The Prevention of Hog Diseases 477 



INFECTIOUS DISEASES 



Hog cholera is the commonest infectious disease occur- 

 ring in farm animals. Tuberculosis is less prevalent 

 among hogs than cattle. In dairy sections of the country, 

 where hogs are exposed to this disease by feeding after 

 tubercular cattle or drinking milk from tubercular herds, 

 a very large percentage become infected. 



Some of the more common infectious diseases, such as 

 infectious pneumonia, necroenteritis, and hemorrhagic 

 septicemia, are not very well understood. The latter 

 group of diseases may cause serious loss in feeding hogs 

 if the herd is not well cared for and the yards and houses 

 are insanitary. The rather common practice of disposing 

 of the apparently well hogs in a herd affected with infec- 

 tious pneumonia or necroenteritis by marketing them, 

 has resulted in stock cars and public stock-yards becoming 

 permanently infected with the germs of these diseases. 

 This condition is responsible for the prevalence of these 

 so-called "mixed infections" in sections of the country 

 where hogs are shipped from public stock-yards to the 

 country for feeding purposes. 



Hog cholera. (Fig. 20.) 



The specific cause of hog cholera is an ultra^microscopic 

 organism that is present in the body excretions and tissues 

 of cholera hogs. This virus cannot be cultivated in the 

 laboratory or seen with the microscope, and the name 

 ultra-microscopic virus is used in speaking of it. The 

 presence of this virus in filtrates of cholera blood, that 

 are free from any visible organism, can be proved by 

 inoculating susceptible hogs. Typical hog cholera is 

 produced, and hogs that are exposed to the sick animals 



