African Horse-Sic-kness. 285 



Infkrkh., 1009, \I, 1; B. t. W., 19(1<J, .SG3.— Sta.lie, B. t. W., 1909, 113.— Stede- 

 feder, D. t. W., 1909, 54(3. 



12. African Horse-Sickness. Pestis equorum. 



{Siidafrilianische Pferdesterhe, [German]; Peste du clieval, 

 [French]; Paardenziehfe, Perrezielxte, [Holland].) 



African horse-sickness is an acute or subacute, infectious 

 disease of solipeds, caused by an ultra visible virus. It exists 

 in an epizootic form in Africa, and is characterized by exten- 

 sive edematous swellings, and hemorrhages of the internal 

 organs. 



History. The disease, which has been lnio\Aai in South Africa 

 for over a century, has in recent times been confused either with 

 anthrax (Lambert, Sander), or with piroplasmosis (Rickmann, Eding- 

 ton). Both views were abandoned since McFadyean (1900), and later 

 Nocard (1901), proved that the virus passes through the porcelain 

 filter. The disease has been studied especially by Theiler, from its 

 etiological and clinical standpoints, while the (juestion of imuumiza- 

 tion has also been investigated by Edington, Koch and Rickmann. 



Occurrence. The disease occurs annually in South Africa 

 during the rainy, warmer months, January to March, especially 

 in low, moist localities. In years with great precipitation the 

 disease rages among horses and mules to such an extent that in 

 the affected localities 35% of the animals succumb, and some 

 of the localities are devastated to such a degree that not a sin- 

 gle horse remains alive unless some of the animals have pre- 

 vious] v withstood the disease in some other place (has been 

 "salted"). 



In the Cape Colony 64,850 horses and mules perished from horse-sickness in 

 1854 and 1855. Since that time the annual losses are estimated at 14,000 animals. 

 In German Southwest Africa the losses amounted in some years to 66%, in 

 Ehodesia to as much as 90% of the entire number of animals. 



According to Memmo and Brumpt the disease occurs also in Abyssinia, and 

 according to Friedrichsen in East Africa. 



Etiology. The causative factor of the disease belongs to 

 the ultra-microscopical micro-organisms, as the filtrate of the 

 blood diluted with physiological salt solution (Berkefeld or 

 Chamberland B and F filters) proves infectious. Blood taken 

 from affected horses in any stage of the disease, and injected 

 subcutaneously, intratracheally, intravenously or into the lungs 

 (0.01-1.0 cc, or only 0.0005 cc.) or administered per os (100-150.0 

 cc), produces the disease in the horse. The exudates and the 

 bronchial secretions also contain the virus, but the infectious- 

 ness of the excrement is considered to be doubtful. Blood from 

 recovered animals has no infectious action. 



Horses are highly susceptible to artificial infections, mules 

 and asses to a lesser extent. According to Edington it is also 

 possible to infect cattle fatally, and to produce febrile reactions 

 in goats and sheep. Theiler & Stockman found, however, that 



