XIV] SURRA 237 



T. minimus — they had four successes, three when there was no 

 interval between the two feeds, and one after a five-minute 

 interval. Ten experiments were performed and in each case 

 only one or two flies were used. Five experiments with 

 Stomoxys and two with Hcematopota under similar conditions 

 gave negative results. A number of Tabanidae were then fed on 

 infected animals and, at varying intervals, emulsions of the 

 body contents of the flies inoculated into susceptible animals. 

 It was found that the trypanosomes in the alimentary canal 

 of Tabanus remained infective for 24 hours, but after longer 

 periods lost their virulence. 



Leese studied the natural transmission of Surra at Mohaud, 

 India, and made experiments with mosquitoes, Stomoxys, 

 Tabanus, Hcematopota and sand-flies. Four Tabanus, which were 

 fed on camels, in two of which trypanosomes were numerous, 

 and transferred immediately to a white rat, produced infection 

 in the latter, and under similar conditions ten Hamatopofa 

 produced infection in a guinea-pig. Of three similar experi- 

 ments, employing Stomoxys, only one gave positive results, so 

 it seems that Tabanus is able to transmit Surra better than 

 Stomoxys. On the other hand, Leese is strongly of the opinion 

 that Tabanus and Hcematopota are not specific transmitters, for 

 outbreaks of the disease have occurred under circumstances that 

 precluded the possibility of their being the carriers. Neverthe- 

 less, in the Punjab the worst " Surra zones " seem to be in 

 places where Tabanus is most numerous. Baldrey has also 

 performed some experiments on the transmission of Surra by 

 various Tabanids and found that the trypanosomes remained 

 virulent in the gut for not longer than 24 hours. An attempt 

 was made to test the possibihty of a cyclical mode of trans- 

 mission, but all the Tabanids died by the end of the nineteenth 

 day. Up to this date the inoculation of their body contents 

 into susceptible animals gave negative results. 



In America, Mohler and Thompson noted an outbreak of 

 Surra following the importation of zebus from India. This 

 herd consisted of 51 cattle that had been imported from Poona, 

 where their blood was examined twice with negative results. 

 On arrival in New York they appeared to be in good condition, 



