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Workshop: MSX workshop



MSX is a microbial parasitic disease in oysters that has been a major problem for oyster growers and harvesters throughout the mid-eastern United States, particularly in Chesapeake Bay and Delaware Bay, since the late 1950's. MSX was unknown in Canadian populations of eastern (American) oysters, Crassostrea virginica), until October 2002, when it was identified as being the cause of mass mortalities of oysters in Bras d'Or Lakes, Cape Breton, Nova Scotia - home to one of Atlantic Canada's major wild and cultured oyster producing areas. The appearance of this disease was associated with estimates of up to 90% mortality of the American oysters on several leases within the St. Patrick's Channel area of the Lakes.

MSX was identified by the Aquaculture Association of Nova Scotia (AANS) as a research priority for the shellfish industry due to oyster operations in Nova Scotia, which were impacted directly by the disease, as well as both oyster and mussel operations indirectly impacted by efforts aimed at controlling the spread of MSX to other oyster producing areas in the Canadian Maritimes region.

A workshop was held in an effort to help coordinate information on MSX disease and the agent causing it, management tools, and discussions of research needs. The recommendations that were identified on the regulatory aspect included having industry's input in the regulatory decision making process; management and control decisions made should be based on a science-risk analysis; maintain close working relationship with US counterparts; and consistency across Maritimes provinces when applying regulations. On the research side the following priorities were identified, the development of MSX resistant oysters by using selective breeding program; determine if exists resistance in oysters that have survived; record environmental parameters in Bras D'Or Lake to assess whether or not there are any correlations that could be used to anticipate peaks in prevalence and intensity of MSX outbreaks in susceptible oyster populations; use environmental and survivor information to develop circumvention measures that could be practically applied to reduce the impact of losses in advance of optimum MSX proliferation conditions, e.g., staggered seeding, early harvest, this could include analysis of processing practices that could be used to live-hold but prevent wash/holding water being discharged directly back into the marine environment; continue efforts as determining what, if any, intermediate host(s) may be involved in the transmission of H. nelsoni in Atlantic Canadian waters; and determine cause of outbreak (human intervention, hitchhiker transfer with boat traffic, pick-nicking discards, or due to changes in environmental factors.

Program Name

Aquaculture Collaborative Research and Development Program (ACRDP)


2003 - 2003



Principal Investigator(s)

Mary Stephenson

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