Changes

Caused By – '''''Viral Haemorrhagic Septicaemia Virus – VHSV – Egtved virus'''''

Caused By: '''''Viral Haemorrhagic Septicaemia Virus — VHSV — Egtved virus'''''

==Introduction==

==Introduction==

Viral Haemorrhagic Septicaemia is an '''economically important haematological disease of fish''', primarily salmonids, caused by a '''bullet shaped, enveloped RNA [[Rhabdoviridae|rhabdovirus]]. '''

Viral Haemorrhagic Septicaemia is an '''economically important haematological disease of fish''', primarily salmonids, caused by a '''bullet shaped, enveloped RNA [[Rhabdoviridae|rhabdovirus]].''' The virus is a member of the genus Novirhabdovirus and they share a common and distinctive feature – the presence of an additional non-virion protein encoding gene.

There are three known serotypes of VSHV with some cross-immunity between them.

There are three known serotypes of VSHV with some cross-immunity between them. Based on phylogenetic analyses of nucleotide sequences the virus has been shown to have four genotypes and they are related to geographical distribution rather than host specficity.

This disease is not zoonotic.

This disease is not zoonotic.

'''Grass carp, rainbow trout, brown trout, grayling, pike, bass, Japanese flounder, turbot, pike, chinook salmon and Atlantic salmon''' can be infected by VHSV.  

'''Grass carp, rainbow trout, brown trout, grayling, pike, bass, Japanese flounder, turbot, pike, chinook salmon and Atlantic salmon''' can be infected by VHSV.  

The number of wild species in which the virus is isolated is large and growing.  

The number of wild species in which the virus is isolated is large and growing and they include both freshwater and marine fish.  

'''Younger fish are more susceptible''' to disease than adults, but this is not exclusive.

'''Younger fish are more susceptible''' to disease than adults, but this is not exclusive.

VHS '''replicates in the vascular endothelial cells, haematopoietic tissues, nephrons''' and the '''leucocytes''' themselves. It then crosses into the blood, accessing and damaging major internal organs. This causes '''impairment of osmotic balance''', haemorrhage and death of the fish.

VHS '''replicates in the vascular endothelial cells, haematopoietic tissues, nephrons''' and the '''leucocytes''' themselves. It then crosses into the blood, accessing and damaging major internal organs. This causes '''impairment of osmotic balance''', haemorrhage and death of the fish.

VHS is the '''most important viral disease of farmed rainbow trout''', causing '''lethargy, darkening of the skin, disorientation and erratic swimming behaviour such as flashing and cork screwing'''. Fish may congregate together in still areas or on the bottom of the tank. '''Exophthalmia''' is often a feature. '''Haemorrhages may be visible in the musculature and around the orbit''' or fish may have a pot bellied appearance due to internal bleeding and/or ascites. The '''gills become markedly pale due to anaemia'''. There are '''three forms''' of disease: '''acute''' which causes clinical signs, behavioural changes and moribund fish; '''chronic''' which produces few or no external signs but has visceral pathology and haematological suppressive effects; and '''nervous''', which causes constant flashing, tail chasing and spiralling behaviour due to its marked tropism for the brain.

VHS is the '''most important viral disease of farmed rainbow trout''', causing '''lethargy, darkening of the skin, disorientation and erratic swimming behaviour such as flashing and cork screwing'''. Fish may congregate together in still areas or on the bottom of the tank. '''Exophthalmia''' is often a feature. '''Haemorrhages may be visible in the musculature and around the orbit''' or fish may have a pot bellied appearance due to internal bleeding and/or ascites. The '''gills become markedly pale due to anaemia'''.  

 

There are '''three forms''' of disease:

:'''acute''' which causes clinical signs, behavioural changes and moribund fish

:'''chronic''' which produces few or no external signs but has visceral pathology and haematological suppressive effects

:'''nervous''', which causes constant flashing, tail chasing and spiralling behaviour due to its marked tropism for the brain

VHS causes '''significant mortality in turbot and Japanese flounder''' in aquaculture.  

VHS causes '''significant mortality in turbot and Japanese flounder''' in aquaculture.  

==Diagnosis==

==Diagnosis==

Virus can be '''isolated from cell cultures''' and confirmed immunologically by'''virus neutralisation, immunofluorescence, [[ELISA testing|ELISA]], immunoperoxidase staining or reverse transcriptase PCR (RT-PCR) '''. Of these, the serological methods such as neutralisation and PCR may be more importamt for detection of carrier fish, while the others are useful for fish with overt disease.

Virus can be '''isolated from cell cultures''' and confirmed immunologically by '''virus neutralisation, [[immunofluorescence]], [[ELISA testing|ELISA]], immunoperoxidase staining or reverse transcriptase PCR (RT-PCR) '''. Of these, the serological methods such as neutralisation and PCR may be more important for detection of carrier fish, while the others are useful for fish with overt disease.

On necropsy, '''widespread haemorrhages''' are seen in the '''liver''', in the '''adipose tissue''' and within the '''musculature. Systemic haemorrhage''' may involve the '''eyes''' and viscera. The '''kidneys''' may be '''red and swollen''' if in early stages of disease or '''pale and necrotic''' with '''white-grey patches''' visible later on. The '''intestines are often full of stringy mucus''' and no food is present.  

On necropsy, '''widespread haemorrhages''' are seen in the '''liver''', in the '''adipose tissue''' and within the '''musculature. Systemic haemorrhage''' may involve the '''eyes''' and viscera. The '''kidneys''' may be '''red and swollen''' if in early stages of disease or '''pale and necrotic''' with '''white-grey patches''' visible later on. The '''intestines are often full of stringy mucus''' and no food is present.  

==Control==

==Control==

'''Official health surveillance and control policies''' are in place and have successfully eradicated the disease from several parts of Europe.  

'''Official health surveillance and control policies''' are in place and have successfully eradicated the disease from several parts of Europe.  

'''Genetic selection and vaccination are in their experimental stages. '''

'''Genetic selection and vaccination are in their experimental stages. '''

{{Learning

{{Learning

==References==

==References==

<references/>

<references/>

Animal Health & Production Compendium, '''Viral Haemorrhagic Septicaemia Virus datasheet''', accessed 31/07/2011 @ http://www.cabi.org/ahpc/

Smail, D.A., Snow, M. (2011). '''Viral Haemorrhagic Septicaemia'''. In: '''Fish Diseases and Disorders, Volume 3''': Viral, Bacterial and Fungal Infections, 2nd edition (eds. P.T.K Woo and D.W. Bruno), ''CABI'', Wallingford, U.K. pages 110-142.

|datasheet = [http://www.cabi.org/ahpc/?compid=3&dsid=66346&loadmodule=datasheet&page=2144&site=160 viral haemorrhagic septicaemia] and [http://www.cabi.org/ahpc/?compid=3&dsid=66348&loadmodule=datasheet&page=2144&site=160 viral haemorrhagic septicaemia virus]

 

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