Isolation of the North American strain of viral hemorrhagic septicemia virus (VHSV) associated with epizootic mortality in two new host species of Alaskan marine fish

Thousands of dead Pacific herring Clupea pallasi, Pacific hake Merluccius p roductus and walleye pollock Theragra chalcogramma were reported in Lisians ki Inlet near Pelican, Alaska, USA, on August 1, 1998. The Pacific hake and pollock continued to die through the end of September. Virological examina tions of dead fish identified the North American strain of viral hemorrhagi c septicemia virus (VHSV) from all 3 species of fish as well as associated high virus titers and possible histopathological lesions. No other primary fish pathogens were detected and there were no apparent environmental cause s for fish mortality. This is the first report of VHSV in 2 new Alaskan fis h host species and of a natural epizootic associated with VHSV in which pro gressive mass mortality was observed simultaneously in herring and 2 other species of free-ranging marine fish.