Shell fishermen learning to keep bacteria at bay
BRIDGEPORT, Conn. -- The good news is oysters in Connecticut are about as safe as just about every other kind of food you can name. The bad news is those in the oyster industry, from harvesters to restaurant chefs, have to be ever-vigilant for Vibrio parahaemolyticus, a bacterium that was all but unknown a few years back.
About 60 shell fishermen turned out recently at the Regional Vocational Aquaculture School to hear scientists and other officials hammer home the need to keep oysters cold and out of the sun from the moment they’re pulled from Long Island Sound, especially from June through September.
"We boarded nine vessels in 2012, and all of you were doing a great job and all of you were aware of the situation," said Melissa Evans, a microbiologist with the U.S. Food and Drug Administration. She said that unlike inspections carried out in previous years, oyster-boat operators were now careful to keep the mollusks in shade and in conditions in which temperatures could be kept below 50 degrees Fahrenheit.
The bacterium is critically sensitive to temperature, according to Kristin DeRosia-Banick, an environmental analyst with the state Department of Agriculture. She said that at 50 degrees, it takes more than 35 hours for the bacteria population to double, more than enough time to get the product under ice.
"But at 80 degrees, that windows shrinks to 1.64 hours," she said.
Most people will recover from a bout of Vibrio parahaemolyticus after about three days of "intestinal discomfort."
Deaths are rare, as are those who suffer lasting effects. Nationally, there were 193 cases in 2012, with 55 requiring hospitalization; six of the victims died. The CDC estimates that there were 4,500 cases in all. However, most went unreported owing to the usually mild nature of the infection.
There was only one confirmed case in Connecticut last year, in Westport, officials said. None have occurred thus far in 2013, although the worst months are coming up -- June, July, August and September. But with prudent harvesting practices, oysters remain safe to eat raw year-round, experts say.
There are a number of new federal regulations that oystermen now have to abide by during the warmer months, thanks to Vibrio parahaemolyticus. These include employing a time-and-temperature recorder to provide a paper trail of how the mollusks were handled once they were hauled out of the water. Also, bins of oysters have to be kept shaded and ventilated.
"When the containers are stacked one atop the other, there’s very little evaporative cooling going on," Evans said.
DeRosia-Banick said that there’s a new strain of Vibrio parahaemolyticus that’s "hot," meaning it’ll cause illness in humans even in low doses. "This is the one that showed up on the West Coast, then in Oyster Bay (N.Y.), then in Westport and then in Spain."
But there are those who are attempting to stamp out the microbe like DeRosia-Banick.
"For starters, in Connecticut we don’t have good landing data," she said, referring to the volume of the annual harvest. "So we don’t really know what the risk assessment is. We suspect it’s very low, but we don’t have the data to assess that."
In addition, the state lacks equipment to analyze oyster pathogens in the field, and lab testing takes days. Field-testing gear would cost about $70,000, something not now in the budget.
She noted that oyster consumers tend to eat them raw. "They also tend to sample them at two or more restaurants in an evening, so it’s hard to tell where the bad oyster came from if there’s an infection," she said.
Still, she commended the state’s oystermen for keeping the disease in check, despite a "very difficult" 2012.
"It was about the hottest summer on record, and we were seeing June water and air temperatures that we never experienced before," she said. "But we still had a great health record and we have you to thank for that. The fact that we did not have an outbreak is really directly the result of all of your hard work in getting the oysters to market. You guys did a great job."
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