Low molecular weight hydrophilic chemicals that attract Echinostoma trivolvis and E. caproni cercariae

A Petri dish bioassay was used to study chemoattraction of the cercariae of Echinostoma trivolvis and E. caproni in the presence of various bench chemicals prepared as 5 mM solutions in agar. The design compared the attraction of cercariae migrating toward the plugs impregnated with chemicals compared to unimpregnated plugs (controls). Cercariae of both species were significantly attracted to an array of amino acids and to some carbohydrates. Cercariae of E. trivolvis but not E. caproni were attracted to the peptide glutathione. Cercariae of E. trivolvis and E. caproni were repelled from valeric and butyric acids, respectively. Cercariae of E. caproni but not E. trivolvis were repelled from dextrose. Although broad specificity exists for echinostome cercarial penetration in snail intermediate hosts, results of these studies suggest that there are specific differences in cercarial chemoattractants between E. trivolvis and E. caproni.