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 – What will the long-term impacts be on the oyster industry?
Q4 – What is the Government of Canada doing to support importation of MSX/Dermo resistant oysters from the United States to Atlantic Canada?

R1 - The Canadian Food Inspection Agency is focused on preventing the spread of these diseases to areas elsewhere in Canada that remain free of them.

Since September 2, 2025, eastern Canada waters (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 oyster movement is now controlled under the Domestic Movement Control Program.

The Canadian Food Inspection Agency continues to engage the industry, provinces, and other federal departments and provincial partners, providing biosecurity advice and supporting coordinated efforts to protect oyster health.
R2 - 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. Support for this program is also provided by Fisheries and Oceans Canada and provincial governments.
R3 - The diseases are changing Atlantic Canada’s oyster industry.

Wild oysters for harvest and wild caught seeds will no longer be enough to support current production.

The sector will have to rely more on hatcheries for resistant oysters suited to the Atlantic waters to meet demands for oysters.

This will mean increasing hatchery capacity and supporting transition. However, it will take time for these new resistant stocks to grow and provide economic sustenance for industry.

Federal 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.
R4 - Due to MSX and Dermo diseases, an importer in Prince Edward Island (PEI) and New Brunswick (NB) applied to import “MSX/Dermo disease resistant” oysters from the United States.

The Canadian Food Inspection Agency assessed the science and allowed imports from the two Maine hatcheries, based on risk assessment.

The Canadian Food Inspection Agency engaged with federal and provincial governments, Indigenous communities and rights holders, as well as stakeholders.

Their input was considered in making this decision.
The Canadian Food Inspection Agency will continue to assess applications for import when they re-submitted.

Multinucleate sphere unknown (MSX)

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.

Although MSX harms oysters, it does not pose any risk to human health and oysters remain safe to consume.

MSX has a significant economic impact. In 2023, oyster aquaculture in Canada was valued at $66 million—making it the most valuable shellfish sector in the country.

MSX and Dermo are reportable diseases in Canada under 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.

MSX has been present in parts of Nova Scotia (Cape Breton East) since the early 2000s.

It was later confirmed in Bedeque Bay, Prince Edward Island (PEI) in July 2024, New Brunswick in November 2024, Quebec in June 2025, and recently in Newfoundland and Labrador in December 2025.

Perkinsus marinus (Dermo)

Dermo is also a serious disease of American oysters (Crassostrea virginica) that is commonly found where MSX appears. It usually causes lower death rates (up to 50-60%), but it affects wild and cultured oysters at a younger age than MSX and still limits production. It is impossible to eliminate Dermo once found in the marine environment and it is transmitted directly between oysters.

Like MSX, Dermo poses no health risks to humans and oysters are safe to consume.

On September 2, 2025, all waters in the four Atlantic provinces and Eastern Quebec were declared areas where MSX and Dermo are present or highly likely to occur.

A Domestic Movement Control Program has been implemented to prevent the spread of both diseases in Canada. The program allows industry to operate without additional permitting requirements and prevents oysters from an area where MSX is known or is highly likely to occur from entering waters where MSX has not been detected.

The federal and provincial governments help manage the diseases. The Canadian Food Inspection Agency (CFIA) is responsible for aquatic animal health in Canada and for developing disease response plans. Fisheries and Oceans Canada supports and conducts research on reportable aquatic animal diseases. It also provides science support and laboratory diagnostic services, as well as 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 Atlantic Canada and Quebec, causing significant mortality in oysters and economic impacts for growers, processors and Indigenous communities.
• MSX and Dermo do not pose a risk to food safety.
• The Government of Canada is working with affected provinces to support industry recovery and is investing in breeding programs for disease resistance, hatchery upgrades and genomic research to secure the industry’s future.
• The Canadian Food Inspection Agency has allowed imports of MSX/Dermo resistant oyster seed and broodstock from the United States for aquaculture use in Prince Edward Island, subject to science‑based conditions designed to protect aquatic animal health.
• The Canadian Food Inspection Agency continues to assess applications for import on a case-by-case basis.