THE MECHANICAL TRANSMISSION OF SURRA BY TABANUS 

 STRIATUS FABRICUS^ 



By M. Bruin Mitzmain 



(From the Veterinary Division," Bureau of Agriculture, Manila, P. I.) 



The Tabanidse have hitherto not been investigated in connec- 

 tion with the transmission of surra in the Philippine Islands, 

 as Stomoxys calcitrans has been the only carrier generally 

 suspected. Recent work ^ has, however, practically eliminated 

 the latter fly from further consideration as an important factor 

 in surra dissemination. In no place has the transmission of any 

 trypanosome infections through the bite of tabanid flies been 

 proved with flies bred in the laboratory. 



The geographical and seasonal distribution of Tabanus striatus 

 have been recorded in the preceding article, and the status 

 thereof marks this species as preeminently the most formidable 

 bloodsucking fly in the Philippines. 



The investigation of which this is a preliminary note has 

 been conducted during the past year in the veterinary research 

 laboratory at Alabang, Rizal Province, Luzon, with tabanid flies, 

 which were for the most part bred from the egg; in some in- 

 stances the flies were obtained from larvee taken from their 

 aquatic habitats; and in a few instances captured adult flies 

 were employed. 



In the present series Tabanus striatus was used in experi- 

 ments on the direct transmission of surra. The flies were first 

 allowed to bite an infected guinea pig or horse for not more 

 than one minute, usually forty-five seconds; they were then 

 transferred to a healthy animal and allowed to complete the 

 meal without interruption. An interval of from five seconds 

 to three minutes intervened during the transfer from the in- 

 fected to the healthy animal. 



' To be published as Bulletin No. 28, Bureau of Agriculture of the Gov- 

 ernment of the Philippine Islands. 

 ' Archibald R. Ward, chief. 

 'This Journal, Sec. B (1912), 7, 475. 



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