Molluscs interfering with the capacity of Fasciola hepatica miracidia to infect Lymnaea truncatula.

Fasciola hepatica miracidia labelled with radioselenium were used to study aspects of their host-finding capacity by determining radioactivity subsequently taken up by exposed 'target' snails (Lymnaea truncatula). Possible interfering effects exercised by a number of non-host snails and bivalves were examined in linear test channels. The infection rate (radioactivity) among 'target' snails was markedly lowered when non-host Lymnaea species (L. pereger, L. palustris, L. stagnalis) were interposed as 'decoys'. The prosobranch Bithynia tentaculata and the bivalve Sphaerium corneum exhibited a slight decoy effect whereas pulmonate species like Anisus vortex, Gyraulus albus, Planorbis planorbis, Physa fontinalis did not interfere with miracidial host-finding. Other experiments showed that miracidia are more strongly attracted towards L. truncatula than L. pereger. Miracidia are not able to penetrate intact egg clusters of L. truncatula.