Vibrio parahaemolyticus, is the leading cause of seafood-associated gastroenteritis in the United States.
Typically, it is associated with the consumption of raw oysters gathered from warm-water estuaries.
Dr Joseph McLaughlin described a recognized outbreak of V parahaemolyticus infection.
The outbreak was associated with the consumption of seafood from Alaska.
The team received reports of the occurrence of gastroenteritis on a cruise ship, and conducted a retrospective cohort study among passengers.
The researchers also undertook an active surveillance throughout Alaska to identify additional cases.
|Water temperatures at the oyster farm increased 0.2°C per year|
|New England Journal of Medicine|
The team then conducted an environmental study to identify sources of V parahaemolyticus and contributors to the outbreak.
Of 189 passengers, 132 were interviewed, and 22 of the interviewees met our case definition of gastroenteritis.
Using multiple logistic-regression analysis, the team found that consumption of raw oysters was the only significant predictor of illness.
The attack rate among people who consumed oysters was 29%.
The researchers noted that active surveillance identified a total of 62 patients with gastroenteritis.
The research team isolated V parahaemolyticus serotype O6:K18 from the majority of patients tested and from environmental samples of oysters.
Patterns on pulsed-field gel electrophoresis were highly related across clinical and oyster isolates.
All oysters associated with the outbreak were harvested when mean daily water temperatures exceeded 15°C.
The team reported that this temperature is the theorized threshold for the risk of V parahaemolyticus illness from the consumption of raw oysters.
Since 1997, mean water temperatures in July and August at the implicated oyster farm increased 0.2°C per year.
The team observed that 2004 was the only year during which mean daily temperatures in July and August at the shellfish farm did not drop below 15°C.
Dr McLaughlin's team concludes, “This investigation extends by 1000 km the northernmost documented source of oysters that caused illness due to V parahaemolyticus.”
“Rising temperatures of ocean water seem to have contributed to one of the largest known outbreaks of V parahaemolyticus in the United States.”