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Blast from the Past

How Infectious Hematopoietic Necrosis (IHN) Got its Name

Beginning in the 1950s, a series of highly explosive disease outbreaks began decimating hatcheries trying to raise young Pacific salmon and trout in several locations on the west coast of North America. The losses from these diseases were so great that many of the hatcheries could not meet their production goals. Following the initial description of the disease by WFRC scientist Robert Rucker and colleagues in 1953 (Rucker et al. 1953), other researchers in Oregon, Washington, California and British Columbia, Canada soon gathered added evidence that all these diseases were likely caused by a virus; however, the diseases were being referred to by a number of names depending on the location or species affected: Chinook salmon disease, Coleman disease, Columbia River sockeye disease, Cultus Lake virus disease, Oregon sockeye disease, Sacramento River Chinook disease and sockeye salmon viral disease. In 1969, WFRC biologists Tosh Yasutake and Don Amend suggested that these different diseases were caused by the same (or a highly similar) virus and, based on the pathological changes observed in the kidney and other blood-forming tissues of affected fish, proposed the name Infectious Hematopoietic Necrosis (Amend et al. 1969). Later, scientists in Oregon, the WFRC, and elsewhere used serological and molecular assays to confirm that the diseases were all caused by different strains of the IHN virus. Today, the WFRC continues work on developing novel diagnostic methods and approaches to minimize the impact of IHN on federal, state, tribal and private sector hatcheries as well as improving our understanding of factors affecting the ecology of IHN throughout its range.

"Blast from the Past" archive.


A: Young fish dying from infectious hematopoietic necrosis (IHN) at a typical West Coast Salmon Hatchery circa 1955. B: Rainbow trout fry experimentally exposed to IHN virus. Typical signs include darkening and exophthalmia (“popeye”) as shown by the fish in the lower portion of the photo. Other external signs may include fluid accumulation in the abdomen, trailing fecal casts, and small hemorrhages in the fins and body musculature. Image provided by USGS.

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