478 



Pork Production 



promptly develop this disease. Bacteria may invade the 

 tissues of the sick hog. These are usually termed second- 

 ary-invading bacteria, and they seem to have an impor- 

 tant part in producing hemorrhages in the tissues and 

 intestinal ulcers. Bacillius suipestifer and B. suisepticus 

 are the most common bacteria found in the tissues of 

 cholera hogs. 



Hog cholera is spread by the susceptible animal coming 

 in direct or indirect contact with the cholera hog. The 



FIG. 20. A hog having acute cholera. 



methods of indirect contact are as follows : dogs and 

 birds feeding on the carcasses of cholera hogs and carry- 

 ing parts of carcasses into neighboring yards ; feeding gar- 

 bage containing scraps of pork ; small streams receiving 

 filth or sewage from neighboring hog-yards; transport- 

 ing hogs in uncleaned stock-cars, and from public stock- 

 yards to the country ; improper methods of vaccination ; 

 and carrying filth on wheels of wagons and shoes of per- 

 sons from infected to non-infected yards. 



