First report of OsHV-1 microvar in Pacific oyster (Crassostrea gigas) cultured in Spain

Increased mortality events in Pacific oysters (Crassostrea gigas) have been detected, since 2008, in their farming areas along the entire French coastline. With regard to the etiological agent of these events, there is a strong correlation with the presence of a variant of Ostreid herpesvirus-1 (OsHV-1), designated OsHV-1 microvar (μvar). During the last ten years, mortalities of Pacific oyster have also affected the shellfish culture regions in Catalonia, and its etiology has been studied in the region since 2000. This research lead to OSHV-1 being detected for the first time by nested PCR in samples collected in 2005 (Elandaloussi et al., 2009). Due to the suspicion of OsHV-1 μvar being responsible for very high mortalities in France since 2008, and since the oyster seed in Catalonia is almost 100% of French origin, different batches of samples from 2005, 2008, 2009 and 2010 were recently analyzed for the presence of OsHV-1 and OsHV-1 μvar.The present study reports the findings from 2005, 2008, 2009 and 2010 for analyses of C. gigas, as they correspond to the first detection of OsHV-1 μvar in Spain.

► Report from 2005, 2008, 2009 and 2010 on detection of OsHV-1 μvar in Spain.
► The present study reports the first detection of OsHV-1 μvar in Spain.
► Samples from 2005 indicated different strains were infecting oysters.