Susceptibility of a number of bivalve species to the protozoan parasite Bonamia ostreae and their ability to act as vectors for this parasite

The protozoan parasite Bonamia ostreae (Pichot et al., 1980) is a serious p athogen of the native European flat oyster Ostrea edulis. Field and laborat ory based experiments were carried out in Ireland and Spain to investigate the susceptibility to this protozoan of the Pacific oyster Crassostrea giga s, the mussels Mytilus edulis and Mytilus galloprovincialis, the European n ative clam Ruditapes decussatus and the Manila clam Ruditapes philippinarum . Their ability to act as vectors or intermediate hosts was also investigat ed. The study corroborated previous findings that demonstrated that flat oy sters can be successfully infected both naturally in the field and experime ntally in the laboratory, and the pathogen can be transmitted directly betw een flat oysters in the laboratory. However, the other bivalves tested coul d not be infected with the parasite either naturally or experimentally, and these bivalves did not appear to act as vectors or intermediate hosts for the parasite. These results have implications for movements of bivalves bet ween areas within the European Union.