VARIANTS OF OYSTER HERPESVIRUS (OsHV-1) ASSOCIATED WITH MORTALITIES OF PACIFIC OYSTER Crassostrea gigas IN NORTHWEST OF MEXICO FROM 2002 TO 2015.  

Nowadays, the oyster pathogen herpesvirus (OsHV-1) that affects early stages and juveniles of the pacific oyster Crassostrea gigas, constitutes one of the most important diseases of cultured pacific oysters in several regions of the world. This virus has been regularly detected in Baja California, Baja California Sur, Sonora in Northwestern Mexico and has been associated with mortality episodes since 2002 (Figure 1). A genetic analysis of DNA samples extracted from gill tissue of C. gigas infected with herpesvirus from 3 states (3 from Baja California, 3 from Sonora and 1 from Baja California Sur) was carried out. Amplification of 2 fragments from region Gp, 3 fragments from region C and 1 fragment from region B of OsHV-1genome was achieved by the conventional PCR method. A high percentage of nucleotide sequence similarity was found between the sequences obtained in this study when compared to the reference OsHV-1 genome over common regions indicating that the amplified and sequenced DNA belongs to oyster herpesvirus type 1 species. It was also found that the C region has a high sequence similarity to the Acute Viral Necrosis Virus (AVNV) classified in the same family of OsHV-1 which is responsible for mortalities in the Chinese scallop Chlamys ferreri.

Region C showed additions of 1 to 8 adenines and 1 to 10 additional "CTA" repetitions in a microsatellite zone, both amplified by the primers C1-C6 and C15-C14, which suggests that the herpesvirus detected in Northwestern Mexico correspond to one or more varieties OsHV-1.