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pressure. When the anterior aspect of the cardia was severed, the 

 stomodeal valve usually everted, and the parasites spewed into the 

 dissecting medium, still attached by their flagella. It should be 

 noted that the short-slender, highly active forms were not attached 

 and thus were able to escape the "blockage." 



Many workers have noted that infected sand flies have difficulty 

 in engorging, but this does not prevent transmission (Ki 1 1 ick-Kendrick 

 eta]., 1977). Ki 11 ick-Kendrick et _al_. (1977) suggested that the 

 feeding behavior of infected flies may be upset by parasites 

 interfering with the activity of internal sensilla monitoring 

 engorgement. The infected fly would have difficulty engorging and 

 would probe many times, thus increasing the chances of the parasites 

 in the proboscis being deposited in the skin. 



The actual process by which the short-slender, highly active 

 promastigotes travel from the stomodeal valve to mononuclear 

 phagocytes in the skin to the mammal is not known. Bray (1981) 

 suggested that sugars in the crop (esophageal diverticulum) are fed 

 into the alimentary canal at the level of the esophagus and exert a 

 chemotactic influence on the promastigotes, thus attracting the 

 promastigotes to the level of the esophagus. This may explain the 

 higher transmission rates with L donovani in sand flies fed on 

 raisins, reported by Smith et aj_. (1940). Bray (1981) suggested that 

 sand flies used for transmission studies should be fed 10% or 20% 

 raffinose. Adler and Theodor (1931) maintained that the tendency of 

 flagellates to pass upwards is a real tropism, accounting at least in 

 part, for their migration into the cardia and eventually beyond. 



