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Comparison of field isolates of Moritella viscosa: characterization and in vivo challenge model development to address winter ulcer mitigation in Canada



Moritella viscosa is a bacteria that is 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. Winter ulcer disease is becoming a high priority problem for Canadian producers, and while mortalities vary according to site, a large number of the remaining fish are also affected by the disease. 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.

This ACRDP project aims to establish a live challenge model (in which the animal is given the bacteria to assess their response) relevant to M. viscosa outbreaks in Canada which can be used for future vaccine development studies. First, a series of in vitro (cell culture) studies will be performed to better understand how the bacteria grow in the presence of salmon cells and determine what differences in immune response may occur between Canadian strains. Secondly, two sources of bacteria will be selected from the study to be used to develop a disease challenge model using live Atlantic Salmon. The challenge model will help to determine: a good candidate strain that will produce testable predictable results; a challenge exposure method; and a culture temperature for exposing animals to Canadian disease strains.

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 due to mortality, antibiotic use, and the downgrading of the product due to ulcer damage.

This project supports the optimal fish health objective of the Aquaculture Collaborative Research and Development Program (ACRDP), and pertains to the 2014-15 national ACRDP priority of health management by increasing knowledge, understanding and developing better management practices with respect to disease impacts on finfish cultured species.

Program Name

Aquaculture Collaborative Research and Development Program (ACRDP)


2014 - 2015



Principal Investigator(s)

Steven Leadbeater

Collaborative Partner(s)

Cooke Aquaculture Inc.

Novartis Animal Health Canada Inc.

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