PHAC investigating 67 illnesses linked to raw oysters

By Joseph James Whitworth

- Last updated on GMT

PHAC advised cooking shellfish before eating
PHAC advised cooking shellfish before eating

Related tags Oyster Canada

The Public Health Agency of Canada (PHAC) is investigating 67 Canadian cases of Vibrio parahaemolyticus infections linked to raw shellfish.

The majority of illnesses have been connected to eating raw oysters, said the agency.

PHAC said work is ongoing to determine the source and distribution of products and illnesses can be avoided if shellfish are cooked before being eaten.

British Columbia and Alberta affected

A total of 67 cases have been reported in British Columbia (48) and Alberta (19) with one person being hospitalized.

Individuals became sick between June 1 and August 7 and all reported consumption of raw shellfish, primarily oysters.

The Canadian Food Inspection Agency and the Department of Fisheries and Oceans and Health Canada are also investigating.

Fisheries and Oceans Canada said Vibrio parahaemolyticus (Vp) is a naturally occurring bacterium that can be present in bivalve shellfish (i.e. clams, oysters, scallops, mussels, cockles) even in harvest areas that are open and approved for shellfish harvesting.

The bacterium is found in higher concentrations in summer months when water and air temperatures rise, increasing risk of infection and illness when bivalve shellfish (like oysters) are consumed raw or undercooked.

Symptoms of infection may include watery diarrhoea, stomach cramps, nausea, vomiting, fever, and headache and usually start within 12 to 24 hours and may last up to three days.

To reduce the risk of illness, bivalve shellfish should only be harvested at the water's edge when the tide is going out and shellfish should be iced, refrigerated or frozen immediately.

PHAC said discard any shellfish that do not open when cooked, eat right away after cooking and refrigerate leftovers and always keep raw and cooked shellfish separate.

It added shellfish should be cooked to a safe internal temperature of 74°C (165°F).

BCCDC findings

The BC Centre for Disease Control (BCCDC) said an ‘unprecedented’ number of shellfish-related illness occurred this summer with 35 cases reported in June and July. 

The majority of illnesses were linked to raw oysters sourced in British Columbia and served in restaurants but there have also been some cases associated with raw oysters bought at retail or self-harvested. 

Marsha Taylor, epidemiologist with the BCCDC, said people should always be aware of the health risks associated with eating raw or undercooked oysters

The risk is especially high this summer, as we can see from the number of Vibrio infections reported during the last two months.”

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