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ARS Home » Northeast Area » Leetown, West Virginia » Cool and Cold Water Aquaculture Research » Research » Publications at this Location » Publication #367539

Research Project: Integrated Research to Improve On-Farm Animal Health in Salmonid Aquaculture

Location: Cool and Cold Water Aquaculture Research

Title: In vivo experiments provide evidence that Flavobacterium psychrophilum strains belonging to multilocus sequence typing clonal complex ST191 are virulent to Rainbow Trout (Oncorhynchus mykiss)

item KNUPP, CHRISTOPHER - Michigan State University
item FAISAL, MOHAMED - Michigan State University
item Wiens, Gregory - Greg
item BRENDEN, TRAVIS - Michigan State University
item LOCH, THOMAS - Michigan State University

Submitted to: Journal of Aquatic Animal Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: Bacterial cold water disease is a significant cause of fish loss for trout farmers. The disease is caused by the bacterium Flavobacterium psychrophilum. We have recently determined there are many strains of F. psychrophilum but it is unknown if these strains differ in their ability to cause disease. We tested ten isolates from five strain types and found all were virulent. However, disease caused by some strain types appeared to vary with fish size and age. Strain types with the highest virulence are prioritized for future research to prevent and control bacterial cold water disease.

Technical Abstract: Flavobacterium psychrophilum, the causative agent of bacterial coldwater disease (BCWD), causes significant economic losses worldwide, particularly in farmed Rainbow Trout Oncorhynchus mykiss. Over the last decade, multilocus sequence typing (MLST) has revealed >30 clonal complexes (CCs) globally, comprised of >320 F. psychrophilum sequence types (STs). Despite the large number of CCs worldwide, CC-ST10, which is currently the largest CC affecting Rainbow Trout, has been the primary focus of F. psychrophilum virulence studies, leaving the role of other CCs as primary causes of BCWD epizootics unclear. To this end, fingerling Rainbow Trout were experimentally challenged with F. psychrophilum strains belonging to the CC now recognized as the second largest in the world (e.g., CC-ST191) alongside CC-ST10 strains. Cumulative percent mortality was 100% in 7 month old Rainbow Trout and between 27.8% and 61.1% in 8 month old Rainbow Trout, respectively. All examined F. psychrophilum STs were virulent to Rainbow Trout and no significant differences in virulence between CC-ST10 and CC-ST191 were detected. Due to their wide distribution and high pathogenic potential, both CC-ST191 and CC-ST10 F. psychrophilum strains are excellent candidates for further research aimed at preventing and controlling BCWD.