Categoría: Gastrointestinal Tract

Infectious Salmon Anaemia (ISA) – Gross Pathology

Multisystem, Gastrointestinal Tract, Liver
by Hugh Ferguson

Infectious salmon anaemia (ISA) is a disease caused by infectious salmon anaemia virus (ISAV), genus Isavirus, family Orthomyxoviridae that affects primarily marine-farmed Atlantic salmon (Salmo salar). Recorded for the first time in 1984 in Norway, it still causes recurrent epidemic outbreaks in Chile. The disease is present in most countries that farm Atlantic salmon: Norway, Scotland, Ireland, Faroe Islands, Canada, USA, and Chile. The virus is adapted to cold-water salmonid fish and has an optimum growth at 15°C. Atlantic salmon is the only species known...

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Gastric dilation & Air sacculitis or “Bloat” in salmonids – Gross Pathology

Gastrointestinal Tract
by Carlos Sandoval
Chinook salmon with “Bloat”. Note the severe abdominal distention.

Bloat is a non-infectious condition of salmonids where the abdomen is abnormally distended by an enlarged, fluid-filled stomach. The wall of the enlarged stomach wall is thin and flaccid. Occasionally the swimbladder is also affected.   The condition is seen in salmonids reared in sea water and fed fishmeal-based pelleted rations. While it has been reported occasionally in Atlantic salmon (Salmo salar L.) members of the genus Oncorhynchus are more susceptible. These include Rainbow trout (O. mykiss), Chinook salmon (O. tshawytscha), and Coho salmon (O....

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Syncytial Hepatitis of Tilapia – Transmission Electron Microscopy

Gastrointestinal Tract, Liver
by Hugh Ferguson
Transmission electron micrograph from liver of fingerling tilapia with SHT. Virus particles, typical of orthomyxovirus, can be seen between and within cells (arrows).

Tilapia are considered to be relatively resistant to many of the common diseases that beset other farmed fish. Viral diseases, however, are not common, and there are only a few reports in the literature. Syncytial Hepatitis of Tilapia (SHT) is a newly described viral disease reported from several countries where tilapia farming is present. This virus is a member of the Orthomyxoviridae family. It has been demonstrated within hepatocytes of affected fish. The described ultrastructural changes provide further evidence to support the previous suggestion of...

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Syncytial Hepatitis of Tilapia – Histopathology

Gastrointestinal Tract, Liver
by Hugh Ferguson
Liver; O. niloticus L.; dissociation of hepatocytes containing brown-staining lipoprotein, degeneration and single cell necrosis, plus early hepatocellular syncytial cell formation and moderate diffuse inflammation H&E.

Syncytial Hepatitis of Tilapia (SHT) is a newly described viral disease reported from Ecuador, Israel, Colombia and several other countries where tilapia farming is present. The most consistently described target organs are the liver and gastrointestinal tract, although there are some reports of lesions within the central nervous system. The presence of a novel virus with close affinity to the family Orthomyxoviridae has been demonstrated within hepatocytes of affected fish. Histopathological lesions include necrotizing hepatitis with distinctive hepatocellular syncytial giant cell formation, dissociation of hepatocytes...

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