Symptoms.—The chief characteristic of this disease is the swellings which may appear on any part of the body, except the tail or below the knee or hock. The thigh and shoulder are most commonly attacked. The swellings rapidly increase in number and may run together. They give a crackling sensation on pressure and are cool and without tenderness in the center. If opened in the center there is no pain and a frothy fluid comes out.
There are also general symptoms as follows: the animal does not eat or chew the cud, loss of strength and general depression, high fever, lameness, stiffness and often dragging of one leg on account of the swellings. These symptoms increase as the disease progresses, the breathing becomes faster, the animal groans and may have attacks of colic. The animal almost always dies in from one and one-half to three days.
Treatment.—The disease is incurable, and diseased animals should be killed at once, the bodies burned and the premises disinfected as given under Abortion, page [122]. The healthy animals should be moved to another pasture and the infected pasture burned off the following winter, this destroys the germs in that pasture.
Cattle may be rendered immune to Black Leg by vaccination. The vaccine with directions for its use is given away to stock owners by the Chief of the Bureau of Animal Industry, U. S. Department of Agriculture, Washington, D. C.
Foot and Mouth Disease—Eczema Epizootica
Definition.—An acute, contagious fever, characterized by the formation of vesicles and ulcers, chiefly about the mouth and hoofs, etc. The eruptions appear on the mucous membrane of the mouth, on the fetlock, and in the cleft of the hoofs, and not unfrequently as a eruption on the udder. The disorder chiefly prevails among cattle and sheep, but under favoring circumstances, also attacks other domestic quadrupeds, and even man.
Causes.—It appears as an epidemic, and spreads exclusively by contagion. The precise nature of the germ is unknown, but it is chiefly limited to the contents of the vesicles, the secretion of the ulcers, the saliva, the blood and the natural secretions and excretions, of the diseased animal; and these convey the disease. The predisposing causes are exposure to cold, wet, currents of cold air, poor fodder, want of cleanliness and good housing; and anything that tends to lower the constitutional vitality. The activity of the virus is preserved for many months. The poison may be conveyed by the clothes of herdsmen and other persons, by manure, tools, fodder, by grass and ground previously trodden by diseased animals, and milk to sucking calves, indeed by almost anything. It finds its way into the system in various ways, not depending on any wound for admission. The communication to man is by drinking the milk of diseased cows. A second attack is rare.
Symptoms.—After a period of incubation, lasting from three to six days, the animal is seized with a shivering fit, and appears dull and stupified. A vesicular eruption soon appears on the mouth, the hoofs, and the teats. Sucking calves have a similar eruption on the fauces and pharynx, with irritation of the whole alimentary canal, attended with inability to suck, and exhausting diarrhea. The eyes are then observed to be dim, watery, congested; the muzzle, ears and horns alternately hot and cold; shivering ensues; rumination is diminished; the milk is less in quantity, yellower and thicker than usual, and much deteriorated in quality; the bag swollen, tender, hot; the back arched; the coat staring and harsh; the pulse somewhat accelerated; the temperature moderately elevated, reaching 102°, or even 104°; the eruption in the month is first seen on the inner surface of the upper lip, the edge of the upper jaw where there are no teeth, on the tip and edges of the tongue, and is indicated by salivation, by pain and loss of power in taking and eating food. The vesicles occur on the mucous membrane, singly or in patches, first as little red spots, then as whitish-yellow, slightly turbid blisters, about the size of a bean, at first transparent, but subsequently filled with a puriform fluid. These vesicles burst in about eighteen hours, discharge their fluid, leaving behind shallow ulcers, which often run together and then form deep and ragged ulcers. The lips, cheeks, tongue, and sometimes the Schneiderian membrane, are affected. The eruption on the feet is first seen around the coronet and in the interdigital space, especially of the hind legs; and the resulting vesicles burst quickly, because of the animal’s movements. The animal evidently suffers intense pain, is lame or unable to stand, and moves reluctantly or cautiously; the hoofs swell; the vascular secreting membranes become inflamed; the hoofs are cast; the bones may become diseased; and serious mischief may ensue. The eruption on the udder turns to vesicles, as in the mouth, and, when the fluid dries or escapes, thin scales are formed. The teats are swollen and sore. In exceptional cases, a vesicular eruption appears on the muzzle, the mucous membrane of the nostrils, the conjunctivae of the eyes, and the mucous membrane of the vagina.
In favorable cases, the fever subsides about the fourth day, the eruption declines, the appetite returns, and in seven to fourteen days the animal recovers. But complications are not uncommon. And in unfavorable cases the fever is high, the ulceration increases, the animal suffers from exhaustion, wasting, discharge of stringy, bloody mucous from the mouth, and of offensive matter from the nostrils; the face is swollen, the breath foul, the respiration rapid and grunting; the pulse small, weak, rapid; the blood becomes impure; the belly and legs œdematous; the hoofs slough off; diarrhea supervenes, and death follows about the ninth or tenth day. An aggravation may occur in milch cows by the bursting of the vesicles when the teat is grasped in milking, for the fluid escapes, the sore bleeds and ulcer spreads; and though the sore be scabbed over between the milking times, the scab is then again pulled off. The consequence is that the cow, feeling intense pain and irritation, kicks, resents the milking, holds back the milk, and thus prevents the “stripping” of the udder. The effect of this may be an attack of inflammation of the udder, which may prove fatal, or may be followed by induration and atrophy of the udder. Or abscesses may form in the udder, and sometimes large portions of it slough away, rendering the cow comparatively useless for milking purposes. Abortion is not uncommon.
This disease may be easily mistaken for Stomatitis, cow pox or fowl of the foot. However in Stomatitis there is no eruption on the foot; and in cow pox and fowl of the foot there is no eruption on the muzzle.