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Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03584

    Elevated temperature inhibits Mycobacterium shottsii infection and Mycobacterium pseudoshottsii disease in striped bass Morone saxatilis

    D. T. Gauthier*, A. N. Haines, W. K. Vogelbein

    *Corresponding author:

    ABSTRACT: Mycobacteriosis occurs with high prevalence in wild striped bass of Chesapeake Bay, USA. Etiologic agents of mycobacteriosis in this system are dominated by Mycobacterium pseudoshottsii and Mycobacterium shottsii, both members of the M. ulcerans/M. marinum clade of mycobacteria. Striped bass occupying Chesapeake Bay during summer months where water temperatures regularly approach and occasionally exceed 30°C are thought to be near their thermal maximum, a condition hypothesized to drive high levels of disease and increased natural mortality due to temperature stress. M. shottsii and M. pseudoshottsii, however, do not grow or grow inconsistently at 30°C on artificial medium, potentially countering this hypothesis. In this work, we examine the effects of temperature (20°C, 25°C, 30°C) on progression of experimental infections with M. shottsii and M. pseudoshottsii in striped bass. Rather than exacerbation of disease, increasing temperature resulted in attenuated bacterial density increase in spleen and reduced pathology in spleen and mesenteries of M. pseudoshottsii-infected fish, and reduced bacterial densities in spleen of M. shottsii-infected fish. These findings indicate that M. pseudoshottsii and M. shottsii infections in Chesapeake Bay striped bass may be limited by thermal tolerances of these mycobacteria, and that maximal disease progression may in fact occur at lower water temperatures.