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Western Fisheries Science News, December 2015 | Issue 3.12

How Infectious Hematopoietic Necrosis (IHN) Got its Name

A: Young fish dying from infectious hematopoietic necrosis (IHN).
A: Young fish dying from infectious hematopoietic necrosis (IHN) at a typical West Coast Salmon Hatchery circa 1955. Image provided by USGS.

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.  

Among the recent work at the WFRC related to IHNV:

B: Rainbow trout fry experimentally exposed to IHN virus.
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.

In 2003, researchers from the WFRC, University of Washington, and the Danish Veterinary Laboratory, published their findings on the evolutionary relationships of IHNV in North America (Kurath et al., 2003).  Their analysis revealed three major virus genogroups in North America, designated U, M and L.  The researchers found that the U genogroup was mostly isolated from sockeye salmon in the northern (‘upper’) portion of the IHNV range, but it also included IHNV isolates from Chinook salmon and steelhead trout in the Columbia River basin.  The M genogroup IHNV was mostly isolated from steelhead and rainbow trout in the Columbia River basin (the ‘middle’ portion of the IHNV range). The L genogroup IHNV isolates were mostly recovered from Chinook salmon in California and Southern Oregon (the ‘lower’ portion of the IHNV range).  These genogroups are used today in assessing risks associated with detection of IHNV throughout the Pacific Northwest.

In 2006, researchers from the WFRC and University of Washington compared the relative virulence of the U, M and L IHNV types in sockeye salmon and rainbow trout (Garver et al. 2006). This study confirmed those previous observations that different IHNV strains can vary in their ability to cause disease depending on the salmonid species. The U genogroup viruses caused the highest mortality in sockeye salmon and kokanee (landlocked sockeye salmon) while the M genogroup caused the highest mortality in rainbow trout. Most recently, a study of M genogroup IHN viruses revealed increasing virulence over time for specific types that have emerged in Columbia River basin steelhead trout since 1980 (Breyta et al. 2016).

All of these studies inform ongoing projects aimed at understanding the ecology and evolution of IHNV. 

Newsletter Author - Debra Becker



USGS Discusses Early Detection Monitoring of Aquatic Invasions in the Columbia River Basin:  On December 16, 2015, research scientist Tim Counihan of the WFRC and Stephen Bollens of Washington State University (WSU) presented findings of a three year study that developed techniques for early detection monitoring of quagga and zebra mussels in the Columbia River Basin (CRB) to the Northwest Power and Conservation Council in Portland, OR. The CRB has already experienced a recent invasion of several species of Asian copepods (small planktonic crustaceans), which raises concerns about how these invasions may increase ecosystem stress and reduce ecosystem resiliency to additional invasions from other species such as zebra and quagga mussels. The research was supported by the Power Division of the Bonneville Power Administration and in-kind contributions from both WSU and USGS. Although tremendous progress was made during 2012-15, the findings highlight the need for additional early detection research and systematic sampling to reduce the risk of introduction and establishment of aquatic invasive species, especially quagga and zebra mussels, in the Columbia River given the potential to impact both the ecosystem and the operation of the Federal Columbia River Power System. 

USGS Hosts Tour for NOAA Western Regional Collaboration Team:  On December 9, 2015, WFRC Director Jill Rolland gave an overview and tour of the WFRC in Seattle, WA, to the NOAA Western Regional Collaboration Team. The 20-member team reflects the diversity of  NOAA’s presence in the region, comprised of subject matter experts (including fisheries, oceans, climate, and weather), one partner organization (Sea Grant), and team members throughout offices across the region. As part of the regional meeting, the team was interested to learn more about WFRC through an overview and tour of the lab facilities at the research center.

USGS Presents Research at Anadromous Fish Evaluation Program Review: On December 8, 2015, research fishery biologist Ken Tiffan gave two presentations at the U.S. Army Corps of Engineers’ annual Anadromous Fish Evaluation Program review in Walla Walla, WA. The first presentation titled, “Smallmouth bass predation on juvenile salmonids in Lower Granite Reservoir on the Snake River, 2013”, summarized predation results from 2013 during which 168,000 salmonids were lost to predation. The second presentation titled, “Non-native food sources in the lower Snake River and their relation to juvenile salmon and resident species,” summarized the ecology and significance of three species in the Snake River. In brief, the opossum shrimp Neomysis may be beneficial to juvenile salmon by providing an abundant food supply. Siberian prawns are probably having a neutral effect on the food
web as they occupy deep habitats and have little interactions with other fishes. Native sandrollers have dramatically increased in abundance and may be competitors with juvenile salmon or act as a predation buffer.

USGS Scientist Travels to China as Part of a World Organization for Animal Health International Project: On December 7-14, 2015, Jim Winton, visited with staff of the Key State Laboratory of Aquatic Animal Diseases in Shenzhen, China as part of an international project funded by the World Organization for Animal Health (OIE). The project involves the exchange of principal investigators and staff between the two laboratories with a goal to increase the number of OIE Reference Laboratories in the world, especially in countries with significant problems from diseases listed by the OIE. The WFRC is currently the sole OIE Reference Laboratory for infectious hematopoietic necrosis (IHN), a virus disease of salmonid fish that was originally endemic to North America, but has emerged to become a significant problem affecting coldwater aquaculture in Asia. The goal of the project is to provide the training and experience to allow the Key State Laboratory of Aquatic Animal Diseases to be designated as a new OIE Reference Laboratory for IHN. While in China, he also presented an invited seminar at the Beijing Fisheries Research Institute.


New Publication on the Health and Condition of Juvenile Endangered Suckers in the Upper Klamath Basin: High mortality in the first year of life limits recruitment to the adult spawning stage of Lost River and shortnose suckers in the Upper Klamath Lake, Oregon. In a recent USGS report, growth, body condition, triglyceride content, histology, and chemical composition of some tissues were compared between suckers in Upper Klamath Lake and another population in Clear Lake Reservoir, California, that appears to have relatively high early life stage survival. Researchers found that water-quality dynamics, as well as species and age compositions of juvenile sucker populations differed substantially between lakes. Differences in sucker health and condition between lakes were considered the most promising clues to the causes of differential juvenile sucker morality between lakes. Recommendations on future avenues of research for understanding early life stage mortality in these endangered species are made.

Burdick, S.M., D.G. Elliott, C.O. Ostberg, C.M. Conway, A. Dolan-Caret, M.S. Hoy, K.P. Feltz, and K.R. Echols. 2015. Health and condition of endangered juvenile Lost River and shortnose suckers relative to water quality and fish assemblages in Upper Klamath Lake, Oregon, and Clear Lake Reservoir, California: U.S. Geological Survey Open-File Report 2015-1217, 56 p.

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