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Winter ulcer disease, caused by the bacterium Moritella viscosa, is the main cause of winter ulcer disease (WUD), and may not be as restricted to cold temperatures as previously thought.

Moritella viscosa is a bacterium considered to be the main cause of cold water ulcers. This disease primarily affects marine farmed salmonid fish during cold periods and can cause ulcers, pale gills and fin rot. To date, there is no vaccine licensed for winter ulcer disease in Canada, and the demand for access to vaccines is growing. Current vaccines are based on European disease strains, and in order for the vaccine to be licensed for use in Canada, its efficacy against Canadian strains must be examined.

Until recently, WUD was thought to be restricted to cold temperatures (< 10°C); however, the disease is being more frequently observed during summer months. Because of this, WUD is becoming a high priority problem for Canadian salmon producers on both East and West coasts due to mortality, antibiotic use and the downgrading of the fish due to ulcer damage.

A project funded by DFO, Cooke Aquaculture and Novartis (Elanco) is being conducted to establish a live challenge model relevant to M. viscosa outbreaks in Canada which can be used by future vaccine development studies.

The knowledge obtained through this research will be useful in the development of future vaccines for M. viscosa, which would provide a non-antibiotic, proactive strategy for this disease. Access to a licensed vaccine would increase the sustainability of salmonid aquaculture through improved animal welfare and reduced economic losses.

The data is expected to be published in 2016.