Variations in local adaptation of allopatric Fasciola hepatica to French Galba truncatula in relation to parasite origin.

Two French populations of Galba truncatula were subjected to experimental infections with Egyptian and French isolates of Fasciola sp. miracidia, originating from cattle and sheep, to compare characteristics of snail infections in allopatric and sympatric groups. All sampled Egyptian isolates were identified as Fasciola hepatica using microsatellite markers. Compared to snails infected with French miracidia, snail survival at day 30 post-exposure was significantly greater in the Egyptian groups, while prevalence of infection was significantly lower (in an Egyptian group infected with cattle-derived miracidia) or did not show any significant differences in the other three cases. The total number of metacercariae was significantly higher in the four Egyptian groups. However, snail population and the mammalian origin of F. hepatica had also a significant effect on this parameter. The dissection of snail cadavers showed a significantly higher number of free rediae in the Egyptian groups, even if snail population also had a significant effect on the redial burden. Both Egyptian isolates of F. hepatica could easily develop in French snails, causing a low mortality in snails and inducing a metacercarial production higher than that noted in sympatric infections. However, the mammalian origin of F. hepatica eggs and the quality of snail populations as intermediate hosts had to be taken into account for studying local adaptation in reason of their effects on this process.