INFECTIOUS DISEASES 



301 



zation is that a more lasting and permanent immunity is produced. 

 The general opinion has prevailed that young pigs could not be per- 

 manently immunized even by the simultaneous method, but accord- 

 ing to a recent report of a series of experiments conducted by or 

 under the supervision of the Bureau of Animal Industry, pigs from 

 one to three weeks of age were permanently immunized against chol- 

 era by the simultaneous method. This experiment simplifies the im- 

 munization of swine against cholera and should be practiced in swine- 

 raising districts as the dosage required for pigs is relatively small 

 and the expense to the owner would be materially less than for the 

 immunization of larger swine. 



A so-called double method has been advocated by some for the 

 prevention of cholera. It consists of the serum-alone immunization, 



Fig. 84. CHOLEKA IMMUNE HOGS. Thcise hogs were used at the Chicago 

 stockyards, and were driven from pen to pen to clean up the food left by 

 cattle and other hogs. They were, of course, constantly exposed to virulent 

 infection. 



followed ten days later by the simultaneous method. This so-called 

 double method should not be used because tlie virus used in the simul- 

 taneous method is apparentlj- rendered inactive or at least a perma- 

 nent immunity is not produced. 



Hog cholera can be controlled by the rational application of anti- 

 hog cholera serum combined with the proper enforcement of sanitary 

 regulations. 



Swine Plague (Hemorrhagic Septicemia) 



Swine plague, also designated hemorrhagic septicemia, is a spe- 

 cific infectious disease of swine caused by the Bacillus snisepticus. 



