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 were detected in the carpet-shell clam Ruditapes decussatus cultured in Galicia (NW Spain). The prevalences and intensities of the parasites found in the histopathological studies were not high enough to explain the high mortality rates. Unenveloped virus-like particles were detected by transmission electron microscopy in the cytoplasm of the connective tissue cells. They had an icosahedrical-spherical shape with a diameter of 27 to 35 nm. These virus-like particles appeared free in the cytoplasm or associated with endoplasmic reticulum membranes. These characteristics suggest that they belong to the Picornaviridae family.