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Seafood can often be a shell game

BCCDC cautions shellfish eaters to properly cook their meals; watch for outbreaks

Along with the season’s beach weather, the BC Centre for Disease Control reminds the public there’s a risk of illness from raw or undercooked bivalve shellfish like oysters, clams, mussels, scallops and cockles.

“We see more illnesses during the summer months and we see it mostly in people who live along the coastal waters,” said CDC epidemiologist Marsha Taylor.

Shellfish can accumulate bacteria (vibrio parahaemolyticus), viruses (norovirus, hepatitis A), toxins (paralytic or diarrhetic shellfish poisoning) and other impurities from the water. Thorough cooking destroys bacteria and viruses, but does not destroy toxins.

“There’s an increase in vibrio parahaemolyticus as the water warms,” Taylor said, pointing out the other risks can be present throughout the year, but there is less self-harvesting so the overall danger is lower.

There were 42 cases of vibrio reported in B.C. last year and over five so far this year.

Illnesses have been linked to raw shellfish served in restaurants, bought retail, or self-harvested across Vancouver Island and the Sunshine Coast including Qualicum Beach and Parksville, Taylor said, but she didn’t have further details on the local illnesses.

The effects run from discomfort to diarrhoea bad enough to keep people home for a week, she said.

If they can track an illness to a specific store or restaurant, they will issue an advisory she said.

Along with the individual cases there are occasional outbreaks, like a 2010 norovirus outbreak from raw oysters that affected over 30 people. In 2011 more than 60 people became ill after consuming cooked mussels contaminated with diarrhetic shellfish poisoning.

“The safest thing is for people to only eat cooked shellfish from approved sources,” Taylor said, explaining that restaurants and retailers must be federally approved and able to provide a shellfish shipper’s tag.

People can harvest their own shellfish but should be up on the latest local details available from the Department of Fisheries and Oceans (DFO) at 1-866-431-3474 or on their website — easiest to Google “DFO shellfish.”

When preparing at home cook oysters to an internal temperature of 90°C (195°F) and be extra careful about cross-contamination with other food. Store raw and cooked seafood separately, cleaning and sanitizing knives and cutting boards and working with clean hands.

Anyone becoming ill after eating shellfish should report it to their local public health office or primary care provider and see a physician if symptoms persist or become severe. Call 8-1-1 for more information.

The BCCDC, an agency of the Provincial Health Services Authority, provides surveillance, detection, treatment, prevention and consultation services for disease control.


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