Schistosoma mansoni miracidial host-finding: species specificity of an Egyptian strain.

The effect of snail-conditioned water (SCW) from Biomphalaria alexandrina, a pigmented and an albino strain of B. glabrata, and Lymnaea stagnalis on the host-finding behavior of miracidia of two Brazilian and one Egyptian strain of Schistosoma mansoni was studied. Miracidia of the Egyptian strain significantly preferred their suitable host B. alexandrina versus the other snail species with their behavior patterns of host location and their responses after contact with the host. However, miracidia of both Brazilian strains did not differentiate between SCW from three of the snail species; only the pigmented B. glabrata elicited weaker responses. The releasing cues of SCW for miracidial host-finding phases are macromolecular glycoconjugates. An analysis of SCW by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), blotting, and subsequent carbohydrate detection showed that the band patterns of glycoconjugates differed significantly among the four snail strains. Therefore, differing chemical characteristics of the signaling glycoconjugates could be the basis for the observed host specificity in miracidial host-finding.