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Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03645

    Effect of water temperature on frog virus 3 disease in hatchery-reared pallid sturgeon Scaphirhynchus albus

    Natalie K. Stilwell*, Salvatore Frasca Jr. , Lisa L. Farina, Kuttichantran Subramaniam, Kamonchai Imnoi, Pedro H. Viadanna, Lacey Hopper, Jeffrey Powell, James Colee, Thomas B. Waltzek

    *Corresponding author:

    ABSTRACT: Ranaviruses are large double-stranded DNA viruses within the genus Ranavirus (family Iridoviridae) that are being detected with increasing frequency among aquacultured and wild fishes. In the USA, multiple sturgeon hatcheries have experienced ranavirus epizootics resulting in significant morbidity and mortality in young-of-year. Significant economic losses have resulted from repeated outbreaks of frog virus 3 (FV3), the type species for the genus Ranavirus, in young-of-year pallid sturgeon Scaphirhynchus albus reared at a hatchery within the Missouri River Basin. Water temperature and stocking density are known to influence the severity of ranavirus disease in ectothermic vertebrates. To determine the effect of water temperature on ranavirus disease in hatchery-raised S. albus, we conducted FV3 challenges at two temperatures (17 and 23˚C) and compared cumulative survival over a 28-day study period. A mean (± standard error) survival rate of 57.5 ± 13.2% was observed in replicate tanks of sturgeon maintained at 23˚C, whereas no mortality was observed among sturgeon maintained at 17˚C. In a second challenge study, we compared the effect of water temperature on disease progression by regularly sampling fish over the study period and evaluating lesions by histopathology and in situ hybridization, and by assessing viral titer and load in external and internal tissues using virus isolation and qPCR, respectively. Results suggest temperature manipulation may be an effective mitigation strategy that sturgeon hatcheries can employ to minimize ranavirus-associated disease.