VANCOUVER — A shellfish toxin has surfaced in B.C. for the first time, poisoning 60 people earlier this month and raising concerns in the province’s aquaculture industry.

Investigators traced the outbreak to mussels that had been harvested off Cortes Island between July 19 and Aug. 2.

The mussels were shipped to retailers and restaurants in British Columbia, Alberta, Saskatchewan, Manitoba and Ontario under five different brand names.

Investigators determined the mussels had been contaminated with a biotoxin that causes diarrhetic shellfish poisoning.

“It was the first-ever documented DSP outbreak in Western Canada,” said Dr. Eleni Galanis, a physician with the BC Centre for Disease Control, who noted Canada’s only other outbreak hit Nova Scotia in the early 1990s.

Galanis said DSP is not fatal, but is often accompanied by diarrhea, nausea, vomiting, abdominal cramps and chills.

She said the outbreak surprised officials, but that it was quickly contained through a recall by the Canadian Food Inspection Agency.

“We have a lot of lessons to learn from this unusual occurrence,” said Galanis, who added work is continuing to determine why it showed up, and what to do if it happens again.

“I don’t think we can prevent it from occurring in ocean waters,” she said, but added that CFIA tests for the poison to prevent contaminated products from making it to consumers.

According to the CFIA website, DSP is one of three “biotoxins of concern” in Canadian waters, the other two being responsible for amnesic shellfish poisoning and paralytic shellfish poisoning.

The CFIA could not be reached for comment on when it started testing for DSP or why. It is not known whether testing was being done before the outbreak.

The presence of the toxic algae in shellfish is impossible for consumers to detect.

It cannot be seen, smelled or tasted. It is also not destroyed by heat, meaning that cooking shellfish does nothing to reduce chances of becoming ill with DSP.

There is no antidote, but recovery usually begins within three days of consuming the biotoxin.

Roberta Stevenson, executive director of the BC Shellfish Growers Association, said DSP is a common toxin in other parts of the world, but not here.

“We’re studying where did it come from (and) is it here forever?” said Stevenson. “We don’t know the answers to those questions.”

According to a 2004 paper on marine biotoxins prepared by the UN Food and Agricultural Organization, Japan, Europe, Chile, Thailand, Canada (Nova Scotia), and potentially Tasmania and New Zealand have all seen cases of DSP.

But the report notes incidents are increasing and “frequently reported from new areas.”

They are not minor nuisances. In 1984, cases of DSP shut down Sweden’s mussel industry for nearly a year.

Alan Rowan of Pacific Northwest Shellfish, an oyster and clam company with a farm in Fanny Bay, on the east coast of Vancouver Island, said producers who ship products to Europe regularly test for DSP.

But he said the first he had ever heard DSP mentioned in relation to local products was during a meeting with CFIA in late June.

“It’s all new ground for most of us in the shellfish industry here in B.C.,” said Rowan.

He said the atypical weather this year may be to blame for the toxin’s strange appearance, but added more work is needed to get “out of the dark” about the algae that causes it.

“We don’t understand enough about the ecology of these organisms.”

Vancouver Sun