New England Sees Spike in Illnesses from Oysters


Oysters are considered an aphrodisiac. But after reading what some oysters off the coast of Edgartown on Martha’s Vineyard detected to have a bacteria called Vibrio parahaemolyticus could do to you, you may want to think twice before grabbing a shell.

According to the Massachusetts Department of Public Health:

When ingested, Vibrio causes watery diarrhea, often with abdominal cramping, nausea, vomiting, fever and chills. Usually these symptoms occur within 24 hours of ingestion and last three days. Severe illness, increased risk of infection, and serious complications, including death, may occur in the very young, elderly, pregnant women, and immune impaired individuals such as people with underlying medical issues, such as liver disease or alcoholism. About 10 percent of cases will develop a blood infection that may require hospitalization.

The state’s Department of Public Health and the Division of Marine Fisheries announced the precautionary closure of oyster beds in Edgartown’s Katama Bay last Wednesday after several cases of the foodborne illness were linked to oysters in the area.

The closure is only expected to last for a week, but this case is one of many that are leading experts to take note of the rise in bacterial infections found in regional raw shellfish over the last three years. Just a year ago, 13 states saw an increase in Vibrio cases.


Last week, the New York State Department of Environmental Conservation also temporarily shut down harvesting of oysters and hard clams from some parts of Long Island after reported illnesses were traced back to shellfish in the area.

“Warm water and warm air temperature causes the emergence of the bacteria,’’ Cheryl A. Whistler, a researcher and associate professor of microbiology and genetics at the University of New Hampshire’s Agricultural Experiment Station, told

The spike in cases may be due to a more aggressive strain — known as the Pacific-Northwest strain — that has made its way to the region, Whistler said.

“It’s a more virulent strain, meaning it takes fewer bacteria to cause someone to get sick,’’ said Whistler.

That means eating only one contaminated oyster could make a person sick.

“It’s most concerning for shellfish growers and managers who never had to deal with this problem before,’’ said Whistler. “Consumers of raw shellfish should be concerned.’’

Vibrio bacteria live in saltwater, and infections are caused by consuming raw or undercooked shellfish, especially oysters, according to the US Centers for Disease Control and Prevention.

According to Whistler, one person was infected last year after swallowing contaminated sea water while swimming at an unidentified Massachusetts beach.


In 2013, similar findings in Massachusetts prompted the departments to close the oyster beds and put a Vibrio control plan in place. As part of the plan, even one reported case of illness that is traced back to consumption of shellfish in a particular area leads to an immediate closure. According to the state’s Department of Public Health, Katama Bay is the first oyster bed closure of 2014.

Consumers shouldn’t swear off oysters or shellfish this season, since there are ways to protect against infection, said Whistler.

“Even the scientists who know don’t stop eating them, we’re just wise on when to eat them,’’ she said.

One of the best ways to eliminate any chance of infection is to cook the seafood, she said. Whistler also advised consumers to keep track of the shellfish they consume and to contact their physician right away if they experience any symptoms.

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