SURRA." 



By Ch. Wardell Stiles, Ph. D., 



Co)isiiltiug Zoologist, Bnrcau of Animal Indiistrii; Zoologist, United tStates 

 Public Health and Marine-Hospital i^crrice. 



Surra is not known to occur in the United States, but it is more or 

 less common in the Philippine Islands and India. It is caused by a 

 microscopic, flagellate animal parasite, known as Trypanosoma 

 Evansi^ 20 to 30 yu long by 1 to 2 yw broad, which lives in the blood and 

 destroys the red-blood corpuscles. In general, the disease is very 

 similar to, and belongs in the same general class with, tsetse-fly dis- 

 ease, or nagana, of Africa and mal cle caderas of South America. 



CLIMATIC CONDITIONS. 



Surra is a wet-weather disease, occurring chiefly during or imme- 

 diately after heavy rainfalls, floods, or inundations. 



ANIMALS AFFECTED. 



Surra attacks esj^ecially horses, asses, and mules, but it may occur 

 in kerabau, camels, elephants, cats, and dogs, and has been trans- 

 mitted to cattle, buffaloes, sheep, goats, rabbits, guinea pigs, rats, and 

 monkeys. No birds, reptiles, amphibia (frogs, etc.), or fish are 

 known to suffer from it. It attacks both male and female animals, 

 young and old. Australian breeds of horses and Avhite and gray 

 mules are said to be more susceptible than animals of other breeds 

 and color. 



LETHALITY DURATION. 



Surra in equines and camels is said to be an invariabl}^ fatal dis- 

 ease, but cattle occasionally recover from it. There is no history of a 

 definite onset of the disease, and the condition is progressive, usually 

 with a number of relapses. The period of incubation may vary some- 

 what ; in experimental cases it is from two to seventy-five (usually 

 six to eight) days, according to conditions. The duration varies with 

 the species of animals attacked, their age, and general condition. The 

 average duration in the horse is reported as less than two months, 

 though some cases nuiy terminate fatally in less than one to two 

 weeks. 



a For a more detailed discussion of this disease see Salmon & Stiles, 1902, 

 Emergency report on surra <P>ul. 42, Bureau Animal Industry, U. S. Dept. 

 Agric, Wash., pp. 1-152, figs. 1-112. Reprinted in Eighteenth Annual Report 

 (for 1901), Bureau of Animal Industry, pp. 41-182, figs. 1-112. 



548 



