Development of a waterborne challenge model for Flavobacterium psychrophilum

Authors

  • Amy Long,

    1. Department of Fish & Wildlife Sciences and the Aquaculture Research Institute, University of Idaho, Moscow, ID, USA
    Current affiliation:
    1. Oregon Department of Fish & Wildlife, Department of Microbiology, Oregon State University, Corvallis, OR, USA
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  • Tyson R. Fehringer,

    1. Department of Fish & Wildlife Sciences and the Aquaculture Research Institute, University of Idaho, Moscow, ID, USA
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  • Benjamin R. LaFrentz,

    1. United States Department of Agriculture, Agricultural Research Service, Aquatic Animal Health Research Unit, Auburn, AL, USA
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  • Douglas R. Call,

    1. Paul G. Allen School for Global Animal Health, Washington State University, Pullman, WA, USA
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  • Kenneth D. Cain

    Corresponding author
    1. Department of Fish & Wildlife Sciences and the Aquaculture Research Institute, University of Idaho, Moscow, ID, USA
    • Correspondence: Kenneth D. Cain, Department of Fish & Wildlife Sciences and the Aquaculture Research Institute, University of Idaho, P.O. Box 441136, Moscow, ID 83844-1136, USA. Tel.: +1 208 885 7608; fax: +1 208 885 9080; e-mail: kcain@uidaho.edu

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Abstract

Flavobacterium psychrophilum is the causative agent of bacterial coldwater disease and can cause significant mortality in salmonid aquaculture. To better evaluate disease prevention or treatment methods for F. psychrophilum in the laboratory, a waterborne challenge model that mimics a natural outbreak is needed. Here we report on the development of a waterborne challenge model for F. psychrophilum in which we incorporated variables that may influence challenge success: specifically, scarification prior to bacterial exposure and culture of F. psychrophilum under iron-limited culture conditions to potentially increase the probability of establishing disease. Additionally, two F. psychrophilum strains, CSF 259-93 and THC 02-90, were used in this model to test whether there were virulence differences between strains. Mortality was significantly higher in scarred fish than unscarred fish (81.5 vs. 19.4%), supporting the hypothesis that disruptions in the dermal layer enhance mortality in F. psychrophilum waterborne challenges. Although mortality differences were not significant between iron-replete and iron-limited treatments, mortality was high overall (> 30%). There was a significant difference in mortality between CSF 259-93 and THC 02-90 treatments, although both strains caused high mortality in injection challenges. In conclusion, this waterborne challenge model can be used to evaluate potential disease prevention and treatment methods.

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