Biomphalaria glabrata: a new threat for schistosomiasis transmission in Egypt

This is the first report on the infestation of irrigation and drainage systems at Giza, Qalyoubiya and Kafr El Shiekh Governorates, with Biomphalaria glabrata (the snail host of Schistosoma mansoni in the new world). Identification of this snail species was based on morphometry of the shell, shape of the radular lateral teeth and presence of the characteristic renal ridge. B. glabrata snails collected from natural water courses in Egypt proved to be susceptible to a local strain of S. mansoni. These snails were infected by 52% versus 75% for Biomphalaria alexandrina (the only local host) under the same laboratory conditions. Meanwhile the periodic total cercarial production was higher in B. glabrata than in B. alexandrina (252 +/- 110 cercariae/snail versus 203 +/- 86 cercariae/snail, respectively). Differences in infection rate, length of schistosome incubation period, duration of cercarial shedding and cercarial production in various sizes of the two snail species are reported and discussed.