FIELD OBSERVATIONS CONCERNING INFECTION OF LYMNAEA-PALUSTRIS BY FASCIOLA-HEPATICA

Fasciola hepatica miracidia were experimentally introduced into five s ites colonized by Lymnaea palustris over a period of 4 or 6 years. In the first four ponds, a progressive increase in the prevalence of the spring-generation juvenile snails was observed (from 0.4 to 18.1%), wi th a corresponding increase in the shell height of infected snails (fr om 3.6 to 7.8 mm). In the fifth habitat, the pond dried in 1990 causin g the prevalence to drop as compared with the initial values and to su bsequently increase in 1991-1992.