Disease data

Oncorhynchus Masou Virus Disease

Previously listed diseases
Fish
  • Nerka virus Towada Lake, Akita Prefecture (NeVTA) (Japan)
  • Niigata tumour virus (NTV) (Japan)
  • Yamame tumour virus (YTV) (Japan)
Viral disease; Herpesvirus; Oncorhynchus masou virus

Summary from the online OIE Diagnostic Manual

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 harbour Pacific salmon. Oncorhynchus masou virus ( OMV ) , the causative virus, is also known as Yamame tumour virus ( YTV ) , Nerka virus Towada Lake, Akita and Amori prefecture ( NeVTA ) , coho salmon tumour virus ( CSTV ) , Oncorhynchus kisutch virus ( OKV ) , coho salmon herpesvirus ( CSHV ) , rainbow trout kidney virus ( RKV ) , or rainbow trout herpesvirus ( RHV ) . For a recent and more detailed review of the condition, see refs 4, 12 and 13.

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) (6).

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 oedema and haemorrhages. Virus multiplication in endothelial cells of blood capillaries, haematopoietic tissue and hepatocytes underlies the clinical signs ( 7, 11 ) . Four months after this first clinical condition, a varying number of surviving fish exhibit epithelioma occurring mainly around the mouth ( upper and lower jaw ) and, to a lesser extent, on the caudal fin, operculum and body surface. These 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 mouth parts 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 haemorrhage and white spots on the liver are observed ( 5, 15, 16 ) .

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

On the basis of antigenic studies conducted with neutralising polyclonal rabbit antisera, OMV differs from Salmonid herpesvirus 1 ( SalHV-1 ) , which is present in the western United States of America and is only weakly pathogenic ( 3, 9, 12 ) .

The reservoirs of OMV are clinically infected fish and covert carriers among groups of cultured, feral or wild fish. Infectious virus is shed via faeces, urine, sexual products and probably skin mucus, while the kidney, spleen, liver and tumours 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 fertilisation 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 ( 14 ) .

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 ( 6 ) . The main environmental factor favouring OMV infection is low water temperature ( below 14°C )( 10 ) .

The screening procedures for OMV are based on direct isolation of the virus in cell culture and co-culture of neoplastic tissues with salmonid cell lines ( 8 ) . Confirmatory testing is by immunological identification using neutralisation or immunofluorescence tests, and virus-specific gene detection using polymerase chain reaction.

Control methods currently rely on the implementation of avoidance and hygiene practices in the operating of salmonid husbandry. The thorough disinfection of fertilised eggs and the incubation of these eggs and rearing of fry and alevins in premises completely separated from those harbouring virus carriers and free from contact with inanimate objects are the key measures needed to decrease contamination of OMV in a defined fish production site ( 14 ) .

Countries affected

Country Year Status View Records
Japan 2006 Reported present or known to be present View Records
Kuwait 2006 Year of last reported occurrence View Records

Species affected

Species Disease occurence Abstract
Oncorhynchus keta Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Oncorhynchus keta Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Oncorhynchus keta Natural occurrence OIE Aquatic Animal Health Code 2005 [8th edition]
Oncorhynchus keta Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).
Oncorhynchus kisutch Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Oncorhynchus kisutch Natural occurrence World Animal Health in 1997. Part 1. Reports on the animal health status and disease control methods.
Oncorhynchus kisutch Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Oncorhynchus kisutch Natural occurrence OIE Aquatic Animal Health Code 2005 [8th edition]
Oncorhynchus kisutch Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).
Oncorhynchus masou Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Oncorhynchus masou Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Oncorhynchus masou Natural occurrence OIE Aquatic Animal Health Code 2005 [8th edition]
Oncorhynchus masou Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).
Oncorhynchus mykiss Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Oncorhynchus mykiss Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Oncorhynchus mykiss Natural occurrence OIE Aquatic Animal Health Code 2005 [8th edition]
Oncorhynchus mykiss Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).
Oncorhynchus nerka Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Oncorhynchus nerka Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Oncorhynchus nerka Natural occurrence OIE Aquatic Animal Health Code 2005 [8th edition]
Oncorhynchus nerka Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).

Countries affected

Country Year Status View Records
Japan 2006 Reported present or known to be present View Records
Kuwait 2006 Year of last reported occurrence View Records

Species affected

Species Disease occurence Abstract
Oncorhynchus keta Experimental demonstration Studies on a new virus (OMV) From Oncorhynchus masou - I. Characteristics and Pathogenicity.
Oncorhynchus keta Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Oncorhynchus keta Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Oncorhynchus keta Natural occurrence OIE Aquatic Animal Health Code 2005 [8th edition]
Oncorhynchus keta Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).
Oncorhynchus kisutch Experimental demonstration Studies on a new virus (OMV) From Oncorhynchus masou - I. Characteristics and Pathogenicity.
Oncorhynchus kisutch Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Oncorhynchus kisutch Natural occurrence World Animal Health in 1997. Part 1. Reports on the animal health status and disease control methods.
Oncorhynchus kisutch Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Oncorhynchus kisutch Natural occurrence OIE Aquatic Animal Health Code 2005 [8th edition]
Oncorhynchus kisutch Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).
Oncorhynchus kisutch Natural occurrence A case of herpesvirus infection on freshwater-reared coho salmon Oncorhynchus kisutch in Japan.
Oncorhynchus masou Natural occurrence Studies on a new virus (OMV) From Oncorhynchus masou - I. Characteristics and Pathogenicity.
Oncorhynchus masou Natural occurrence Surveillance and control of infectious hematopoietic necrosis virus (IHNV) and Oncorhynchus masou virus (OMV) of wild salmonid fish returning to the northern part of Japan 1976-1991.
Oncorhynchus masou Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Oncorhynchus masou Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Oncorhynchus masou Natural occurrence OIE Aquatic Animal Health Code 2005 [8th edition]
Oncorhynchus masou Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).
Oncorhynchus mykiss Experimental demonstration Studies on a new virus (OMV) From Oncorhynchus masou - I. Characteristics and Pathogenicity.
Oncorhynchus mykiss Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Oncorhynchus mykiss Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Oncorhynchus mykiss Natural occurrence OIE Aquatic Animal Health Code 2005 [8th edition]
Oncorhynchus mykiss Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).
Oncorhynchus nerka Experimental demonstration Studies on a new virus (OMV) From Oncorhynchus masou - I. Characteristics and Pathogenicity.
Oncorhynchus nerka Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Oncorhynchus nerka Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Oncorhynchus nerka Natural occurrence OIE Aquatic Animal Health Code 2005 [8th edition]
Oncorhynchus nerka Natural occurrence OIE Manual of Diagnostic Tests for Aquatic Animals (5th edition, 2006).