Illness outbreak forces closure of oyster farms
Seven southern B.C. sites affected; norovirus sickens more than 300
The federal government has closed oyster farming at seven diverse locations in southern B.C. waters, and several other commercial growers have voluntarily stopped selling amid the worst norovirus outbreak to ever hit the industry.
To date, a total of 304 illnesses have been reported in B.C., Alberta, and Ontario from eating raw or undercooked oysters from the West Coast, said Darlene Winterburn, executive director of the Comox-based B.C. Shellfish Growers’ Association.
While human sewage is considered the most likely source of the outbreak, officials cannot identify the cause, Winterburn said. “Some (of the oyster farms) are in remote areas and some are not. We can’t point our finger and say, ‘Oh, it was this septic system, or there is a break in a line.’ Everybody is scratching their heads and everybody is looking.”
The industry and various government agencies meet weekly to discuss the problem. The unusually inclement winter is also being considered, she said, noting that there have been oyster closures in the Comox area over the years during heavy rains when pollutants flow off the land and into the ocean.
Winterburn said in an interview she doesn’t know the exact number of growers who have voluntarily stopped shipping to market, but speculated it “could be more than 10.”
She added: “Nobody wants to make people sick.”
Growers with multiple sites will do better than small single-site farms. Normally, this is the period when oyster farmers are spending money to buy seed, she said, adding it is more difficult to keep staff when farmers are not bringing in money.
The Public Health Agency of Canada reports there are currently emergency closures on harvesting bi-valve shellfish in six areas where norovirus has been detected, including Baynes Sound-Henry Bay, the west coast of Denman Island (two sites), and southeast of Union Bay, as well as sites west of Read Island at Hoskyn Channel, and Trevenen Bay in Malaspina Inlet. The seventh site, Deep Bay at Baynes Sound, is closed due to E. coli contamination.
The agency warns in a statement on its website that contaminated oysters may still be in the market, including restaurants, seafood markets and grocery stores, and there “continues to be a risk of norovirus infection and gastrointestinal illness associated with the consumption of these oysters.”
The crisis garnered headlines starting last November when dozens of people became ill at the Clayoquot Oyster Festival in Tofino. Winterburn is confounded by the fact that most oysters grown in B.C. are sold to the U.S. and Asia, where there have been no reported illnesses.
She emphasized that it’s not the oyster, per se, that’s the problem; the norovirus is in the water the oysters filter. “Oysters are the canary in the coal mine.”
According to the Ministry of Agriculture, the aquaculture industry produced 9.1 million tonnes of oysters with a wholesale value of $14.4 million in 2015, which compares with 7.6 million tonnes and $9 million in 2010.
While raw oysters continue to be sold in some restaurants, Winterburn wouldn’t condemn those operators or consumers. “You have to do what’s right for you.”
Several Vancouver restaurants specializing in oysters declined to officially comment Tuesday on the outbreak, but employees did say that they are also carrying east coast oysters not subject to the same contamination scare.
The B.C. Centre for Disease Control reported an outbreak involving raw oysters and norovirus involved 36 persons believed “contaminated by ill shellfish workers during harvesting activities” at a single site in 2010.
A 2004 case involved “26 confirmed and 53 clinical cases”of norovirus in 2004. Oysters were traced to 14 geographically dispersed harvest sites, 18 suppliers, and 45 points of purchase. The contamination source was never identified.
In 2015, the B.C. industry was also hit by a large outbreak involving 82 cases Vibrio parahaemolyticus, a naturally occurring bacterium associated with raw oysters.
Illnesses can be avoided if oysters are cooked to an internal temperature of 90 C for a minimum of 90 seconds, and proper handwashing and food safety practices are followed.
Noroviruses are a group of viruses that can cause gastroenteritis in people, including diarrhea and vomiting. Noroviruses are found in the stool or vomit of infected people and are highly contagious.
Oysters are the canary in the coal mine.