On the pathogenicity of attenuated Schistosoma mansoni cercariae released from metabolically disturbed Biomphalaria alexandrina

Biomphalaria alexandrina were treated with sublethal concentrations (LC10) of dry powdered leaves Solanum nigrum or whole dry Ambrosia maritima. The two plants affected the development of schistosome parasite within snails by disturbing the glycolytic flux, the most important metabolic pathway for schistosome-infected snails. Attenuated cercariae released from treated snails were used to infect male albino mice to evaluate their pathogenicity compared to control cercariae shed from untreated snails. The mean number of worms established declined from about 70 +/- 17.6 worms/mouse infected with control cercariae to 23.4 +/- 20.33 and 14.18 +/- 10.06 worms/mouse infected with S. nigrum and A. maritima-attenuated cercariae respectively. Most males and females detected in these animals measured 0.4-0.6 and 0.6-1.2 mm respectively compared to 1.2-1.4 and 1.4-1.7 mm in males and females released from mice infected with normal cercariae. Egg count in the liver and intestine of mice infected with attenuated cercariae was remarkably lower showing reduced fecundity of worms developed from attenuated cercariae. Number and size of granulomatous reactions showed remarkable reduction in attenuated cercariae-infected mice. Biochemical analyses for pathogenicity achieved with attenuated cercariae showed that while serum aspartate and alanine aminotransferases (AST &ALT) were more or less similar, depleted glycogen and elevated lipid peroxides were normalized when compared to those infected with normal cercariae.

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.