Investigators search for culprit in norovirus outbreak in BC oysters


Shawn Chesney smiles as he deftly cracks open a steep oyster shell with a chunky knife and releases the glistening meat inside. Shellfish aren’t just a starter at Oyster Express, its Vancouver restaurant.

“Oysters really transcend class. They transcend race. They transcend age,” Chesney said. “Nutritionally, they’re perfect for you. There’s obviously a romantic aspect to that.”

But that romance comes with risks when the draw of an oyster eats it raw. Between January and April, more than four hundred people in the United States and Canada fell ill with norovirus traced back to raw shellfish from Baynes Sound oyster farms.

The narrow 40 kilometer channel between Vancouver Island and Denman Island is British Columbia’s most prolific oyster farming region.

Recalls affecting industry reputation

Norovirus causes stomach cramps, nausea and diarrhea. The pathogen that makes people sick is spread through human feces and vomiting. Cooking oysters at 90°C for 90 seconds kills the virus. It can also kill business.

“Even if people like oysters, they’ll take a break or they’ll stay away,” Chesney said, reflecting on how months of food safety recalls and warnings affected his restaurant until this that the epidemic was declared over at the end of April.

Shawn Chesney prepares a plate of raw oysters at his Oyster Express restaurant in Vancouver. (Curt Petrovich/CBC)

The damage to the BC brand was much greater, according to Nico Prins, executive director of the BC Shellfish Growers Association.

“I think this has a huge impact on the reputation of the entire BC industry,” Prins said of international headlines and recall notices that buried details of the issue in fine print. : contamination was attributed to only 14 of more than 500 growing. sites.

The Department of Fisheries and Oceans has closed the affected sites under the direction of the Canadian Food Inspection Agency.

Prins said the publicity of the recalls is something that “sticks with importers and food safety officials in other governments and other countries for much longer than it does with the consumer.”

The outbreak has thwarted an expected recovery after oyster sales plummeted during the pandemic. The most recent figures from the British Columbia Ministry of Agriculture and Food peg provincial oyster sales at just under $20 million in 2020, up from more than $28 million the year. previous.

Although his shellfish business, Mac’s Oysters, is based in the heart of Baynes Sound, chief executive Gordy McLellan says none of the 250 hectares he leases from the BC government have been affected by contamination from norovirus. He says his competitors haven’t fared as well.

“There are a few guys who are quite upset because they haven’t been sick and their orders have dropped.”

Detect noroviruses

Like all producers, McLellan is subject to regular and routine review under the Canadian Shellfish Sanitation Program (CSSP), which is administered by no less than three federal departments: Environment and Climate Change Canada (ECCC) , Fisheries and Oceans Canada (DFO) and the Canadian Food Inspection Agency (CFIA).

McLellan says if any of his sites go a week without water quality testing during the summer, alarm bells go off in government offices and the site is shut down.

Gordy McLellan has been an oyster farmer for over 50 years and runs Mac’s Oysters, the family business based in Fanny Bay, BC. (Curt Petrovich/CBC)

“Keep your head down and try not to make anyone sick,” he said with a smile that belies the burden of work involved in preventing disease.

Oysters are not tested for norovirus before being shipped. This is partly because test results would take too long for a product with a limited shelf life. Norovirus can also be difficult to detect. While a gram of human waste the size of a quarter teaspoon can contain up to 10 billion norovirus particles, it only takes 10 particles to cause illness.

But testing the oysters themselves for norovirus isn’t practical. Conclusive results for the presence of viable virus can take weeks. Producers therefore work with ECCC to look for E. coli in the water where oysters are grown, which may reveal exposure to sewage. But a finding of low or no levels of E. coli does not mean there is no norovirus clinging to the oyster. Additionally, producers are responsible for testing for a variety of toxins such as Paralytic Shellfish Poisoning (PSP).

Each bag of oysters shipped to market must be tagged describing where and when the shellfish were harvested, so they can be traced back to exact beaches or growing sites in the event of an outbreak. Retailers and restaurants must retain the tag for 90 days in the event of a reported illness and subsequent investigation.

Food safety investigators rely on tags that must be attached to every bag of oysters shipped to market, such as those from Mac’s Oysters. (Curt Petrovich/CBC)

Contamination events like this are becoming more common, according to Lorraine McIntyre, food safety specialist at the BC Centers for Disease Control (BCCDC).

“We had outbreaks in 2015, 2016, 2017, 2018,” McIntyre said. “We had a little break with COVID. And now here we are in 2022.”

Sewage spill suspected as cause of outbreak

When the BCCDC investigated the latest event, it pointed to commercial fishing boats which were anchored a few meters from certain farms.

Transport Canada regulations prohibit discharging untreated sewage within three nautical miles (5.5 km) of shore. Boats without sewage treatment on board are expected to use marina based pumping stations.

The BCCDC says station operators contacted for its investigation said commercial vessels rarely, if ever, use them. There are no regulations requiring ships or stations to keep records. Most shipowners refused to answer the BCCDC’s questions, although one of them admitted that sewage dumping was a common occurrence.

Food safety specialist Lorraine McIntyre of the British Columbia Centers for Disease Control in Vancouver is investigating the latest outbreak of norovirus to hit oyster farms in British Columbia. (Curt Petrovich/CBC)

“Well, that’s tough,” McIntyre said of 100% compliance with existing sewage disposal regulations. “Education only works for people who listen.”

Transport Canada can enforce dumping regulations with everything from verbal warnings to summary convictions. However, a spokesperson told CBC News that the department had not recorded any fishing vessel violations since 2018, but had found what it called “deficiencies” in sewage treatment systems or reservoirs. retention on 50 vessels of all types over 15 gross tons over the past three years. years. The spokesman said prosecutions would require DNA taken from the dump to be traceable to an offender.

The ministry has produced brochures encouraging all ship operators to comply with the law. Every two years, Transport Canada conducts targeted inspections of fishing vessels. Last year, that was 101 ships nationwide.

Last year, the U.S. Coast Guard (USCG) boarded or inspected 3,323 vessels to check for sewage discharge compliance in U.S. waters right next to some B.C. oyster farms, according to the chief of the USCG Inspections Division for Puget Sound. Commander Lee Bacon told CBC News the Coast Guard issued three citations for non-compliance.

Robert Morely, spokesman for the commercial herring fleet, is reluctant to blame the fishing boats, telling CBC News in an email that there are recreational and cruise boats in the area year-round.

He also said other potential sources of the outbreak include “sewer overflows, sewage treatment plants and municipal raw sewage discharges and local septic tank overflows.”

Residential developments and industrial operations encroach on Baynes Sound, a sensitive body of water upon which shellfish producers depend.

A short drive from Mac’s Oysters, the booming village of Cumberland dumps treated sewage into Baynes Sound via the River Trent. Union Bay Estates, which is still under development, envisions nearly three thousand homes in a development right on the shore, next to a shipbreaking operation being pursued by the Comox Valley Regional District.

“It’s possible there was septic seepage. It’s possible there was a spill from a commercial ship, but that doesn’t explain everything,” McIntyre said of this year’s outbreak. which is still under investigation. The only thing certain about contamination is that it is caused by people.