Chronic or accidental exposure of oysters to Norovirus: is there any difference in contamination?

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Ventrone, Iole | Schaeffer, Julien | Ollivier, Joanna | Parnaudeau, Sylvain | Pepe, Tiziana | Le Pendu, Jacques | Le Guyader, Soizick

Edité par CCSD ; International Association for Food Protection -

International audience. Bivalve molluscan shellfish such as oysters may be contaminated by human pathogens. Currently, the primary pathogens associated with shellfish-related outbreaks are noroviruses. This study was conducted to improve understanding of oyster bioaccumulation when oysters were exposed to daily contamination or one accidental contamination event, i.e., different modes of contamination. Oysters were contaminated with two representative strains of norovirus (GI.1 and GII.3) and then analyzed with real-time reverse transcription PCR. Exposure to a repeated virus dose for 9 days (mimicking a growing area subjected to frequent sewage contamination) led to an additive accumulation that was not significantly different from that obtained when the same total dose of virus was added all at once (as may happen after accidental sewage discharge). Similarly, bioaccumulation tests performed with mixed strains revealed additive accumulation of both viruses. Depuration may not be efficient for eliminating viruses; therefore, to prevent contaminated shellfish from being put onto the market, continuous sanitary monitoring must be considered. All climatic events or sewage failures occurring in production areas must be recorded, because repeated lowdose exposure or abrupt events may lead to similar levels of accumulation. This study contributes to an understanding ofnorovirus accumulation in oysters and provides suggestions for risk management strategies.

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