The disease frequently extends to the nasal cavities, producing a thin, yellowish, or greenish-yellow, sticky discharge which adheres closely to the borders of the nostrils. Their edges also show caseous patches similar to those in the mouth. Sometimes the nasal passage is obstructed by great masses of the necrosed exudate, thus causing extreme difficulty in breathing. When the caseous process involves the larynx and trachea there result cough, wheezing, and dyspnea, together with a yellowish mucopurulent expectoration.
When life is prolonged three or four weeks, caseous foci may be established in the lung, giving rise to all the signs of a bronchopneumonia. Many of these cases are associated with a fibrinous pleurisy. The invasion of the gastrointestinal tract is announced by diarrheal symptoms. This disease principally attacks sucklings not more than 6 weeks of age, but calves 8 and 10 months old are frequently affected, and several cases in adult cattle have been reported to this office.
In its very acute form many of the cases run their course in from five to eight days. In these the local lesions are not strongly marked, and death seems due to acute intoxication. In other enzootics the majority of the affected animals live from three to five weeks. These are cases that occasionally present the pulmonary and intestinal symptoms, and sometimes develop also caseo-necrotic lesions in the liver.
Ordinarily cases show no tendency to spontaneous cure. Left to themselves they die. On the contrary, if taken in hand early, the disease is readily amenable to treatment. In the latter event the prospects of recovery are excellent.
Differential diagnosis.—Necrotic stomatitis may be differentiated from foot-and-mouth disease by the fact that in the latter there is a rapid infection of the entire herd, including the adult cattle, as well as the infection of hogs and sheep. The characteristic lesion of foot-and-mouth disease is the appearance of vesicles containing a serous fluid upon the mucous membrane of the mouth and upon the udder, teats, and feet of the affected animals. In necrotic stomatitis vesicles are never formed, necrosis occurring from the beginning and followed by the formation of yellowish, cheesy patches, principally found in the mouth. Mycotic stomatitis occurs in only a few animals of the herd, chiefly the adult cattle, and the lesions produced consist of an inflammation of the mouth and lips and of the skin between the toes, followed in a few days by small irregular ulcers in the mouth. This disease appears sporadically, usually in the early fall after a dry summer, does not run a regular course, and can not be inoculated.
Prevention.—Prophylaxis should be carried out along three lines:
(1) Separation of the sick from the healthy animals.
(2) Close scrutiny and thorough disinfection once or twice daily for five days of the mouths and nasal passages of those animals that have been exposed.
(3) Complete disinfection of all stalls and sheds.
The disease appears to break out in winter and hold over to spring. It is conceivable that exposure to cold might so disturb the normal circulation of the oral tissues as to make the mucous membrane an excellent location for the causative factor of the disease. There is another possibility, however, which bears on the third line of prophylaxis. The so-called diphtheritic inflammations of the vagina and uterus in cows are caused by the same organism that induces necrotic stomatitis. A European writer has recently pointed out the almost constant relation of such attacks to previous occurrences of foul foot or foot rot in the same or other cattle on the place.