New insight in the Lymnaeids intermediate host of Fasciola hepatica in Belgium

The present work was carried out in the frame of a Belgian Science Policy project (PONDSCAPE -“Towards a sustainable management of pond diversity at the landscape level”). During the summer 2008, 7103 lymnaeids snails were collected from 125 ponds distributed in 5 clusters of 25 ponds each. Each cluster was located in a different geological region of Belgium. These snails belonged to the following species or genus: 2474 Galba truncatula (the main intermediate host of Fasciola hepatica in Belgium) and 4629 Radix sp. Moreover, several biological (presence of trampling and dungs, snail size …) and non biological factors (pH, depth, fences …) were also registered from the different biotopes. DNA was extracted based on Chelex® technique. Then the snail DNAs were screened through a multiplex PCR that amplifies the lymnaeid internal transcribed spacer 2 sequence (500-600 bp) (acting as an internal control) and a 124 bp Fasciola sp. sequence. Lymnaeid snails were found in 93 biotopes (66%). Thirty Galba truncatula (1.31%) and 7 Radix sp. (0.16%) were found positive for Fasciola sp. A classification and regression tree (CART) analysis was performed in an attempt to better understand the relative importance and relationships among the different recorded factors. For example, the geographic localization is one of the best explanatory variables for the abundance of the different snail species and the presence/absence of faecal material is the best explanatory variable for the presence of specific F. hepatica DNA material in the different screened snails.