Influence of low temperatures on the survival of the Pacific oyster (Crassostrea gigas) infected with Ostreid herpesvirus type 1

• Published in: Aquaculture
• Main Authors: Pernet, Fabrice, Tamayo, David, Petton, Bruno
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier Science Bv 2015
• Subjects: Bivalve; Disease; OsHV-1; Oyster; Temperature; Virus; Pacific; Crassostrea gigas; Pacific oyster
• Online Access: https://archimer.ifremer.fr/doc/00259/37047/35555.pdf; https://doi.org/10.1016/j.aquaculture.2015.04.010; https://archimer.ifremer.fr/doc/00259/37047/

Mortalities of oyster seed of Crassostrea gigas associated with ostreid herpes virus OsHV-1 μVar have been observed in many oyster producing countries since 2008. The objective of this study was to further investigate whether low temperature treatments can offer a viable option to mitigate oyster mortalities. An experiment was set-up to further evaluate the effect of low temperature treatments (10 and 13°C vs. 21°C) and their duration (6 d to 83 d) on the survival of oysters previously infected with OsHV-1 μVar by means of exposure to field conditions in areas where mortalities were occurring. Average survival of oysters infected with OsHV-1μVar was 71% after 83 d at low temperatures compared to only 23% in controls maintained at 21°C. During cold-exposure, levels of OsHV-1 DNA in oyster tissues gradually decreased, down to nearly the detection limit after 24 d. However, when cold-acclimated oysters were suddenly exposed at 21°C in the laboratory, they exhibited high levels of mortality along with an enhancement of OsHV-1 DNA concentration in their tissues. Therefore, OsHV-1 persists in oysters even at low temperature and is reactivated during subsequent thermal elevation to 21°C. Low temperature treatments did not improve overall survival of oyster seed infected with OsHV-1. These results suggest that moving infected oysters to a cooler area only delays mortality and may increase the risk of infection in neighbouring stocks when rising temperatures become permissive for viral replication.