DAO prepress abstract  -  DOI: https://doi.org/10.3354/dao03384

Fine-scale temporal dynamics of herpes virus and vibrios in seawater during a polymicrobial infection in the Pacific oyster Crassostrea gigas

Bruno Petton, Julien de Lorgeril, Guillaume Mitta, GaƩtan Daigle, Fabrice Pernet*, Marianne Alunno-Bruscia***

*Email: marianne.alunno.bruscia@ifremer.fr

ABSTRACT: The Pacific oyster Crassostrea gigas is currently being impacted by a polymicrobial disease that involves an early viral infection by the Ostreid herpesvirus (OsHV-1) followed by a secondary bacterial infection leading to death. A widely used method of infection consists of placing specific pathogen-free oysters (called “recipients”) in cohabitation in the laboratory with diseased oysters that were naturally infected in the field (called “donors”). With this method, we evaluated the temporal dynamics of pathogen release in the seawater and the cohabitation time necessary for disease transmission and expression. We showed that OsHV-1 and Vibrio spp. in the seawater peaked concomitantly during the first 48 h and decreased thereafter. We found that 1.5 h of cohabitation with donors was enough to transmit pathogens in recipients and to induce mortality later, reflecting the highly contagious nature of the disease. Finally, mortality of recipients was associated with increasing cohabitation time with donors up until reaching a plateau at 20%. This reflects the cumulative effect of exposure to pathogens. The optimal cohabitation time was 5 to 6 d, the mortality of recipients occurring 1 to 2 d earlier.