258 Hoy Cholera. 



History. The disease has l)een recognized in their studies of 

 American diseases of hogs by Sahnon & Smith (1885) as an independent 

 affection (hog cholera) as the cause of which they designated a short 

 motile rod. Based on these findings they sharply separated the disease 

 from swine septicemia (swine plague), considering this as identical with 

 swine plague of Germany, which was recognized just about that time. At 

 the same time they proved that the two diseases are frequently present 

 in one and the same animal, and that the severity of the American 

 outbreaks is brought on by such mixed infections. The same stand- 

 point was accepted in America by Moore and de Schweinitz, in Europe 

 by Raccuglia and Affanasieff. The frequent simultaneous occurrence 

 of the two forms of diseases, that is the frequency of the mixed infec- 

 tions, caused Billings in America, and Silberschmidt and Voges in 

 Europe, to take a stand against the identity of these two diseases and 

 their supposed causative agent (the common name of "pneumonoenterite 

 infectieuse" used in France and England corresponds with this con- 

 ception), while Bang, Schiitz, Jensen and Preisz (1898) confirmed the 

 correctness of the original stand of Salmon and Smith. 



Through the experimentaf investigations of the last decade the etiol- 

 ogy of the disease appears to have been definitely established. In 1904: 

 the American investigators de Schweinitz & Dorset made the discovery 

 that a disease occurring in the State of Iowa which clinically resembled 

 hog cholera was transmissible from affected animals to healthy hogs 

 by filtered bacteria-free blood. Soon afterward Dorset, Bolton and 

 McBryde proved that the disease was identical with hog cholera, and 

 therefore that this disease is also caused by a filtrable virus, whereas 

 the formerly supposed causative agent, the bacillus suipestifer, produces 

 the characteristic changes in the intestines only secondarily in the 

 already affected animal. Similar results were also obtained in Michigan 

 almost at the same time by Boxmeyer (1904), while Hutyra (1906), 

 then the Board's Laboratory of England, Ostertag (1907), as well 

 as Uhlenhuth, Xylander, Hiibener & Bohtz (1907), later Carre, 

 Leclainche & Vallee, also Wassermaun, confirmed the correctness of 

 the new conception of the disease in Europe and Theiler in South 

 Africa. At the same time the views concerning the part of the bacillus 

 suisepticus in the production of the secondary affection of the organs 

 were changed, whereby the disease formerly considered swine plague, 

 is now considered in most cases to be a complication of hog cholera. 



The accurate determination of its etiology directed the combating 

 of the disease into new lines, and the attempts at immunization by 

 Dorset, McBryde and Niles, as well as those by Uhlenhuth and his 

 co-workers, also those by Hutyra, have given valuable practical results. 



Occurrence. Hog cholera is at present very widely spread 

 in America, and in almost every European country, causing 

 annually great losses among hogs.' The disease, which in 

 itself is not very malignant, becomes very fatal as a result of 

 the frequent, secondary inflammatory processes in the in- 

 testines and in the lungs, which, especially in young animals, 

 exist in an epizootic form. It causes the greatest loss in places 

 where hogs are kept in large herds, whereas in localities with 

 smaller droves the disease is combated with better success. 



Hog cholera is supposed to have first appeared in North America 

 in the State of Ohio in 1833, and from there it spread over the entire 



