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 freshwater
and marine fish in several parts of the northern hemisphere

Northern Hemisphere

The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...

.
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."

Historically, VHS was associated mostly with freshwater salmonids in western Europe,
documented as a pathogenic disease among cultured salmonids since the 1950s. Today it is still a major concern for many fish farms in Europe and is therefore being watched closely by the European Community Reference Laboratory for Fish Diseases

European Community Reference Laboratory for Fish Diseases

The European Community Reference Laboratory for Fish Diseases is currently located in Aarhus in Denmark at the National Veterinary Institute ....

.
It was first discovered in the US in 1988 among salmon returning from the Pacific in Washington State. 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 northeastern
Pacific Ocean, the North Sea, and the Baltic Sea. Since 2005, massive die-offs

Fish kill

The term fish kill, known also as fish die-off and as fish mortality, is a localized die-off of fish populations which may also be associated with more generalised mortality of aquatic life...

 have occurred amongst a wide variety of freshwater species in the Great Lakes

Great Lakes

The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...

 region of North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

.

Virus taxonomy

VHSV is a negative-sense

Sense (molecular biology)

In molecular biology and genetics, sense is a concept used to compare the polarity of nucleic acid molecules, such as DNA or RNA, to other nucleic acid molecules...

 single-stranded RNA

RNA

Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....

 virus
of the order Mononegavirales

Mononegavirales

The order Mononegavirales is the taxonomic home of numerous related viruses. Members of the order that are commonly known are, for instance, Ebola virus, human respiratory syncytial virus, measles virus, mumps virus, Nipah virus, and rabies virus. All of these viruses cause significant disease in...

, family Rhabdoviridae

Rhabdoviridae

Rhabdoviruses are viruses belonging to the family Rhabdoviridae, which is in the order Mononegavirales. The name is derived from the Greek rhabdos meaning rod referring to the shape of the viral particles. Rhabdoviruses infect a broad range of hosts throughout the animal and plant kingdoms...

, and genus Novirhabdovirus.
(ICTV

International Committee on Taxonomy of Viruses

The International Committee on Taxonomy of Viruses is a committee which authorizes and organizes the taxonomic classification of viruses. They have developed a universal taxonomic scheme for viruses and aim to describe all the viruses of living organisms. Members of the committee are considered to...

 virus classification

Virus classification

Virus classification is the process of naming viruses and placing them into a taxonomic system. Similar to the classification systems used for cellular organisms, virus classification is the subject of ongoing debate and proposals. This is mainly due to the pseudo-living nature of viruses, which...

, unlike biological classification, begins with the order.) Its NCBI

National Center for Biotechnology Information

The National Center for Biotechnology Information is part of the United States National Library of Medicine , a branch of the National Institutes of Health. The NCBI is located in Bethesda, Maryland and was founded in 1988 through legislation sponsored by Senator Claude Pepper...

-assigned Taxonomy ID is 11287. Another related fish rhabdovirus in the Novirhabdovirus genus is the Infectious hematopoietic necrosis virus

Infectious hematopoietic necrosis virus

-Introduction:Infectious hematopoietic necrosis virus , 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 like trout and...

 (IHNV), which causes infectious hematopoietic necrosis (IHN) disease in solmonidae.

The viral cause of the disease was discovered in 1963 by M. H. Jenson. The virus is an enveloped, bullet-shaped particle, about 180 nm long by 60 nm in diameter, covered with 5 to 15 nm long peplomer

Peplomer

A peplomer is a glycoprotein spike on a viral capsid or viral envelope. These protrusions will only bind to certain receptors on the host cell: they are essential for both host specificity and viral infectivity...

s.

Molecular Virology

The genome of VHSV is composed of approximately 11-kb of single stranded RNA, which contains six genes that are located along the genome in the 3′-5′ order: 3′-N-P-M-G-NV-L-5′, nucleocapsid protein (N), polymerase-associated phosphoprotein (P), matrix protein (M), surface glycoprotein (G), a unique non-virion protein (NV), and virus polymerase (L).

Reverse genetics is a powerful tool to study and characterize the previously unknown viral genes. Reverse genetics system is currently available for VHSV. A vaccinia virus free reverse genetic system for Great Lakes VHSV (Genotype IVb) was developed by a research group from the USA. This system allows the investigators to explore the functional properties of individual viral genes of VHSV in detail. This system was immediately utilized to characterize the non-virion (NV) gene of Novirhabdoviruses. Even though it has been demonstrated that the NV gene is not necessary for viral replication, it is highly essential for viral pathogenesis. A new role of NV protein has been discovered and demonstrated that it inhibits apoptosis at the early stage of viral infection. This discovery unlocked the mystery of presence of NV protein in Novirhabdoviruses.

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 systems, 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	Prevalent host type and location
I-a	Farmed rainbow trout and a few other freshwater fish in continental Europe
I-b	Marine fish of the Baltic Sea Baltic Sea The Baltic Sea is a brackish mediterranean sea located in Northern Europe, from 53°N to 66°N latitude and from 20°E to 26°E longitude. It is bounded by the Scandinavian Peninsula, the mainland of Europe, and the Danish islands. It drains into the Kattegat by way of the Øresund, the Great Belt and... , Skagerrak Skagerrak The Skagerrak is a strait running between Norway and the southwest coast of Sweden and the Jutland peninsula of Denmark, connecting the North Sea and the Kattegat sea area, which leads to the Baltic Sea.-Name:... , Kattegat Kattegat The Kattegat , or Kattegatt is a sea area bounded by the Jutland peninsula and the Straits islands of Denmark on the west and south, and the provinces of Västergötland, Scania, Halland and Bohuslän in Sweden on the east. The Baltic Sea drains into the Kattegat through the Øresund and the Danish... , North Sea North Sea In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively... , Japan Japan Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
I-c	Farmed rainbow trout Denmark Denmark Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
I-d	Farmed rainbow trout in Norway Norway Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million... , Finland Finland Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside... , Gulf of Bothnia Gulf of Bothnia The Gulf of Bothnia is the northernmost arm of the Baltic Sea. It is situated between Finland's west coast and Sweden's east coast. In the south of the gulf lie the Åland Islands, between the Sea of Åland and the Archipelago Sea.-Name:...
I-e	Rainbow trout in Georgia, farmed and wild turbot in the Black Sea Black Sea The Black Sea is bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and the Aegean seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects that sea to the Aegean...
II	Marine fish of the Baltic Sea Baltic Sea The Baltic Sea is a brackish mediterranean sea located in Northern Europe, from 53°N to 66°N latitude and from 20°E to 26°E longitude. It is bounded by the Scandinavian Peninsula, the mainland of Europe, and the Danish islands. It drains into the Kattegat by way of the Øresund, the Great Belt and...
III	Marine fish of the British Isles and northern France, farmed turbot in the UK and Ireland, and Greenland halibut (Reinhardtius hippoglossoides) in Greenland
IV-a	Marine fish of the Northwest Pacific (North America), North American north Atlantic coast, Japan, and Korea
IV-b	Freshwater fish in North American Great Lakes region

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.

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

North Sea

In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...

.
1996 saw the first VHSV in Japan, among Japanese flounder farmed in the Seto Inland Sea, 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) mummichog (Fundulus heteroclitus), stickleback (Gasterosteus aculeatus aculeatus), brown trout (Salmo trutta

Brown trout

The brown trout and the sea trout are fish of the same species....

), 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.

To keep track of the distribution of different VHSV genotypes, a database called Fishpathogens.eu

Fishpathogens.eu

Fishpathogens.eu is a database created to store data on isolates of different fish pathogens and their sequences. The site was launched June 2009 with a database on Viral hemorrhagic septicemia virus...

 has been created to store data on different fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 pathogens (including VHSV) and their sequences.

Great Lakes Type IV-b

The Type IV-b strain of VHSV has been spreading among freshwater fish in the Great Lakes

Great Lakes

The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...

 region since
at least 2003, resulting in some massive die-offs

Fish kill

The term fish kill, known also as fish die-off and as fish mortality, is a localized die-off of fish populations which may also be associated with more generalised mortality of aquatic life...

 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 first detection in freshwater was in Lake Ontario in 2005, and then in an archived 2003 sample from Lake St. Clair. The isolate was named MI03GL and was sequenced for its entire genome.

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

Lake Saint Clair (North America)

Lake St. Clair is a fresh-water lake named after Clare of Assisi that lies between the Province of Ontario and the State of Michigan, and its midline also forms the boundary between Canada and the United States of America. Lake St. Clair includes the Anchor Bay along the Metro Detroit coastline...

of Great Lakes muskellunge

Muskellunge

A muskellunge , also known as a muskelunge, muscallonge, milliganong, or maskinonge , is a large, relatively uncommon freshwater fish of North America. Muskellunge are the largest member of the pike family, Esocidae...

 is the earliest confirmed case of VHSV within the Great Lakes region. Lake St. Clair connects to Lake Erie

Lake Erie

Lake Erie is the fourth largest lake of the five Great Lakes in North America, and the tenth largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and therefore also has the shortest average water residence time. It is bounded on the north by the...

 through the Detroit River

Detroit River

The Detroit River is a strait in the Great Lakes system. The name comes from the French Rivière du Détroit, which translates literally as "River of the Strait". The Detroit River has served an important role in the history of Detroit and is one of the busiest waterways in the world. The river...

 to the south, and to Lake Huron

Lake Huron

Lake Huron is one of the five Great Lakes of North America. Hydrologically, it comprises the larger portion of Lake Michigan-Huron. It is bounded on the east by the Canadian province of Ontario and on the west by the state of Michigan in the United States...

 through the St. Clair River

St. Clair River

The St. Clair River is a river in central North America which drains Lake Huron into Lake St Clair, forming part of the international boundary between the Canadian province of Ontario and the U.S. state of Michigan...

 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

Lake Ontario

Lake Ontario is one of the five Great Lakes of North America. It is bounded on the north and southwest by the Canadian province of Ontario, and on the south by the American state of New York. Ontario, Canada's most populous province, was named for the lake. In the Wyandot language, ontarío means...

freshwater drum

Freshwater Drum

-Introduction:The freshwater drum, Aplodinotus grunniens, is a fish endemic to North and Central America. It is the only species in the genus Aplodinotus. The Freshwater drum is a member of the family Sciaenidae, and is the only member of the species that inhabits freshwater for its entire life...

 and Lake Huron

Lake Huron

Lake Huron is one of the five Great Lakes of North America. Hydrologically, it comprises the larger portion of Lake Michigan-Huron. It is bounded on the east by the Canadian province of Ontario and on the west by the state of Michigan in the United States...

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

Niagara River

The Niagara River flows north from Lake Erie to Lake Ontario. It forms part of the border between the Province of Ontario in Canada and New York State in the United States. There are differing theories as to the origin of the name of the river...

, which connects Lake Erie to Lake Ontario. It was also found in a walleye

Walleye

Walleye is a freshwater perciform fish native to most of Canada and to the northern United States. It is a North American close relative of the European pikeperch...

 die-off in the landlocked inland Conesus Lake

Conesus Lake

Conesus Lake is one of the minor Finger Lakes in western New York. It is western-most of eleven total Finger Lakes. The lake's outlet is in Lakeville, New York a hamlet in the Town of Livonia, New York in Livingston County, south of Rochester, New York. The lake's inlet is in the Town of Conesus,...

, the westernmost of the Finger Lakes

Finger Lakes

The Finger Lakes are a pattern of lakes in the west-central section of Upstate New York in the United States. They are a popular tourist destination. The lakes are long and thin , each oriented roughly on a north-south axis. The two longest, Cayuga Lake and Seneca Lake, are among the deepest in...

 in western New York state. This was the first case in the region outside waters contiguously connected to the Great Lakes.

On May 12, 2007, the Wisconsin DNR

Wisconsin Department of Natural Resources

The Wisconsin Department of Natural Resources is an agency of the state of Wisconsin. Its purpose is to preserve, protect, manage and maintain the natural resources of the state. The WDNR has the authority to set policy for itself and to recommend regulations for approval by the State Legislature...

 announced the likely presence of VHS in Wisconsin's inland Little Lake Butte des Morts

Little Lake Butte des Morts

Little Lake Butte des Morts is a lake in the state of Wisconsin, USA, eight miles north of Lake Butte Des Morts. It is part of the Fox-Wisconsin Waterway and receives its inflow from a short segment of the Fox River which drains from the north end of Lake Winnebago around Doty Island. The north end...

. 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

Lake Winnebago

Lake Winnebago is a freshwater lake in eastern Wisconsin, United States. It is the largest lake entirely within the state.-Statistics:...

. Preliminary tests later indicated VHS in specimens from Lake Winnebago. The lakes drain through the Fox River to Lake Michigan

Lake Michigan

Lake Michigan is one of the five Great Lakes of North America and the only one located entirely within the United States. It is the second largest of the Great Lakes by volume and the third largest by surface area, after Lake Superior and Lake Huron...

's Green Bay.

On May 17, 2007, the Michigan DNR

Michigan Department of Natural Resources

The Michigan Department of Natural Resources is the agency of the state of Michigan charged with maintaining natural resources such as state parks, state forests, and recreation areas. It is governed by a director appointed by the Governor and accepted by the Natural Resources Commission...

 confirmed the presence of VHS in the Michigan's inland Budd Lake

Budd Lake (Michigan)

Budd Lake is a lake in Clare County, in the central region of Michigan's lower peninsula. Wilson State Park borders the lake to the northwest.A popular lake for anglers seeking muskies, it offers two boat ramps....

, a popular fishing destination is in the central part of Michigan's lower peninsula. A major die-off of VHS-positive muskies

Muskellunge

A muskellunge , also known as a muskelunge, muscallonge, milliganong, or maskinonge , is a large, relatively uncommon freshwater fish of North America. Muskellunge are the largest member of the pike family, Esocidae...

, bluegill

Bluegill

The Bluegill is a species of freshwater fish sometimes referred to as bream, brim, or copper nose. It is a member of the sunfish family Centrarchidae of the order Perciformes.-Range and distribution:...

s, and black crappie began on April 30, 2007.

On May 24, 2007, preliminary tests indicated the presence of VHS in a brown trout from Lake Michigan

Lake Michigan

Lake Michigan is one of the five Great Lakes of North America and the only one located entirely within the United States. It is the second largest of the Great Lakes by volume and the third largest by surface area, after Lake Superior and Lake Huron...

, 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.

On July 14, 2007, federal labs confirmed the presence of VHS in Skaneateles Lake

Skaneateles Lake

Skaneateles Lake is one of the Finger Lakes in central New York in the United States. The name Skaneateles means long lake in one of the local Iroquoian languages. The lake is sometimes referred to as "The Roof Garden of the Lakes" because its altitude is higher than the other Finger Lakes. It...

, the second of New York's Finger Lakes to test positive for the disease. 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, and US states of Michigan, New York, Ohio, Pennsylvania, and Wisconsin, while they are currently being drafted in Illinois, Indiana, and Minnesota. Additionally, the USDA's Animal and Plant Health Inspection
Service 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.

Transmission

VHSV can be spread from fish to fish through water transfer, as well as through contaminated eggs,
and bait fish from infected waters. The emerald shiner

Emerald shiner

The Emerald Shiner is one of hundreds of small, silvery, slender fish known as shiners. The identifying characteristic of the emerald shiner is the silvery emerald color on its sides...

 is a particularly popular bait fish in the Great Lakes region, and is among the species afflicted.

Survivors of the disease can become lifelong carriers 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 the
digestive 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.

There may also be a nervous form of the disease where fish are constantly flashing and showing abnormal behaviour.

Field diagnosis

Living fish afflicted with VHS may appear listless or limp, hang just
beneath the surface, or swim very abnormally, such as constant flashing
circling 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) and
at base of fins.

Genetics researchers at the Lake Erie Research Center at the University of Toledo are developing a test that will speed diagnosis from a month to a matter of hours.

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 internal
muscle tissue, and petechial or severe hemorrhaging in internal organs and
other tissues. Internal hemorrhaging can be observed as red spots inside
a dead fish, particularly around the kidney, spleen, and intestines, as
well as the swim bladder, which would normally have a clear membrane.
The liver may be pale, mottled with red hyperemic areas, the kidney
may be swollen and unusually red, the spleen may be swollen, and the digestive
tract may be empty.

External signs are not always present, but if they are, hemorrhaging on the
skin's surface can appear as anywhere from tiny red dots (petechia

Petechia

A petechia is a small red or purple spot on the body, caused by a minor hemorrhage ."Petechiae" refers to one of the three major classes of purpuric skin conditions. Purpuric eruptions are classified by size into three broad categories...

e) to
large red patches.

Histopathology (Microscopic tissue analysis)

Preliminary diagnosis involves histopathological

Histopathology

Histopathology refers to the microscopic examination of tissue in order to study the manifestations of disease...

 examination,
observing tissues through a microscope. Most tissue changes can be observed
as minor to major necrosis (cell death) in the liver, kidneys, spleen, and
skeletal muscle. The hematopoietic (blood-forming) areas of the kidney and
spleen 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 not
adequate for definitive diagnosis.

The Manual or Diagnostic for Aquatic Animals, 2006, is the standard
reference for definitive tests. In most cases, cell culturization
is recommended for surveillance, with antibody tests and reverse transcription
polymerase chain reaction (RT-PCR) and genetic sequencing and comparison
for definitive confirmation and genotype classification.

Virus neutralisation is another important method of diagnosis, especially for carrier fish.

Prevention

Thoroughly cleaning boats, trailers, nets and other equipment when traveling between different lakes and streams also
helps. The only EPA-approved disinfectant proven effective against VHS is Virkon

Virkon

Virkon is a multi-purpose disinfectant. It contains oxone , sodium dodecylbenzenesulfonate, sulphamic acid; and inorganic buffers. It is typically used for cleaning up hazardous spills, disinfecting surfaces and soaking equipment...

 AQUATIC (made by Dupont). Chlorine bleach

Bleach

Bleach refers to a number of chemicals that remove color, whiten, or disinfect, often via oxidation. Common chemical bleaches include household chlorine bleach , lye, oxygen bleach , and bleaching powder...

 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.

External links

• Invading Species.com Ontario Ministry of Natural Resources and Ontario Federation of Anglers and Hunters
• Rocky Mountain News
  Rocky Mountain News
  The Rocky Mountain News was a daily newspaper published in Denver, Colorado, United States from April 23, 1859, until February 27, 2009. It was owned by the E. W. Scripps Company from 1926 until its closing. As of March 2006, the Monday-Friday circulation was 255,427...
  
  : Colorado searches for tiger muskie source amid virus, Ed Dentry, January 3, 2007
• PDF paper on virus from Michigan DNR
• New York Times: Fish-Killing Virus Spreading in the Great Lakes, Susan Saulny, April 21, 2007
• Species Profile - Viral hemorrhagic septicemia (Novirhabdovirus), National Invasive Species Information Center, United States National Agricultural Library
  United States National Agricultural Library
  The United States National Agricultural Library is one of the world's largest agricultural research libraries, and serves as a National Library of the United States and as the library of the United States Department of Agriculture...
  
  . Lists general information and resources for viral hemorrhagic septicemia.
• Fishpathogens.eu A database on VHSV isolates and their sequences
• European Community Reference Laboratory for Fish Diseases
• Great Lakes Echo: Great Lakes fish hatcheries could benefit from new test for deadly VHS virus, Sarah Coefield, June 18, 2009