Viral Diseases as a Possible Cause of Salmon Mortality in the North Pacific Ocean

• Main Authors: Evi Emmenegger, Ryan Troyer, Kyle Garver, Eric Anderson, Gael Kurath
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: IHNV; phylogeny; diversity; transmission; Canada; Djupvik; Kattegat; Nylund; Pacific; Rodger; Atlantic salmon
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.518.6076; http://www.npafc.org/new/publications/Technical Report/TR4/page 76-78(Emmenegger).pdf

Many viruses have been isolated from wild fish species from marine ecosystems. Whether these viruses can initiate an infection, cause disease, and eventually cause mortality of fish in ocean environments is not well understood. However, mortalities linked to viral infections in cultured marine fish have been reported. Three major virus pathogens that have been associated with outbreaks of cultured fish in salt water include infectious salmon anemia, viral hemorrhagic septicemia virus, and infectious hematopoietic necrosis virus. Infectious salmon anemia (ISA) is an established viral disease of cultured Atlantic salmon in the marine environment (Nylund et al. 1999). Outbreaks were first reported from Norwegian cultured Atlantic salmon (Thorud and Djupvik 1988), but reported mortalities due to ISA soon followed in Scotland (Rodger et al. 1998) and on the east coast of Canada (Lovely et al. 1999) in Atlantic salmon reared in salt water net pens. Wild fish in the waters near where the marine outbreaks occurred have tested positive for the virus, but do not exhibit any clinical signs of disease (Raynard et al. 2001). Originally, viral hemorrhagic septicemia virus (VHSV) was identified in association with high mortalities of rainbow trout reared in fresh water culture facilities in central Europe. Since 1979, VHSV has been isolated from many species of fish present in salt water from the Atlantic Ocean near continental Europe, Baltic Sea, Kattegat, Skagerrak, and the North Sea (Mortensen et al. 1999). Most wild marine fish infected with VHSV show no clinical