First studies on the susceptibility of Omphiscola glabra (Gastropoda: Lymnaeidae) from central France to Fascioloides magna.

Experimental infections of Omphiscola glabra (preadult snails), originating from central France, to a Czech isolate of Fascioloides magna miracidia were carried out to determine if the local populations of O. glabra may ensure the larval development of this parasite and to compare these results with those noted for a natural snail host, Galba truncatula. The presence of experimentally infected snails was noted in the six populations of snails studied. However, only a few snails shed their cercariae (O. glabra 5.3 to 17.1%, G. truncatula 15.1% in the first population, and no shedding in the other). The shell heights of cercariae-shedding (CS) snails were significantly greater than those of other infected snails, for O. glabra as well as for G. truncatula. The number of metacercariae noted in each snail group was low and showed insignificant variations. When experimental infections of O. glabra were performed in relation to the shell height of snails (from 1 to 14 mm) at miracidial exposure, the prevalence of infected snails significantly decreased with increasing shell heights at exposure. However, the presence of CS snails was only noted from the 5-6 to the 9-10 mm groups, and the mean number of metacercariae per group ranged from 27 to 44.2. Despite the high infectivity of the Czech isolate of F. magna miracidia, there was an incomplete adaptation with the French G. truncatula and O. glabra used in this study, as the metacercarial production was low, and cercarial shedding only occurred for snails which showed a strong increase of their shell height during F. magna infections.