The BC shellfish industry is bracing for another hit as outbreaks of norovirus contamination are now being linked to BC-sourced oysters. But with experts saying that rising global temperatures are to blame for the proliferation of waterborne illnesses, the trend towards more and more shellfish recalls and bans may become a permanent reality for the province.
On January 13, the BC Centre for Disease Control sent out a warning to the public over a rise in gastrointestinal illness connected to the consumption of raw oysters, stating that since December, 2016, more than 70 cases of oyster-related illness have been reported in the province.
And while the CDC hasn’t yet confirming the source of the problem, over in Ontario, the province’s chief medical health officer is pointing the finger right at BC oysters. Dr. David McKeown has issued a public health warning against the consumption of oysters from the West Coast, stating that 24 cases of gastrointestinal illness had been reported in the province from people who at raw and undercooked oysters and confirming that the symptoms were consistent with norovirus.
“Food-borne outbreaks of norovirus illness can occur when food is contaminated with the virus,” stated Dr. McKeown. “Some foods can be contaminated at the source. Shellfish such as oysters can become contaminated from the water before they are harvested.”
No recall or ban on BC oysters has yet been proclaimed, and the BC Shellfish Growers’ Association says that it’s “doing everything they can to ensure the safety of the food they are producing.” Association executive director Darlene Winterburn said, “All oysters that are farmed and distributed through the province actually have to go through a federally regulated processing plant. During that time they are given a tag that will enable all of the regulatory bodies to take it back to the farm, the site and the date where it was harvested,” said Winterburn to the Powell River Peak.
The recent outbreak is the second in two years to have hit the BC shellfish industry. In August of 2015, shellfish farmers and restauranteurs were livid over a province-wide ban on serving raw BC oysters, issued by the Canadian Food Inspection Agency and prompted by a rise in food poisoning connected to the vibrio parahaemolycus bacterium, which occurs naturally in shellfish and appears in greater quantities in warmer water.
The pattern may become more common as climate change causes ocean temperatures to rise. A report last year from the United States Centres for Disease Control found that vibrio infections in the US have increased by an average of roughly 390 a year from the late 1990s onwards, with researchers stating that the evidence showed a direct link between warmer water temperatures and increases in bacterial outbreaks. The study found that even in Alaska where vibrio contamination used to be more than a rarity due to the normally colder waters, cases are now coming in of people getting sick from eating raw oysters.
The trend seems unavoidable. Because oysters are filter feeders, proliferation of a given contaminant in the surrounding waters are sure to be found in the oyster as well, meaning that there’s little to stop the contamination and potential for illness connecting to eating raw oysters.
Over on the other coast, while shellfish farmers may have benefitted from past BC bans, their time may be coming, too. No recent vibrio outbreaks have hit Nova Scotia’s oyster industry, but as the CBC has reported, a 2016 study found that as ocean temperatures increase, a strain of vibrio is moving northward along the Atlantic coast. In response, the Nova Scotia Aquaculture Association said that it’s launching a monitoring program to track water temperatures and vibrio levels around the province.
Meanwhile in Vancouver, seafood restaurants continue to serve raw BC oysters. For now.