[The influence of Echinostoma caproni metacercariae (Trematoda) on the survival of biomphalaria molluscs (Pulmonata)].

The infrapopulation of the Echinostoma caproni partenites has a development of prolong character (Ataev et al, 2005). However, in laboratory conditions, Biomphalaria molluscs infested with this parasite die within 1--3 weeks after the beginning of cercariae emission. It has been suggested that autoinvasion of the mollusc host with the cercariae, which use it as second intermediate host, is the cause of this phenomenon. Studying the dynamics of metacercariae accumulation in the host (both infected and non-infected with the Echinostoma caproni rediae) and experiments where quantity of cercariae around molluscs reduced by different ways, confirmed this hypothesis. Evidently, pathogenicity of metacercariae for molluscs is lesser in nature, because the concentration of cercariae reduces to the values, which do not result in lethal effect: some part of cercariae dies, but another part uses other animals as a host (Haas, 2000).