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'''''

==Clinical Signs==

==Clinical Signs==

IHN causes a '''characteristic “pop-eye” appearance''' in infected fish. The '''skin and fins may be darkened and demonstrate pinpoint haemorrhages'''. Abdominal distension sometimes occurs and the gills may be pale. Casts may be visible trailing from the vent. Fish often '''behave abnormally sporadically.'''

IHN causes a '''characteristic [[Exopthalmos - Fish|“pop-eye”]] appearance''' in infected fish. The '''skin and fins may be darkened and demonstrate pinpoint haemorrhages'''. Abdominal distension sometimes occurs and the gills may be pale. Casts may be visible trailing from the vent. Fish often '''behave abnormally sporadically.'''

Signs can also vary with species, for example Chinook salmon often show subdermal haemorrhage immediately behind their heads<ref>Amend, D. F (1974) '''Infectious Hematopoietic Necrosis (IHN) Virus Disease'''. Fish Disease Leaflet 39. ''USA: United States Department of the Interior'', pp6</ref> and sock-eye salmon smoults have clubbed/fused lamellae.

Signs can also vary with species, for example Chinook salmon often show subdermal haemorrhage immediately behind their heads<ref>Amend, D. F (1974) '''Infectious Hematopoietic Necrosis (IHN) Virus Disease'''. Fish Disease Leaflet 39. ''USA: United States Department of the Interior'', pp6</ref> and sock-eye salmon smoults have clubbed/fused lamellae.

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 '''pathognomonic '''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>

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