Salmon isavirus

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Salmon isavirus
Virus classification OOjs UI icon edit-ltr.svg
(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Negarnaviricota
Class: Insthoviricetes
Order: Articulavirales
Family: Orthomyxoviridae
Genus: Isavirus
Species:
Salmon isavirus
Synonyms

Infectious salmon anemia virus [1]

Infectious salmon anemia (ISA) is a viral disease of Atlantic salmon (Salmo salar) caused by Salmon isavirus. It affects fish farms in Canada, Norway, Scotland and Chile, causing severe losses to infected farms. ISA has been a World Organisation for Animal Health notifiable disease since 1990. [2] In the EU, it is classified as a non-exotic disease, and is monitored by the European Community Reference Laboratory for Fish Diseases.

Contents

Virology

ISA is caused by the infectious salmon anemia virus (ISAV). ISAV, a segmented RNA virus that is the only species in the genus "Isavirus", which is in the family Orthomyxoviridae, and therefore related to the influenza viruses.

The genome encodes at least 10 proteins. [3]

There are several distinct strains of the virus. The most common are a European strain and a North American strain. [4]

Pathology

ISA virus causes severe anemia in infected fish. Unlike the mature red blood cells of mammals, the mature red blood cells of fish contain DNA, and can become infected by viruses. [5] The fish develop pale gills, and may swim close to the water surface, gulping for air. However, the fish may show no external signs of illness and maintain a normal appetite, until suddenly dying. The disease can progress slowly throughout an infected farm and, in the worst cases, death rates may approach 100%. Post-mortem examination of the fish has shown a wide range of causes of death. The liver and spleen may be swollen, congested or partially already dead. The circulatory system may stop working, and the blood may be contaminated with dead blood cells. Red blood cells still present burst easily, and the numbers of immature and damaged blood cells are increased.

Infectious salmon anemia appears to be most like influenza viruses. Its mode of transfer and the natural reservoirs of infectious salmon anemia virus are not fully understood. Apart from Atlantic salmon, both sea-run Brown trout (Salmo trutta) and Rainbow trout (Onchorhyncus mykiss) can be infected, but do not become sick, so it is thought possible that these species may act as notable carriers and reservoirs of the virus.

Research shows that while several species of Pacific salmon can be carriers of the virus, even highly pathogenic strains, Pacific salmon currently show high relative resistance and no ISAV-related symptoms. However, the potential for ISAV adaptation to Pacific salmon exists. [6] [7]

Epidemiology

In the autumn of 1984, a new disease was observed in Atlantic salmon being farmed along the southwest coast of Norway. The disease, which was named infectious salmon anemia, spread slowly, but caused the death of up to 80% of salmon stock in some hatcheries. [8] By June 1988 it had become sufficiently widespread and serious to require the Norwegian Ministry of Agriculture, Fisheries and Food to declare it a notifiable disease.

In the summer of 1996, a new disease appeared in Atlantic salmon being farmed in New Brunswick, Canada. The death rate of the fish on affected farms was very high and, following extensive scientific examination of the victims, the disease was named "hemorrhagic kidney syndrome." Although the source and distribution of this disease was not known, the results of studies by Norwegian and Canadian scientists showed conclusively that the same virus was responsible for both infectious salmon anemia and hemorrhagic kidney syndrome.

In May 1998, a salmon farm at Loch Nevis on the west coast of Scotland reported its suspicions of an outbreak of infectious salmon anemia. The suspicions were confirmed, and by the end of the year, the disease had spread to an additional fifteen farms not only on the Scottish mainland but also on Skye and Shetland.

In 2008, there was an outbreak of ISA in Shetland. [9] ISA was detected in fish from just one site. There is no evidence the disease has spread beyond this site, but two nearby SSF cages are under suspicion of carrying the disease and are also now clear of fish.

In 2011, two wild Pacific salmon taken from the central coast of British Columbia were suspected to have ISA after preliminary tests showed possible evidence of the virus. However, extensive testing by the Canadian Food Inspection Agency to try to amplify and culture the virus were unsuccessful, prompting the agency to conclude that the ISA virus was not present. [10] In February 2012, a confirmed outbreak of ISA in Nova Scotia resulted in the destruction of up to 750,000 salmon. [11] In July 2012, a confirmed outbreak of infectious salmon anemia in Newfoundland and Labrador, Canada, prompted the destruction of 450,000 farmed salmon by the Canadian Food Inspection Agency [12] and an outbreak was also confirmed at another site in late 2012.[ citation needed ] In mid-2012, another outbreak was identified in Nova Scotia, with the 240,000 fish being allowed by CFIA to mature to market size before being harvested in early 2013 by the operator and processed for the consumer market. After being held by the CFIA, the fish was declared fit for human consumption despite the presence of the virus as the disease "poses no risk to human health". [13] In January 2016, it was announced that the virus had been discovered in farmed and wild salmon British Columbia for the first time. [14]

In Chile, ISA was first isolated from a salmon farm in the 1990s and described for the first time in 2001, [15] although the initial presence never resulted in widespread problems. However, since June 2007, the national industry has been dealing with a serious ISA outbreak which has not yet been completely brought under control and has been responsible for an important decline in the industry, closure of many farms and high unemployment. The virus was detected in an Atlantic salmon farm in Chiloé Archipelago in Los Lagos Region and spread to the fjords and channels of Aysén Region to the south almost immediately. [16] [17]

Transmission

The virus is spread by contact with infected fish or their secretions, or contact with equipment or people who have handled infected fish. The virus can survive in seawater, so a major risk factor for any uninfected farm is its proximity to an already infected farm.

The Lepeophtheirus salmonis sea louse, a small crustacean parasite that attacks the protective mucus, scales and skin of the salmon, can carry the virus passively on its surface and in its digestive tract. Under laboratory conditions Lepeophtheirus salmonis can passively transfer ISA. [18] It is not known whether the ISA virus can reproduce itself in the sea louse, although this is a possibility as viruses can use secondary vectors for transmission, for example Arboviruses such as dengue fever, West Nile virus, or African swine fever virus.

Diagnosis

Clinical signs and pathology may suggest infection. Viral identification is possible using immunofluorescence and PCR. [19]

Treatment and control

There is no treatment once fish are infected. [19]

ISA is a major threat to the viability of salmon farming and is now the first of the diseases classified on List One of the European Commission’s fish health regime. Amongst other measures, this requires the total eradication of the entire fish stock should an outbreak of the disease be confirmed on any farm. The economic and social consequences of both the disease and the measures used to control it are thus very far reaching.

Infectious salmon anemia is currently regarded as a serious threat not only to farmed Atlantic salmon, but also to dwindling stocks of wild Atlantic salmon. Recent research involving a multi-year study of wild Atlantic salmon from North America shows that infected salmon that survive infection generate antibodies against the virus. [20] Work is now underway to develop a vaccine against ISA.

Evolution

There are several distinct strains of the virus, some are pathogenic and some are not. The most common are a European strain and a North American strain. [4]

Genetic research into the ISA virus shows that the European and North American strains of the virus diverged from each other sometime around 1900. [21] This research points out that starting in 1879 when rainbow trout were first brought to Europe from North America, there were many transfers of fish across the Atlantic ocean which may have carried the ISA virus. Some species were introduced to Europe from North America, and some species were introduced to North America from Europe. Given that the virus did not evolve into two separate strains until around 1900, and given how many transfers of fish there were, according to this research, "At present it is therefore not possible to suggest a geographical origin of the ISA virus."

Another study suggests that this virus was introduced into Norway between 1932 and 1959 and that the original strain was the European subtype found in North America. [22] The strains found in Chile were transmitted from Norway between 1995 and 2007.

Related Research Articles

<span class="mw-page-title-main">Fish farming</span> Raising fish commercially in enclosures

Fish farming or pisciculture involves commercial breeding of fish, most often for food, in fish tanks or artificial enclosures such as fish ponds. It is a particular type of aquaculture, which is the controlled cultivation and harvesting of aquatic animals such as fish, crustaceans, molluscs and so on, in natural or pseudo-natural environments. A facility that releases juvenile fish into the wild for recreational fishing or to supplement a species' natural numbers is generally referred to as a fish hatchery. Worldwide, the most important fish species produced in fish farming are carp, catfish, salmon and tilapia.

<i>Orthomyxoviridae</i> Family of RNA viruses including the influenza viruses

Orthomyxoviridae is a family of negative-sense RNA viruses. It includes seven genera: Alphainfluenzavirus, Betainfluenzavirus, Gammainfluenzavirus, Deltainfluenzavirus, Isavirus, Thogotovirus, and Quaranjavirus. The first four genera contain viruses that cause influenza in birds and mammals, including humans. Isaviruses infect salmon; the thogotoviruses are arboviruses, infecting vertebrates and invertebrates. The Quaranjaviruses are also arboviruses, infecting vertebrates (birds) and invertebrates (arthropods).

<span class="mw-page-title-main">Atlantic salmon</span> Species of fish

The Atlantic salmon is a species of ray-finned fish in the family Salmonidae. It is the third largest of the Salmonidae, behind Siberian taimen and Pacific Chinook salmon, growing up to a meter in length. Atlantic salmon are found in the northern Atlantic Ocean and in rivers that flow into it. Most populations are anadromous, hatching in streams and rivers but moving out to sea as they grow where they mature, after which the adults seasonally move upstream again to spawn.

<i>Chicken anemia virus</i> Species of virus

Chicken anemia virus, or CAV, is currently a member of the Anelloviridae family which is found worldwide. The virus only affects chickens. CAV is a non-enveloped icosahedral single stranded DNA virus, which causes bone marrow atrophy, anemia, and severe immunosuppression. Clinical signs of CAV infection are predominantly found in young chicks due to vertical transmission from the breeder hens whose maternal antibodies have not yet formed following exposure. Clinical disease is rare today because of the widespread practice of vaccinating breeders, but the subclinical form of the disease—which normally affects birds more than two weeks of age following horizontal transmission of the virus via the fecal–oral route—is ubiquitous. The virus is very resistant in the environment, making elimination very difficult.

<span class="mw-page-title-main">Sea louse</span> Family of copepods

Sea lice are copepods of the family Caligidae within the order Siphonostomatoida. They are marine ectoparasites that feed on the mucus, epidermal tissue, and blood of host fish. The roughly 559 species in 37 genera include around 162 Lepeophtheirus and 268 Caligus species.

<span class="mw-page-title-main">Rabbit hemorrhagic disease</span> Disease that affects wild and domestic rabbits

Rabbit hemorrhagic disease (RHD), also known as viral hemorrhagic disease (VHD), is a highly infectious and lethal form of viral hepatitis that affects European rabbits. Some viral strains also affect hares and cottontail rabbits. Mortality rates generally range from 70 to 100 percent. The disease is caused by strains of rabbit hemorrhagic disease virus (RHDV), a lagovirus in the family Caliciviridae.

<span class="mw-page-title-main">Viral hemorrhagic septicemia</span> Disease of fish

Viral hemorrhagic septicemia (VHS) is a deadly infectious fish disease caused by Viral hemorrhagic septicemia virus. It afflicts over 50 species of freshwater and marine fish in several parts of the Northern Hemisphere. Different strains of the virus occur in different regions, and affect different species. There are no signs that the disease affects human health. VHS is also known as Egtved disease, and the virus as Egtved virus.

Infectious hematopoietic necrosis virus (IHNV), is a negative-sense single-stranded, bullet-shaped RNA virus that is a member of the Rhabdoviridae family, and from the genus Novirhabdovirus. It causes the disease known as infectious hematopoietic necrosis in salmonid fish such as trout and salmon. The disease may be referred to by a number of other names such as 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. IHNV is commonly found in the Pacific Coast of Canada and the United States, and has also been found in Europe and Japan. The first reported epidemics of IHNV occurred in the United States at the Washington and the Oregon fish hatcheries during the 1950s. IHNV is transmitted following shedding of the virus in the feces, urine, sexual fluids, and external mucus and by direct contact or close contact with the surrounding water. The virus gains entry into fish at the base of the fins.

<span class="mw-page-title-main">Aquaculture in Maine</span>

Maine, in the United States, has a tradition of having a large fishing and lobster industry. However today some of that industry has switched to salmon farming or aquaculture. Of late aquaculturists in Maine are most concerned about the outbreak of Infectious Salmon anemia(ISA) in the Bay of Fundy, New Brunswick. The Canadian and US salmon raising industries in the bay are geographically near one another and are therefore ecologically integrated. Machias Bay, which is 50 miles west of the Bay of Fundy, is also a location of salmon raising in Maine close to the Bay of Fundy.

<span class="mw-page-title-main">Salmon louse</span> Parasitic crustacean of fish

The salmon louse is a species of copepod in the genus Lepeophtheirus. It is a sea louse, a parasite living mostly on salmon, particularly on Pacific and Atlantic salmon and sea trout, but is also sometimes found on the three-spined stickleback. It feeds on the mucus, skin and blood of the fish. Once detached, they can be blown by wind across the surface of the sea, like plankton. When they encounter a suitable marine fish host, they adhere themselves to the skin, fins, or gills of the fish, and feed on the mucus or skin. Sea lice only affect fish and are not harmful to humans.

<span class="mw-page-title-main">Foot-and-mouth disease</span> Infectious disease affecting cattle

Foot-and-mouth disease (FMD) or hoof-and-mouth disease (HMD) is an infectious and sometimes fatal viral disease that affects cloven-hoofed animals, including domestic and wild bovids. The virus causes a high fever lasting two to six days, followed by blisters inside the mouth and near the hoof that may rupture and cause lameness.

<span class="mw-page-title-main">Aquaculture of salmonids</span> Fish farming and harvesting under controlled conditions

The aquaculture of salmonids is the farming and harvesting of salmonid fish under controlled conditions for both commercial and recreational purposes. Salmonids, along with carp and tilapia, are the three most important fish groups in aquaculture. The most commonly commercially farmed salmonid is the Atlantic salmon.

<span class="mw-page-title-main">Fish disease and parasites</span> Disease that affects fish

Like humans and other animals, fish suffer from diseases and parasites. Fish defences against disease are specific and non-specific. Non-specific defences include skin and scales, as well as the mucus layer secreted by the epidermis that traps microorganisms and inhibits their growth. If pathogens breach these defences, fish can develop inflammatory responses that increase the flow of blood to infected areas and deliver white blood cells that attempt to destroy the pathogens.

<span class="mw-page-title-main">Diseases and parasites in salmon</span> Diseases and parasites in salmon

Diseases and parasites in salmon, trout and other salmon-like fishes of the family Salmonidae are also found in other fish species. The life cycle of many salmonids is anadromous, so such fish are exposed to parasites in fresh water, brackish water and saline water.

<i>Infectious pancreatic necrosis virus</i> RNA virus infecting salmonid fish

Infectious pancreatic necrosis virus (IPNV) is a double-stranded RNA virus from the family Birnaviridae, in the genus Aquabirnavirus. Causing the highly infectious disease Infectious pancreatic necrosis, the virus primarily affects young salmonids resulting in high mortality, occasionally surpassing 90 percent in the early stages. IPNV or IPNV-like viruses have been isolated worldwide from at least 32 families of saltwater and freshwater salmonids and non-salmonids fish including salmon, flatfish, pike, eels and others. Other aquatic organisms infected include 11 molluscs and 4 species of crustaceans. Due to its wide host range and high mortality, the virus is of great concern to global aquaculture. In addition to persistence in hosts, IPNV is also perpetual in the environment, surviving across a range of conditions and capable of infecting fish with as little as 101TCID50/ml of the virus. Found in Europe, North America, South America, Africa, Asia, and Australia, the virus has led to significant losses in the mariculture of Atlantic salmon, brook trout, and rainbow trout.

Piscirickettsia salmonis is the bacterial causative agent of piscirickettsiosis, an epizootic disease in salmonid fishes. It has a major impact on salmon populations, with a mortality rate of up to 90% in some species. The type strain, LF-89, is from Chile, but multiple strains exist, and some are more virulent than others. P. salmonis and piscrickettsiosis are present in various geographic regions from Europe to Oceania to South America, but the Chilean salmon farming industry has been particularly hard-hit. Different strategies of controlling the disease and farm-to-farm spread have been the subject of much research, but a significant amount is still unknown.

Tilapia tilapinevirus, or Tilapia lake virus (TiLV), is a negative-strand RNA virus that infects both wild and aquacultured populations of tilapia. It is the only species in the monotypic genus Tilapinevirus, which in turn is the only genus in the family Amnoonviridae. Thus far it has been recorded in various regions across Asia, Africa, and South America. The virus was first discovered and identified in 2014 when the Sea of Galilee in Israel experienced a major noticeable decline in tilapia catch quantities.

Salmon Pancreas disease is caused by a species of Salmonid Alphavirus (SAV) called Salmon pancreas disease virus (SPDV). The virus was first described in 1976 in Scotland and in 1989 in Norway. It affects farmed Atlantic salmon caused by Marine SAV2 and SAV3 and has also been identified in Rainbow trout in the seawater phase caused by SAV2 where the disease is commonly referred to as Sleeping Disease (SD).

<i>Piscine orthoreovirus</i> Species of virus

Piscine orthoreovirus (PRV) is a species in the genus Orthoreovirus that infects fish exclusively, PRV was first discovered in 2010 in farmed Atlantic salmon exhibiting Heart and Skeletal Muscle Inflammation (HSMI) and has been found present at higher concentration in fish with various diseases. These diseases include HSMI, jaundice syndrome, proliferative darkening syndrome and erythrocytic body inclusion syndrome. PRV is thought to mainly affect aquacultured and maricultured fish stocks, and recent research has been focused around the susceptibility of wild stock. However, whether PRV is virulent with respect to HSMI remains a topic of debate. PRV has been in the public eye mostly due to a potential linkage to farmed Atlantic Salmon exhibiting HSMI. Public concern has been raised regarding the possibility of open ocean-net farms transmitting PRV to wild salmon populations and being a factor in declining populations. PRV has not been confirmed to be pathogenic in wild salmon stocks.

Mycobacteroides salmoniphilum is a species of bacteria from the phylum Actinomycetota belonging to the genus Mycobacteroides. It was first identified as the causative agent of mycobacteriosis in chinook salmon and steelhead trout, but has since been found to cause disease in Atlantic cod, Atlantic salmon, burbot, coho salmon, freshwater ornamental fish, and Russian sturgeon. It has also been isolated from tap water. It is not known to infect humans. M. salmoniphilum is susceptible to amikacin.

References

  1. ↑ "ICTV Taxonomy history: Salmon isavirus". International Committee on Taxonomy of Viruses (ICTV). Retrieved 13 January 2019.
  2. ↑ Kibenge, F.S.B.; Kibenge, M.J.T. (2016). "19.2 Orthomyxoviruses of fish. Genus Isavirus". In Kibenge, Frederick S. B.; Godoy, Marcos (eds.). Aquaculture Virology. Academic Press. pp. 305–315. ISBN   9780128017548.
  3. ↑ Tello, M; Vergara, F; Spencer, E (5 July 2013). "Genomic adaptation of the ISA virus to Salmo salar codon usage". Virology Journal. 10: 223. doi: 10.1186/1743-422X-10-223 . PMC   3706250 . PMID   23829271.
  4. 1 2 "Infectious Salmon Anemia" (PDF). The Center for Food Security & Public Health. Institute for International Cooperation in Animal Biologics. Iowa State University. March 2010. Retrieved 2017-11-13.
  5. ↑ Roossinck, Marilyn J. (2016). "Infectious salmon anemia virus". Virus: An Illustrated Guide to 101 Incredible Microbes. Princeton University Press. pp. 116–117. ISBN   978-0-691-16696-4.
  6. ↑ Rolland, JB; Winton, JR (September 2003). "Relative resistance of Pacific salmon to infectious salmon anaemia virus" (PDF). Journal of Fish Diseases. 26 (9): 511–20. Bibcode:2003JFDis..26..511R. doi:10.1046/j.1365-2761.2003.00473.x. PMID   14575369 . Retrieved 2017-11-13.
  7. ↑ Kibenge, FS; Kibenge, MJ; Groman, D; McGeachy, S (September 2006). "In vivo correlates of infectious salmon anemia virus pathogenesis in fish". The Journal of General Virology. 87 (Pt 9): 2645–52. doi: 10.1099/vir.0.81719-0 . PMID   16894204. Open Access logo PLoS transparent.svg
  8. ↑ Collins Edexcel International GCSE Biology, Student Book ( ISBN   978-0-00-745000-8) p. 328
  9. ↑ "Report into the Epidemiology and Control of an Outbreak of Infectious Salmon Anaemia in the Shetland Islands, Scotland". Scottish Marine and Freshwater Science Reports Aquaculture.
  10. ↑ "No Confirmed Cases of Infectious Salmon Anaemia in British Columbia". Canadian Food Inspection Agency. Archived from the original on 15 November 2011.
  11. ↑ Salmon virus confirmed at N.S. fish farm cbc.ca, from 8 March 2012
  12. ↑ "450,000 salmon to be destroyed after outbreak in Newfoundland and Labrador". The Globe and Mail. 7 July 2012. Retrieved 24 January 2013.
  13. ↑ "Infected salmon declared fit for human consumption by Canadian Food Inspection Agency". The Toronto Star. 1 February 2013. Retrieved 1 February 2013.
  14. ↑ Kibenge, Molly JT; Iwamoto, Tokinori; Wang, Yingwei; Morton, Alexandra; Routledge, Richard; Kibenge, Frederick SB (2016). "Discovery of variant infectious salmon anaemia virus (ISAV) of European genotype in British Columbia, Canada". Virology Journal. 13 (1): 3. doi: 10.1186/s12985-015-0459-1 . ISSN   1743-422X. PMC   4702313 . PMID   26732772.
  15. ↑ Kibenge F.S.B; Garate O.N; Johnson G; Arriagada R; Kibenge M.J.T; Wadowska D (2001). "Isolation and identification of infectious salmon anaemia virus (ISAV) from Coho salmon in Chile". Dis. Aquat. Org. 45 (1): 9–18. doi: 10.3354/dao045009 . PMID   11411649.
  16. ↑ "Analizan posible presencia de variante de virus ISA" (in Spanish).
  17. ↑ Godoy, MG; Aedo, A; Kibenge, MJ; Groman, DB; Yason, CV; Grothusen, H; Lisperguer, A; Calbucura, M; Avendaño, F; Imilán, M; Jarpa, M; Kibenge, FS (4 August 2008). "First detection, isolation and molecular characterization of infectious salmon anaemia virus associated with clinical disease in farmed Atlantic salmon (Salmo salar) in Chile". BMC Veterinary Research. 4: 28. doi: 10.1186/1746-6148-4-28 . PMC   2519066 . PMID   18680586.
  18. ↑ "OIE ISA fact sheet" (PDF). Archived from the original (PDF) on 2011-11-11.
  19. 1 2 Infectious Salmon Anaemia expert reviewed and published by WikiVet, accessed 10 October 2011.
  20. ↑ Cipriano, R. C. (18 May 2009). "Antibody against infectious salmon anaemia virus among feral Atlantic salmon (Salmo salar)". ICES Journal of Marine Science. 66 (5): 865–870. doi: 10.1093/icesjms/fsp124 . Open Access logo PLoS transparent.svg
  21. ↑ Krossøy, B; Nilsen, F; Falk, K; Endresen, C; Nylund, A (26 January 2001). "Phylogenetic analysis of infectious salmon anaemia virus isolates from Norway, Canada and Scotland". Diseases of Aquatic Organisms. 44 (1): 1–6. doi: 10.3354/dao044001 . hdl: 11250/108366 . PMID   11253869.
  22. ↑ Plarre, H; Nylund, A; Karlsen, M; Brevik, Ø; Sæther, PA; Vike, S (December 2012). "Evolution of infectious salmon anaemia virus (ISA virus)". Archives of Virology. 157 (12): 2309–26. doi:10.1007/s00705-012-1438-0. PMID   22886279. S2CID   6256736.

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