Changes

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>