VIII, B, 3 Mitzmain: Transmission of Surra 229 



Table IV. — Inoculations with suspensions of flies fed on infected animals. 



Ex- 

 peri- 

 ment 



No. 



Animal inoculated. 



Flies 

 em- 

 ployed. 



Inter- 

 val 

 after 



feeding 

 of fly 

 on in- 

 fected 



animal. 



Presence of 



trypanosomes 



in the fly. 



Result. 



Guinea pig 86 .. 

 Guinea pig 89 _. 

 Guinea pig P--. 

 Guinea pig 131 . 

 Guinea pig 130 . 



Rabbit ._. 



Guinea pig 97 . 

 Guinea pig 98 . 

 Guinea pig R-- 



Hours. 

 6 

 10 

 124 

 26 

 30 

 30 

 48 

 48 

 96 



Positive -. 



do-.. 



do.-.. 



do.... 



do..-. 



do -.-. 



Negative. 



do .... 



do.... 



Positive. 



Do. 

 Negative. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



• The dejecta from this fly were found swarming with trypanosomes two and one-half 

 hours after the fly bit the sick animal. 



CONCLUSIONS 



1. Tabamis striatus Fabricus for the first time recorded has 

 been found to play a role in the transmission of surra. Bred 

 horseflies have been employed for the first time in such experi- 

 ments. Errors resulting from naturally infected wild flies have 

 thus been eliminated. 



2. Three experiments were successful in the direct or me- 

 chanical transmission by "interrupted" feeding when only a 

 short interval was allowed between the bites on infected and 

 healthy animals. In 16 experiments the minimum number of 

 flies with which the infection could be transmitted was 2. 



3. Trypanosomes of surra were not found to be transmitted 

 hereditarily in Tabanus striatus Fabricus. 



4. The contaminated labellum of the fly does not appear to 

 be a factor in the conveyance of infection. 



5. The maximum length of time that Trypanosoma evansi has 

 been demonstrated microscopically in the gut of this species of 

 fly after feeding on infected blood is thirty hours ; the organisms 

 were found in the fly's dejecta two and one-half hours after 

 biting the infected animal ; and suspensions of flies, when injected 

 subcutaneously, were found infective for animals for a period of 

 ten hours after the flies had fed on infected blood. 



