Infectious haematopoietic necrosis virus (IHNV) is a rhabdovirus that causes an economically significant disease in Pacific salmon (Oncorhynchus spp.), Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss). The disease was first observed in cultured sockeye salmon (Oncorhynchus nerka) on the west coast of North America (Rucker et al., 1953; Watson et al., 1954) and IHNV was first isolated in cell culture by Wingfield et al. (1969). Typically, IHNV causes necrosis of the haematopoietic tissues, and the disease was named infectious haematopoietic necrosis (IHN) by Amend et al. (1969). Economic losses from IHNV can be a direct consequence of fish mortality, or indirect from regulations restricting the movement of IHNV-infected fish or the destruction of infected fish stocks to control the spread of the virus. Infectious haematopoietic necrosis is the most important constraint to the profitability and continued growth of the US commercial salmonid aquaculture industry, with lost revenue in the Idaho trout industry estimated at $3 million annually (Congleton, 1988). At government hatcheries along the Columbia River, upwards of 70 million fish and eggs have been destroyed as a result of IHNV infection since 1981. The value of these fish has been conservatively estimated at $350 million (Leong et al., 1995). In addition to the Pacific North-West, IHNV is also endemic in salmonid fish in Japan and has been isolated in several countries in Asia and Europe.

Several excellent reviews of IHN and IHNV have been published (Pilcher and Fryer, 1980a,b; Nicholson, 1982; Wolf, 1988). This chapter will review all aspects of IHNV and IHN.

© CAB INTERNATIONAL 1999. Fish Diseases and Disorders, Volume 3: Viral, Bacterial and Fungal Infections (eds P.T.K. Woo and D.W. Bruno)

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