Changes

Also Known As – '''''ISA'''''

Also Known As: '''''ISA'''''

Caused By – ''Infectious Salmon Anaemia Virus – ISAV''

Caused By: '''''Infectious Salmon Anaemia Virus –-  ISAV'''''

==Introduction==

==Introduction==

Norway, Canada, Scotland, Eastern USA, Chile and Ireland.

Norway, Canada, Scotland, Eastern USA, Chile and Ireland.

The virus '''replicates within the sea trout''', forming a marine reservoir for the virus, and their migration allows distant distribution of the disease.

ISAV '''replicates in Atlantic salmon''', forming a marine reservoir for the virus, and their migration allows distant distribution of the disease. The virus also replicates in other fish species (e.g. rainbow trout, Atlantic cod, chum, coho and Chinook salmon, Arctic Char) but no disease has been observed under aquaculture conditions. However, these species may serve as reservoir hosts for the virus.

Transmission is mainly '''via the water, virus being shed into it in mucus, faeces, urine and also via the skin'''.<ref name="TD"> Thorud, K., Djupvik, H. O (1988) '''Infectious anaemia in Atlantic salmon (Salmo salar L.)'''. Bulletin of the European Association of Fish Pathologists, 8(5):109-111</ref> It then enters vulnerable fish via the '''gills or broken skin'''. ISA also has a crustacean vector for transmission.  

Transmission is mainly '''via the water, virus being shed into it in mucus, faeces, urine and also via the skin'''.<ref name="TD"> Thorud, K., Djupvik, H. O (1988) '''Infectious anaemia in Atlantic salmon (Salmo salar L.)'''. ''Bulletin of the European Association of Fish Pathologists'', 8(5):109-111</ref> It then enters vulnerable fish via the '''gills or broken skin'''. ISA also has a crustacean vector for transmission.  

Spread between netpens is usually slow, and mortality and severity often varies between them.  

Spread between netpens is usually slow, and mortality and severity often varies between them.  

==Signalment==  

==Signalment==  

A range of salmonid fish can be affected including rainbow trout, sea trout, Atlantic cod, chum, coho, Chinook and atlantic salmon and arctic charr. Both wild and farmed fish are susceptible.

A range of salmonid fish can be affected including rainbow trout, sea trout, Atlantic cod, chum, coho, Chinook and Atlantic salmon and Arctic Char. Both wild and farmed fish are susceptible.

==Clinical Signs==

==Clinical Signs==

Disease results in '''severe anaemia and multi-organ haemorrhage. This may be''' seen as '''pallor, abdominal distension, scale oedema or fluid accumulation''' in the abdomen and musculature. The '''gills often pale''' first and most markedly. Fish may develop a “pop-eye” appearance '''(exopthalmos)''', be lethargic and '''sink''' to the bottom of their habitat.

Diseased fish are usually in normal nutritional condition but may swim sluggishly near the water surface or "hang" listlessly at the wall of the netpen and eventually sink to the bottom.

 

ISA infections eventually cause '''severe anaemia and multi-organ haemorrhage'''. This may be seen as '''pallor, abdominal distension, scale oedema or fluid accumulation''' in the abdomen and musculature. The '''gills '''are often '''pale''' first and most markedly. Fish may develop a “pop-eye” appearance '''([[Exopthalmos - Fish|exopthalmos]])'''.

'''Haematocrit values below 10''' are seen in advanced disease, commonly being found <25 and thus leading to multi-organ dysfunction.

'''Haematocrit values below 10''' are seen in advanced disease, commonly being found <25 and thus leading to multi-organ dysfunction.

==Diagnosis==

==Diagnosis==

'''Clinical signs and pathological/histopathological findings''' are highly suggestive of ISA. '''Hepatomegaly, ascites and splenomegaly''' are marked with white/grey patches of necrosis often visible on the liver and dark red splenic congestion. '''Petechiation in the adipose tissue and swim bladder''' is also common.<ref name="TD" /> The major histopathological feature is'''multifocal haemorrhagic necrosis of the liver''' that may become confluent.<ref> Evensen, O., Thorud, K. E., Olsen, Y. A (1991) '''A morphological study of the gross and light microscopic lesions of infectious anaemia in Atlantic salmon (Salmo salar)'''. Research in Veterinary Science, 51(2):215-222; 23</ref> This leads to '''congestion and sinusoid dilation which eventually fill with blood'''. The sinusoid endothelium degenerates and eventually disappears entirely. In diseased fish in the USA in particular, '''renal interstitial haemorrhage''' is a dominant feature, with tubular necrosis, congestion and cast formation.

'''Clinical signs and pathological/histopathological findings''' are highly suggestive of ISA. '''Hepatomegaly, ascites and splenomegaly''' are marked with white/grey patches of necrosis often visible on the liver and dark red splenic congestion. '''Petechiation in the adipose tissue and swim bladder''' is also common.<ref name="TD" /> The major histopathological feature is '''multifocal haemorrhagic necrosis of the liver''' that may become confluent.<ref> Evensen, O., Thorud, K. E., Olsen, Y. A (1991) '''A morphological study of the gross and light microscopic lesions of infectious anaemia in Atlantic salmon (Salmo salar)'''. ''Research in Veterinary Science'', 51(2):215-222; 23</ref> This leads to '''congestion and sinusoid dilation which eventually fill with blood'''. The sinusoid endothelium degenerates and eventually disappears entirely. In diseased fish in the USA in particular, '''renal interstitial haemorrhage''' is a dominant feature, with tubular necrosis, congestion and cast formation.

The virus can also now be '''isolated in cell cultures, detected by Indirect Immunofluorescent Antibody Testing (IFAT) in tissue imprints or detected in fixed sections by immunostaining''' for definitive diagnosis. '''PCR''' tests are also available in the form of RT-PCR.  

The virus can also now be '''isolated in cell cultures, detected by [[Immunofluorescence|indirect immunofluorescent antibody testing (IFAT)]] in tissue imprints or detected in fixed sections by immunostaining''' for definitive diagnosis. '''PCR''' tests are also available in the form of RT-PCR.  

==Treatment==

==Treatment==

==References==

==References==

<references/>

<references/>

Animal Health & Production Compendium, '''Infectious Salmon Anaemia Virus datasheet''', accessed 07/07/2011 @ http://www.cabi.org/ahpc/

Rimstad, E., Dale, O.B., Dannevig, B.H. and Falk, K. 2011. '''Infectious Salmon Anaemia.''' In: '''Fish Diseases and Disorders, Volume 3: Viral, Bacterial and Fungal Infections,''' 2nd edition (eds. Woo, P.T.K. and Bruno, D.W.), ''CABI'', Wallingford, UK. Pp143-165.

|datasheet = [http://www.cabi.org/ahpc/?compid=3&dsid=79288&loadmodule=datasheet&page=2144&site=160  infectious salmon anaemia] and [http://www.cabi.org/ahpc/?compid=3&dsid=59942&loadmodule=datasheet&page=2144&site=160 infectious salmon anaemia virus]

 

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