Under this name has been described a papular eruption occurring in horses, cattle, sheep and dogs in the hot season, but also occasionally, in winter, in hot, confined stables.
It is seen especially on the neck, back, croup and thighs, is common in fine bred horses with delicate skins, and nervous temperament, and is pre-eminently a disease of hot weather. Over-driving, heating food, a drink of cold water when heated or indigestion connected with unsuitable food may be the occasion of its irruption or tend to perpetuate it. In the same way different chronic affections of the stomach, liver, kidneys or other organs may be causative factors.
Symptoms. The affection usually begins with a few minute papules, isolated or in clusters, which dry up into scales or crusts. These are mostly situated at the roots of the mane or tail or on the sides of the neck, withers or trunk, and as a rule produce a pruritus, resembling that of scabies in its intensity. When the exudate agglutinates a tuft of hair, enclosing it in a dense crust, the hairs may be lifted from their follicles and thus small, round spots of depilation appear. If recovery ensues and new hair starts, it differs in color from the old and gives a dappled appearance to the skin. In many cases, however, the points of eruption and encrustation become confluent and an extensive area of bareness, with more or less abrasion, and even ulceration may be formed.
Megnin mentions two cases and the author can adduce another in which the eruption appeared in vertical lines, so that the skin of the trunk was raised in a series of elevated lines or ridges, running transversely to the body, like the stripes of a zebra. In the author’s case the skin seemed to be thrown into a series of folds to the production of which the cutaneous muscle evidently took part. The itching was doubtless the immediate cause.
Diagnosis is based largely on the suddenness of the eruption; on its limitation to a given area instead of spreading from the primary seat of invasion as in acariasis; on the fact that it is usually confined to a single animal and has not spread with the use of the same brush, comb and rubber; and on the absence of acari and vegetable parasites from the affected parts. The absence of chicken roosts or manure is another valuable indication.
Prognosis. Appearing in spring or early summer, the disease is liable to persist until the advent of cold weather in fall, and even after a winter’s intermission there is a strong tendency to its re-appearance on the following spring or summer. The intolerable itching interferes seriously with docility and steadiness in harness, and the loss of hair renders the subject very unsightly, and as a family or driving horse practically useless.
Treatment. As in cases of eczema the general and special causes should be corrected by hygienic and general medicinal measures, laxatives, diuretics, antacids, tonics, and in the advanced stages, alteratives coming in as important factors. (See under acute eczema). Great care should be taken to prevent irritation by pressure of the harness, and shade and daily cold spraying may be availed of.
PITYRIASIS: SQUAMOUS SKIN DISEASE: HORSE.
Dry, scaly, or powdery affection. Causes: Fine, thin, dry skin with little hair, race, Arab, Barb, racer, trotter, nervous temperament, age, dry summer heat, dry winter cold, foul skin, caustic soaps, ingestion of salt, iodides, bromides, etc., derangement of internal organs bacteria or cryptogams. Symptoms: scurfy patches, general or circumscribed, where little hair is, where harness rubs, depilation of ears, crest, tail, shoulder, back. Diagnosis, from eczema by lack of pruritus, of rapid extension, of thickening of the skin, from acariasis by absence of acarus. Treatment: correct disorder of stomach, liver, or kidneys: green, succulent or nutritive food; alkalies; arsenic; tonics; locally potash soaps, ointments of tar, birch oil, creolin, creosote, naphthalin, lysol, mercury, iodine, salicylic acid, zinc oxide.
This is a skin disease characterized by excessive production of epidermic scales, and depilation without any attendant elevation of the skin. The desquamation may be of fine scales like wheat bran, or of a fine dust like flour.