Cattle are very susceptible to the disease, and in its virulent type all those exposed are said to become infected. Buffaloes, sheep, and goats are likewise susceptible, but in a less degree.
It is also claimed that animals after having passed through one attack successfully resist future attacks. Inoculation with virus is said to produce immunity, but in many cases the process of inoculation itself is followed by death.
Symptoms.—The symptoms of rinderpest are not very characteristic, and hence the diagnosis of a suspected case in the beginning of an invasion is attended with difficulties. Certain appearances which are characteristic of one epizootic may be absent in another. Different observers are not quite agreed as to the most constant and important.
The period of incubation, i. e., the time between the exposure to infection and the earliest outward symptoms, varies from three to nine days. The first sign is a very high fever, which may reach 107° F. The heat of the skin varies in different parts of the body, and may be felt at the base of the ears and horns. Repeated chills are frequently observed. The pulse reaches 50 to 60 beats a minute, and in very severe attacks may rise to 90 or 100.
The animal manifests great debility. The head droops and rests on some object of support. One or both ears may droop. The coat is staring and the muzzle dry. The secretion of milk diminishes very rapidly. Within twelve to twenty hours the usual quantity may have become reduced one-half or two-thirds. The back is arched, and the four limbs are brought together under the body.
As the disease progresses, symptoms with reference to the digestive and respiratory organs become prominent. The mucous membrane of the mouth and the nose, as well as that of the rectum and vagina, becomes reddened, either in patches or diffusely, and assumes a scarlet hue. The discharges, at first firm, become softer, and soon diarrhea sets in. This is said to be one of the most constant symptoms. The rectum may become everted and paralyzed, and the bowels move spontaneously. The discharges become fetid, viscid, and streaked with blood. Coughing is a common symptom, and by some is considered characteristic. It is associated with discharges from the nose and vagina and dribbling of saliva from the mouth. The eyes also are affected. There is an increased formation of a viscid secretion which flows down the face.
Another series of changes prominent in some epizootics and mild or absent in others are the ulcers, or so-called "erosions," in the mouth. These begin as red patches and streaks. The mucous membrane in such localities is converted into a grayish-white slough, which, when shed, leaves a small erosion, or ulcer. At the same time similar changes may go on in the skin of the thighs, the udder, or the scrotum, or about the vagina, which lead to small sloughs.
In severe cases, which are the most common in the susceptible cattle of western Europe, death ensues four to seven days after the first appearance of the disease, and is preceded by great emaciation and debility, fetid, purulent discharges from the nose and mouth, and the relaxed rectum and vagina.
After death, if the animal is opened and the organs carefully examined, the chief changes are found in the digestive organs. The lining membrane of the mouth and pharynx is covered with mucus, is reddened in spots, and shows superficial, yellowish-gray, cheesy patches, which represent dead tissue, and when removed expose ulcerated depressions. The same reddening in spots and the yellowish-gray, cheesy deposits or patches are found in the fourth stomach, the small intestines, and more rarely in the cecum, while the third stomach, or manyplies, is more or less impacted with dry, hard feed. Similar changes may be found on the mucous membrane of the nasal cavity, larynx, trachea, the uterus, vagina, and rectum. The lungs may be injected, edematous, or pneumonic. The heart muscle is pale and flabby, and frequently hemorrhages are observed in its internal membrane. The liver may be pale or injected with blood, and at times shows hemorrhages beneath its capsule. The bile is thin and watery in consistence. The kidneys may be inflamed or contain small hemorrhages within their substance or under the capsule. The lymphatic glands may be swollen and injected or even hemorrhagic.
Treatment.—On account of the danger of spreading the infection, neither medicinal treatment nor inoculation is permitted in European countries, with the exception of Russia, where the disease is more generally diffused. The most effective method of exterminating rinderpest in those districts in which the disease is not indigenous has been found to be the slaughter of all affected and exposed animals. Where the disease is general, successful efforts adopted for its control have followed the immunization by inoculation of the exposed animals and a strict application of appropriate sanitary measures. This protective inoculation has been practiced with very gratifying results in Russia, South Africa, and in the Philippine Islands. An active immunity is thus induced in susceptible animals which lasts until the danger from exposure to the disease is over. This immunity may be attained (1) by the inoculation of pure bile from an animal which recently died of rinderpest, (2) by the inoculation of glycerinated bile, followed by pure bile or virulent blood, or (3) by the simultaneous inoculation of strong standardized serum and virulent blood.