In situ characterisation of pathogen dynamics during a Pacific Oyster Mortality Syndrome episode

Marion Richard (1) , Jean Luc Rolland (2) , Yannick Gueguen (2) , Julien de Lorgeril (2) , Juliette Pouzadoux (2) , Behzad Mostajir (3) , Beatrice Bec (3) , Sébastien Mas (4) , David Parin (4) , Patrik Le Gall (1) , Serge Mortreux (1) , Annie Fiandrino (1) , Franck Lagarde (1) , Grégory Messiaen (1) , Martine Fortune (1) , Emmanuelle Roque d’Orbcastel (1)

1 LSEA MARBEC - Laboratoire Service d' Experimentations Aquacoles [Palavas les Flots]
2 IHPE - Interactions Hôtes-Pathogènes-Environnements
3 UMR MARBEC - MARine Biodiversity Exploitation and Conservation
4 OSU OREME - Observatoire de REcherche Méditerranéen de l'Environnement

Significant mortality of Crassostrea gigas juveniles is observed systematically every year worldwide. Pacific Oyster Mortality Syndrome (POMS) is caused by Ostreid Herpesvirus 1 (OsHV-1) infection leading to immune suppression, followed by bacteraemia caused by a consortium of opportunistic bacteria. Using an in-situ approach and pelagic chambers, our aim in this study was to identify pathogen dynamics in oyster flesh and in the water column during the course of a mortality episode in the Mediterranean Thau lagoon (France). OsHV-1 concentrations in oyster flesh increased before the first clinical symptoms of the disease appeared, reached maximum concentrations during the moribund phase and the mortality peak. The structure of the bacterial community associated with oyster flesh changed in favour of bacterial genera previously associated with oyster mortality including Vibrio, Arcobacter, Psychrobium, and Psychrilyobacter. During the oyster mortality episode, releases of OsHV-1 and opportunistic bacteria were observed, in succession, in the water surrounding the oyster lanterns. These releases may favour the spread of disease within oyster farms and potentially impact other marine species, thereby reducing marine biodiversity in shellfish farming areas

Mots clés: Crassostrea gigas; Aquaculture; Disease; Ostreid herpesvirus 1; Microbiota Bacteria; Thau lagoon

Domaines: Médecine vétérinaire et santé animale; Zootechnie; Bactériologie

Marion Richard, Jean Luc Rolland, Yannick Gueguen, Julien de Lorgeril, Juliette Pouzadoux, et al.. In situ characterisation of pathogen dynamics during a Pacific Oyster Mortality Syndrome episode. Marine Environmental Research, 2021, 165, pp.105251. ⟨10.1016/j.marenvres.2020.105251⟩. ⟨hal-03128530⟩