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Diseases of Aquatic Organisms

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DAO 69:145-151 (2006)  -  doi:10.3354/dao069145

Effects of temperature on infectivity and of commercial freezing on survival of the North American strain of viral hemorrhagic septicemia virus (VHSV)

Kristen D. Arkush1,*, Holly L. Mendonca1, Anne M. McBride1, Susan Yun2, Terry S. McDowell2, Ronald P. Hedrick2

1Bodega Marine Laboratory, PO Box 247, Bodega Bay, California 94923, USA
2Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, One Shields Avenue, Davis, California 95616, USA

ABSTRACT: Temperature affected the growth of the North American strain of viral hemorrhagic septicemia virus (VHSV) in experimentally infected cell cultures and in Pacific sardine Sardinops sagax. In addition, commercial freezing significantly reduced the infectivity of VHSV in tissues of experimentally infected sardine. Isolates of VHSV representing the geographic range of North American VHSV replicated in the EPC (Epithelioma papulosum cyprini) cell line at 10, 15 and 20°C, but the more northern isolates from British Columbia, Canada, demonstrated significantly reduced growth at 20°C compared to VHSV from more southern locations (p <0.001). An injection challenge of Pacific sardine with VHSV from California resulted in 66.7% mortality at a seawater temperature of 13°C compared to 6.7% at 20°C. Commercial blast-freezing of sardine experimentally infected with VHSV reduced median concentrations of virus in the kidney and spleen from 5.25 × 106 to 5.5 × 103 pfu (plaque-forming units) g–1. Decreased growth of the California isolate of VHSV at higher temperatures following experimental infection of the sardine and reduced virus survival following commercial freezing of infected sardine are factors that would lessen the risk of transmission of VHSV through frozen baitfishes.

KEY WORDS: VHSV · Baitfishes · Sardine · Temperature

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