CHAPTER XX. 

 HOG CHOLERA. 



Hog cholera exists principally in the corn belt of the 

 United States. Its prevalence is not uniform from year 

 to year and when the disease does appear it does not have 

 the same degree of virulence; that is, sometimes com- 

 paratively few of the hogs that have it will die, while at 

 other times nearly every individual in an entire herd will 

 be taken. When it once appears it spreads very rapidly, 

 not only among the individuals of a herd, but across the 

 country from farm to farm. Thus it is one of the prin- 

 cipal drawbacks to the pork-producing industry of the 

 United States. Many times when a breeder gets nicely 

 started and gets a bunch of hogs almost ready for market, 

 the disease may suddenly attack and destroy his entire 

 herd. This will give him a severe set-back from which it 

 is very hard to recover, and it is the cause for the fact 

 that not as many hogs are raised as would be if this dis- 

 ease were not so prevalent. 



CAUSE OF THE DISEASE. 



Hog cholera is primarily a germ disease. It was for- 

 merly supposed to be caused by a germ called Bacillus 

 cholera suis. Recent investigations, however, have shown 

 that this is not the case, but that the disease is caused by 

 some living organism which is so small that it can pass 

 through the finest kind of a porcelain filter and is so small 

 that it has never been detected with the most powerful 

 microscope. Furthermore, the bacillus of the virus has 



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