Oviposition of Lymnaea truncatula infected by Fasciola hepatica under experimental conditions

Experimental infections of Lymnaea truncatula by Fasciola hepatica (one, tw o, or three miracidia per snail) were carried out under laboratory conditio ns to analyze the oviposition of infected snails and determine the characte ristics of their egg masses. In the infected snails from the three groups, egg-laying steadily decreased until week 4 postexposure and stopped afterwa rd until the end of the experiment, except for the cercaria-shedding snails from the one-miracidium group, for which low numbers of egg masses were no ted between weeks 9 and 12. In uninfected snails the number of egg masses d ecreased until week 4 and remained low during subsequent weeks. At weeks 11 and 12 postexposure the natality rate was 98.9% in controls, 56% in the ce rcaria-shedding snails from the one-miracidium group, and 59.2-68.5% in uni nfected snails. In the cercaria-shedding snails from the one-miracidium gro up the restoration of reproduction activity after week 8 may be explained b y a lower parasite burden in these snails than in those from the two- and t hree-miracidium groups.