Drakes Bay Oyster Company halted sales and harvesting of oysters from Drakes Estero in Marin County a month ago, following a state warning that its products may have been tainted by a naturally occurring bacterium.

The California Department of Public Health warned consumers on Aug. 10 not to eat the company's oysters due to possible contamination by Vibrio parahaemolyticus, a bacterium that can cause serious illness.

Three illnesses in California had been linked to products from the Marin County oyster farm, the department said at the time.

Consumers who had purchased any of the company's oysters harvested since July 17 were advised to throw them away.

The closure ordered in August was backdated to July 17, requiring the company to recall all oysters harvested and distributed since that date, public health agency spokesman Ronald Owens said.

The company and the health department are collaborating on an oyster sampling and testing program, and harvesting will not resume until the oysters are found to be free of any Vibrio contamination, he said.

Kevin Lunny, who runs the family-owned oyster farm, said they sold hundreds of thousands of oysters during the period cited by the state. The shutdown has cost him $100,000 to $200,000 in sales during one of the busiest times of year, he said.

Lunny said there has never been a case of Vibrio contamination in Drakes Estero oysters and doubts there was any this year, but nonetheless complied with the state orders.

"We're following the rules," Lunny said. "We don't think the oysters were ever a risk, but the health department needs to be completely comfortable with that."

His company is the only oyster farm on Drakes Estero, a 2,500-acre estuary in the Point Reyes National Seashore. Lunny is bidding for renewal of a federal permit that allows his commercial operation in an area designated as potential wilderness.

Symptoms of a Vibrio infection include vomiting, abdominal cramps, diarrhea, headache, fever and chills. Most people recover without treatment in a few days, the public health department said, but there are rare cases of severe illness and death.

An estimated 4,500 cases of Vibrio infection occur each year in the nation, according to the federal Centers for Disease Control and Prevention.

The bacterium is commonly found in waters where oysters are cultivated, and it thrives under certain temperature and salinity conditions, the CDC said.

(You can reach Staff Writer Guy Kovner at 521-5457)

or guy.kovner@pressdemocrat.com.