Viral hemorrhagic septicemia

Viral hemorrhagic septicemia (VHS) is a deadly infectious fish disease caused by the"Viral hemorrhagic septicemia virus" (VHSV, or VHSv). It afflicts over 50 species of freshwaterand marine fish in several parts of the northern hemisphere. [http://www.cfsph.iastate.edu/Factsheets/pdfs/viral_hemorrhagic_septicemia.pdf Disease Factsheets: Viral Hemorrhagic Septicemia] Iowa State University, The Center for Food Security & Public Health. Last updated May 17, 2007. Retrieved on 2007-07-12.] VHS is caused by the viral hemorrhagic septicemia virus (VHSV), different strains of which 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 VHSV as "Egtved virus."McAllister, Philip E. [http://www.lsc.usgs.gov/fhb/leaflets/83.asp Fish Disease Leaflet 83: Viral Hemorrhagic Septicemia of Fishes] . United States Department of the Interior, U.S. Fish and Wildlife Service. 1990. Retrieved on 2007-07-12.]

Historically, VHS was associated mostly with freshwater salmonids in western Europe,documented as a pathogenic disease among cultured salmonids since the 1950s. [http://www.virustaxonomyonline.com/virtax/lpext.dll/vtax/agp-0013/nsr05/nsr05-sec1-0005 Description of Viruses: Family Rhabdoviridae, Genus Novirhabdovirus] . "Virus Taxonomy Online: Seventh Report of the International Committee on Taxonomy of Viruses". 2000. Retrieved on 2007-07-12.] It was first discovered in the US in 1988 among salmon returning from the Pacific in Washington State. [Meyers, T. R., J. Sullivan, E. Emmenegger, J. Follett, S. Short, W. N. Batts, and J. R. Winton. [http://www.int-res.com/articles/dao/12/d012p167.pdf Identification of viral hemorrhagic septicemia virus isolated from Pacific cod Gadus macrocephalus in Prince William Sound, Alaska, USA] . "Diseases of Aquatic Organisms". Vol. 12: 167-175. 1992-04-23. Retrieved on 2007-07-12.] This North American genotype was identified as a distinct, more marine-stable strain than the European genotype. VHS has since been found afflicting marine fish in the northeasternPacific Ocean, the North Sea, and the Baltic Sea. Since 2005, massive die-offs have occurred amongst a wide variety of freshwater species in the Great Lakes region of North America.

Virus Taxonomy

Taxobox
name = "Viral hemorrhagic septicemia virus"
virus_group = V
ordo = "Mononegavirales"
familia = "Rhabdoviridae"
genus = "Novirhabdovirus"
species = "Viral hemorrhagic septicemia virus"VHSV is a negative-sense single-stranded RNA virusof the order "Mononegavirales", family "Rhabdoviridae", and genus "Novirhabdovirus". [ [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=11287&lvl=3&lin=f&keep=1&srchmode=1&unlock NCBI Taxonomy browser (Viral hemorrhagic septicemia virus).] NCBI Taxonomy Database. United States Department of Health and Human Services, National Institutes of Health, National Library of Medicine, National Center for Biotechnology Information. Retrieved on 2007-07-14.] (ICTV virus classification, unlike biological classification, begins with the order.) [http://www.virustaxonomyonline.com/virtax/lpext.dll/vtax/ictvb/ictvb-sec1-0001 The Virus Species Concept: Introduction] "Virus Taxonomy Online: Seventh Report of the International Committee on Taxonomy of Viruses". 2000. Retrieved on 2007-07-12.] Its NCBI-assigned Taxonomy ID is 11287. Another related fish rhabdovirus in the "Novirhabdovirus" genus is the Infectious hematopoietic necrosis virus (IHNV), which causes infectious hematopoietic necrosis (IHN) disease in solmonidae.

The viral cause of the disease was discovered in 1963 by M. H. Jenson.Kipp, Rebekah M. and Anthony Ricciardi. [http://www.glerl.noaa.gov/res/Programs/ncrais/docs/vhs_factsheet.pdf VHS Factsheet] . 2006-12-08. Retrieved on 2007-07-16.] The virus is an enveloped, bullet-shaped particle, about 180 nm long by 60 nm in diameter, covered with 5 to 15 nm long peplomers.

Virus subtypes

Different isolates (unique strains) of VHSV are typically grouped by genotyping. It is found that genotype groups are divided more geographically than by host species. Earlier studies used different numbering systemsNishizawa, T., H. Iida, R. Takano, T. Isshiki, K. Nakajima, K. Muroga. [http://www.int-res.com/articles/dao2002/48/d048p143.pdf Genetic relatedness among Japanese, American and Europeanisolates of viral hemorrhagic septicemia virus (VHSV) based on partial G and P genes] "Diseases of Aquatic Organisms", Vol. 48: 143–148, 2002. 2002-03-11. Retrieved on 2007-07-16.] [Thiéry, R., C. de Boisséson, J. Jeffroy, J. Castric, P. de Kinkelin, A. Benmansour. [http://www.int-res.com/articles/dao2003/52/d052p029.pdf Phylogenetic analysis of viral haemorrhagic septicaemia virus (VHSV) isolates from France (1971–1999)] "Diseases of Aquatic Organisms", Vol. 52: 29–37, 2002. 2002-11-07. Retrieved on 2007-07-16.] , but the following system has come into common usage based on genotype similarity based on sequencing of the N- and G-genes. Types I-III are enzootic to Europe, and Type IV to North America, and Type I and type IV isolates are further subdivided, as follows:

Type I-a was the only strain known from VHSV's discovery in 1963 until the late 1988, isolated to fish farms in continental Europe, affecting primarily rainbow trout and occasionally brown trout or pike.Crane, M. [http://www.oie.int/eng/normes/fmanual/A_00022.htm Chapter 2.1.5: Viral Hemorrhagic Septicaemia] Manual of Diagnostic Tests for Aquatic animals 2006. Retrieved 2007-07-16.]

In 1988, the first marine strain of VHSV, now designated type IV, was found in normal-appearing salmon returning from the Pacific to rivers of Washington State. This strain and other marine strains was not lethal to rainbow trout. The discovery prompted further studies, and by the mid-1990s, marine VHSV was found in eight species along the northern North America's Pacific coast, and 14 species in and around the Atlantic's North Sea. [ [http://www.daff.gov.au/__data/assets/word_doc/0012/42501/2003-15a.doc Importation of pilchards (Sardinops sagax) for direct introduction into natural waters: Biosecurity policy review of viral haemorrhagic septicaemia virus (VHSV), Draft Report, June 2003] . Commonwealth of Australia. 2003. Retrieved 2007-07-16.] 1996 saw the first VHSV in Japan, among Japanese flounder farmed in the Seto Inland Sea, [Isshik, T., T. Nishizawa, T. Kobayashi, T. Nagano, T. Miyazaki. [http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=11775799 An outbreak of VHSV (viral hemorrhagic septicemia virus) infection in farmed Japanese flounder Paralichthys olivaceus in Japan.] (Pubmed abstract). "Disease of Aquatic Organisms", 2001-11-08;47(2):87-99.] and different genotypes have appeared in different areas since then. Type IV was later found off North America's northern Atlantic coast,in Atlantic herring ("Clupea harengus") [Elsayed E., M. Faisal, M. Thomas, G. Whelan, W. Batts, J. Winton. [http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2761.2006.00755.x?journalCode=jfd solation of viral haemorrhagic septicaemia virus from muskellunge, "Esox masquinongy" (Mitchill), in Lake St Clair, Michigan, USA reveals a new sublineage of the North American genotype] "Journal of Fish Diseases" Volume 29 Issue 10 Page 611-619, 2006-October. Retrieved 2007-07-18.] mummichog ("Fundulus heteroclitus"), stickleback ("Gasterosteus aculeatus aculeatus"), brown trout ("Salmo trutta"), and striped bass ("Morone saxatilis"), as well as dozens of freshwater species in the Great Lakes.

VHSV continues to be found in new geographical areas, in new species of fish. This is thought to represent both the spread of the virus into new areas, as with VHSV egg and live fish transfers from North America to Asia, or feeding of raw marine fish to inland farmed trout in Finland, as well as discovery of existing populations, as with an apparently well established marine reservoir in the Black Sea.

Great Lakes Type IV-b

The Type IV-b strain of VHSV has been spreading among freshwater fish in the Great Lakes region sinceat least 2003, resulting in some massive die-offs since 2005 of many species in the affected lakes. Originally found off the Atlantic coast of Canada, it was considered a low mortality marine strain. Its firstdetection in freshwater was in Lake Ontario in 2005, and then in an archived 2003 sample from Lake St. Clair. [http://www.colaqua.org/articles.htm CSU Research Proposal - "Economic impacts of private sector aquaculture-based recreational fishing in the western USA"] Colorado Aquaculture Association. Retrieved on 2007-07-12.]

The North American genotype of the virus, in addition to moderate mortality to salmonid species, including various varieties of trout, is also proving virulent among a wide variety of warm-water species previously considered resistant to VHS. The Great Lakes region variant has killed lake trout, steelhead trout, chinook salmon, yellow perch, gobies, emerald shiners, muskies, whitefish, and walleye. While the European strain of VHSV is particularly deadly to rainbow trout, the Great Lakes region variant affects the species only mildly, as is typical with primarily marine genotypes.

Great Lakes Regional Distribution

An archived 2003 sample from Lake St. Clair of Great Lakes muskellunge is the earliest confirmed case of VHSV within the Great Lakes region.Whelan, Gary E. [http://www.michigan.gov/documents/dnr/Viral-Hemorrhagic-Septicemia-Fact-Sheet-11-9-2006_178081_7.pdf Viral Hemorrhagic Septicemia (VHS) Briefing Paper] . Michigan Department of Natural Resources. 2007-02-26. Retrieved 2007-07-13.] Lake St. Clair connects to Lake Erie through the Detroit River to the south, and to Lake Huron through the St. Clair River to the north. The sample was not tested for VHS until 2005, after the disease was detected in Lake Ontario.

2005 samples of Lake Ontario freshwater drum and Lake Huron lake whitefish were infected with VHS. Initially classified as an unknown rhabdovirus, the Lake Ontario sample was confirmed to be VHSV in 2006, while the Lake Huron sample was confirmed to be VHSV in 2007.

2006 saw mass die-offs from VHS in Lake Erie, the St. Clair River, the Detroit River, and the St. Lawrence River, which connects the Great Lakes to the Atlantic Ocean. VHS was further detected in the Niagara River, which connects Lake Erie to Lake Ontario. [ [http://web.vet.cornell.edu/Public/FishDisease/AquaticProg/highlights/VHSV/VHSV%20NYS%20Public.htm Viral Hemorrhagic Septicemia in New York State] "Highlights". Cornel University, College of Veterinary Medecine,Department of Microbiology and Immunology, Aquatic Animal Health Program. Retrieved 2007-07-14.] It was also found in a walleye die-off in the landlocked inland Conesus Lake, the westernmost of the Finger Lakes in western New York state. [ [http://www.dec.ny.gov/outdoor/25328.html Viral Hemorrhagic Septicemia (VHS) in New York] . New York State Department of Environmental Conservation. Retrieved 2007-07-14.] This was the first case in the region outside waters contiguously connected to the Great Lakes.

On May 12, 2007, the Wisconsin DNR announced the likely presence of VHS in Wisconsin's inland Little Lake Butte des Morts. Preliminary tests of samples of freshwater drum collected on May 2 were positive, and the announcement came amidst a die-off of hundreds of freshwater drum there and on neighboring Lake Winnebago. [ [http://dnr.wi.gov/org/caer/ce/news/rbnews/BreakingNews_Lookup.asp?id=543 Fish likely infected with deadly virus found in Little Lake Butte des Morts; Menasha Lock closed; Public asked to take steps to stop the spread] . (News release). Wisconsin Department of Natural Resources. 2007-05-12. Retrieved 2007-07-13.] Preliminary tests later indicated VHS in specimens from Lake Winnebago. [ [http://dnr.wi.gov/org/caer/ce/news/rbnews/BreakingNews_Lookup.asp?id=557 Lake Winnebago Fish Preliminarily Test Positive for VHS] . (News release). Wisconsin Department of Natural Resources. 2007-05-18. Retrieved 2007-07-13.] The lakes drain through the Fox River to Lake Michigan's Green Bay.

On May 17, 2007, the Michigan DNR confirmed the presence of VHS in the Michigan's inland Budd Lake, a popular fishing destination is in the central part of Michigan's lower peninsula. [Barta, Jim. [http://www.michigansportsmanmag.com/fishing/muskies-pike-fishing/mi_aa072604a/ Michigan's Best Bets for Muskies] . "Michigan Sportsman". Retrieved July 15, 2007.] A major die-off of VHS-positive muskies, bluegills, and black crappie began on April 30, 2007. [ [http://www.michigan.gov/dnr/0,1607,7-153-10371_10402-168753--,00.html Fish Disease Discovered in Budd Lake, Clare County] . (Press Release). Michigan Department of Natural Resources. May 17, 2007. Retrieved July 15, 2007.]

On May 24, 2007, preliminary tests indicated the presence of VHS in a brown trout from Lake Michigan, the second largest freshwater lake in the United States. Contamination in the lake had been expected for months by experts, since the presence of VHS was confirmed in the connected Lake Huron. [ [http://dnr.wi.gov/org/caer/ce/news/rbnews/BreakingNews_Lookup.asp?id=562 Trout from Lake Michigan likely VHS positive] . (News release). Wisconsin Department of Natural Resources. 2007-05-24. Retrieved 2007-07-13.]

On July 14, 2007, federal labs confirmed the presence of VHS in Skaneateles Lake, the second of New York's Finger Lakes to test positive for the disease. [Figura, Dave. [http://www.syracuse.com/articles/sports/index.ssf?/base/sports-1/1173434142263520.xml&coll=1 Federal Lab Confirms VHS Caused Fish Kill] . "The Post-Standard". 2007-07-14. Retrieved on 2007-07-15.] The disease caused a large die-off of bass in the spring of 2007.

Government Regulation

Before the Type IVb die-offs in the Great Lakes, few states regulated transfer of live species other than for salmonids. Since 2005, new policies have been adopted concerning fish and egg transfer, use of live bait, and water transfer, aimed at curtailing the spread to new lakes and rivers in the region. As of July 13, 2007, new rules have been enacted in the Canadian province of Ontario, [ [http://www.mnr.gov.on.ca/mnr/csb/news/2007/jan8nr_07.html Ontario Government Acting Swiftly to Control Further Spread of New Fish Virus] . (Press release). Ontario Ministry of Natural Resources. 2007-01-08.Retrieved on 2007-07-15.] , and US states of Michigan, New York, Ohio, Pennsylvania, and Wisconsin, while they are currently being drafted in Illinois, Indiana, and Minnesota. [Sander, Libby. [http://www.nytimes.com/2007/07/13/us/13fishing.html Michigan’s Summer Fishing Turns Less Carefree] "New York Times." 2007-07-13. Retrieved 2007-07-13.] Additionally, the USDA's Animal and Plant Health InspectionService issued a federal order in the fall of 2006 barring the transfer of all live susceptible species from the eight states bordering the lower Great Lakes, as well as importing such species from The Canadian provinces of Ontario and Quebec. [Gustafson, Lori [http://www.aphis.usda.gov/vs/ceah/ncahs/nsu/outlook/issue13_jan07/outlook_jan07_vhs.pdf VHS Surveillance Planning Under Way] "NAHSS Outlook", Quarter One 2007. Retrieved 2007-07-16.] [ [http://www.fws.gov/midwest/IronRiver/VHS.pdf Feature Story: Viral Hemorrhagic Septicemia:A New Invader in the Great Lakes] "Fish Lines", Vol. 5, No. 5, FY 2007. Retrieved 2007-07-16.]

Transmission

VHSV can be spread from fish to fish through water transfer, as well asthrough contaminated eggs,and bait fish from infected waters.Kipp, Rebekah M. and Anthony Ricciardi. [http://www.glerl.noaa.gov/res/Programs/ncrais/vhs_factsheet.html Viral Hemorrhagic Septicemia (VHS) Factsheet] . NOAA National Center for Research on Aquatic Invasive Species, Great Lakes Aquatic Nonindigenous Species Information System (GLANSIS). 2006-12-08. Retrieved 2007-07-13.] The emerald shiner is a particularly popular bait fish in the Great Lakes region, and is among the species afflicted.Boomgaard, Jon. [http://www.greatlakesdirectory.org/mi/011007___great_lakes.htm New fish virus could be a little as 2 years away from Lake Michigan] . "Ludington Daily News". 2007-01-09. Retrieved 2007-07-13.]

Survivors of the disease can become lifelong carrirs of the virus, contaminating water with urine, sperm, and ovarian fluids. The virus has been shown to survive two freeze/thaw cycles in a conventional freezer, suggesting both live and frozen bait could be a transmission vector. In Europe, the gray heron has spread the virus, but it does so mechanically; the virus is apparently inactive in thedigestive tract of birds.

Symptoms

Fish that become infected experience hemorrhaging of their internal organs, skin, and muscle. Some fish show no external symptoms, but others show signs of infection that include bulging eyes, bloated abdomens, bruised-looking reddish tints to the eyes, skin, gills and fins. Some infected fish have open sores that may look like the lesions from other diseases or from lamprey attacks. [ [http://www.greatlakesdirectory.org/on/012507__great_lakes.htm 01/25 - VHS disease has entered Great Lakes ] ]

Diagnosis

Field Diagnosis

Living fish afflicted with VHS may appear listless or limp, hang justbeneath the surface, or swim very abnormally, such as constant flashingcircling due to the tropism of the virus for the brain.

External signs may include darker coloration, exophthalmia (“pop eye”),pale or red-dotted gills, sunken eyes, and bleeding around orbits (eye sockets) andat base of fins.Groocock, Geoffrey H. [http://www.vet.cornell.edu/Public/FishDisease/AquaticProg/NEUSAHA%202007%20VHS%20and%20SVC.pdf Viral Hemorrhagic Septicemia and Spring Viremia of Carp: Threats to Aquaculture] Cornell University, College of Veterinary Medicine, Department of Microbiology and Immunology, Aquatic Animal Health Program. 2007. Retrieved on 2007-07-18.]

Gross Pathology (Non-laboratory)

VHSV is a hemorrhagic disease, meaning it causes bleeding. Internally,the virus can cause petechial hemorraging (tiny spots of blood) in internalmuscle tissue, and petechial or severe hemorrhaging in internal organs andother tissues. Internal hemorrhaging can be observed as red spots insidea dead fish, particularly around the kidney, spleen, and intestines, aswell as the swim bladder, which would normally have a clear membrane.The liver may be pale, mottled with red hyperemic areas, the kidneymay be swollen and unusuall red, the spleen may be swollen, and the digestivetract may be empty.

External signs are not always present, but if they are, hemorrhaging on theskin's surface can appear as anywhere from tiny red dots (petechiae) tolarge red patches.

Histopathology (Microscopic tissue analysis)

Preliminary diagnosis involves histopathological examination,observing tissues through a microscope. Most tissue changes can be observedas minor to major necrosis (cell death) in the liver, kidneys, spleen, andskeletal muscle. The hematopoietic (blood-forming) areas of the kidney andspleen are the initial area of infection, and should show necrosis.The gill may have thickened lamellae, and the liver may have pyknotic nuclei.Skeletal muscle accumulates blood but does not suffer much damage.

Virology (Definitive testing)

Electron microscopy can reveal the bullet-shaped rhabdovirus, but is notadequate for definitive diagnosis.

The Manual or Diagnostic for Aquatic Animals, 2006, is the standardreference for definitive tests. In most cases, cell culturizationis recommended for surveillance, with antibody tests and reverse transcriptionpolymerase chain reaction (RT-PCR) and genetic sequencing and comparisonfor definitive confirmation and genotype classification.

Prevention

Thoroughly cleaning boats, trailers, nets and other equipment when traveling between different lakes and streams alsohelps. The only EPA-approved disinfectant proven effective against VHS is Virkon® AQUATIC (made by Dupont). [http://www.mlswa.org/Misc/Mi%20VS%20VHS%20Virus.pdf] Chlorine bleach kills the VHS virus, but in concentrations that are much too caustic for ordinary use. Disinfecting stations can be found at various inland lake boat launches in the Great Lakes region.

References

External links

* Rocky Mountain News: [http://www.rockymountainnews.com/drmn/recreation_columnists/article/0,1299,DRMN_85_5253099,00.html Colorado searches for tiger muskie source amid virus] , Ed Dentry, January 3, 2007
* [http://www.michigan.gov/documents/dnr/Viral-Hemorrhagic-Septicemia-Fact-Sheet-11-9-2006_178081_7.pdf PDF paper on virus] from Michigan DNR
* New York Times: [http://www.nytimes.com/2007/04/21/us/21fish.html Fish-Killing Virus Spreading in the Great Lakes] , Susan Saulny, April 21, 2007