Parasite that kills oysters may be present in New Brunswick

Oysters harvested from a farm are inspected by a worker in Brunswick, Maine, on June 12, 2022 THE CANADIAN PRESS/AP, Robert F. Bukaty

The New Brunswick government’s surveillance program says a deadly parasite may be present in oysters found in Spence Cove along the province’s east coast.

The province says the Canadian Food Inspection Agency – the federal regulatory lead for animal disease issues – collected samples for analysis.

“Our department will continue to work collaboratively with the Canadian Food Inspection Agency throughout this investigation,” said Agriculture, Aquaculture and Fisheries Minister Pat Finnigan in a news release.

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“The department is committed to keeping industry stakeholders informed and ensuring that they have access to timely updates and essential information. We recognize the uncertainty surrounding the full economic impact of this situation and we are prepared to work with affected producers as more information becomes available.”

MSX (multinucleate sphere unknown) is caused by a protozoan, called Haplosporidium nelsoni, and can result in high levels of mortality in oyster populations. The disease typically kills oysters that are at least two years old, with mortality rates as high as 95 per cent within two to three years of the initial infection.

Ryan Carnegie, a professor at the Virginia Institute of Marine Science in Gloucester Point, Va., says not every detection of the parasite is associated with very high levels of disease and mortality.

“In northern parts of the U.S. and New England where it was present for many years in the later part of the last century, it was present for many years before it actually expressed very, very high levels of disease and mortality,” he says.

“I definitely want to make the point that this is not necessarily a catastrophic situation, discovering it in a new place necessarily right away, there are other factors that influence whether or not there may be a big disease event.”

Carnegie said the parasite requires an intermediate host.

“So it lives in some other marine organism when it’s not infecting oysters. We don’t know what that host is, but if that host is not very abundant in New Brunswick waters, for example, then maybe those areas will remain free of the worst impacts of this disease,” he says.

MSX does not pose a risk to human life and affected oysters are safe to consume, according to a provincial news release.

As officials wait for the test results, the department’s chief veterinary officer of aquaculture, under the authority of the Aquaculture Act, has ordered a quarantine in the area, prohibiting the movement of oysters.

Carnegie said the parasites tend to move around through a combination of human activities.

“We can move these around by virtue of the fact that we have commercial traffic and ships moving up and down our coastlines, even if we’re not introducing infected oysters from the U.S. to Canada, which nobody thinks that has occurred, and there’s also natural dispersal with the currents.”

Carnegie said there is also a lot of thought given beyond the immediate establishment of control zones

“Where do we go from there? And there’s certainly a lot of attention given to the development of MSX-resistant lines and families and so on for use in aquaculture context,” he said. “Now that we know these areas are endemic, or potentially endemic, for this pathogen, dealing with it, battling it head-on is really going to be a key tool in our approach to moving forward.”

Parasite previously found in P.E.I., N.S. oysters

MSX was previously found in oysters in Prince Edward Island and certain areas of Cape Breton.

In July, the province confirmed the presence of MSX for the first time in P.E.I. in Bedeque Bay, which is located to the west of Summerside.

Last month, Kathy Brewer-Dalton, a director general with the Canadian Food Inspection Agency, said the parasite has likely spread to a majority of the bays and rivers around the province.

In 2002, MSX was reported in Nova Scotia for the first time. It killed millions of oysters in Cape Breton's brackish Bras d'Or Lake, destroying virtually all of the island's oyster industry within a few months.

Although it has yet to recover, the federal government has invested $2 million in developing a land-based oyster hatchery in the area.

With files from The Canadian Press and CTV Atlantic's Alana Pickrell.

For more New Brunswick news, visit our dedicated provincial page.