Temperature effect on susceptibility of four species of lymnaea snails to infection wit fasciola hepatica (Trematoda)

The possibility of temperature-dependent susceptibility of the snails Lymnaea trunca· tula, L. cubensis, L. tomentosa and L. columella to infection with the liver fluke Fasciola hepatica (Trematoda) was investigated by exposing individual snails to 5 or 10 miracidia of the fluke at different temperatures within the range of 12-32°C. Infection (or noninfection) of the exposed snails was subsequently gauged either by the presence of larval stages of the fluke within dying snails or release of cercariae by surviving snails. Generally the infection rate rose with increasing temperatures up to 24°C and diminished with further elevation of temperature: it was highest in L. truncatula between 16°C and 24°C, in L. columella at 20°C and in L. tomentosa and L. cubensis at 24°C. The data support the hypothesis that infection of Lymnaea snails by miracidia of Fasciola hepatica is temperature dependent and also suggest that temperature changes affect largely the miracidium and to a lesser extent the snail.