Predator-prey interaction is a key factor determining transmission intensity of trophically transmitted parasite. However, few studies document the relationship between prey availability, prey consumption by predators, and its consequence on transmission. We investigated how the variation of density of two small mammal E. multilocularis intermediate hosts (IH) in the field, on a local scale (n x 10km2), impact fox diet and subsequently parasite transmission intensity in foxes? Ten study sites were sampled in Franche-Comté (France) in winter from 1995 to 1999. IH population densities were estimated using index methods. Fox faeces were collected in the field to estimate (i) the occurrence of IH in the diet, and (ii) the infection status of the fox population (coproantigen detection). Mixed-effects models were used to account for site pseudo-replication. Results suggest no correlation between M. arvalis density in the field and its occurrence in the diet, and a significant positive correlation between A. terrestris density and its occurrence in the diet. The median infection level measured in faeces, as well as the high infection values were significantly correlated to the biomass of A. terrestris only. This study suggests an opportunistic behavior of foxes towards A. terrestris, and a preference (or a better accessibility to) for M. arvalis. Here, A. terrestris, the bigger IH species, seemed to play a dominant role in transmission.