Identification of MSX vectors to support decisions related to the inter-provincial movements of mussels: are mussels a vector for MSX transmission?



Multinucleated sphere “X” (MSX) is an infectious disease that causes high mortalities in American oysters (Crassostrea virginica) although it does not affect human health. The transfer of all live shellfish from one area to another is regulated under the Fisheries Act. Transfers are reviewed on a case-by-case basis by the Introductions and Transfers Committee (ITC). The movement of mussels from MSX positive areas would benefit from identifying organisms that transmit MSX to mitigate the risks of MSX exposure to naïve populations. The ITCs have taken a precautionary approach by recommending that mussels from MSX infected areas be considered as potentially infected and that mitigation measures be undertaken before and during the transfer activities. Targeted sampling of wild oysters, mussels and associated organisms including Polychaetes, Isopods, Gastropods, Amphipods, and crabs will be performed in East Bay, Nova Scotia, an MSX infected area within the Bras d’Or Lakes. In the laboratory, organisms were screened for MSX through histological and/or qPCR analysis. The results of this research project will provide the aquaculture industry and the ITCs with information that will be used during risk assessments related to the movement of mussels from MSX affected areas and will help to make more informed decisions.





Program name

Program for Aquaculture Regulatory Research (PARR)



Principal investigator

Mary Stephenson
Head Shellfish Health Unit, Gulf Fisheries Centre, Moncton, NB