FDA links vibriosis cases to Washington oyster area

Aug 14, 2007 (CIDRAP News) – The US Food and Drug Administration (FDA) recently warned consumers to avoid eating raw oysters harvested from the southern tip of Hood Canal in Washington state after receiving at least six reports of patients who contracted vibriosis.

The contaminated oysters were harvested from "growing area 6" in Hood Canal on or after Jul 3, the FDA said in an Aug 10 press release, adding that the six ill patients are from Washington and California.

States are investigating additional cases. Oysters from the affected area were distributed in California, Florida, Hawaii, Idaho, New York, Oregon, Washington, British Columbia, Hong Kong, Malaysia, and Singapore, the FDA said.

Vibriosis is a bacterial illness caused by Vibrio parahaemolyticus, which naturally occurs in seawater. The pathogen can reach high levels in summer. Symptoms include watery diarrhea, nausea, vomiting, and chills, which usually occur within 24 hours of eating contaminated oysters, the FDA said in an Aug 10 press release. Vibriosis usually resolves without treatment after about 3 days. Severe disease is rare but can occur in people who have weakened immune systems; the FDA says these people should avoid raw oysters regardless of their source.

The Washington Department of Health (WDH) said in an Aug 3 press release that it has closed two growing areas on the southern tip of Hood Canal and has asked the shellfish industry to recall oysters from these areas.

In a report last year, the WDH said it usually records about 20 vibriosis cases each season. In 2006 at least 60 cases were reported, marking one of the worst vibriosis outbreaks in the last decade.