Disease

There are four major infectious diseases that affect salmon in industrial farming operations:

  • Infectious Salmon Anaemia (ISA)
  • Infectious Hematopoietic Necrosis (IHN)
  • Furunculosis
  • Bacterial Kidney Disease

One of the most devastating diseases is Infectious Salmon Anaemia (ISA). ISA was first detected in Norway in 1984. Since then, it has spread Scotland, eastern Canada and the USA. In 2007 an outbreak among Chilean salmon farms became an epidemic leading to the death or destruction of 70% of the country’s farmed salmon. Now for the first time the ISA virus has been detected in the North Pacific. See CAAR’s statement on the discovery of ISA in BC.

Infectious Hematopoietic Necrosis (IHN) is a virus that affects both wild and farmed salmon. Sockeye, chinook, coho, rainbow trout and Atlantic salmon can all contract the virus, but Atlantic salmon are particularly susceptible. IHN is a virus and not a bacterial infection and infected fish are not treated with antibiotics.

Furunculosis is another highly infectious disease. It is caused by the bacterium Aeromonas salmonicida, Both Atlantic and Pacific salmon are susceptible to this disease at all stages of their lifecycle. It causes large boils to appear on the surface to the skin.

In 2005 furunculosis killed 1.8 million Atlantic salmon smolts at a single commercial salmon hatchery on Vancouver Island. The disease occurs in salmon farms throughout Scotland, Norway, Canada, the Broughton Archipelago in British Columbia, and Washington State.

Bacterial Kidney Disease is a chronic systemic bacterial condition of fish of the family Salmonidae caused by Renibacterium salmoninarum. Infection can result in significant mortalities in both wild and farmed salmonids. Nearly all age groups of fish can be affected, although the disease is rare in very young fish. Losses are generally chronic, occurring over an extended period. It affects fish in freshwater and seawater environments and can have a serious economic impact, particularly in seawater Atlantic salmon farms.

The first outbreak of bacterial kidney disease in farmed salmonids in Scotland was recorded in 1976. Since thn it has been found in salmon farming operations around the world.

Vaccines and antibiotics are used in salmon aquaculture to control infections. Vaccines are given by inoculation but antibiotic treatments are typically done through medicated baths and medicated feed. The latter two methods of delivery increase the chance that antibiotics will pass into the environment, affecting wildlife and other organisms, and remaining for long periods of time.

Learn more about antibiotic use in open net-cage salmon aquaculture or learn about closed containment systems, techology that may help control the spread of disease to wild stocks.

ISA and IHN are listed as reportable diseases by the World Organization for Animal Health. This means that immediate notification to the world body is required within 24 hours if an outbreak of these disease occurs in a country or zone or compartment of the country that was previously considered to be free of that particular disease.


References

European Commission: Health and Consumer Protection Directorate General. 1999. Bacterial Kidney Disease. Report of the Scientific Committee on Animal Health and Animal Welfare. Adopted 8 December 1999

Ferguson, H.W. (1989). Systemic Pathology of Fish. Iowa State University Press. Ames

Kent, M.L. and Poppe, T.T. 1998. Diseases of seawater netpen-reared salmonid fishes. Pacific Biological Station. Namaimo.

Kent M.L., G.S. Traxler, D. Kieser, J. Richard, S.C. Dawe, G. Prosperi-porta, J. Ketcheson, T.P.T. Evelyn. Survey of Salmonid pathogens in Ocean-caught Fishes in British Columbia Canada. Department of Fisheries and Oceans, Pacific Biological Station, Nanaimo, British Columbia, V9R 5K6, Canada. In American Fisheries Society’s Fish Health Newsletter, Volume 26, 1998.

McDaniel T.R., Pratt K.M., Meyers T.R., Ellison T.D., Follet J.E., Burke J.A. 1994. ALASKA SOCKEYE SALMON CULTURE MANUAL. Special Publication Number 6. Alaska Department of Fish and Game, Commercial Fisheries Management and Development Division, Juneau, Alaska 99802-5526.

Traxler, G.S. and J. Richard. 1996. First detection of infectious hematopoietic necrosis virus in marine fishes. Fish Health Section/AM. Fish. Soc. Newsletter 24(3):7.

World Organization for Animal Health 2001. International Aquatic Animal Health Code. Part 2.