20 HOG CHOLEEA 



ing percentage of cases to infect yards with hogs 

 sick of cholera so that susceptibles placed in them 

 subsequently will contract the disease. In spite 

 of these facts, though, we must in handling hog 

 cholera be guided by the practically universal 

 clinical experience which teaches that when hog 

 cholera once finds its way into a farm herd it will 

 eventually infect all individuals in it, irrespective 

 of the fact that the herd may consist of several 

 pens of hogs kept some distance apart. 



It is impossible, and indeed unnecessary, to dis- 

 cuss in detail the various influences which occa- 

 sionally are instrumental in carrying hog cholera 

 virus from herd to herd, and likewise it is impos- 

 sible to assign to each influence a relative import- 

 ance. It is much more important, in concluding 

 this chapter, to call attention again to the fact 

 that in the great majority of cases hog cholera 

 virus travels in certain quite definite channels, and 

 that new outbreaks are usually the direct or in- 

 direct result of shipping or moving infected hogs, 

 or else they originate from the practice of garbage 

 feeding, or that of using hog cholera virus indis- 

 criminately in seeking to immunize against the 

 disease. 



