Fasciola hepatica: the infection rate and the development of redial generations in Lymnaea truncatula exposed to miracidia after experimental desiccation and activation in water.

Adult Lymnaea truncatula were subjected to 10 days of experimental desiccation and then remained in water for 1 or 8 days before each was exposed to a single miracidium. The infection rate was lower in these snails than in infected controls that were not exposed to stress (52-54% vs 73%). The redial burden clearly decreased in stressed snails (18-25 rediae per snail) than in controls (43 rediae). This numerical decrease concerned essentially: i) live independent rediae of the first generation and the first cohort of the second generation, and ii) dependent rediae of subsequent generations. Mature rediae were more numerous in the first cohort of the second generation than in the other generations. Desiccation before exposure limited the size of the redial burden but placement in water for 8 days just after the stress attenuated the effects of this factor.