334 AGRICULTURAL BACTERIOLOGY 



to weaken the animal makes it more likely to acquire hog 

 cholera in case the organisms are taken into the body. It 

 is generally believed that the feeding of new corn produces 

 the disease. The feeding of large quantities of new corn 

 may produce digestive troubles and make the animal more 

 susceptible to cholera, but it can not cause hog cholera. 



If cholera makes its appearance in the herd, all the 

 healthy animals should be removed at once to another field. 

 One can not rely on the appearance of the animals to tell 

 whether they are infected or not. A much more reliable 

 way is to take the temperature of each animal, and to re- 

 tain all showing any fever in the yard with the diseased 

 animals. The normal temperature of grown animals 

 ranges from 101 to 103 F. In young animals the tem- 

 perature will run somewhat higher, but in separating the 

 herd all animals having a temperature of more than 103.5 

 should be considered as infected. 



The carcasses of hogs that have died should be burned 

 if possible. If this can not be done, they should be buried 

 deeply. All infected litter should be burned. The care- 

 less disposal of carcasses is one of the chief ways of spread- 

 ing and perpetuating the disease. 



The hogs should be pastured in fields that do not border 

 on the road and that are not traversed by streams, since 

 infection may be introduced in either of these ways. 



The most effective way of protecting the herd against 

 the disease is to apply the preventive treatment described 

 later. Many cures for hog cholera have been proposed 

 and are widely advertised. It is certain, however, that no 

 treatment other than the administering of the protective 

 serum is of any value. 



Protective treatment. A hog that has recovered from 

 a natural attack acquires an immunity to the disease, due 

 to the presence in the blood of protective substances that 



