Highland populations of Lymnaea truncatula infected with Fasciola hepatica survive longer under experimental conditions than lowland ones

Abstract.

A retrospective study was carried out on the experimental infections of Lymnaea truncatula with Fasciola hepatica performed over the last 20 years to determine if the populations of snails living in highland or lowland countries had the same ability to sustain trematode larval development. The six highland populations originated from the Peruvian Altiplano (altitude 2,800 m), the French Alps (2,300 m), and the Massif Central (900–1,400 m), whereas the 13 lowland populations came from different sites located in central France (90–250 m). Bimiracidial infections of 4-mm-high snails were performed to study cercarial shedding and to quantify their redial burden. Compared to lowland populations, snail survival at day 30 post-exposure was significantly higher in the highland L. truncatula (57–75% compared to 31–45%) and their lifespan was greater (a mean of 87–96 days for cercaria-shedding snails compared to 64–77 days). The prevalences of F. hepatica infections, the numbers of free rediae within snail bodies, and the numbers of cercariae did not show any significant differences between highland and lowland snails although the numbers of cercariae were clearly higher in the Peruvian and three French highland populations of L. truncatula. The long survival times of highland snails under laboratory conditions might be an adaptation of these L. truncatula to the more extreme highland climate. The better ability of highland snails to sustain parasite larval development suggests that they would be better intermediate hosts in the life cycle of F. hepatica than lowland populations.