Common Diseases of Farm Animals

by Robert Alexander Craig

[Illustration: FIG. 109.—Cleaning up and disinfecting premises where an outbreak of foot-and-mouth disease has occurred.]

The specific cause is a pin-shaped germ, the Bacillus tetani (Fig. 110), that is present in the soil, especially those that are rich and well manured. The germ enters the body by way of a wound, especially punctured wounds. Infection may take place through some wound in the mucous membrane lining the mouth, or other parts of the digestive tract. Infection may follow a surgical operation, such as castration. In any case, the germ requires an absence of air (oxygen) for its development.

The period of incubation varies from one to two weeks, the length of time depending on the nearness of the wound to a large nerve trunk or brain.

[Illustration: FIG. 110.—Bacillus tetani.]

The first symptom observed is a stiffness of the muscles, especially those nearest the point of inoculation or wound. The muscles of the head, neck, back and loins are often affected first, and when pressed upon with the fingers feel hard and rigid. The disease rapidly extends, producing spasms of other muscles of the body. In breathing, the ribs show less movement than normal, the head is held in one position and higher than usual, the ears are stiff or pricked, the nostrils dilated, the lips rigid or drawn back and the eyes retracted, causing the "third eyelid" to protrude over a portion of the eye (Fig. 111). In most cases the muscles of mastication and swallowing are affected. The animal may be unable to open its mouth and swallows with difficulty. When standing, the limbs are spread out so as to increase the base of support, and in acute cases about to terminate fatally, the pulse is quick and small and the respiration shallow, rapid and labored. The animal sweats profusely, falls down and struggles violently, but remains conscious to the end.

[Illustration: FIG. 111.—Head of horse affected with tetanus, showing "third eyelid" protruding over the eye.]

In the subacute form (Fig. 112) the symptoms are mild, and the animal may be able to move about, eat and drink without very great effort.

[Illustration: FIG. 112.—A subacute case of tetanus.]

Treatment is largely preventive. All wounds should be carefully disinfected. This is especially advisable in punctured wounds of the foot. In communities, or on premises where tetanus is a common disease, animals that have punctured or open wounds should be given a protective dose of tetanus antitoxin.

The curative treatment is largely good care. If a wound is present, it should be thoroughly disinfected. The animal may be supported by placing it in a sling. A comfortable box-stall, where the animal is not annoyed by noises or worried by other animals, is to be preferred. A fresh pail of water should be given the animal several times daily.