Following the detections of two aquatic animal diseases, multinucleate sphere unknown (MSX) and Dermo (also known as perkinsosis), in several eastern Canadian provinces, the Canadian Food Inspection Agency (CFIA) is introducing new oyster movement controls covering Prince Edward Island, Nova Scotia, New Brunswick, Newfoundland and Labrador, and Québec.
Neither MSX nor Dermo pose risks to human health or food safety, but they can cause increased oyster mortality and decreased growth rates.
Starting on September 2, 2025, the waters of eastern Canada - meaning Prince Edward Island, New Brunswick, Nova Scotia, Newfoundland and Labrador and Québec - will be declared as areas where the aquatic animal diseases, 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 will be managed according to the CFIA's established Domestic Movement Control Program (DMCP).
Under the DMCP, oysters that have been grown to commercial size and processed for human consumption can still be exported and sold. However, oysters that are not ready for the commercial market (and are still growing) are not permitted to be moved outside of the declared areas. These changes simplify the permitting process for oyster growers, harvesters, and processors in eastern Canada, as CFIA permits will no longer be required for the movement of oysters or gear within the declared areas. Fisheries and Oceans Canada (DFO) continues to manage oyster movements within and between provinces in eastern Canada through the Introductions and Transfer (I&T) Licensing Program, in collaboration with the respective provincial authority and, when appropriate, in consultation with the CFIA.
We understand the detections of MSX and Dermo have had serious impacts on oyster growers, harvesters, processors, other industry members, and Indigenous communities. We greatly appreciate their support and cooperation as we continue working together to manage and respond to these diseases.
Quick facts
- Haplosporidium nelsoni causes multinucleate sphere unknown (commonly known as MSX) in cultured and wild American oysters (Crassostrea virginica). Perkinsus marinus causes Perkinsosis (also known as Dermo) in cultured and wild American oysters.
- These diseases do not affect other bivalves in this area, including mussels, scallops, or clams; however, they can cause increased oyster mortality and decreased growth rates in oysters.
- With MSX, research is ongoing, but it is presumed there is an unknown intermediary host which makes it harder to determine how it is spreads. Dermo can be transmitted from oyster to oyster, or from contaminated water to oysters.
- Canada's National Aquatic Animal Health Program (NAAHP), co-delivered by the CFIA and DFO, aims to prevent the introduction and consequential spread of aquatic animal diseases of finfish, molluscs, and crustaceans.
- The CFIA implements domestic movement controls to prevent the spread of endemic reportable aquatic animal diseases, including MSX and Dermo. In general, zones are either declared as:
- Infected areas, where the reportable disease is known or highly likely to occur; or
- Buffer areas, where the reportable disease may occur because of a link to a declared infected area; or
- Free areas, where the reportable disease does not occur.
