In soft-sediment coastal waters of Europe, the common cockle Cerastoderma edule is an abundant organism, occuring from Marocco to Norway. This cockle provides space for a variety of parasitic organisms. Via bivalve filtration current, trematodes infect their intermediate hosts by free-swimming propagules (miracidia or cercariae larvae). Infection success and kinetics are closely related to host dynamics (especially growth rates) and to environmental parameters (especially temperature).Parasite species richness and environmental parameters have been surveyed since March 2005 in the same cockle cohort at each site. We investigated trematode infections of C. edule at Moulay Bousselham (Morocco), Aveiro (Portugal), Arcachon (France), Saint-Brieuc (France), Sylt (Germany) and Skallingen (Denmark). Comparisons of the different parasite infracommunities showed no general trend of diversity decline along the latitudinal gradient. A species rich community in the investigated cockles was discovered at all sites with Meiogymnophallus minutus occurring everywhere except in Denmark.With respect to the wide latitudinal distribution of C. edule, this parasite host system is an excellent model for studying the role of climatic factors in determining the diversity as well as distribution and abundance of parasites.