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Ministry of Agriculture

Infectious Hematopoietic Necrosis Virus (IHNV)

Infectious Hematopoietic Necrosis (IHN) is a viral disease of wild salmon, first recognized in the 1950s. In British Columbia, the virus has been isolated in sockeye, chinook, coho, rainbow trout and Atlantic salmon as well as a variety of wild, non-salmonid marine fish. Susceptibility to disease varies between the species and with the strain of the virus.

Fisheries and Oceans Canada maintains a complete listing of the occurrence of this virus in wild stocks in British Columbia. IHN has been recently identified as the cause of significant mortalities in farmed and enhanced salmon in the Pacific Northwest.

Outbreaks of the disease in wild salmon have been reported primarily in juvenile sockeye and occasionally chum salmon in freshwater. The IHN virus has also affected immature kokanee (freshwater sockeye) adults.

Outbreaks of this disease in Atlantic salmon farms in British Columbia occurred in 1992, 1995, 1996,1997 and 2001. All reported cases occurred within the Campbell River area.

When salmon farming companies report that the IHN virus is suspected on a salmon farm in British Columbia, Ministry of Agriculture and Lands fish health staff inspect the site and collect samples to test for the disease. These samples are submitted to the Animal Health Centre Laboratory. Farms affected by the disease must immediately implement isolation measures to reduce the risk of spread of the disease.

If there are other fish farms within the same area, or other farms are believed to be at risk, ministry fish health staff will also visit these sites to test for the presence of the virus.

Ministry staff work with Fisheries and Oceans Canada staff to ensure a coordinated approach to management of any outbreak of the IHN virus.

Updated: May 16, 2004