INFECTIOUS DISEASES 



275 



sociated infection with the filtrable virus, the disease resulting being 

 a mixed infection of hog cholera and swine plague. 



Spiroehseta suis has been investigated by King and Hoffman. 

 Their experiments indicate that this micro-organism is of constant 

 occurrence in swine affected with hog cholera and further that they 

 could be demonstrated in intestinal lesions in swine in which pure 

 cultures had been xised to induce disease. 



From the foregoing it will be noted that there has been some con- 

 tention as to the specific cause of hog cholera. 



Fig. 71. Mucous membrane of the intestine. A, normal; B, showing 



effect of chronic inflammation due to hog cholera; C, typical 



hog cholera ulcers. 



Predisposing causes. — The various microbial! agents aforemen- 

 tioned are important factors in predisposing swine to the .filtrable 

 virus. Many cases have been observed, particularly in stocker swine 

 that have been immunized against hog cholera in public markets, 

 of so-called "serum, breaks" in which the symptoms and autopsy 

 findings indicated that hog cholera was a factor in causing the death 

 of what were thought to be cholera immune swine. These accidents 



