of value for the expulsion ‘of worms from the horse, have been found to be practically worthless for this purpose when critically tested. Among such preparations may be mentioned iron sulphate, arsenic, copper sulphate, and tartar emetic. These drugs are frequently prescribed for adminstration in the feed, a method which is very unsatisfactory and ineffective even with drugs known to be effective when given in capsule or by stom- ach tube. For this reason it is essential to administer worm reme- dies in accordance with the methods recommended in this circular. Before the administration of worm remedies animals should be fasted for the length of time prescribed under the various treat- ments. The withholding of feed reduces the bulk of the contents of the digestive tract and permits the drug to reach the parasites more certainly and effectively. Water should be allowed during the period of preliminary fasting, but it is advisable to withhold both feed and water for four or five hours after dosing. To keep 4 CIRCULAR 148, U. S. DEPARTMENT OF AGRICULTURE parasitic infestation at a minimum and avoid losses from this source, it is advisable to adopt a program of regular treatment. The usual procedure is to administer treatments twice a year. In the northern part of the United States, animals may be treated for worm para- sites in the late spring or early summer and in. the fall, and for bots in late November or December and again in February, if necessary, to remove those which have developed since the first treatment. In the South, owing to the shorter and milder winter and the more abundant warmth and moisture, it may be necessary to treat oftener. Judgment, based on experience, is a better basis for procedure than any ‘general rule. Internal parasites occur in various locations in the body of the host animal, such as the alimentary canal, lungs, liver, kidneys, blood, and FAO organs and tissues sane than the Pe They include various forms of animal life known as Protozoa, worms, the larval forms of certain insects, and some forms closely related to insects. The various kinds are discussed in detail in the following pages: PROTOZOA Protozoa are relatively low forms of animal life, microscopic in size, and consisting of but a single cell. The parasitic Protozoa of domesticated animals are known to occur in various jocations, and are especially common in the alimentary canal and in the blood. Fortunately, horses in the United States are relatively free from certain disease-producing protozoan parasites which occur in horses in other parts of the world where they constitute a hmiting factor in horse production. The only known pathogenic protozoan para- site of horses in this country is the organism, one of the trypano- somes, which produces dourine.? Trypanosomes closely related to this organism occur in the blood of horses in South America, Asia, the Philippine Islands, and elsewhere and produce serious and fatal diseases. Up to the present time these parasites have not become established in this country, and quarantine measures to keep them out are enforced. Protozoan parasites of various kinds often occur in large num- bers in the cecum and the upper colon of horses, but these forms are not definitely known to produce any digestive or other disturb- ances and are usually regarded as comparatively harmless. WORM PARASITES As already stated, the worm parasites of horses include. flukes, tapeworms, and roundworms, the last-mentioned group being the most common and the most injurious. FLUKES Flukes or trematodes are soft, more or less flattened, leaf-shaped worms, occurring in various locations, especially in the digestive tract and in organs which communicate with the digestive tract. Only a few kinds of flukes are known to occur in horses, and several information concerning dourine is published in Farmers’ Bulletin 1146, Dourine of orses PARASITES AND PARASITIC DISEASES OF HORSES 5 of the forms which have been reported from these animals normally occur in other hosts and are only accidental parasites of the horse. The only fluke likely to be encountered in horses in this country is the common liver fluke of cattle and sheep, which is occasionally found in the horse. Horses on the west coast, in the South, and in the Southwest are likely to become infested with liver flukes, espe- cially if they have access to pastures on which fluky sheep and cattle have grazed. Liver fiukes occur in the bile ducts of the liver and produce a serious disease, especially in sheep. The larval forms of these worms require snails as intermediate hosts and can maintain themselves only on pastures sufficiently wet to favor the occurrence of certain kinds of snails. Liver-fluke disease in horses has not been extensively studied, because it is relatively rare in these animals. Prevention consists in keeping horses off low and swampy pastures, and these precautions should be especially observed in those parts of the United States where liver flukes are known to occur. Such pastures favor parasites in general. Farmers’ Bulletin 1330 gives information on fluke control. Treatment.—There is no established treatment for liver-fluke in- festation in the horse. However, carbon tetrachloride in small doses has a specific action on the common liver fluke of sheep and is widely used as a treatment for fluke infestation in these animals. Carbon tetrachloride may be given with safety to adult horses in doses of from 6 to 12 fluid drams (25 to 50 cubic centimeters) and in these doses should be effective for the destruction of the flukes. TAPEWORMS A tapeworm is an elongated flattened worm consisting of a head and a chain of segments. Each mature segment contains both male and female organs. The head of a horse tapeworm is provided with four suckers by means of which the parasite attaches itself to the wall of the gut. The segments of these tapeworms are considerably wider than long and those which are farthest from the head are the ones which contain eggs. The ripe or gravid segments which con- tain the eggs become detached from the rest of the chain and are expelled from the body with the droppings. Beyond this point nothing is known as regards the further development of horse tapeworms. Horses are known to harbor three species of tapeworms, as follows: The large horse tapeworm, Anoplocephala magna (fig. 1), usually is from 314 to 10 inches long. The head is about two-fifths of an inch in width and bears four prominent suckers. With the excep- tion of those immediately adjoining the head, the segments are con- siderably wider than the head. This parasite occurs in the small intestine and occasionally also in the stomach. The dwarf tapeworm of horses, Anoplocephala mamillana (fig. 2), is only from about one-fourth of an inch to 2 inches long and from one-sixth to one-fourth of an inch wide; the head of this worm is very minute and is barely visible to the naked eye. This tapeworm occurs in the small intestine and is occasionally found in the stomach. A third species of tapeworm, intermediate in size between the large tapeworm and the dwarf tapeworm, is known as the perfoliate tapeworm, Anoplocephala perfoliata. It is usually from about 6 CIRCULAR 148, U. S. DEPARTMENT OF AGRICULTURE three-fifths of an inch to over 3 inches long. It occurs usually in the cecum and is also found in the lower portion, rarely in the upper portion, of the small intestine. This species is apparently much less common in American horses than the other two species of tapeworms. . Symptoms and lesions—In light infestations no symptoms are present. Horses which are heavily infested with tapeworms may FictrEe 1.—Almost a gallon of large tapeworms, Anoplocephala magna, removed post- mortem from a horse. About one-half natural size. (Photograph by courtesy of the Agricultural and Mechanical College of Texas) suffer from intestinal catarrh, show digestive disturbances of vari- ous sorts, and in cases of very severe infestations they may become emaciated and anemic. The perfoliate tapeworm of the horse often occurs in large numbers when present at all, and is said to produce inflammation of the intestines; sometimes it ruptures the wall of the cecum. The attachment of tapeworms of this species to the wall of the cecum produces small ulcers in the regions to which the worms are attached. Treatment.—Very little is known regarding treatment for tapeworms in the horse. The fol- Ficure 2—The dwarf lowing treatments have been recommended but een mumillans, o: have not had critical test to determine their pre- the horse. Natural ecjse value. = Oil of turpentine is said to be an effective remedy. This is given in a dose of 2 fluid ounces (60 cubic centi- meters) in capsules. followed every second day by 1 ounce (30 cubic centimeters) in capsule until five or six doses have been given. The last dose is immediately preceded or followed by 1 quart of raw linseed oil. It would seem that the drugs used for the treatment of tapeworm infestation in other animals would offer more promise. PARASITES AND PARASITIC DISEASES OF HORSES Ee Areca nut may be of value for the removal of tapeworms from the horse. Areca nut, freshly ground, may be given to adult horses in doses of from 1 to 1.5 ounces (30 to 45 grams) in capsules after fasting the animals for 24 to 36 hours. The drug has a purgative action, but if the bowels do not move within four or five hours, it is advisable to administer 1 to 2 pints of raw linseed oil. Areca nut should not be given to very old or very young animals or to those in a weakened condition. Kamala may be found to be of value for the removal of horse tapeworms. Kamala may be given to adult horses in doses of 1 ounce (30 grams) in capsule, after they are fasted from 24 to 36 hours. The drug itself has a purgative action and seldom needs to be followed by a purgative. Kamala should not be given to very young or very old.animals, to those in a weakened condition, or to those suffering from febrile diseases, such as influenza, distemper (strangles), and infectious anemia (Swamp fever). Oleoresin of male fern is another drug which may be of value for the expulsion of tapeworms from the horse. This drug may be given to adult horses in doses of 3 to 6 drams (10 to 20 grams) in capsules after fasting the animal for 24 hours. The drug should be immediately preceded or followed by 1 quart of raw linseed oil. The foregoing drugs should be used with caution and given only to animals in good condition and presumably able to withstand any poisonous effects of the drugs. Prevention.—In the absence of information concerning the life histories of horse tapeworms no definite control measures can be recommended. It should be remembered in this connection that the eggs present in gravid segments which are eliminated with the manure are the starting points of new infestations. Any measures which are taken with reference to the proper disposal of manure will aid in preventing infestation with these parasites, especially if the manure is stored and permitted to undergo self sterilization by heating, so far as the destruction of parasite eggs and larvee is con- cerned. This procedure is described later in this circular. ROUNDWORMS Roundworms or threadworms comprise the vast majority of para- sites which infest horses. These worms, which are also known as nematodes, are elongated, cylindrical in shape, and usually tapering at both ends. Some roundworms are almost white, some are grayish white, most of them are yellowish in color, and some are pinkish or blood red. Roundworms occurring in the horse have a considerable range of size, the large, intestinal roundworm or ascarid being from 6 inches to over a foot long, while the small stomach worm is only about one-fifth of an inch long. Roundworms reproduce by means of eggs which are deposited by the female worms. The eggs are usually eliminated from the horse’s body with the manure. Some species of roundworms must be taken up by an intermediate host in which they. undergo part of their development, while other species are transmitted from one animal to another directly by eggs or by larvee which have emerged from eggs. Most roundworms which, oc- cur in the horse are transmitted directly by eggs and larve, with- out the use of an intermediate host. 8 CIRCULAR 148, U. S. DEPARTMENT OF AGRICULTURE ROUNDWORMS IN THE STOMACH Two kinds of worms are present in the stomach of horses. One kind, designated here as the large stomach worms, is represented by three distinct species in the horse; these parasites are transmitted by flies. The other kind, designated as the small stomach worm of the horse, is represented by only one species. The small stomach worm 1s acquired by horses directly as the result of swallowing infective larvee which occur on pastures. The larve may also be taken in by horses with water and with dry feed. THE LARGE STOMACH WORMS The large stomach worms (fig. 3) are relatively long and slen- der, are whitish in color, and occur either free in the stomach, em- bedded in mucus, attached to the wall of the stomach, or in tumors of the stomach wall, for which tumors these worms are respon- sible. : One species, Carter’s stomach worm, Habronema muscae, of the horse, is from about one-third \ inch to nearly an inch long. This parasite occurs free in the stomach or attached to the wall of the stomach. By Marion Imes. ® From photomicographs by W. T. Huffman, of the Bureau of Animal Industry. PARASITES AND PARASITIC DISEASES OF HORSES 3 FigurE 24.—Sucking louse of horses (Haematopinus asini): A, Male; B, female. (Magnified 25 times) Figure 25.—Biting louse of horses (T'richodectes pilosus): A, Male; B, female. (Magnified 25 times) 36 CIRCULAR 148, U. S. DEPARTMENT OF AGRICULTURE During cold weather, when the hair on coe: is long, lice increase very rapidly ; but when the animals shed their hair in the spring the parasites seem to disappear. Some of the lice usually remain on the animals throughout the summer, but not in sufficient numbers to cause annoyance or to be easily detected. The animals, therefore, usually go into the winter infested. Since the most efficacious rem- edies are > liquid dips, which can not be used safely on horses during cold weather, fall dipping should be practiced whenever horses have been lousy a at shedding time. Symptoms.—The sucking louse obtains its food by puncturing the skin of the horse and sucking blood and lymph. When not feed- ing it moves about on the hair “and skin. The biting lice do not suck blood from the host, but apparently feed on particles of hair, scales, and exudations from the skin. The irritation and itching which result from either or both methods of feeding are shown by the efforts of infested animals to obtain relief. Infested horses rub and bite themselves, and often kick and stamp and manifest extreme uneasiness and irritation. The coat becomes rough; the frequent rubbing destroys the hair in patches and often causes bruises or wounds in the skin. If lice are present in sufficient numbers to cause considerable itching and irritation they can usually be found, especially if the infested animal is placed in the sunshine. All species of horse lice are easily seen with the naked eye and often congregate in groups or colonies on parts of the animal. The favorite locations are the sides of the neck, around the flanks, and under the jaws. In cases of gross infestation, however, lice may be found all over the body and ‘legs. When horses are lousy, close examination should be made to learn what kind or species of lice is present. It is not especially impor- tant, from a practical standpoint, to distinguish between the two. species of biting lice, but it is important to ‘know whether the ani- mals are infested with biting or sucking lice or with both kinds. Method of spreading.—More cases of infestation originate from direct contact with lousy animals than in any other way. Under reasonably good sanitary conditions stables, yards, and other prem- ises which have contained lousy horses are not a source of great danger to horses free from lice. It seems probable, however, “that occasionally lice may become dislodged from their host and drop on mangers, floors, etc., and from these ‘Joeations find their way to a new host. When separated from their host sucking lice live about three days the biting lice not to exceed 10 days. Ordinarily eggs are not te. posited except on the host, but when the hair to which they are attached is removed and kept under favorable conditions they may continue to hatch for as long as 20 days. The newly hatched lice live only two or three days unless they “find a host. It is therefore possible for premises to remain infested for 25 or 30 days from the time they were occupied by infested horses. When lousy horses are clipped the hair should be burned and the ground or floor where the clippings dropped should be thoroughly treated with an insecticide. Lice may be carried from one animal to another on currycombs, brushes, and blankets, or by harness, saddles, and other equipment moved directly from a lousy horse to one free from lice. Curry- PARASITES AND PARASITIC DISEASES OF HORSES - ai combs and brushes should be treated each time a horse is groomed. Harness, saddles, blankets, and other equipment used on lousy ani- mals should not be put on horses that are free from lice unless the equipment has been thoroughly cleansed. When cleaning stables and yards remove all litter and manure down to a smooth surface, then spray well with a good insecticide. The coal-tar cresote dips, diluted in accordance with the instruc- tions printed on the label of the container, are suitable for ridding premises of the lice. Treatment.—None of the dips recommended for use in treating horses can be depended on to eradicate lice at one dipping. The first dipping, if properly done, will probably kill all the lice, but it may not destroy all the eggs. The nits or eggs which survive dipping often hatch, forming a new generation of lice. This new generation should be destroyed by a second dipping after hatching is completed and before the young lice become mature and begin depositing eggs. Since these two periods overlap somewhat and vary greatly, and be- cause the periods from hatching to egg laying are different for the sucking and biting lice, it is impossible on this basis to calculate the exact period that should elapse between dippings. Young lice ap- pear on dipped animals as early as the third day after the first dip- ping, and since the average period of maturation is about 12 days it seems evident that the second dipping should be given in about two weeks. Experience has shown that two dippings with an interval of from 14 to 16 days usually can be depended on to control both sucking and biting lice. The dips commonly used for destroying lice on horses, mules, and asses, named in the order of their effectiveness, are arsenical solution, coal-tar creosote, and nicotine. The arsenical solution is poisonous, and unless handled with due precaution injury to man and animal may result. When properly used, however, it is the most depend- able known dip for destroying lice. The coal-tar creosote dip is ef- fective when used in reasonably good water. Two dippings, from 14: to 16 days apart, in either of these dips can usually be depended on to eliminate horse lice. Two dippings in nicotine solution will ordi- narily free horses from lice. On account of the difficulties in dipping in cold weather, and the unsatisfactory nature of hand treatments, most of them only palliative, it is advisable to dip for lice, when they are present, in the fall of the year before the onset of cold weather. Hand applications of dusting powders and oils and greases are often resorted to in treating horses for lice. Some of the dusting powders are of value in holding the parasites in check, but, as a rule, they are not effective in controlling sucking lice. Biting lice can be destroyed with sodium fluoride applied in the form of a powder or mixed with water in the proportion of about 1 ounce to 1 gallon; but sodium fluoride is not effective against sucking lice. Care should be taken not to apply sodium fluoride too freely around the natural body openings or where the skin is very thin and hairless, and not to rub it into the skin. It may be applied with a dust gun, or a shaker, or by hand. Oils and greases, such as crude petroleum, crank-case oils, or equal parts of cottonseed oil and kerosene, are effective remedies for lice; but ordinarily they are not suitable for use on horses, as they cause the hair to come out, and they often blister the skin. 38 CIRCULAR 148, U. S. DEPARTMENT OF AGRICULTURE Fumigating horses with the fumes from burning sulphur (sulphur dioxide) will kill horse lice, but many of the eggs survive, and two treatments two weeks apart are necessary to effect eradication. The advantage of this method of treatment is that it can be used when the weather is too cold for dipping. The disadvantages are that it is necessary to have a gas-tight inclosure and the animal’s eyes and nostrils must be kept away from the gas. A concentration of about 1 per cent sulphur dioxide is necessary to kill the parasites, and 7 serious injury or death may result if the gas comes in con- tact with the eyes or nostrils. After fu- migation it is neces- sary to hand treat that part of the head that was not fumi- gated. (Vig. 26.) HORSE MANGE 3 = cS Seabies in_ horses, commonly known as mange, itch, or scab, is a Name given to a eroup of contagious skin diseases caused by minute parasites known as mites, which live on or in the skin. Four species of these parasites are found on domesticated animals, but horses are com- monly affected by only three of them. These parasites are classified zoologically in three different genera — Sarcoptes, Psoroptes, and Cho- rioptes. Mites of the Figure 26.—Fumigation with sulphur gas for lice. Eyes first two genera are and nostrils must be kept away from the gas. Part of : : Sd head not fumigated must be hand treated shown in Figures 24 and 30. In obtaining their food from the host and preparing a resting place in or on the tissues, the mites cause wounds or lesions in the skin. As each kind of mite possesses distinctive habits, the location and nature of the lesions in the early stages are more or less charac- teristic. Each kind of mite, therefore, causes a specific kind of mange which is named after the generic name of the mite. Thus we have in horses sarcoptic, psoroptic, and chorioptic mange. The sar- coptic variety is the one most common on horses in the United States. PARASITES AND PARASITIC DISEASES OF HORSES 39 SARCOPTIC MANGE SARCOPTIC MANGE MITE The mites which cause sarcoptic or common mange of horses are small, white, or yellowish parasites known technically as Sarcoptes scabici equi. (Fig. 27.) The female when full grown measures about one-fiftieth and the male about one-sixtieth of an inch in length. When placed on a dark background they are visible to the naked eye. The general form of the body is more nearly round than oval, and the bluntly rounded head is as broad as it is long. When mature, these mites have four pairs of short, thick legs, the fourth pair and usually the third pair also not extending beyond the margin of the body. Under a high-power miscroscope a number of short, backward-projecting spines may be seen on the ere surface of the body. The sarcoptic mites penetrate the upper layer of the skin and exca- vate burrows or galleries in which the mating of the sexes occurs and the eggs are laid. Each female may lay from 10 to 25 eggs during the egg-laying period, which probably lasts from 12 to 15 days. When that period is completed the female dies in her burrow. The entire life cycle is passed on the body of the host animal. The eggs hatch in from 3 to 10 days, and the young mites after passing through several molts reach maturity and begin laying eggs in 10 or 12 days. As the average period of incuba- age ese pe tignson: the animalis abeut four ~ ete Grecnes jolene days, and the average period after hatching until egg laying begins is about 11 days, a new generation of mites may be. produced in about 15 days. If the first treatment or dipping could be depended on to kill all the mites on the animal the time for the second treatment could be calculated accurately. Unfortunately, the first treatment usually does not kill all the sarcoptic mites on the animal because of the difficulty of getting the dip or other insecticidal substances into the burrows and in contact with the mites. Practical experience has shown that the interval between treatments or dippings should be from five to seven days. Symptoms.—tIn the early stages of sarcoptic mange in horses the first visible lesions usually occur on the neck or shoulders or around the head, but the disease may start on the breast, flanks, sides, or other parts of the trunk. From these parts the disease spreads until the entire surface of the body may become involved. The mites penetrate the upper layer of the skin, each female making a separate burrow or gallery, which usually extends to the sensitive tissues or “ quick.” The presence and activities of the mites 40 CIRCULAR 148, U. 8. DEPARTMENT OF AGRICULTURE on the sensitive tissues cause great irritation and itching, and the skin becomes inflamed and swollen, so that small nodules are formed over and around the burrows. As the disease developes vesi- cles are formed which break and discharge serum. As the serum dries, small scabs are formed, and the hair over the affected parts stands erect and some of it drops out. In some cases the affected areas of skin become dry and scurfy, and may have a leatherlike appearance. (Fig. 28.) The mechanical injury to the skin resulting from rubbing and biting causes large scabs to form, which adhere firmly to the under- = lying tissues. The large scabs often are broken by the movements FIGURE 28. Sarcoptic mange. Head, neck, and shoulders involved af the animal, and blood or serum may stain the scabs a reddish vellow. As the disease advances the skin becomes more or less bare in ir- regular-shaped, bald patches, and is greatly thickened and thrown into wrinkles or folds. (Fig. 29.) In severe cases the horse loses flesh rapidly, becomes greatly weakened, and unless properly treated may die. Contagiousn spe- cies of sitinal to ie and also from animals to man. Ordi- narily when one species of animal contracts the contagion from an- other species the mites live only a limited time on the new host. Sarcoptic mites of the sheep, hog, camel, dog, cat, and rabbit may PARASITES AND PARASITIC DISEASES OF HORSES Al live on horses, and those of the horse, dog, and hog are known to be readily transmissible to man. ) Sarcoptic mange of horses is contagious to all classes of horses and is usually transmitted by direct contact with infested animals. It may, however, be transmitted by other objects, such as currycombs, blankets, or harness, or in stables or other premises. It is important that mangy horses be isolated and all equipment kept separate until the disease is eradicated. Apparently the disease spreads slowly during warm weather, especially among horses on pasture, but it makes rapid headway in horses closely confined or crowded together in small inclosures. Exposure to cold, inclement weather, insufficient feed, or feed of poor quality, or any other circumstances tending to lessen the vitality or functional activities of horses hastens the spread and development of mange. When the mites are active under favorable conditions the FIGURE 29.—A well-advanced case of sarcoptic mange lesions extend rapidly, and the entire body surface may become involved in about six weeks. Although they do not propagate themselves except on the bodies of animals, the mites as well as their eggs may retain their vitality for a considerable time off the host animal. When exposed to sun- ght in dry places the sarcoptic mites live only a few days, but in moist, protected places they may live three weeks or even longer. Although it is difficult to infect horses experimentally from infested premises, the possibility that the disease may be contracted from such sources should not be overlooked. It is good sanitary practice to clean and disinfect all stables and small inclosures which have been occupied by mangy horses, also all currycombs, brushes, blan- kets, and other objects used on such horses, before using them for clean animals. Cleaning and disinfecting for sarcoptic mange may be done in the same manner as for lice. Treatment—On account of their burrowing habits, sarcoptic mites are difficult to eradicate. The common dips, such as lime- 42 CIRCULAR 148, U. 8. DEPARTMENT OF AGRICULTURE sulphur, nicotine, and coal-tar creosote, will kill sarcoptic mites if the dip can be brought into direct contact with the parasites. This method, however, requires thorough, frequent, and persistent applica- tions. From four to six dippings, five to seven days apart, in lime- sulphur or nicotine solution will usually effect a cure in ordinary cases, especially if all affected areas are soaked well with warm dip and scrubbed with a brush just prior to the first dipping. Affected animals should be held in the bath from two to three minutes. Two or more applications, a week apart, of unprocessed crude petroleum will usually eradicate sarcoptic mange, if treatment is applied before the disease becomes chronic. Crude oils, however, often cause the hair to come out and may blister the skin. Crude oil is not a suitable dip for common use on horses, but it 1s of value in hand treatment for holding mange in check during the winter months when the temperature is too low for dipping. Crank-case drainings may be substituted for crude petroleum, but such oils also cause loss of hair and often blister the skin. Fumigation of mangy horses with sulphur dioxide has been recom- mended by some European investigators. The Bureau of Animal Industry has conducted some field tests with this method of treat- ment, but the equipment and methods of application so far devised are too complicated and expensive for general use except where large numbers of horses are assembled for treatment under the supervision of a veterinarian. Apparently this method of treatment has no dis- tinct advantage over dipping except that it can be used when the temperature is too low for dipping. In applying home treatment or fumigating for mange the medicament has a better chance of reach- ing the parasites if the hair over and around the lesions is first clipped and singed. Cases of sarcoptic mange of long standing, which have been neglected and allowed to develop until the affected skin has become greatly thickened and leatherlike, are usually incurable by any ordi- nary method of treatment. In cases of suspected mange prompt and vigorous action should be taken, as the disease can be eradicated in the early stages at comparatively low cost. PSOROPTIC MANGE PSOROPTIC MANGE MITE The mite (Psoroptes communis equi) which causes psoroptic mange lives on the surface of the skin and does not form burrows. Psoroptic mites are slightly larger than sarcoptic mites, the mature female measuring about one-fortieth and the male about one-fiftieth of an inch in length. (Fig. 30.) The entire life cycle is passed on the host animal. Each female may deposit from 15 to 24 eggs, which hatch in three to four days. The young mites reach matur- ity, mate, and the female deposits eggs in from 10 to 12 days. Dipping, if properly done, kills all psoroptic mites, but can not be depended on to destroy the eggs. Some of the eggs may hatch after dipping, thus forming a new generation of mites. To effect eradica- tion it is necessary to give a second dipping after hatching is com-- pleted and before the young mites reach maturity and begin laying eggs. It is evident that the interval between the first and second dip- pings should be from 10 to 12 days. PARASITES AND PARASITIC DISEASES OF HORSES 43 Symptoms.—Psoroptic mange may start on any part of the body: covered thickly with hair, but the first lesions usually appear on the head under the foretop, on the top of the neck around the mane, or on the rump. From the starting point the disease spreads slowly over the body. 7 The mites prick the skin and probably introduce a poisonous se- cretion into the wound. A slight inflammation is caused, accom- panied by an intense itching. In the early stages of the disease the lesions are not sufficiently prominent to attract attention, but the animals rub and bite ; themselves to relieve the intense itching, and these symptoms should always be in- vestigated to learn the cause. As the mites multi- ply, large numbers of small wounds are made in the skin, fol- lowed by the forma- tion of papules, in- creased inflammation and itching, and the exudation of serum. The serum which oozes to the surface becomes mixed with foreign matter and microorganisms, and this mass soon hard- ens into yellowish or gray-colored scabs. The scabs are fre- quently stained with blood. In the early stages the hairs around the lesion Bark be glued ie FIGURE 30.—Psoroptic mange mite. Female. (Magnified gether. in a_ small 100 times) clump and the nodule or scab may be about the size of a pea. As the mites constantly seek the healthy skin around the edges of the wound, the scab or lesion gradually increases in size. Some of the mites migrate to other locations and start new lesions, which extend until they cover large areas. As the disease advances the skin becomes thickened, tumefied, and thrown into wrinkles or folds. Large areas become denuded of hair and covered with thick, adherent scabs. When the disease reaches this stage it is difficult to differentiate it from sarcoptic mange. Itching is intense and irritation continues throughout the course of the disease. The skin becomes bruised and raw from the reck- less rubbing against any available surface. The uniform thickening 44 CIRCULAR 148, U. S. DEPARTMENT OF AGRICULTURE and hardening of the skin is characteristic of mange, but the most certain diagnosis consists in finding and identifying the mite which causes the disease. In the early stages of psoroptic mange the mites may usually be found in scrapings “taken with a blunt- edged knife from around the edges of fresh lesions. In the advanced stages scrapings taken from the edges of scabs or from the bottoms “of the folds of skin may contain mites. In the early stages psoroptic mange may be distinguished from sarcoptic mange by the character of the lesions and the manner of spreading, but the most dependable diagnosis consists in finding the mite. For practical purposes where facilities for examination are limited the principal differences in form and structure of the two species of mites may be summarized thus: The sarcoptic mite is slightly smaller than the psoroptic mite, and the body of the former is more nearly round than oval. (Fig. 27.) Adults of both species have four pairs of legs. those of the psoroptic mites being long, and all four pairs extend beyond the margin of the body. (Fig. 30.) The sarcoptic mites have shorter legs, and the fourth or hind pair and usually the third pair do not extend beyond the margin of the body. The head of the common scab mite is tapering or cone-shaped and is longer than it is broad, whereas that of the psoroptic variety is bluntly rounded in front and is as broad as it is long. It is advisable to examine several specimens in all cases, because under low-power magnifying glasses the females of the two species are more easily distinguished from one another than the males. On account of the burrowing habits of the sarcoptic mites, they are difficult to find, especially in the early stages of the disease. They are situated in burrows under conical papille, and by scraping the infested area until the blood oozes from the tissue, the mites some- times may be found in the scrapings Contagiousness.—Each species of domesticated animal has its own peculiar variety of psoroptic mange, and the variety which lives on the horse, ass, or mule is not transmissible to other animals, with the possible exception of the camel. The disease is more highly con- Cae to all classes of horses than sarcoptic mange. The predis- posing causes, manner of spreading, carriers of the mites, and pre- cautions to be observed in isolating infected animals and cleaning and disinfecting premises are practically the same as for sarcoptic mange. Treatment.—As the psoroptic mites live on the surface of the skin, they are more easily eradicated than the sarcoptic variety. The rem- edies recommended for sarcoptic mange are effective in eradicating this disease. Two dippings from 10 to 12 days apart may usually be depended on to cure ordinary cases. Four or more dippings may be necessary in chronic cases. CHORIOPTIC MANGE CHORIOPTIC MANGE MITE Chorioptic or symbiotic scabies, commonly known as foot mange, is caused by a mite (Chorioptes equi) which closely resembles the PARASITES AND PARASITIC DISEASES OF HORSES Ad5 psoroptic mite. Chorioptic mites live on the surface of the skin and produce lesions similar to those of psoroptic mange. The lesions of chorioptic mange are usually confined to the lower part of the limbs around the foot and fetlock. Occasionally the mites spread over the legs above the hocks, and may reach even the thighs and abdomen, but usually the disease remains localized around the feet. Infested animals paw and kick and rub the pastern with the oppo- site foot and often try to bite the affected parts. Some of the hair comes out and the skin has the thickened and hardened condition characteristic of scabies. The remedies recommended for sarcoptic mange are effective in eradicating foot mange. The affected areas should be well soaked in warm lime-sulphur dip, and the treatment repeated every 10 days until a cure is effected. Driving the horses through a shallow wad- ing tank filled with dip is a quick and effective method of treatment for foot mange. TICKS There are many different kinds of ticks which may attack horses, but since the habits and life cycles of the different species vary greatly discussion in this circular is necessarily limited to general information, except for the ear tick, which is discussed more fully. When only a few ticks are found on horses they may be removed by hand or covered with crude petroleum, cylinder oil, kerosene, or other oil, which usually causes them to detach and drop to the ground. In removing ticks by hand the writer has observed that they may sometimes be detached without leaving the head embedded in the skin by twisting them around as they are pulled loose. In the southern and western parts of the United States it is not uncommon for horses to become grossly infested with ticks. In some sections the infestation may occur only infrequently; in others it may occur more or less regularly each year. In the region in- fested with cattle-fever ticks where eradication work is in prog- ress tick-infested horses are dipped in arsenical solution to kill the parasites. In any locality where the horses become infested with ticks and the infestation is extensive the State livestock sanitary authorities should be notified in order that the ticks may be identified and proper measures taken for control. Control or eradication methods to be successful must be based on a knowledge of the life history and habits of the tick involved. SPINOSE EAR TICK Nature and habits—The spinose ear tick (Ornithodoros méqnini) is prevalent on horses in the Southwest and causes serious damage to the livestock industry. Spinose ear ticks (fig. 31) enter the ears of animals as small, 6-legged seed ticks and attach themselves in the external canal well below the hair line, where in a week or two they become engorged larve. The engorged larve molt to form nymphs or young ticks having eight legs. The young ticks remain in the ears from one to seven months, or until fully grown and engorged, 46 CIRCULAR 148, U. S. DEPARTMENT OF AGRICULTURE FigurRp 31.—A, Har ticks and débris from ear of animal (about natural size); B, en- gorged larva (magnified 5 times) ; C, young tick (magnified 5 times); D, partially engorged young tick (magnified 5 times); ZH, fully engorged young tick (magnified 5 times) ; F, adult female (magnified 5 times) ; G, adult male (magnified 5 times) PARASITES AND PARASITIC DISEASES OF HORSES 47 when they drop to the ground, crawl up into dry, protected places above the ground, and again molt. The skin of the nymph is covered with spines, but that of the mature tick is smooth. So far as is known the adult tick does not attach itself to animals nor does it take food. Mating and egg laying take place off the animal, and when egg laying is completed the female dies. The eggs may hatch as early as 10 days after they are laid. Shortly after hatching the seed ticks are ready to attach themselves to any suitable host. They may live as long as three months if no host is found. \ Symptoms.—W hen animals are grossly infested and the ear canals packed full of ticks the parasites are visible on superficial examina- tion, but when the degree of infestation is light or moderate the ticks may be overlooked. They usually attach themselves in the deep folds of the ear or crawl into the ear canal and follow it inward, sometimes as far as the eardrum. As the ticks increase in size and others enter, they and the excretions, with the wax from the ear, accumulate in masses or plugs sufficient in some cases to close up the ear passages completely. These conditions give rise to various symptoms. The infested animal usually shakes its head and re- peatedly turns it from side to side, meanwhile inverting, or turning down, first one ear and then the other. When irritation and itching are more intense on one side the animal > Ee CMR st ahead GREE SSG a so that the more se- 21 ey aes riously affected ear Figurb 32.—Ear probe made of baling wire is held downward. There is a tendency to rub and scratch the ears, and young animals often run as though endeavoring to relieve the nervous tension. In all cases where ear-tick infestation is suspected the animals should be examined, and if no ticks are visible the ears should be probed. A convenient and effective instrument for probing the ears, removing ticks from the ear canals, and breaking down masses of — ear wax and ticks may be made from a piece of ordinary baling wire, as shown in Figure 32, the loop end being used for dislodging the ticks. Treatment.—Complete eradication of spinose ear ticks is a diffi- cult matter, on account of the habits and great vitality of the ticks and the wide range of animals which they may infest. Results of investigations conducted by the Bureau of Animal Industry have shown that dipping in any of the known dips or the injection into the ear passages of bland oils, crude petroleum, or various dips, etc., is not effective in killing the ticks or causing them to leave the ears. Gasoline and kerosene when apphed undiluted kill the ticks, but cause blistering of the skin and are not suitable for use on horses. Chloroform, undiluted or mixed with a bland oil, is commonly used on horses and dogs and is effective. Such substances as chloroform evaporate rapidly, and therefore afford no protection against reinfestation. The remedy for ear ticks formulated and thoroughly tested by the Bureau of Animal Industry consists of a mixture of two parts by volume of ordinary pine tar and one part by volume of cottonseed oil. In mixing the ingredients add the cottonseed oil to the pine tar 48 CIRCULAR 148, U. S. DEPARTMENT OF AGRICULTURE and stir until a uniformly smooth mixture is obtained. When neces- sary the ingredients should be warmed before mixing, so that they will mix readily and flow freely. The mixture remains uniform without separation or deterioration, and may safely be used on any species of domesticated animal. Being of a sticky consistence, it remains in the ears and affords protection against reinfestation from 30 to 60 days. The only known effective method of applying treat- ment is to inject the remedy into the ear passages by hand. Most horses oppose the insertion of anything into their ears, and some form of restraint is necessary. Gentle farm horses can usually be controlled with the twitch or other well-known methods of re- straint, but in treating wild range horses special equipment is neces- sary. An ordinary crowding chute not more than 3 feet wide is suitable for treating horses for ear ticks. An ordinary metal or hard-rubber syringe holding from 1 to 2 ounces is the best instrument to use for injecting the pine-tar-cot- tonseed-oil mixture. Have the mixture warm enough to flow freely, fill the syringe, grasp the ear with the left hand, then insert the nozzle into the opening of the ear canal and inject about one-half ounce of the fluid. Hold the ear in an upright position for a few seconds and manipulate to force the mixture into the deeper parts. If too much fluid is injected it will overflow and run down over the head and face, where it may cause blistering. The mixture causes very little irritation except on parts exposed to the direct rays of the sun. When the ear passages contain masses of hard wax and ticks, such masses should be broken down and scraped out with a wire loop before treatment is applied. Treatment should be applied as often as necessary to keep the ears free from ticks. One treat- ment properly apphed can be depended on to kill all ticks in the ears and to prevent reinfestation for about 30 days. It should be re- membered, however, that the eggs of the tick are not deposited or hatched in the ears of animals, and a new crop of seed ticks may find lodgment at any time on animals kept in infested places. TREATING HORSES FOR EXTERNAL PARASITES The three commonly used methods of treating horses, mules, and asses for external parasites are (1) hand applications, (2) spraying, and (3) dipping. A fourth method, not in common use but recom- mended by some European investigators, is fumigation with sulphur dioxide. HAND APPLICATIONS Infested animals may have parasites on any or all parts of the body surface, and to effect complete eradication usually it is neces- sary to cover the entire surface of the skin with the medicament. On account of the difficulty of applying treatment by hand over the entire body surface, hand applications are recommended only as a temporary measure for holding parasites in check until the ani- mals can be dipped or sprayed. SPRAYING Common parasites on or in the skin can be eradicated by proper spraying, but the method commonly practiced is not economical, PARASITES AND PARASITIC DISEASES OF HORSES AQ It is difficult to wet the hair coat of an animal with a spray, and much of the liquid runs off and is wasted. Spraying is not effective unless all parts of the skin and hair are well soaked. An ordinary orchard-spraying outfit or a common hand pump equipped with hose and spray nozzle may be utilized for spraying animals. FUMIGATING Fumigation consists in exposing animals to the fumes of burning sulphur (sulphur dioxide) or some other gas. The animals to be fumigated are placed in a gas-tight chamber with the head project- ing through an opening and the nose and eyes protected from the gas. (Fig. 26.) This method is often recommended for treating animals for external parasites. Investigations conducted by the Bureau of Animal Industry have shown that the present known methods of fumigating animals are not suitable for general use. The minimum effective concentration of sulphur dioxide for mange apparently is about 4 per cent and for lice about 1 per cent. Under ordinary conditions the concentration or percentage of gas in the air can not be raised to more than about 1.5 or 2 per cent by burning sulphurin the gas chamber unless special apparatus is installed. Sulphur dioxide compressed to a liquid and stored in steel cylinders is available on the market. By using the compressed gas any desired concentration in the chamber within certain limits may be obtained. In winter, when the temperature is too low for dipping, fumigation is feasible if a large number of horses are to be treated and competent men are available to super- vise the work. This method apparently has no other distinct advan- tage over dipping. DIPPING Dipping is the most effective known method of applying treat- ment for common external parasites. Dipping plants are so ar- ranged that the animals are immersed in lquid deep enough to swim in, and the entire body surface is well soaked. For dipping horses the dip in the vat should be kept at a depth of 70 to 80 inches, or sufficient to immerse completely the tallest animal to be dipped. Horses will carry out and retain from 2 to 4 quarts of dip each, and the depth of the liquid in the vat will be lowered accord- ingly. The total estimated quantity of dip which the animals carry out plus that required to charge the vat should equal the total quan- tity required, provided none is lost by leakage or otherwise wasted. The capacity of the vat is usually obtained by multiplying, in terms of inches, the average length by the average width, then the product by the depth. This gives approximately the number of cubic inches of space to be filled with dip. Divide this by 231 (the number of cubic inches in a gallon), and the result will be the number of gallons of dip needed to charge the vat. (Fig. 33.) To obtain the average length, add the length at the bottom to the length at the dip line and divide by two. The average width is ob- tained in the same manner. The depth should be taken at the center of the vat and from the bottom to the dip line only, and not to the 50 . CIRCULAR 148, U. S. DEPARTMENT OF AGRICULTURE top. All measurements should be made only of the space to be filled with dip, and not above the dip line. The capacities of the various tanks are obtained by a like process. Before dipping, the contents of the vat should be well stirred in order that the dip may be of uniform strength and temperature throughout. The pens, chutes, vat, etc., should be examined for pro- jecting nails or any object that might puncture or wound the horses, as the dip may injure those having fresh wounds. In dipping wild range horses it 1s nec- essary to have a gate or bar in the chute to prevent the animals from piling up in the vat. Horses should be watered and fed from two to four hours before dipping, and if heated by driv- ing they should be allowed to cool off be- fore entering the vat. The head of each animal should be completely submerged for an instant at least once while in the vat. The head should not be held under, but quickly ducked with a dipping fork and released. Two duck- ings of the head are advisable, especially if the animals are affected with scabies. Care should be taken to see that the inner surface of the ear is well soaked. In dipping for lice it is not necessary to FIGURE 33.—Dipping vat being filled with liquid hold horses in the vat, but if they have scabies they should be held in the vat two or three minutes. After leaving the vat the animals should be held in the draining pens until all surplus dip has drained off their bodies. (Fig. 34.) Dipping should be finished for the day early enough to dry the ani- mals before sunset. Before approving a dip for use in official dipping one of the requirements of the Bureau of Animal Industry is that there shall be PARASITES AND PARASITIC DISEASES OF HORSES 51 a practical field test for such dip. Of the various classes of dips meee on horses, three only are on the approv phur, and nicotine. Of these the two most ee used are vie lime-sulphur dip for mange and the ar- senical dip for lice and ticks. ARSENICAL DIP Arsenical dip, when properly used, eradicates biting and sucking lice, but it is not an effective rem- edy for mange. Pre- pared arsenical dips have been placed on the market, but those which are permitted by the Government for use in dipping cattle for southern fever ticks are suit- able for use in dip- ping horses, mules, and asses for lice. The instructions on the label of the con- tainer should be fol- lowed in diluting and using ready-prepar- ed dips. The arseni- cal dip is not usually warmed or heated in the vat. It should be remem- bered that arsenical dip is a poison, and precaution should be taken to prevent in- | ee. ik ees jury to man or ani- IGURE 34.— Exit Seger coe pens of horse- mal. When it is handled and used with proper care it is a safe and effective remedy. Care should be taken not to get the clothing wet with the dip, and the hands should be washed frequently to prevent possible absorption of arsenic. Freshly treated animals should be held in the draining pens or other suitable place until all surplus dip has drained off. (Figs. 34 and 35.) If allowed to drain where pools of dip collect from which the animals may drink, or if the pasture or feed becomes soiled with arsenical dip, losses are hable to occur. If homemade arsenical dip is preferred to the pr oprietary brands, see United States Department of Agriculture Farmers’ Bulletin 1057 for full instructions for making it. 52 CIRCULAR 148, U. S. DEPARTMENT OF AGRICULTURE LIME-SULPHUR DIP Proprietary brands of liquid lime-sulphur may be purchased, and many of them are equal to or even better than the homemade product. Manufacturers have also placed on the market a product commonly known as dry lime-sulphur, made by evaporating, in vacuo or in the presence of an inert gas, concentrated lime- sulphur solution to which a small amount of cane sugar has been added to act as a stabilizing agent. Dry lme-sulphur is readily soluble in hot water, and it is being extensively used as a dip for animals and as an insecticide for plants. Prepared dips should be diluted and used in accordance with instructions printed on the label of the container. Lime-sul- phur dips are efficacious and dependable remedies for mange, but they are not effective against lice and ticks.. Homemade lime- sulphur dip is made in the proportion of 12 pounds of unslaked lime (or 16 pounds of commercial hydrated FIGURE 35.—Superstructure and draining pen of cage vat lime) and 24 pounds of flowers of sulphur to 100 gallons of water. The lime and sulphur should be weighed and the water measured; do not trust to guess work. Slake the lime in a shallow, water- tight box or tank and add water enough to form a thin paste. Sift the sulphur into the paste and mix well with a broad hoe until a mixture of about the consistence of mortar is formed, adding water as re- quired. Put the mixture into 30 gallons of boiling water, adding it slowly so as not to interrupt the boiling, and boil until the sulphur disappears from the surface. The boiling should be continued for from one and a half to two hours without cessation, and the mixture stirred to prevent settling and caking on the bottom. When the sul- phur has disappeared from the surface and the mixture is of a choco- late or dark-amber color, the boiling should be discontinued. The contents of the boiling tank should be drawn off or dipped out and placed in the settling tank and allowed to stand until all solids have settled to the bottom and the liquid is clear. An ordinary water- tight barrel will serve very well for a settling tank at a small vat. A PARASITES AND PARASITIC DISEASES OF HORSES 53 settling tank of any kind should have an outlet at least 4 inches from the bottom in order that the clear liquid may be drawn off without becoming mixed with any of the sediment. When the sediment has fully settled draw off the liquid into the dipping vat and add warm water to make a total of 100 gallons of dip. When mixed and cooked as specified above the concentrate is three and one-third times the strength required for the dip in the vat, so that to every 30 gallons of such concentrate 70 gallons of warm water should be added to make a dip of the required strength. In preparing lime-sulphur dip in large quantities several hun- dred gallons of concentrate are often made at one time in a single large cooking tank. The quantity made at one boiling is limited only by the facilities at hand. If the boiling tank is of sufficient capacity, a large enough quantity of dip should be cooked at one FIGURE 36.—Cage vat in operation time to dip the herd. The quantity of mixture in the cooking tank may be varied at will, but the proportions of the various ingredients should not be altered. NICOTINE DIPS The nicotine dips sold under various trade names are commonly used for dipping animals and spraying plants for insect_pests. They are efficacious remedies for horse lice and mange when diluted with water so that the solution contains not less than five one-hun- dredths of 1 per cent nicotine. If used much stronger, they are liable to injure horses, especially if the animals are dipped while they are warm from exercise or hot weather. Nicotine dips are generally used warm, but should not be heated above 110° F. The temperature of the bath should be maintained at 90° to 95°. Sulphur is sometimes added to nicotine dips in the proportion of 16 pounds of flowers of sulphur to 100 gallons of 54 CIRCULAR 148, U. S. DEPARTMENT OF AGRICULTURE diluted dip. The addition of sulphur increases the effectiveness of the dip for mange and extends the period of protection against reinfestation. These dips should be diluted and used in accordance with instructions printed on the label of the container. Do not use a nicotine dip the strength of which is not given on the label. ‘COAL-TAR CRESOTE DIPS The coal-tar creosote dips, commonly known as coal-tar dips, are sold under many trade names. They are made from coal-tar derivatives, and the principal ingredient is creosote oil, which is made miscible with water by means of soap. When diluted with soft water they are efficacious in eradicating lice, but they are not dependable remedies for sarcoptic mange. Before using a coal-tar creosote dip in hard or alkaline water, dilute a small, measured quantity of the dip with the water in the proportion to be used in dipping and place in a clean glass container. If, after standing for one hour, an oily layer or mass of globules appears either at the top or at the bottom of the liquid, the dip should not be used with that kind of water, as it is liable to injure the animals. Injury may occur even when there is no apparent sepa- ration in the dip so tested. The coal-tar creosote dips may be used cold or warm, but the temperature of the bath should not exceed 95° F. They should be diluted and used in accordance with the instructions printed on the label of the container. OIL DIPS Kerosene, crude petroleum, crank-case drainings from gasoline motors, and other oils and greases are commonly used in treating horses for external parasites. When properly used they will control mange and lice, but they often injure horses by blistering the skin and causing the hair to fall out. Oil dips are not recommended for common. use in dipping horses. Cottonseed oii and kerosene, equal parts, or kerosene one-half pint to 1 pound of lard or crude petroleum is often applied by hand to hold mange and lice in check when the weather is too cold for dipping. DIPPING VATS In those sections of the United States where there are a large number of horses to be dipped cattle-dipping vats usually are avail- able, and they can be utilized for dipping horses. (Fig. 33.) Plans of cattle-dipping vats suitable for dipping horses are given in Farmers’ Bulletins 1017 and 1057. The so-called cage vats are sometimes used for dipping horses. (Fig. 35.) In these vats the animal is placed in a movable cage and lowered into the bath by means of a windlass or other mechanical apparatus. (Fig. 36.) The operations are much slower than in the longitudinal vat. Portable, galvanized-metal vats may be purchased, and they are suitable for dipping a small number of animals. After digging a trench and setting the vat so that the top is flush with the surface of the ground, a chute and slide board should be provided as a means of getting the horses into the vat. hit ORGANIZATION OF THE UNITED STATES DEPARTMENT OF AGRICULTURE WHEN THIS PUBLICATION WAS LAST PRINTED NECrelary-o) Agriculture.” "se ARTHUR M. HyYDEs. PUSSESLONT "SECTCLOI Ie 2 eo te os Be R. W. DUNLAP. PITCCLOl: Of. MSGLENLI Gs WOTK =~ = ee A. F. Woops. Director of Regulatory Work______________- WALTER G. CAMPBELL, UX CCLOTGf, HEtension. WoOniIb = 22 oe C. W. WARBURTON. Director of Personnel and Business Adminis- W. W. STOCKBERGER. tration. PDITCCLORA GI tat) OlIMNGNON=— = a M. S. EISENHOWER. Si DULG NAD, RE SG IE SE a ee E. L. MARSHALL. CTA Cia UNCC ee rns ee Ds CHARLES F, MArvin, Chief. burcat of Animal Industry... se JOHN R. MOHLER, Chief. BUCO. Of Dairy Industry. = — = O. E. REED, Chief. PU COU Of Lani. INGUSITY = =~ 2s ee WILLIAM A. TAytor, Chief. SEIOIE SEADSC RV LCC ee aes hoe Bee gn R. Y. Stuart, Chief. Bureau of Chemistry and Soils._______. ___.__ H. G. Knicut, Chief. EAL COM Oe ELONTOLOG Ie ee C. L. Maruatt, Chief. Bureau of Biological. Survey_— —_-____--___- PAUL G. REDINGTON, Chief. TAU CO AO le eELOUC ROGGS= Ss 2 ea ee THomAS H. MAcDOoNALD, Chief. Bureau of Agricultural Hconomics________~-. Nits A. OLSEN, Chief. PAUrCat Of ome LE: CGON@MACS= = . LOUISE STANLEY, Chief. Plant Quarantine and Control Administration_. LEE A. Strone, Chief. Grain Futures Administration_______-___-__. J. W. T. DuvEL, Chief. Food and Drug Administration_____-_-____ __. WALTER G. CAMPBELL, Director of Regulatory Work, in Charge. Office of Experiment Stations_______________- —____—_—_—_—., Chief. Ojfice of Cooperative Extension Work____--~- C. B. SmituH, Chief. LR TAA Las 5 OE i a oa ee pe eee CLABIBEL R. BARNETT, Librarian. This cireular is a contribution from Bureau of Animal Industry________________._- JOHN R. MoHLER, Chief. ZAGBGTECRL DIViIStOn._— = Maurice C. HAtt, Principal Zoologist, Chief. 05 U.S. GOVERNMENT PRINTING OFFICE: 1930 For sale by the Superintendent of Documents, Washington, D. C. - - - - - - Price 15 cents