Laboratory and preliminary field studies were conducted to evaluate the role of the guppy (Lebistes reticulatus) as an active predator on Schistosoma mansoni cercariae.
When guppies were introduced into spring water containing about 1,000 cercariae per fish, a dramatic reduction in the number of cercariae was observed. In many experiments no cercariae could be found after 60 minutes. In one laboratory experiment, the infection rate and worm burden of mice exposed to cercariae shed by Biomphalaria glabrata in the presence of guppies was also greatly reduced.
Groups of mice were exposed to cercariae shed by infected B. glabrata, in nylon-screen cages partially immersed in natural pond water. The conditions of exposure were similar in all experiments, the only difference being the presence or absence of guppies in the cages. In three experiments the mean numbers of worms recovered from mice exposed in cages with infected B. glabrata in the presence of guppies were approximately 2, 4 and 9, whereas in the control cages, with the same number of infected B. glabrata, but without guppies, the mean numbers were 29, 48 and 126.
It was concluded that under special conditions the guppy may play an important role as a limiting factor in the infection of vertebrate hosts with S. mansoni.
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