Question Period Note: MSX AND DERMO IN ATLANTIC CANADA

Q1 – What measures has the Government of Canada put in place to address the issue of MSX and Dermo in Oysters from the Atlantic? Q2 – Does the Canadian Food Inspection Agency monitor for MSX and Dermo? Q3 – Does MSX or Dermo pose a health risk to humans? Q4 – What will the long-term impacts be on the oyster industry?

R.1 - The Canadian Food Inspection Agency is now working to prevent the spread of these diseases to areas elsewhere in Canada that remain free of them. As of September 2, 2025, the waters of eastern Canada – meaning PEI, New Brunswick, Nova Scotia, Newfoundland and Labrador and Québec – have been declared as areas where MSX and Dermo are present or very likely to be present. This means that the movement of oysters which are not yet ready for commercial sale are now managed according to the Canadian Food Inspection Agency’s established Domestic Movement Control Program (DMCP).

The Canadian Food Inspection Agency continues to engage the shellfish industry by providing specific biosecurity advice. It also advises the Introduction and Transfer Committee, made up of Fisheries and Oceans Canada and provincial partners, to help protect oyster health and promote biosecurity. R.2 - The Canadian Food Inspection Agency maintains real-time awareness of MSX and Dermo in all Canadian waters and responds to notifications according to our obligations to the World Organisation for Animal Health. The Canadian Food Inspection Agency leads this program with the support of Fisheries and Oceans Canada and Provincial Governments. R.3 - These diseases pose no risk to human health, nor do they pose a risk to food safety. R.4 - The Canadian Food Inspection Agency is working to prevent the spread of these diseases to areas elsewhere in Canada that remain free of them. Moving to the Domestic Movement Control Program for MSX and Dermo simplifies the Canadian Food Inspection Agency permitting process for eastern Canada oyster growers, harvesters, and processors. This allows industry activities to proceed, including the export of oysters to domestic and international markets for human consumption. Government of Canada departments and agencies are collaborating to determine long-term impacts and ensure the proper supports are in place to aid the oyster industry in its recovery.

Fisheries and Oceans Canada has made funding available to support scientific research into the disease and into finding resistant species.

MSX and Dermo are reportable disease in Canada according to the Health of Animals Act. Not all infected oysters show signs of disease. Diagnosis of an MSX and Dermo infections requires the identification of the disease through laboratory testing.

Multinucleate sphere unknown (MSX) is a serious disease of American oysters (Crassostrea virginica) that can cause significant mortality (up to 90-95%) and reduces the production and harvest of both cultured and wild oysters. It is impossible to eliminate MSX once found in the marine environment and the full life cycle of the parasite, including the intermediate host, remains unknown. While MSX prevents oysters from thriving, this disease is not a food safety concern as it poses no risk to human health and oysters remain safe to consume.

The economic impact of MSX is considerable. In 2023, oyster aquaculture in Canada was valued at $66 million—making it the most valuable shellfish sector in the country.

In July 2024, the Canadian Food Inspection Agency (CFIA) confirmed the presence of MSX in oyster samples collected in Bedeque Bay, Prince Edward Island (PEI). Subsequently, the presence of MSX was confirmed in New Brunswick in November 2024 and in Quebec in June 2025. MSX has been present in the Cape Breton East area of Nova Scotia since the early 2000s. To date, MSX has not been detected in Newfoundland and Labrador.

On February 7, 2025, the province of PEI was declared as an area where MSX is known or is highly likely to occur. The Domestic Movement Control Program allows industry to operate without additional permitting requirements and prevents oysters from PEI from entering waters where MSX has not been detected.

Perkinsus marinus (Dermo) is also a serious disease of American oysters (Crassostrea virginica) and is commonly found in populations of oysters that have MSX. Mortality rates are lower than MSX (can be up to 50-60%), but it restricts production of wild and cultured oysters at a younger age than MSX. It is impossible to eliminate Dermo once found in the marine environment and it is transmitted directly between oysters. Dermo poses no health risks to humans and Atlantic Canadian oysters are safe to consume.

In November 2024, the presence of Dermo was officially confirmed in New Brunswick for the first time in Canada. Since that time, it has been detected in all Atlantic provinces and in the Baie des Chaleurs region of Quebec.

On September 2, 2025, the waters of all 4 Atlantic provinces and Eastern Quebec have been declared as areas where MSX and Dermo are known to exist or are highly likely to occur. This new control measure has been implemented to prevent the spread of both diseases in Canada.

The federal and provincial governments play a role in monitoring MSX and Dermo. The CFIA is the Competent Authority for aquatic animal health in Canada and responsible for developing disease response plans. Fisheries and Oceans Canada supports and conducts research on reportable aquatic animal diseases – and provides funding to support research. It also provides science support and laboratory diagnostic services and manages shellfish aquaculture issuing and managing leaseholds on provincial seabed where shellfish aquaculture takes place.

As key partners, provincial governments manage endemic diseases within their provincial boundaries. They oversee the shellfish health program and provide support to the industry through monitoring and sharing of information, through the prevalence trends of MSX and/or Dermo in their waters and using it as part of the decision tree for proposed oyster movements.

• MSX and Dermo are serious diseases affecting oysters in Canada. Both can cause significant mortality rates reducing production and harvest, leading to substantial economic losses.

• MSX and Dermo do not pose a threat to food safety.

• These diseases are having a devastating economic impact on Canada’s $66 million oyster industry.

• The waters of eastern Canada are now declared as areas where MSX and Dermo are present or very likely to be present.

• The Government of Canada is working with the impacted provinces to ensure the proper supports are in place to help the oyster industry recover.