Virus-like particles associated with mortalities of the carpet-shell clam Ruditapes decussatus

During the late summer and early fall of 1997 and 1998 heavy mortalities we re detected in the carpet-shell clam Ruditapes decussatus cultured in Galic ia (NW Spain). The prevalences and intensities of the parasites found in th e histopathological studies were not high enough to explain the high mortal ity rates. Unenveloped virus-like particles were detected by transmission e lectron microscopy in the cytoplasm of the connective tissue cells. They ha d an icosahedrical-spherical shape with a diameter of 27 to 35 nm. These vi rus-like particles appeared free in the cytoplasm or associated with endopl asmic reticulum membranes. These characteristics suggest that they belong t o the Picornaviridae family.