Crassostrea gigas mortality in France: the usual suspect, a herpes virus, may not be the killer in this polymicrobial opportunistic disease

Type Article
Date 2015-07
Language English
Author(s) Petton Bruno1, Bruto Maxime2, 3, James Adele2, 3, Labreuche Yannick2, 3, Alunno-Bruscia MarianneORCID1, Le Roux Frederique2, 3
Affiliation(s) 1 : IFREMER, LEMAR, UMR6539, Argenton En Landunvez, France.
2 : IFREMER, Unite Physiol Fonct Organismes Marins, Plouzane, France.
3 : Univ Paris 06, Univ Paris 04, CNRS,Stn Biol Roscoff,UMR 8227, LBI2M,Equipe Genom Vibrios,Integrat Biol Marine M, F-29688 Roscoff, France.
Source Frontiers In Microbiology (1664-302X) (Frontiers Research Foundation), 2015-07 , Vol. 6 , P. -
DOI 10.3389/fmicb.2015.00686
WOS© Times Cited 42
Keyword(s) pacific oysters, summer mortality, herpes virus, vibrio pathogenicity, experimental infection
Abstract Successive disease outbreaks in oyster (Crassostrea gigas) beds in France have resulted in dramatic losses in production, and subsequent decline in the oyster-farming industry. Deaths of juvenile oysters have been associated with the presence of a herpes virus (OsHV-1 µvar) and bacterial populations of the genus Vibrio. Although the pathogenicity of OsHV-1 µvar, as well as several strains of Vibrio has been demonstrated by experimental infections, our understanding of the complexity of infections occurring in the natural environment remains limited. In the present study, we use specific-pathogen-free (SPF) oysters infected in an estuarine environment to study the diversity and dynamics of cultured microbial populations during disease expression. We observe that rapid Vibrio colonization followed by viral replication precedes oyster death. No correlation was found between the vibrio concentration and viral load in co-infected animals. We show that the quantity of viral DNA is a predictor of mortality, however, in the absence of bacteria, a high load of herpes virus is not sufficient to induce the full expression of the disease. In addition, we demonstrate that juvenile mortalities can occur in the absence of herpes virus, indicating that the herpes virus appears neither essential nor sufficient to cause juvenile deaths; whereas bacteria are necessary for the disease. Finally, we demonstrate that oysters are a reservoir of putative pathogens, and that the geographic origin, age, and cultivation method of oysters influence disease expression.
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Petton Bruno, Bruto Maxime, James Adele, Labreuche Yannick, Alunno-Bruscia Marianne, Le Roux Frederique (2015). Crassostrea gigas mortality in France: the usual suspect, a herpes virus, may not be the killer in this polymicrobial opportunistic disease. Frontiers In Microbiology, 6, -. Publisher's official version : https://doi.org/10.3389/fmicb.2015.00686 , Open Access version : https://archimer.ifremer.fr/doc/00271/38220/