Pseudechinoparyphium echinatum (Digenea: Echinostomatidae): experimental observations on cercarial specificity toward second intermediate hosts.

Infectivity of Pseudechinoparyphium echinatum cercariae to 11 species of gastropod was examined experimentally. Broad specificity and differential host-parasite compatibility were exhibited. Nine gastropod species functioned as second intermediate hosts. Planorbarius corneus, Physa fontinalis, Lymnaea peregra and Biomphalaria alexandrina showed high levels of compatibility with the parasite. In single-species exposures over 90% of cercariae encysted in each of these hosts. Low compatibility with the first intermediate host species Lymnaea stagnalis may be a mechanism preventing super-infection of emitting snails. Cercariae did not infect the prosobranchs Bithynia tentaculata and Viviparus viviparus. Experimental infection of a host community comprised of 8 European gastropod species revealed an order of host utilization similar to that shown in single-species exposures. However, cercarial transmission success in P. fontinalis and L. peregra (compared to that in P. corneus) was significantly reduced. This may have been due to the marked preference of cercariae for P. corneus compared to the other two highly suitable hosts for whom cercariae showed equal preference.