Herpes-like virus associated with eroded gills of the Pacific oyster Crassostrea gigas in Mexico

Since 1997, high mortality episodes of cultured oysters have occurred in Bahia Falsa, Mexico. Studies on the possible association of these mortalities with pathogens have showed some similar characteristics to those found in the Portuguese oyster Crassostrea angulata and the Japanese oyster Crassostrea gigas infected by an iridoviridae-like particles in the lately 1960s. This infection was named gill necroses virus infection (GNV). In a recent study, we could not find any virus using transmission electron microscopy (TEM) in adult oysters with clinical and histologic signs similar to those described for GNV. However, new TEM images showed the presence of viral particles in eroded gills of oysters. Morphologic characteristics, such as thin-walled icosahedric shape, the presence of capsids in an extension of the nucleus or in a vacuole and size varying from 80 to 90 out suggest that the viruses belong to the Herpes viridae family. This virus could be involved in the mortality episodes in the Bay and it is different to those described as causal agent of GNV.