Animal Parasites of the Skin

Acariasis, or Mange.

This affection is due to the irritation of the skin caused by the presence of nearly microscopic acari, or mites. The disease varies, however, according to the species of acarus which infests the skin, so that we must treat of several different kinds of acariasis.

Parasite: Sarcoptes scabiei equi. Malady: Sarcoptic acariasis.—This is the special Sarcoptes of the horse, but under favorable conditions it can be transmitted to ass and mule, and even to man, and may live indefinitely on the human skin. The mite (Pl. XXXIX, fig. 1) is nearly microscopical, but may be detected with a magnifying lens among moving scurf taken from the infected skin. Like all Sarcoptes, it burrows little galleries in and beneath the scurf skin, where it hides and lays its eggs and where its young are hatched. It is therefore often difficult to find the parasite on the surface, unless the skin has been heated by a temporary exposure to the sun or in a warm room. The mite may be detected more readily by placing scrapings on black cardboard and warming, or better by macerating scabs or scrapings in a solution of caustic soda or potash and then examining them microscopically. Like other acari, this is wonderfully prolific, a new generation of fifteen individuals being possible every fifteen days, so that in three months the offspring of a single pair may produce generations aggregating 1,500,000 young. The Sarcoptes have less vitality than the nonburrowing acari, as they die in an hour when kept apart from the skin in dry air at a heat of 145° F. They live 12 to 14 days apart from the skin in the damp air of a stable. On a piece of damp hide they lived till the twenty-fourth day, when they began to die, and all were dead on the twenty-eighth.

Symptoms.—The symptoms are an incessant, intolerable, and increasing itching of some part of the skin (head, mane, tail, back, etc.), the horse inclining himself toward the hand that scratches him, and moving his lips as if himself scratching. The hairs may be broken and rubbed off, but the part is never entirely bald, as in ringworm, and there may be papules or any kind of eruption or open sores from the energy of the scratching. Scabs of any thickness may form, but the special features are the intense itching and the presence of the acarus.

Treatment consists in the removal of the scabs by soapsuds, and, if necessary, a brush and the thorough application of tobacco 1-1/2 ounces and water 2 pints, prepared by boiling. This may be applied more than once, and should always be repeated after 15 days, to destroy the new brood that may have been hatched in the interval. All harness and stable utensils should be similarly treated; blankets and rubbers may be boiled, and the stalls should be covered with a whitewash of quicklime, containing one-fourth pound of chlorid of lime to the gallon.

When there are too many animals to treat by means of hand dressings, the lime-and-sulphur dip or the tobacco dip may be used and are very effective, though the cresol dips are fairly effective. These dips may be purchased and made up in the dilution called for on the container. The affected animals may be dipped when the number warrants it and facilities are available; otherwise the dips may be applied with a swab or a spray pump. Directions for constructing a dipping vat may be obtained from the United States Department of Agriculture on application. Any treatment used should be repeated in the course of 10 to 14 days. If the stables are not disinfected, animals should be removed after treatment and put in clean stables or on clean pasture for at least a month to allow the mites in the infested stables to die. Otherwise the disease may recur.

Parasite: Psoroptes equi (Dermatocoptes equi, Dermatodectes equi). Malady: Psoroptic acariasis.—Psoroptic mange is less common than sarcoptic mange in horses, and as the parasite (Pl. XXXIX, fig. 3) only bites the surface and lives among the crusts under the shelter of the hair, it is very easily discovered. It reproduces itself with equal rapidity and causes similar symptoms to those produced by the Sarcoptes. The same treatment will suffice and is more promptly effectual. The purifying of the stable must be more thorough, as the Psoroptes will survive twenty to thirty days in the moist atmosphere of a stable, and may even revive after six or eight weeks when subjected to moist warmth. Infested pastures will therefore prove dangerous to horses for that length of time, and, with rubbing posts, etc, should not be used.

Parasite: Chorioptes equi (Symbiotes equi, Dermatophagus equi, Chorioptes spathiferus). Malady: Foot mange.—The acarus (Pl. XXXIX, fig. 2) attacks the heels and lower parts of the legs, especially the hind ones, and may be present for years without extending upon the body. Like the Psoroptes; it lives on the surface, on the hairs, and among the scabs. It gives rise to great itching, stamping, rubbing of the one leg with the other, and the formation of papules, wounds, ulcerous sores, and scabs. The intense itching will always suggest this parasite, and the discovery of the acarus will identify the disease. The treatment is the same as for the Sarcoptes, but may be confined to the legs and the parts with which they come in contact.

Parasite: Dermanyssus gallinæ, or chicken acari. Malady: Poultry acariasis.—This is a large-sized acarus, though usually miscalled "hen louse," and the disease "poultry lousiness." The mite (Pl. XXXIX, fig. 4) lives in droppings and in crevices of chicken houses, but temporarily passes on to the skin of man and of the horse and other quadrupeds, when occasion serves. It causes much irritation, with the eruption of papules or vesicles and the formation of sores and scabs. The examination of the skin is usually fruitless, as the attacks are mostly made at night and the effects only may be seen during the day. The proximity of hen manure swarming with the acari explains the trouble, and the removal of this and a white-washing with quicklime, with or without chlorid of lime, will prevent future attacks. The skin may still require bland ointments or lotions, as for congestion.

Parasite: Larva of a Trombidium, Leptus americanus, or harvest bug, misnamed jigger (chigoe). Malady: Autumn mange.—This parasite is a brick-red acarus, visible to the naked eye on a dark ground, and living on green vegetation in many localities. It attacks man, and the horse, ox, dog, etc., burrowing under the skin and giving rise to small papules and intolerable irritation. This continues for two or three days only from a single invasion, but will last until cold weather sets in if there is a fresh invasion daily. Horses at pasture suffer mainly on the lower part of the face. If kept indoors the disease will disappear, or if left at pasture a weak tar water or solution of tobacco may be applied to the face.

Ticks.

The wood ticks are familiar to inhabitants of uncultivated lands, and prove troublesome parasites to man and beast alike. The tick lives on bushes, and attaches itself to the mammal only to secure a feast of blood, for when gorged it drops off to sleep off its debauch on the soil. The tick produces great irritation by boring into the skin with its armed proboscis. If pulled out, the head and thorax are often left in the skin. They may be covered with oil to shut out the air from their breathing pores, or by touching them with a hot penknife they will be impelled to let go their hold.

Grubs in Skin.

Parasite: Hypoderma lineata. Malady: Larvæ (grubs) under the skin.—The larvæ of a fly (probably Hypoderma lineata, whose larvæ in the skin of cattle are commonly known as "warbles") are occasionally found in little sacs beneath the skin of horses. The mature larva escapes in early summer and develops into a fly. In districts where they exist the grubs should be pressed out of the skin in the course of the winter and destroyed.

Larvæ (Grubs) on the Skin, or Flyblow.

The following flies, among others, deposit their eggs on open sores or on wet, filthy parts of the skin, where their larvæ or grubs give rise to serious trouble: Lucilia cæsar (bluebottle), Cochliomyia macellaria (screwworm fly), Musca vomitoria (meat fly), and Sarcophaga carnaria (flesh fly). To prevent their attacks, wet, filthy hair should be removed and wounds kept clean and rendered antiseptic by a lotion of carbolic acid 1 part, water 50 parts, or by a mixture of 1 ounce oil of tar in 20 ounces sweet oil, or by some other antiseptic. If the grubs are already present they should be picked off and one of these dressings freely applied.

Flies.

A number of flies attack horses and suck their blood, producing great annoyance and in some instances death. These insects not only suck the blood, but also often instill an acid poison into the skin, and in exceptional cases transfer infectious germs from animal to animal by inoculation.

Various devices are resorted to to prevent the attacks, as to sponge the skin with a decoction of walnut or elder leaves, of tobacco, to dust with Persian insect powder, to keep a light blanket or fly net on the horse, to close doors and windows with fine screens and destroy by pyrethrum any flies that have gained admission, to remove all manure heaps that would prove breeding places for flies, to keep the stalls clean, deodorize by gypsum, and to spread in them trays of dry chlorid of lime. For the poisoned bites apply ammonia, or a solution of 1 part of carbolic acid in 20 parts of sweet oil or glycerin, or one-fourth ounce bicarbonate of soda and 1 dram of carbolic acid in a quart of water may be used.

A large number of fly repellents have been recommended, but most of them must be applied daily in order to maintain the protective effect. Among the things used are carbolic solutions, pine tar, oil of tar, fish oil, laurel oil, oil of citronella, oil of sassafras, oil of camphor, and cod-liver oil. These things must be used judiciously or they will result in poisoning or removal of the hair from the animal in some instances. Ten per cent oil of tar in Beaumont oil or in cottonseed oil was found to be safe and efficacious by Graybill.

The use of the fly-maggot trap noted under stomach worms of the horse, and of the various forms of the Hodge flytrap, is recommended.

Fleas.

The flea of man and those of poultry, when numerous, will bite the horse and give rise to rounded swellings on the skin. To dispose of them it is needful to clear the surroundings of the grublike larvæ as well as to treat the victim. The soil may be sprinkled with quicklime, carbolic acid, coal tar, or petroleum; the stalls may be deluged with boiling water and afterwards painted with oil of turpentine and littered with fresh pine sawdust, and all blankets should be boiled. The skin may be sponged with a solution of 1 part carbolic acid in 50 parts of water. Other animals should be kept free from fleas or kept away from the vicinity of the stable.

The chigoe (Pulex penetrans) of the Gulf coast is still more injurious, because it burrows under the surface and deposits its eggs to be hatched out slowly with much irritation. The tumor formed by it should be laid-open and the parasite extracted. If it bursts so that its eggs escape into the wound, they may be destroyed by introducing chloroform into the wound.

Lice, or Pediculi.

Two kinds of lice attack the horse, one of which is furnished with narrow head and a proboscis for perforating the skin and sucking the blood, and the other—the broad-headed kind—with strong mandibles, by which it bites the skin only. The poor condition, itching, and loss of hair should lead to suspicion, and a close examination will detect the lice. They may be destroyed by rubbing the victim with sulphur ointment, or with sulphuret of potassium 4 ounces, water 1 gallon, or with tar water, or the skin may be sponged with benzine. The application should be repeated a week later to destroy all lice hatched from the nits in the interval. Buildings, clothes, etc., should be treated as for fleas.

Stings of Bees, Wasps, and Hornets.

These are much more irritating than the bites of flies, partly because the barbed sting is left in the wound and partly because of the quantity and quality of the venom. When a swarm attacks an animal the result may prove fatal.

Treatment consists in the application of wet clay, or of a lotion of soda or ammonia, or of carbolic acid, or permanganate of potash, 2 grains to the ounce; or of sugar of lead 2 drams, laudanum 1 ounce, and water 1 pint. The embedded stings should be extracted with fine forceps or even with the finger nails.

Tarantula and Scorpion.

The bite of the first and the sting of the second are poisonous, and may be treated like other insect venom, by carbolated glycerin, or a strong solution of ammonia, or permanganate of potash.

Snake Bites.

These are marked by the double incision caused by the two fangs, by the excessive doughy (dark red) swelling around the wounds, and in bad cases by the general symptoms of giddiness, weakness, and prostration. They are best treated by enormous doses of alcohol, whisky, or brandy, or by aqua ammonia very largely diluted in water, the object being to sustain life until the poison shall have spent its power. As local treatment, if the wound is in a limb, the latter may have a handkerchief or cord tied around it above the injury and drawn tight by a stick twisted into it. In this way absorption may be checked until the poison can be destroyed by the application, of a hot iron or a piece of nitrate of silver or other caustic. A poultice of tobacco leaves is a favorite remedy, and may be used to soothe the sore after cauterization.

A treatment which has been highly recommended consists in prompt and vigorous scarification at the site of puncture and rubbing crystals of potassium permanganate into the wound.

Burns and Scalds.

These subjects are discussed in the following chapter.

Wounds of the Skin.

Wounds of the skin are fully discussed in the next chapter.