Changes

Also Known As – '''''IHN – Chinook Salmon Disease – Coleman Disease – Columbia River Sockeye Disease – Cultus Lake Virus Disease – Oregon Sockeye Disease – Sacramento River Chinook Disease – Sockeye Salmon Viral Disease'''''

Also Known As: '''''IHN — Chinook Salmon Disease — Coleman Disease — Columbia River Sockeye Disease — Cultus Lake Virus Disease — Oregon Sockeye Disease — Sacramento River Chinook Disease — Sockeye Salmon Viral Disease'''''

Caused By – ''Infectious Haematopoietic Necrosis Virus – IHNV – Sockeye Salmon Virus''

Caused By: '''''Infectious Haematopoietic Necrosis Virus — IHNV — Sockeye Salmon Virus'''''

==Introduction==

==Introduction==

In some outbreaks a '''sudden increase in mortality''' may be the first sign noted. Epizootics can begin as groups of moribund fish that whirl sporadically or exhibit periods of hyperactivity.  

In some outbreaks a '''sudden increase in mortality''' may be the first sign noted. Epizootics can begin as groups of moribund fish that whirl sporadically or exhibit periods of hyperactivity.  

Some recovered fish can become '''covert carriers'''.<ref> Kim, C. H., Dummer, D. M., Chiou, P. P., Leong, J. C (1999) '''Truncated particles produced in fish surviving infectious hematopoietic necrosis virus infection: mediators of persistence?'''. J Virology, 73(1):843-849</ref>

Some recovered fish can become '''covert carriers'''.<ref> Kim, C. H., Dummer, D. M., Chiou, P. P., Leong, J. C (1999) '''Truncated particles produced in fish surviving infectious hematopoietic necrosis virus infection: mediators of persistence?'''. ''J Virology'', 73(1):843-849</ref>

Mortality in yolk-sac fry and fish <2 months old can reach '''90%'''. Mortality is lower in older fish.

Mortality in yolk-sac fry and fish <2 months old can reach '''90%'''. Mortality is lower in older fish.

Bloodwork of infected fish features '''leucopaenia, neutropaenia, increased numbers of erythrocytes which may be bilobed''', cellular debris, anaemia and low levels of bicarbonate, calcium, phosphorus, chloride and bilirubin.  

Bloodwork of infected fish features '''leucopaenia, [[neutropaenia]], increased numbers of erythrocytes which may be bilobed''', cellular debris, [[:Category:Anaemia|anaemia]] and low levels of bicarbonate, calcium, phosphorus, chloride and bilirubin.  

==Diagnosis==

==Diagnosis==

One of the '''most rapid tests, taking only 15 minutes, is staphylococcal agglutination''' which is performed upon '''cell cultures or infected fish tissues''' using formalin fixed ''Staphylococcus aureus'' cells sensitised with rabbit antiserum which caused agglutination of bacterial cells, visible under a standard light microscope. This test is specific but has poor sensitivity.  

One of the '''most rapid tests, taking only 15 minutes, is staphylococcal agglutination''' which is performed upon '''cell cultures or infected fish tissues''' using formalin fixed ''Staphylococcus aureus'' cells sensitised with rabbit antiserum which caused agglutination of bacterial cells, visible under a standard light microscope. This test is specific but has poor sensitivity.  

Virus can be identified by '''Virus Neutralisation (VN),, Indirect Fluorescent Antibody Testing (IFAT), ELISA, PCR or DNA probe technology'''. It can be isolated from cell culture using kidney, spleen and sometimes mucus in non-lethal sampling methods. Ovarian fluid should be used if breeding stock are being tested. '''The approved test is Virus Neutralisation''' but this is expensive and time consuming, hence the development of more practical, rapid tests, however these are not officially approved.

Virus can be identified by '''Virus Neutralisation (VN),, [[FAT|Indirect Fluorescent Antibody Testing (IFAT)]], [[ELISA testing|ELISA]], PCR or DNA probe technology'''. It can be isolated from cell culture using kidney, spleen and sometimes mucus in non-lethal sampling methods. Ovarian fluid should be used if breeding stock are being tested. '''The approved test is Virus Neutralisation''' but this is expensive and time consuming, hence the development of more practical, rapid tests, however these are not officially approved.

On necropsy of infected fry, the liver, '''spleen and kidneys are pale due to anaemia and ascites is common'''.  The stomach will be full of '''milky fluid''' but no food. Petechial haemorrhages are common throughout many organs. Yellowish fluid or mucus in the intestines is seen in both young and adult fish. The haematopoietic tissues of the kidney and the spleen in young fish are most severely affected, demonstrating small, pale multifocal areas with macrophage infiltration and degenerating lymphoid cells.

On necropsy of infected fry, the liver, '''spleen and kidneys are pale due to anaemia and ascites is common'''.  The stomach will be full of '''milky fluid''' but no food. Petechial haemorrhages are common throughout many organs. Yellowish fluid or mucus in the intestines is seen in both young and adult fish. The haematopoietic tissues of the kidney and the spleen in young fish are most severely affected, demonstrating small, pale multifocal areas with macrophage infiltration and degenerating lymphoid cells.

A '''pathognomic histological feature of IHN is degeneration and necrosis of granular cells in the lamina propria, stratum compactum and stratum granulosum of the gastrointestinal tract'''.

A '''pathognomic '''histological feature of IHN is '''degeneration and necrosis of granular cells in the lamina propria, stratum compactum and stratum granulosum of the gastrointestinal tract'''.

On cytopathology, cells appear '''balloon shaped and nuclei are displaced''' to one side.<ref>Engelking, H. M., Leong, J. C (1981) '''IHNV persistently infects chinook salmon embryo cells.''' Virology, 109(1):47-58</ref>

On cytopathology, cells appear '''balloon shaped and nuclei are displaced''' to one side.<ref>Engelking, H. M., Leong, J. C (1981) '''IHNV persistently infects chinook salmon embryo cells.''' ''Virology'', 109(1):47-58</ref>

Detection of antibodies to IHN is difficult and no test appears to give reliable results at present.

Detection of antibodies to IHN is difficult and no test appears to give reliable results at present.

Animal Health & Production Compendium, '''Infectious Haematopoietic Necrosis datasheet''', accessed 06/07/2011 @ http://www.cabi.org/ahpc/

Animal Health & Production Compendium, '''Infectious Haematopoietic Necrosis datasheet''', accessed 06/07/2011 @ http://www.cabi.org/ahpc/

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