Common Diseases of Farm Animals

by Robert Alexander Craig

CHAPTER XXVI

HOG-CHOLERA

HOG-CHOLERA is a highly infectious disease of swine. It is characterized by an inflammation, of the lymphatic glands, kidneys, intestines, lungs and skin. The inflammation is hemorrhagic in character, the inflamed organs usually showing deep red spots or blotches.

Hog-cholera is especially prevalent in the corn-raising States which possess a denser hog population than any other section of the United States. In this country the loss from hog-cholera in 1913 amounted to more than $60,000,000, and it may be considered of greater economic importance than any of the other animal diseases.

SPECIFIC CAUSE.—The specific cause of hog-cholera is an ultra-visible organism that is present in the excretions, secretions and tissues of a cholera hog. De Schweinitz and Dorset in 1903 produced typical hog-cholera by inoculating hogs with cholera-blood filtrates that were free from any organism that could be demonstrated by microscopical examination or any cultural method. The term ultra-visible virus is applied to the virus of hog-cholera.

The ultra-visible virus is eliminated from the body of the cholera hog with the body secretions and excretions. Healthy hogs contract the disease by eating feed or drinking water that is infected with the virus. There are other methods of infection, but field and experimental data show that hog-cholera is commonly produced by taking the germs into the body with food and drinking water.

ACCESSORY CAUSES.—The usual method of introducing hog-cholera into a neighborhood is through the importation of feeding or breeding hogs that were infected with the disease before they were purchased, or became infected through exposure to the disease in the public stock-yards and stock-cars. The shipping of feeding hogs from one section of the country to another, and from public stock-yards, has always been productive of hog-cholera. Dr. Dorset states that more than fifty-seven per cent of the hog-cholera outbreaks are caused by visiting, exchanging work, exposure on adjoining farms and harboring the infection from year to year (Fig. 79), and more than twenty-three per cent to purchasing hogs and shipping in infected cars, birds and contaminated streams.

[Illustration: FIG. 79.—A hog yard where the disease-producing germs may be carried over from year to year.]

In neighborhoods where outbreaks of hog-cholera occur necessary precautions against the spread of the disease are not taken. The exchange of help at threshing and shredding time in neighborhoods where there is an outbreak of hog-cholera is the most common method of spreading the disease. Visiting farms where hogs are dying of cholera; walking or driving a team and wagon through the cholera-infected yards; stock buyers, stock-food and cholera-remedy venders that visit the different farms in a neighborhood may distribute the hog-cholera virus through the infected filth that may adhere to the shoes, horses' feet and wagon wheels. Cholera hogs may carry the disease directly to a healthy herd when allowed to run at large. Streams that are polluted with the drainage from cholera-infected yards are common sources of disease.

Pigeons, dogs, cows and buzzards that travel about the neighborhood and feed in hog yards and on the carcasses of cholera hogs may distribute the disease. Because of the active part that dogs, birds and surface drainage take in the distribution of hog-cholera, the practice of allowing the carcasses of dead hogs to lie on the ground and decompose is responsible for a large percentage of the hog-cholera outbreaks.