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Research Document 2019/022

Characterization of Yersinia ruckeri and enteric redmouth disease (ERM) to inform pathogen transfer risk assessments in British Columbia

By Wade, J.


Yersina ruckeri is a gram-negative enterobacterium that causes enteric redmouth disease (ERM), a septicemic bacterial disease of fishes. It is a common pathogen of salmonids and particularly Rainbow Trout (Oncorhynchus mykiss). All salmonid life history stages are susceptible, but the disease is most acute in Rainbow Trout fry and fingerlings and presents as chronic in older, larger fish.

Yersinia ruckeri and ERM are most commonly found in freshwater life history stages but have been reported from fish in the marine environment. Y. ruckeri is often found in freshwater salmonid hatcheries but can be prevented with proper egg disinfection and husbandry, including minimizing fish stress and vaccination. Should disease occur, it is readily and effectively treatable with antibiotics.

Yersinia ruckeri and ERM have been identified in both the freshwater and marine life history stages of Atlantic Salmon although, reports in the marine life history stage are not common. Outbreaks have occurred in Atlantic Salmon (Salmo salar) in both marine and freshwater. Y. ruckeri isolates from Sockeye Salmon (O. nerka) have been used experimentally but it was not possible, based on the literature, to determine if disease in this species has occurred. Although there are several genetic strains of Y. ruckeri, in cultured salmonids, ERM is mainly caused by the highly virulent, serotype O1a, biotype 1. Outbreaks have occurred in salmonids attributable to other serotypes but to date, there is no indication that new isolates or serotypes have been identified in Atlantic Salmon in North America.

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