Brown ring disease and parasites in clams (Ruditapes decussatus and R-philippinarum) from Spain and Portugal

Signs of brown ring disease (BRD) have been detected in Ruditapes decussatus and Ruditapes philippinarum cultured in Galicia (NW of Spain) and Aveiro (W of Portugal). Clams found on the surface had higher BRD prevalences than did burrowing ones. BRD signs were also detected in R. philippinarum imported from Gore (Italy) into a depuration plant located in the Ria de Vigo. Histopathological studies revealed the presence of several potential pathogens, the most prevalent being (maximum prevalences given) a chlamydia-like organism (86%), a haplosporidian (100%), and a Perkinsus-like organism (60%). Bacterial growth was also found in some of the histologically examined samples. A positive relation between the parasitic load and BRD signs was found.