THE MOST COMMON DISEASES OF SWINE 539 



the return of hogs which have been shown at fairs is 

 chiefly due to the fact that such hogs are generally 

 transported by rail, unloaded in public stock yards, or 

 driven along public roads. It is well known that sick 

 liogs are frequently shipped by rail, and the roads over 

 which they are driven, the stock yards, and the railroad 

 cars thus become contaminated with the germs. The 

 only safe plan is to place new arrivals in lots entirely 

 separated from those occupied by the main herd, and to 

 keep them isolated until all danger of their developing 

 hog cholera has passed. 



"Aside from the danger of introducing infection 

 through the hogs themselves, the germ may be trans- 

 ported in a minute particle of dirt on the feet of attend- 

 ants or neighbors who have previously visited farms 

 where cholera exists. It may also be carried in this way 

 by dogs, and by crows and other birds. It has been 

 claimed that the disease may be carried downstream 

 from herds which are affected above. It is therefore 

 well to avoid placing hogs so that they will have access 

 to streams which pass through other farms. 



"After cholera has visited a farm, the lots, houses, 

 feeding troughs, and implements used for cleaning have 

 naturally become contaminated with the germs, and if 

 new stock is placed in such yards soon after these were 

 occupied by sick hogs, the new hogs are very likely to 

 contract the disease, but if such yards are left unoccu- 

 pied the germs will die out after a while. It is not 

 ])ossible to tell just how long a time is required for 

 these germs to die out. It is safest to wait as long as 

 p()ssi1)le before placing new hogs in lots tliat ha\e been 



