328 ACUTE GENERAL INFECTIOUS DISEASES 



with imported hogs or bacon from Europe. Following closely 

 in the wake of the development of transportation facilities, espe- 

 cially railways, it spread from the Middle West to all parts of 

 the country, especially toward the West, where the breeding 

 of swine had become a profitable industry. The losses from 

 cholera are enormous, reaching as high as $200,000,000 

 (45,000,000 hogs infected) in 1888 and averaging close to 

 $50,000,000 annually. The farmers of the corn-belt naturally 

 suffer the brunt of damage wrought by the disease. Like 

 most infectious diseases assuming an epizootic form the out- 

 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 wide-spread and especially malignant. As fan as 

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



Etiology. — The cause is an ultramicroscopic organism found 

 in the blood, urine, and sometimes in the feces of cholera-sick 

 hogs. The parts played by the Bacillus suipestifer and the 

 Bacterium suisepticum are probably incidental, the former in- 

 ducing principally the chronic gastro-intestinal and the latter 

 the lung and pleural lesions. 



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 via 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: 



1. By infected hogs: These may stray from neighboring 

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

 purchase, 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. 



2. 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 



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