Fasciola hepatica: An assessment of the vectorial capacity of Radix labiata and R. balthica commonly found in Belgium

A previous study in Belgium revealed that genetic material of Fasciola sp. was present in four local snail species: Galba truncatula, Radix peregra, Radix ovata and Lymnaea stagnalis. Laboratory cultures of these four species were experimentally infected with F. hepatica. The collected metacercariae were fed to rats and the infection in that vertebrate hosts was monitored through several techniques. The mortality rates in the breeding unit was less than 10 % in G. truncatula, R. peregra, and L. stagnalis colonies. Microscopy revealed the presence of larval stages in 78.3 % and 48 % of G. truncatula and R. peregra snails, respectively. These data were confirmed by a PCR that amplifies a parasite specific sequence. R. peregra shed fewer metacercariae and more irregularly than G. truncatula. In R. ovata and L. stagnalis the infection rates were low. Specific DNA was detected in both cases by PCR but no metacercariae were shed. The metacercariae shed by R. peregra were as infective to rats as those from G. truncatula. The PCR technique was more sensitive than microscopic examination. This study demonstrated that R. peregra may act as an accidental intermediate host for F. hepatica in Belgium.