THERMAL CHALLENGE AS A SANITARY QUALIFICATION TEST OF Crassostrea gigas SPAT AND ON GROWING AREAS IN REGARD TO THE HERPESVIRUS OSHV-1 MVAR

摘要

Since 2008, mass mortalities of Crassostrea gigas juveniles associated with ostreid herpevirus OsHV-1 uVar (Segarra et al.,2010) have occurred along all coasts of France when seawater temperature exceeds 16° C (Pernet et al., 2012). Laboratory experiments have established a direct link between oyster mortalities and infection with OsHV-1 uVar (Schikorski et al.,2011) . OsHV-1 DNA can be detected and quantified by quantitative polymerase chain reaction (qPCR) above a threshold of 102 copies mg'1 of wet tissues (Pepin et al., 2008), but this threshold does not identify asymptomatic individuals. To improve detection of OsHV-1 in oyster spat, we propose a two-step approach to assess the sanitary status of spat, both hatchery-produced and wild-caught, and level of infection of the ecosystem. The first step applies a thermal challenge under controlled conditions toinduce replication of nascent OsHV-1 infections in spat. In a second step, naive spat are deployed in areas where mortalities related to OsHV-1 uVar have been suspected to occur. Thereafter spat are returned to the laboratory to undergo a thermal challenge, thereby determining the level of infection of the spat on-growing areas. The aim of this sanitary qualification method was to provide an objective and accurate test to qualify the status of spat and on-growing oyster areas that can be used as a management tool of OsHV-1 uVar sanitary risk.