358 ACUTE GENERAL INFECTIOUS DISEASES 



breaks come in waves. While some years swine are compara- 

 tively free from the infection, or it assumes a mild form, in 

 ■ others it is widespread and especially mahgnant. As far as 

 is known, hogs are the only animals which take the disease. 



Etiology. — The cause is an ultramicroscopic organism 

 occurring in the blood, urine, and sometimes in the feces of 

 cholera-sick hogs. The parts played by the Bacillus suipesti- 

 fer and the Bacterium suisepticum are probably incidental, 

 the former inducing principally the chronic gastro-intestinal 

 and the latter the lung and pleural lesions. (See Swine 

 Plague.) 



Natural Infection. — As the organism of cholera is found in 

 the urine and feces, the pens, yards, etc., in which sick hogs 

 have been kept, become contaminated with it. Healthy but 

 susceptible swine become infected largely «ia the digestive tract 

 through food and water polluted with the secretions and 

 excretions of the diseased. Hog-cholera is introduced into a 

 non-infected farm as follows: 



(a) By infected hogs: These may stray from neighboring 

 infected herds, be borrowed (breeding boars), brought in by 

 pvuchase, or show-swine returned from fairs, expositions, etc., 

 may bring the infection home. Hogs introduced during the 

 incubative stage of the disease. Such swine may seem 

 healthy at the time of purchase, but a few days later the 

 symptoms appear. Hogs suffering from cholera in a chronic 

 form ("germ carriers"), especially old breeding boars and 

 sows, showing no typical symptoms. 



(b) The infection may also be brought into the premises by 

 such intermediary agents as stray dogs, crows, fowls. Per- 

 sons can also carry it on their boots and clothing. Once the 

 disease breaks out it is spread, as noted, by the urine, feces, 

 and other discharges of the sick, aiid by careless disposition 

 of the dead (throwing carcasses into waterways or leaving 

 them on the fields; too shallow burial, incomplete cremation, 

 etc.) . Hauling the carcasses in wagons through the premises 

 and along the roadways is a further factor in the spread of the 

 disease. It is a common practice when hog-cholera is dis- 

 covered to exist on a farm for the owner to attempt getting 

 rid of the disease by selling those hogs which are in a market- 



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