Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide


Oncorhynchus masou virus disease



Oncorhynchus masou virus disease


  • Last modified
  • 04 October 2022
  • Datasheet Type(s)
  • Animal Disease
  • Preferred Scientific Name
  • Oncorhynchus masou virus disease
  • Overview
  • Oncorhynchus masou virus disease (OMVD) is an oncogenic and skin ulcerative condition among salmonid fish in Japan, and probably in the coastal rivers of eastern Asia that harbor Pacific salmon. Oncorhynchus masou virus (OMV), the ca...

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Preferred Scientific Name

  • Oncorhynchus masou virus disease

Other Scientific Names

  • Coho salmon herpesvirus
  • Coho salmon tumour virus
  • Nerka virus Towada lake, Akita and Amori prefecture
  • Oncorhynchus kisutch virus
  • Rainbow trout herpesvirus
  • Rainbow trout kidney virus
  • Salmonid herpesvirus 2
  • Yamame tumour virus

Local Common Names

  • Japan: Basal cell carcinoma; Herpesviral disease of salmonid

English acronym

  • COTV
  • CSTV
  • NeVTA
  • OKV
  • OMVD
  • RHV
  • RKV
  • SalHV-2
  • YTV


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Oncorhynchus masou virus disease (OMVD) is an oncogenic and skin ulcerative condition among salmonid fish in Japan, and probably in the coastal rivers of eastern Asia that harbor Pacific salmon. Oncorhynchus masou virus (OMV), the causative virus, is also known as Nerka virus Towada Lake, Akita and Amori prefecture (NeVTA), yamame tumor virus (YTV), Oncorhynchus kisutch virus (OKV), coho salmon tumor virus (COTV), coho salmon herpesvirus (CSHV), rainbow trout kidney virus (RKV), or rainbow trout herpesvirus (RHV). For other reviews of the condition, see Kimura and Yoshimizu (1989), Wolf (1988) and Yoshimizu et al. (1995).

[Based upon material originally published in Woo PTK, Bruno DW, eds., 1999. Fish diseases and disorders, Vol. 3 Viral, bacterial and fungal infections. Wallingford, UK: CABI Publishing.]

Host Animals

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Animal nameContextLife stageSystem
Oncorhynchus keta (chum salmon)Aquatic|FryEnclosed systems/Aquaria (marine / freshwater ornamentals)
Oncorhynchus kisutch (coho salmon)Aquatic|AdultEnclosed systems/Cages; Enclosed systems/Pens; Enclosed systems/Ponds
Oncorhynchus masou masou (cherry salmon)Aquatic|Adult; Aquatic|Broodstock; Aquatic|FryEnclosed systems/Ponds; Enclosed systems/Raceways / running water ponds; Open water systems/Enhancements and culture-based fisheries (inc. ranching and stock enhacement)
Oncorhynchus mykiss (rainbow trout)Aquatic|Adult; Aquatic|Broodstock; Aquatic|FryEnclosed systems/Ponds
Oncorhynchus nerka (sockeye salmon)Aquatic|Fry; Aquatic|LarvalEnclosed systems/Ponds

Hosts/Species Affected

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Fish species that are susceptible to OMV include: kokanee (sockeye) salmon (Oncorhynchus nerka), masou salmon (O. masou), chum salmon (O. keta), coho salmon (O. kisutch) and rainbow trout (O. mykiss) (Kimura et al., 1983).

Salmonids are the only fish species susceptible to OMV infection; the order of the fish species from the most to the least susceptible is: kokanee salmon, chum salmon, masou salmon, coho salmon and rainbow trout. The age of the fish is critical and 1-month-old alevins are the most susceptible target for virus infection (Kimura et al., 1983). The main environmental factor favoring OMV infection is low water temperature (below 14°C) (Suzuki et al., 1986).


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Yoshimizu and Nomura (2001) report that OMV has only been identified in Japan, especially on Hokkaido and Honshu Islands. USA, Center for Food Security & Public Health and USA, Institute for International Cooperation in Animal Biologics (2007) report that the disease disease occurs in Japan, probably exists throughout eastern Asia in coastal rivers that contain Pacific salmon, and has been reported from Kuwait.

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Last updated: 10 Jan 2020
Continent/Country/Region Distribution Last Reported Origin First Reported Invasive Reference Notes


BotswanaAbsent, No presence record(s)
BurundiAbsent, No presence record(s)
Cabo VerdeAbsent, No presence record(s)
CameroonAbsent, No presence record(s)
Central African RepublicAbsent, No presence record(s)
Congo, Democratic Republic of theAbsent, No presence record(s)
DjiboutiAbsent, No presence record(s)
EritreaAbsent, No presence record(s)
EswatiniAbsent, No presence record(s)
EthiopiaAbsent, No presence record(s)
GhanaAbsent, No presence record(s)
KenyaAbsent, No presence record(s)
MadagascarAbsent, No presence record(s)
MauritiusAbsent, No presence record(s)
SudanAbsent, No presence record(s)
TogoAbsent, No presence record(s)
TunisiaAbsent, No presence record(s)
UgandaAbsent, No presence record(s)
ZimbabweAbsent, No presence record(s)


BahrainAbsent, No presence record(s)
BruneiAbsent, No presence record(s)
GeorgiaAbsent, No presence record(s)
Hong KongAbsent, No presence record(s)
IndonesiaAbsent, No presence record(s)
IranAbsent, No presence record(s)
IraqAbsent, No presence record(s)
JapanPresentPresent based on regional distribution
-HokkaidoPresent, Localized1978InvasiveOriginal citation: Kimura et al. (1981a)
-HonshuPresent, Localized1988InvasiveOriginal citation: Yoshimizu et al. (1995)
KazakhstanAbsent, No presence record(s)
KuwaitPresent, Few occurrencesOriginal citation: USA, Center for Food Security & Public Health and USA, Institute for International Cooperation in Animal Biologics (2007)
-Peninsular MalaysiaAbsent, No presence record(s)
MongoliaAbsent, No presence record(s)
North KoreaAbsent, No presence record(s)
SingaporeAbsent, No presence record(s)
South KoreaAbsent, No presence record(s)
Sri LankaAbsent, No presence record(s)
SyriaAbsent, No presence record(s)
TaiwanAbsent, No presence record(s)
ThailandAbsent, No presence record(s)
TurkmenistanAbsent, No presence record(s)
UzbekistanAbsent, No presence record(s)


AndorraAbsent, No presence record(s)
BelarusAbsent, No presence record(s)
Bosnia and HerzegovinaAbsent, No presence record(s)
BulgariaAbsent, No presence record(s)
CyprusAbsent, No presence record(s)
CzechiaAbsent, No presence record(s)
DenmarkAbsent, No presence record(s)
EstoniaAbsent, No presence record(s)
FinlandAbsent, No presence record(s)
FranceAbsent, No presence record(s)
GreeceAbsent, No presence record(s)
HungaryAbsent, No presence record(s)
IcelandAbsent, No presence record(s)
IrelandAbsent, No presence record(s)
Isle of ManAbsent, No presence record(s)
ItalyAbsent, No presence record(s)
JerseyAbsent, No presence record(s)
LatviaAbsent, No presence record(s)
LiechtensteinAbsent, No presence record(s)
LithuaniaAbsent, No presence record(s)
LuxembourgAbsent, No presence record(s)
MaltaAbsent, No presence record(s)
MoldovaAbsent, No presence record(s)
NetherlandsAbsent, No presence record(s)
North MacedoniaAbsent, No presence record(s)
NorwayAbsent, No presence record(s)
PolandAbsent, No presence record(s)
PortugalAbsent, No presence record(s)
RussiaAbsent, No presence record(s)
SlovakiaAbsent, No presence record(s)
SloveniaAbsent, No presence record(s)
SpainAbsent, No presence record(s)
SwedenAbsent, No presence record(s)
UkraineAbsent, No presence record(s)
United KingdomAbsent, No presence record(s)
-Northern IrelandAbsent, No presence record(s)

North America

BarbadosAbsent, No presence record(s)
BelizeAbsent, No presence record(s)
BermudaAbsent, No presence record(s)
British Virgin IslandsAbsent, No presence record(s)
CanadaAbsent, No presence record(s)
Cayman IslandsAbsent, No presence record(s)
Costa RicaAbsent, No presence record(s)
CubaAbsent, No presence record(s)
DominicaAbsent, No presence record(s)
Dominican RepublicAbsent, No presence record(s)
GuatemalaAbsent, No presence record(s)
HaitiAbsent, No presence record(s)
HondurasAbsent, No presence record(s)
JamaicaAbsent, No presence record(s)
MexicoAbsent, No presence record(s)
NicaraguaAbsent, No presence record(s)
PanamaAbsent, No presence record(s)
Saint Kitts and NevisAbsent, No presence record(s)
Saint Vincent and the GrenadinesAbsent, No presence record(s)
Trinidad and TobagoAbsent, No presence record(s)
United StatesAbsent, No presence record(s)


AustraliaAbsent, No presence record(s)
French PolynesiaAbsent, No presence record(s)
New ZealandAbsent, No presence record(s)
VanuatuAbsent, No presence record(s)

South America

ArgentinaAbsent, No presence record(s)
BoliviaAbsent, No presence record(s)
BrazilAbsent, No presence record(s)
ChileAbsent, No presence record(s)
ColombiaAbsent, No presence record(s)
Falkland IslandsAbsent, No presence record(s)
French GuianaAbsent, No presence record(s)
GuyanaAbsent, No presence record(s)
ParaguayAbsent, No presence record(s)
PeruAbsent, No presence record(s)
UruguayAbsent, No presence record(s)
VenezuelaAbsent, No presence record(s)


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OMV is pathogenic and more significantly oncogenic for cherry salmon and several other salmonid fish (Kimura et al., 1981b). One month old kokanee salmon (Oncorhynchus nerka) were shown to exhibit the greatest sensitivity. Cherry salmon and chum salmon (Oncorhynchus keta) also exhibited high susceptibility. Coho salmon and rainbow trout were shown to be less susceptible to OMV infection (Tanaka et al., 1984). Recently, epizootics occurred in cultured rainbow trout weighing between 10 and 1,500 g at a fish farm in Hokkaido, Japan and several prefectures in Honshu Island, Japan. Highly infected titers were recorded in the internal organs and multiple necrotic foci were observed in the liver (Furihata et al., 2003).

In an experiment by Yoshimizu et al. (1987) where salmonid species were experimentally infected, the incidence of tumour-bearing fish approached more than 60%. Epithelial tumours were found on 12-100% of the surviving chum, coho and cherry salmon, and rainbow trout beginning at about 4 months and persisting for at least 1 year post-infection.


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The screening and diagnostic procedures for OMV are based on direct methods. These are the isolation of the virus in cell culture and co-culture of neoplastic tissues with salmonid cell lines followed by its immunological identification (conventional approach) (Lannan et al., 1984; Yoshimizu, 1996), or the immunological demonstration of OMV antigen in infected fish tissues (Hayashi et al., 1993; Kimura et al., 1983).

Confirmatory testing is by immunological identification using neutralization, immuno-fluorescence tests, or ELISA, and virus-specific gene detection using polymerase chain reaction (Aso et al., 2001).

Due to insufficient knowledge of the serological responses of fish to virus infections, the detection of fish antibodies to viruses has not thus far been recognized as a valuable diagnostic method for assessing the viral status of fish populations. However, the validation of some serological techniques for diagnosis of certain fish virus infections could arise in the near future, rendering the use of fish serology more widely acceptable for diagnostic purposes.

List of Symptoms/Signs

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SignLife StagesType
Finfish / Darkened coloration - Skin and Fins Aquatic|Adult Sign
Finfish / Haemorrhagic lesions - Skin and Fins Aquatic|Adult Sign
Finfish / Haemorrhagic lesions - Skin and Fins Aquatic|Adult Sign
Finfish / Haemorrhagic lesions - Skin and Fins Aquatic|Adult Sign
Finfish / Haemorrhagic lesions - Skin and Fins Aquatic|Adult Sign
Finfish / Intestines white-grey patches (haemorrhage / necrosis / tissue damage) - Organs Aquatic|Adult Sign
Finfish / Liver - white / grey patches (haemorrhage / necrosis / tissue damage) - Organs Aquatic|Adult Sign
Finfish / Pop-eye - Eyes Aquatic|Adult Sign
Finfish / Skin erosion - Skin and Fins Aquatic|Adult Sign
Finfish / Swelling - Organs Aquatic|Adult Sign

Disease Course

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Clinically, the initial infection by OMV (taxonomically known as Salmonid Herpesvirus 2; SalHV-2) appears as a systemic and frequently lethal infection that is associated with edema and hemorrhages. Virus multiplication in endothelial cells of blood capillaries, hematopoietic tissue and hepatocytes underlies the clinical signs (Kimura et al., 1981a; Tanaka et al., 1984). Four months after this first clinical condition, a varying number of surviving fish exhibit epithelioma occurring mainly around the mouth (upper and lower jaw, see photo), and to a lesser extent, on the caudal fin, operculum and body surface. This neoplasia may persist for up to 1 year post-infection. In the case of coho salmon, 1-year-old infected fish in particular show ulcers on the skin, white spots on the liver and neoplastic tissues around the mouthparts or body surface. In rainbow trout, the diseased fish exhibit almost no external signs, although some fish manifest ulcerative lesions on the skin. Internally, intestinal hemorrhage and white spots on the liver are observed (Kimura et al., 1981a; Yoshimizu et al., 1987; Yoshimizu et al., 1988).

Following the septicemia phase of OMV infection, an immune response takes place that results in the synthesis of neutralizing antibodies to OMV. A carrier state frequently occurs that leads to virus shedding via the sexual products at the time of spawning.


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The reservoirs of OMV are clinically infected fish and covert carriers among groups of cultured, feral or wild fish. Infectious virus is shed via faces, urine, sexual products and probably skin mucus, while the kidney, spleen, liver and tumors are the sites where virus is the most abundant during the course of overt infection. The transmission of OMV is horizontal and possibly ‘egg-surface associated’. Horizontal transmission may be direct or vectorial, water being the major abiotic factor. Animate vectors and inanimate objects also act in OMV transmission. Disinfection of the eggs just after fertilization and eyed stage is effective in preventing OMV infection. OMV disease was not reported in alevins originating from disinfected eggs that had been incubated and hatched in virus-free water (Yoshimizu et al., 1993).

Between 1978 and 1999, 27937 females of 6 species of mature salmonid fish were collected to survey the incidence of this virus in Hokkaido, Japan and the northern part of Japan. OMV was isolated from Oncorhynchus masou (cherry salmon) at all the investigated sites with the exception of one hatchery (Yoshimizu et al., 1993; Kasai et al., 2004). Based on our epizootiological study, the roots of OMV in Japan were assumed to be along the coast of Hokkaido, Japan and the presumed original host species was Oncorhynchus masou. In the 1960's, eggs of O. masou were transported to the mainland of Japan. Through the movement of fish, the virus spread to several places in Honshu, Japan, where the first cancer causing disease of O. masou was observed (Kimura, 1976). Subsequently, coho salmon (Oncorhynchus kisutch) and rainbow trout (Oncorhynchus mykiss) were cultured in the same water systems where cherry salmon were cultured (Yoshimizu and Nomura, 2001).

Impact Summary

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Fisheries / aquaculture Negative

Impact: Economic

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Diseased fish that show tumours around the mouth and ulcers on the skin (See photos) are not marketable to consumers (Yoshimizu, 1996). Economic loss was reported in pen culture of coho salmon and pond culture of rainbow trout (Furihata et al., 2003).


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Aso Y, Wani J, Klenner DAS, Yoshimizu M, 2001. Detection and identification of Oncorhynchus masou virus (OMV) disease by polymerase chain reaction (PCR). Bull. Fish. Sci. Hokkaido University, 52, 111-116

Eaton WD, Wingfield WH, Hedrick RP, 1991. Comparison of the DNA homologies of five salmonid herpesvirus. Fish Pathology, 26:183-187

Furihata M, Hosoe A, Takei K, Kohara M, Nakamura J, Motonishi A, Yoshimizu M, 2003. Outbreak of salmonid herpesviral disease in cultured rainbow trout. Gyobyo Kenkyu = Fish Pathology, 38(1):23-25

Gou DF, Kodama H, Onuma M, Kimura T, Yoshimizu M, 1991. Comparison of different Oncorhynchus masou virus (OMV) strains by DNA restriction endonuclease cleavage analysis. Japanese Journal of Veterinary Research, 39:27-37

Hayashi Y, Izawa H, Mikami T, Kodama H, 1993. A monoclonal antibody cross-reactive with three salmonid herpesviruses. Journal of Fish Diseases, 16(5):479-486

Hedrick RP, McDowell T, Eaton WD, Kimura T, Sano T, 1987. Serological relationships of five herpesviruses isolated from salmonid fishes. Journal of Applied Ichthyology, 3(2):87-92

Horiuchi M, Miyazawa M, Nakata M, Iida K, Nishimura S, 1989. A case of herpesvirus infection of fresh water-reared coho salmon Oncorhynchus kisutch in Japan. Suisan-Zoushoku, 36:297-305

Igari T, Fukuda H, Sano T, 1991. Restriction endonuclease cleavage patterns of the DNA of salmonid herpesvirus strains. Gyobyo Kenkyu = Fish Pathology, 26(1):45-46

Kasai H, Nomura T, Yoshimizu M, 2004. Surveillance and control of salmonid viruses of wild salmonid fish returning to the northern part of Japan, from 1976 to 2002. In: Proceedings of the 3rd Japan-Korea Joint Seminar on Fisheries Sciences, 142-147. 15-16 December, 2003. Jinju-Tongyeong, Korea

Kimura I, 1976. Tumor of lower vertebrates. In: Sugiyama T, Yamamoto Y, eds. Cancer. Tokyo: Iwanami-shoten, 270-283

Kimura T, Suzuki S, Yoshimizu M, 1983. [I] In vitro antiviral effect of 9-(2-hydroxyethoxymethyl) guanine on the fish herpesvirus, Oncorhynchus masou virus (OMV). [II] In vivo antiviral effect of 9-(2-hydroxymethyl) guanine on experimental infection of chum salmon (Oncorhynchus keta) fry with Oncorhynchus masou virus (OMV). Antiviral Research, 3(2):93-101, 103-108

Kimura T, Yoshimisu M, 1989. Salmon herpesvirus: OMV, Oncorhynchus masou virus. In: Ahne W, Kurstak E, eds. Viruses of Lower Vertebrates. Berlin, Germany: Springer-Verlag, 171-183

Kimura T, Yoshimizu M, Tanaka M, 1981. Studies on a new virus (OMV) from Oncorhynchus masou. II. Oncogenic nature. Fish Pathology, 15(3/4):149-153

Kimura T, Yoshimizu M, Tanaka M, 1983. Susceptibility of different fry stages of representative salmonid species to Oncorhynchus masou virus (OMV). Fish Pathology, 17(4):251-258

Kimura T, Yoshimizu M, Tanaka M, Sannohe H, 1981. Studies on a new virus (OMV) from Oncorhynchus masou. I. Characteristics and pathogenicity. Fish Pathology, 15(3/4):143-147

Kumagai A, Takahashi K, Fukuda H, 1994. Epizootics caused by salmonid herpesvirus type 2 infection in maricultured coho salmon. Gyobyo Kenkyu = Fish Pathology, 29(2):127-134

Lannan CN, Winton JR, Fryer JL, 1984. Fish cell lines: establishment and characterization of nine cell lines from salmonids. In Vitro, 20(9):671-676

OIE Handistatus, 2005. World Animal Health Publication and Handistatus II (data set for 2004). Paris, France: Office International des Epizooties

OIE, 2003. Manual of Diagnostic Tests for Aquatic Animals, 4th Edition. Paris, France: Office International des Epizooties, 358 pp

Roizman B, 1991. Family Herpesviridae. In: Francki RI, Fauque CM, Knudson DL, Brown F, eds. Classification and Nomenclature of Viruses. Archives of Virology, (Supplement 2). New York, USA and Vienna, Austria: Springer, 103-110

Sano T, 1976. Viral diseases of cultured fishes in Japan. Fish Pathology, 10(2):221-226; [1 pl.]

Sano T, Fukuda H, Okamoto N, Kaneko F, 1983. Yamame tumor virus: lethality and oncogenicity. Bulletin of the Japanese Society of Scientific Fisheries, 49(8):1159-1163

Suzuki K, 1993. A new viral disease on rainbow trout. Shikenkenkyuwa-Ima, 165:1-2

Suzuki S, Kimura T, Saneyoshi M, 1986. Characterization of DNA polymerase induced by salmon herpesvirus, Oncorhynchus masou virus. Journal of General Virology, 67:405-408

Tanaka M, Yoshimizu M, Kimura T, 1984. Oncorhynchus masou virus: pathological changes in masu salmon (Orcorhynchus masou), chum salmon (O. keta) and coho salmon (O. kisutch) fry infected with OMV by immersion method. Bulletin of the Japanese Society of Scientific Fisheries, 50(4):431-437

USA, Center for Food Security & Public Health, USA, Institute for International Cooperation in Animal Biologics, 2007. Oncorhynchus masou virus disease. Iowa, USA: Center for Food Security and Public Health, Iowa State University.3 pp.

Wolf K, 1988. Fish viruses and fish viral diseases. Fish viruses and fish viral diseases., xii + 476 pp

Yoshimisu M, Nomura T, Ezura Y, Kimura T, 1993. Surveillance and control of infectious hematopoietic necrosis virus (IHNV) and Oncorhynchus masou virus (OMV) of wild salmonid fish retruning to the northern part of Japan 1976-1991. Fisheries Research, 17:163-173

Yoshimizu M, 1996. Salmonid herpesvirus. Virus, 46:53-59

Yoshimizu M, Fukuda H, Sano T, Kimura T, 1995. Salmonid herpesvirus 2. Epizootiology and serological relationship. Veterinary Research, 26(5/6):486-492

Yoshimizu M, Nomura T, 2001. Oncorhynchus masou virus (OMV). Epidemiology and its control strategy. Bulletin of the National Research Institute of Aquaculture, Supplement, 5:11-14

Yoshimizu M, Tanaka M, Kimura T, 1987. Oncorhynchus masou virus (OMV): incidence of tumor development among experimentally infected representative salmonid species. Fish Pathology, 22(1):7-10

Yoshimizu M, Tanaka M, Kimura T, 1988. Histopathological study of tumors induced by Oncorhynchus masou virus (OMV) infection. Fish Pathology, 23(2):133-138

Distribution References

CABI, Undated. Compendium record. Wallingford, UK: CABI

CABI, Undated a. CABI Compendium: Status inferred from regional distribution. Wallingford, UK: CABI

OIE Handistatus, 2005. World Animal Health Publication and Handistatus II (dataset for 2004)., Paris, France: Office International des Epizooties.

OIE, 2003. Manual of Diagnostic Tests for Aquatic Animals, 4th Edition., Paris, France: World Organisation for Animal Health.


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Main Author
M Yoshimizu
Hokkaido University, Japan

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