For immediate release: May 16, 2008 (08-077)

Contacts:
Cari Franz-West, Office of Shellfish and Water Protection 360-236-3326
Allison Cook, Communications Office 360-236-4022

Warm weather brings risk of illness from raw oysters

OLYMPIA ¾ With warm weather approaching, people are heading to the beach for oysters. It’s important to know raw oysters can make people sick under certain conditions.

Spring and summer temperatures can warm the waters where oysters live, and that may promote the growth of bacteria such as Vibrio parahaemolyticus. These naturally-occurring bacteria can cause an illness called vibriosis when oysters taken from warm water are eaten raw. Vibriosis is usually mild to moderate and lasts for two to seven days; it can be life threatening to people with lowered immunity or chronic liver disease. Symptoms include diarrhea, stomach cramps, nausea, vomiting, headache, fever, and chills. These symptoms usually appear within 12 hours of eating infected shellfish.

Recreational harvesters can protect themselves against vibriosis by making sure oysters are placed on ice or refrigerated as soon as possible after harvest, by not harvesting oysters that have been exposed by the receding tide for a long time (“if the temperature’s high, pass them by”), and by thoroughly cooking oysters. Vibrio bacteria are destroyed when oysters are cooked to 145° F.

Commercial harvesters will take extra precautions as well. A Vibrio parahaemolyticus Control Plan recently adopted by the state Board of Health specifies special control measures for raw oysters intended for human consumption during the warm summer months  The rule becomes effective May 19.

The rule is a result of a comprehensive review of illness data, harvest operations, and analysis of environmental factors (air temperature, water temperature, salinity, and oyster tissue test results). A committee of industry, tribal, federal, and state representatives reviewed the information to determine the best ways to prevent the possibility of vibriosis illnesses from eating raw oysters. The new rule requires shellfish companies to quickly refrigerate oysters after they are harvested; the goal is to prevent growth of the bacteria.

The Department of Health works with the shellfish industry to assure swift notification of reported illnesses, to investigate illnesses, and to ensure continued prevention efforts to reduce the risk of illness.

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