Fasciola hepatica: the infectivity of cattle-origin miracidia had increased over the past years in central France.

A retrospective study on experimental infections of Galba truncatula, originating from four populations, was carried out to determine the infectivity of Fasciola hepatica miracidia in snails either subjected to single-miracidium or bimiracidial exposures in 2006 and to compare it with results found before 1990 in other experiments using the same protocol. In single-miracidium infections, the prevalence of snail infection was significantly greater in 2006 than in experiments performed before 1980, while snail survival at day 30 postexposure showed insignificant differences. In bimiracidial infections, snail survival in two snail groups was significantly lower in 2006 than in experiments performed from 1981 to 1990, while insignificant differences were found for the other two populations of G. truncatula. Compared to results found between 1981 and 1990, the prevalence of snail infection did not significantly differ in 2006. In each population considered alone, the mean number of cercariae shed by infected snails did not significantly vary, whatever the date of experiment and the number of miracidia used for each exposure. The greater infectivity of F. hepatica miracidia towards snails might be the consequence of specific molecules such as triclabendazole used since 1990 to treat fasciolosis in cattle from central France.