Outbreaks of Vibrio parahaemolyticus gastroenteritis from raw oyster consumption: Assessing the risk of consumption and genetic methods for detection of pathogenic strains

During the summers of 1997 and 1998, large outbreaks of V. parahaemolyticus gastroenteritis occurred from the consumption of raw oysters in the US. The West Coast outbreak was the first to have occurred in this country from the consumption of raw molluscan shellfish; over 200 culture-confirmed cases were identified. Over 400 cases were confirmed from oysters harvested from Galveston Bay in Texas and 20 cases were confirmed in New York and Connecticut from oysters originating from Long Island Sound. Distinct serogroups of the pathogen were responsible for illnesses on the West Coast in contrast to those on the East and Gulf Coasts. Monitoring of shellfish samples by State and federal authorities found low levels of V. parahaemolyticus in all implicated growing areas, suggesting strains of low infectious dose. FDA has completed a risk assessment study for consumption of raw molluscan shellfish as part of the Food Safety Initiative. Newly developed genetic techniques were employed for the first time to determine levels of V. parahaemolyticus in shellfish and detect the pathogenic strains of the species