Aquatic Network Research Project: Preliminary investigation into a proprietary feed-based probiotic to reduce natural coldwater disease in rainbow trout aquaculture in Ontario

Project Lead:  Marcia Chiasson (Ontario Aquaculture Research Centre – University of Guelph)

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Bacterial coldwater disease (BCWD) is the single biggest production limiting infectious disease in Ontario salmonid aquaculture. BCWD is caused by Flavobacterium psychrophilum and causes disease in water temperatures between 4 and 12oC. This bacterium is established around the world, with outbreaks reported in all countries that raise freshwater salmonids, as well as other important commercially species. F. psychrophilum can live in the aquatic environment for months to years outside of a fish host and infection occurs through skin wounds. F. psychophilum spreads into muscle, creating deep ulcerations, gill necrosis, anemia, lethargy and spiral swimming. Mortality rates are highly variable, ranging from 1% in some chronic infections to 90% in epizootic infections in rainbow trout.

By volume, rainbow trout represents 94% of the total aquaculture production in Ontario and BCWD is the single biggest production limiting infectious disease. Few treatment options exist, in Ontario, treatment for BCWD is limited to two antibiotics, Oxytetracycline and Florfenicol. Oxytetracycline has a long withdrawal time at cold water temperatures (at least 80 days) and antibiotic resistance has been detected at commercial farms. Florfenicol cannot be used in fish when water temperatures are below 5oC. There are no standalone commercial non-antibiotic treatments. A pilot trial testing a would provide a valuable information on the effectiveness of a probiotic feed additive to reduce natural morbidity and mortality while improving on-farm animal welfare without using antimicrobial products.

The Cain laboratory at the University of Idaho has developed a promising probiotic treatment (C6-6) designed to be administered orally in feed. Laboratory data has shown some evidence that the probiotic can reduce natural infection of BCWD. This pilot project aims to test this probiotic in Ontario to see if the laboratory data can be replicated in a farm-environment.