14 



farmers' bulletin 834. 



MODES OF INFECTION WITH HOG CHOLERA. 



Hog cholera does not occur in a herd except through the intro- 

 duction of the specific germ of that disease. So far as known, 

 the germs of hog cholera develop and propagate only in the bodies 

 of hogs. There is no more certain way of introducing hog cholera 

 than by placing in the herd a hog already infected with the disease. 

 The sick hog, then, must be regarded as the most dangerous agent 

 in the spread of cholera. Hogs affected with cholera discharge the 

 germs of the disease from their bodies in the urine, the feces, and the 

 secretions of the nose and eyes. Therefore the manure, bedding, 

 litter of all sorts, and the dirt itself in pens where sick hogs are kept 

 contain the germs of the disease. These germs may enter the hog's 

 system by means of food or drink and probably also through wounds 

 or abrasion of the skin. 



The extensive shipment of hogs to market by rail has resulted in 

 the germs of cholera being deposited in public stockyards, in 

 unloading chutes and pens, and in the railroad cars used for hauling 

 hogs. Consequently if healthy hogs are shipped in ordinary stock 

 cars, or if they are unloaded in public stockyards or through public 

 chutes they are likely to become infected with cholera. Similarly, 

 it is believed that any agency which will serve to carry litter, manure, 

 or material of any sort from public stockyards or cars to farms may 

 result in an outbreak of cholera on the farm. Such infected material 

 may adhere to the feet of horses or other stock, to wagon wheels, or 

 to the shoes of men who have entered these public places. 



What is true of public stockyards and stock cars is true to an 

 even greater extent of farms where cholera exists, and it may be 

 expected that the disease will be carried from an infected farm to 

 healthy herds if care is not taken to prevent the carrying of the 

 germs on the feet of men or animals, on wagon wheels, or perhaps 

 even by dogs roaming from one farm to another. Streams passing 

 through infected farms may wash the germs down to other farms 

 perhaps miles away. If the carcasses of dead animals have not been 

 disposed of promptly, dogs may carry portions to neighboring farms. 

 It is generally believed that buzzards and crows may carry the germs 

 of cholera to clean farms. At certain seasons it is common for 

 farmers to exchange labor and farm implements when thrashing, 

 shelling corn, filling silos, and delivering grain or stock to market. 

 Unless proper precautions are taken it can be seen that these prac- 

 tices may serve to disseminate cholera. It has been said that cholera 

 has been traced in some instances to the visits of stock buyers and 

 vendors of stock remedies who go from farm to farm and from hog 

 lot to hog lot. If hogs on a clean farm are not kept in lots properly 

 fenced they may range to contaminated streams or to adjoining 



