428 VETERINARY BACTERIOLOGY 



Bacteriological Diagnosis. This may occasionally be accom- 

 plished by a microscopic examination of the fluids from the lesions 

 and the identification of the characteristic trypanosome in stained 

 mounts. The organisms can rarely be found in the blood of the 

 general circulation. The blood-tinged fluid secured from the 

 plaques when they first appear is the most favorable material 

 for their identification. They may be found in the blood-stream 

 of artificially infected laboratory animals. 



Transmission. The disease is commonly transmitted from one 

 animal to another through coition. Whether or not the organism 

 can enter through the intact mucosa is not certainly known, but 

 appears probable. Blood containing the organism will infect 

 a rabbit if placed in the conjunctival sac. Sieber and Gonder 

 claim to have succeeded in transmitting the disease through the 

 medium of the fly Stomoxys caltitrans, but this certainly is not the 

 common method. No developmental stages could be observed 

 in the fly. 



Trypanosoma evansi 



Synonym. Spirochoeta evansi. 



Disease Produced. Surra in horses, cattle, carabou or water 

 buffalo, camels, dogs, goats, and sheep. 



The disease has been known for a long time from southern Asia. 

 The organism was first described from India by Evans in 1880. 



Distribution. The disease is known from India, China, the 

 Philippines, Africa, and Australia. 



Morphology. The organism as it occurs in the blood is actively 

 motile. It is usually between 20 and 30 [*> in length, and from 1 to 

 2 ^ in diameter. It tapers to the anterior end, but the posterior 

 is somewhat blunt. The undulating membrane and the free 

 flagellum are well differentiated. This organism can scarcely 

 be separated from Tr. brucei on the basis of morphology. 



Cultivation. This organism has been cultivated on Novy and 

 MacNeal's medium, but only after repeated trials. 



Pathogenesis. The disease may be readily transmitted to 

 susceptible animals by the injection of blood containing the 

 trypanosome. The disease itself is characterized in the horse as a 

 relapsing fever, with eruptions, either generalized or localized 

 in the skin. Petechial hemorrhages of the mucosae are frequent. 



