Schistosoma mansoni: effects of zinc on cercarial and schistosomule viability.

The effects of ZnCl2 on the viability and morphology of cercariae and schistosomules of Schistosoma mansoni were examined. The longevity of cercariae was inversely proportional to the zinc concentration from 0.05 to 5 micronM. Zinc caused body-tail separation and crenation of bodies but not of tails of cercariae, as well as alteration of the staining of cercariae in the indirect immunofluorescence test. Zinc was also effective in reducing penetration of cercariae into mice in a brief (10 min) exposure period. Although the effects on schistosomule morphology were not as conspicuous as with cercariae, 5mM ZnCl2 also affected this stage of the parasite.