For more information

Publications:

Batts, W.N., Arakawa, C.K., Bernard, J., and Winton, J.R., 1993, Isolates of viral hemorrhagic septicemia virus from North America and Europe can be detected and distinguished by DNA probes: Diseases of Aquatic Organisms, v. 17, p. 67-71.

Kocan, R., Bradley, M., Elder, N., Meyers, T., Batts, W., and Winton, J., 1997, The North American strain of viral hemorrhagic septicemia virus is highly pathogenic for hatchery-reared Pacific herring (Clupea pallasi): Journal of Aquatic Animal Health, v. 9, p. 279-290.

Meyers, T.R., and Winton, J.R., 1995, Viral hemorrhagic septicemia virus in North America: Annual Review of Fish Diseases, v. 5, p. 3-24.

Genetic Tool Differentiates Strains of Deadly Fish Virus, Saves Fish

Millions of hatchery-raised salmon and trout have been saved from possible destruction because DNA probes developed by USGS biologists can now be used to distinguish between European and North American strains of a highly feared fish disease agent, viral hemorrhagic septicemia virus (VHSV).

To safeguard the health of salmon and trout in North America, Federal and State fish disease control policies require immediate quarantine, killing of fish, and disinfection of hatcheries upon discovery of certain exotic fish pathogens. In 1988 and 1989, more than 5 million fish and eggs in western Washington were destroyed after scientists discovered VHSV in North America during routine examinations of adult salmon returning to hatcheries from the Pacific Ocean. Until then, scientists believed that VHSV was confined to Europe, where it has caused high mortality and losses of over $40 million a year at rainbow trout farms.

Scientists at the USGS Western Fisheries Research Center in Seattle, Washington, began research that has completely changed the understanding of the geographic distribution and epidemiology of VHSV. Their partners in this work are the Washington Department of Fisheries and Wildlife, Northwest Indian Fisheries Commission, Alaska Department of Fish and Game, Department of Fisheries and Oceans Canada, and U.S. Fish and Wildlife Service.

Using laboratory facilities at Seattle and Marrowstone Island, Washington, USGS scientists found that the North American strain of VHSV was much less virulent for salmon and trout than the European variety. Additional findings of VHSV in Pacific cod and Pacific herring led to the realization that this strain of VHSV is endemic among marine fish species along the Pacific coast of North America.

USGS scientists applied techniques from molecular biology -- genetic fingerprinting and sequence analysis of the genome -- to show genetic differences between North American and European strains. They used this information to develop three DNA probes and sets of primers for DNA amplification to rapidly identify the virus and distinguish the strain. This

USGS scientist loading a "dot-blot" device for identification of viral hemorrhagic septicemia virus and differentiation of European and less virulent North American strains.

Destruction of several million fish at the Makah National Fish Hatchery following initial discovery of viral hemorrhagic septicemia virus at the facility.

method has greatly increased the speed and precision of detecting VHSV. Within hours, instead of weeks, scientists can now determine the identity of the fish disease agents. These diagnostic tools have been transferred to the U.S. Fish and Wildlife Service, and tribal, State, and Canadian fish disease diagnostic laboratories, as well as the private sector's aquaculture industry.

Results from the USGS studies have been of critical importance to the State, Federal, and tribal fishery programs in the Western United States, where management policies have changed. Recent work by these scientists has shown that the North American strain of VHSV is quite lethal for Pacific herring. These findings may help to explain the decline in certain stocks of this valuable commercial species in Alaska; however, the costly destruction of all fish at salmon and trout hatcheries where the North American strain of VHSV is found is no longer required.

Results of the test using strains of the viral hemorrhagic septicemia virus from North America (left column) and Europe (right column). The strip on the left has been reacted with a non-radioactive probe that recognized all strains of the virus. The middle strip was reacted with a probe that reacted only with the North American strains while the right strip was reacted with a probe for the European strain. The test takes only a few hours rather than the traditional cell culture-based assay requiring two weeks.