Confirmation of Galba truncatula as an intermediate host snail for Calicophoron daubneyi in Great Britain, with evidence of alternative snail species hosting Fasciola hepatica

Background: Fasciola hepatica is a highly prevalent parasite infecting livestock in Great Britain, while Calicophoron daubneyi is an emerging parasite within the GB livestock industry. Both F. hepatica and C. daubneyi require an intermediate host snail to complete their life-cycles and infect ruminants; however, there has been no confirmation of the intermediate host of C. daubneyi in GB, while there are questions regarding alternative host snails to Galba truncatula for F. hepatica. In this study, PCR was used to identify C. daubneyi hosting snail species on Welsh pastures and to identify any alternative snail species hosting F. hepatica. Findings: Two hundred and sixty four snails were collected between May-September 2015 from six farms in mid-Wales known to have livestock infected with C. daubneyi and F. hepatica. Fifteen out of 134 G. truncatula were found positive for C. daubneyi, one of which was also positive for F. hepatica. Three snail species were found positive for F. hepatica [18/134 G. truncatula, 13/52 Radix balthica, and 3/78 Potamopyrgus antipodarum (New Zealand mud snail)], but no evidence of C. daubneyi infection in the latter two species was found. Conclusion: This study indicates that G. truncatula is a host for C. daubneyi in GB. Galba truncatula is also an established host of F. hepatica, and interactions between both species at intermediate host level could potentially occur. Radix balthica and P. antipodarum were found positive for F. hepatica but not C. daubneyi. This could indicate a role for alternative snail species other than G. truncatula in infecting pastures with F. hepatica in GB.