Viral Hemorrhagic Septicemia Virus (VHSV) - MMFS

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Fish Virus

Viral Hemorrhagic Septicemia Virus (VHSV)

Juvenile herring with classic signs of VHS

Juvenile herring with classic signs of VHS including focal hemorrhaging around the eyes, mouth, and fin bases. Credit: Paul Hershberger, USGS - Western Fisheries Research Center. (Public domain)

The North American strain of VHSV (Genogroup IVa) is periodically associated with epizootics and fish kills in wild marine fishes, where it can be highly virulent.  The capture and confinement of Pacific herring, Pacific sandlance, and surf smelt routinely results in locally severe VHS epizootics among the confined populations. As larvae and juveniles, Pacific herring are highly susceptible to VHS, with laboratory exposures often resulting in 66-100% mortality. In the wild, juvenile herring become exposed to VHSV as early as 3 months post-hatch, shortly after their metamorphosis from larvae. Herring that survive exposure to VHSV develop protective antibodies that subsequently confer life-long protection from recurrences of the disease.