Counting the dead to determine the source and transmission of the marine herpesvirus OsHV-1 in Crassostrea gigas

• Published in: Veterinary Research
• Main Authors: Whittington, Richard, Paul-Pont, Ika, Evans, Olivia, Hick, Paul, Dhand, Navneet
• Other Authors: The University of Sydney, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: DISEASE-INDUCED MORTALITY; FARMED PACIFIC OYSTERS; OSTREID HERPESVIRUS-1; MU-VAR; RISK-FACTORS; PATHOGEN TRANSMISSION; HUSBANDRY PRACTICES; WATER TEMPERATURE; RIVER ESTUARY; ACL; [SDV.SPEE]Life Sciences [q-bio]/Santé publique et épidémiologie; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; New Zealand; Pacific; Crassostrea gigas
• Online Access: https://hal.science/hal-02373679; https://hal.science/hal-02373679/document; https://hal.science/hal-02373679/file/Whittington_etal_VR_2018.pdf; https://doi.org/10.1186/s13567-018-0529-7

International audience Marine herpesviruses are responsible for epizootics in economically, ecologically and culturally significant taxa. The recent emergence of microvariants of Ostreid herpesvirus 1 (OsHV-1) in Pacific oysters Crassostrea gigas has resulted in socioeconomic losses in Europe, New Zealand and Australia however, there is no information on their origin or mode of transmission. These factors need to be understood because they influence the way the disease may be prevented and controlled. Mortality data obtained from experimental populations of C. gigas during natural epizootics of OsHV-1 disease in Australia were analysed qualitatively. In addition we compared actual mortality data with those from a Reed-Frost model of direct transmission and analysed incubation periods using Sartwell's method to test for the type of epizootic, point source or propagating. We concluded that outbreaks were initiated from an unknown environmental source which is unlikely to be farmed oysters in the same estuary. While direct oyster-to-oyster transmission may occur in larger oysters if they are in close proximity (< 40 cm), it did not explain the observed epizootics, point source exposure and indirect transmission being more common and important. A conceptual model is proposed for OsHV-1 index case source and transmission, leading to endemicity with recurrent seasonal outbreaks. The findings suggest that prevention and control of OsHV-1 in C. gigas will require multiple interventions. OsHV-1 in C. gigas, which is a sedentary animal once beyond the larval stage, is an informative model when considering marine host-herpesvirus relationships.