What are the clinical signs of Infectious Salmon Anaemia (ISA)?

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Multiple Choice

What are the clinical signs of Infectious Salmon Anaemia (ISA)?

Infectious Salmon Anaemia is a systemic viral infection that causes widespread damage to blood vessels and red blood cells. The hallmark is severe anemia, which, together with vascular injury, leads to variable hemorrhages and necrosis in multiple organs such as the spleen, kidney, liver, and heart. Clinically, affected fish are often pale, lethargic, and may show signs of poor feeding with abdominal swelling or edema from vascular leakage and ascites. Autopsy typically reveals pale gills and pale, hemorrhagic, necrotic organs, reflecting the extensive systemic involvement. This pattern—severe anemia with multisystem hemorrhages and necrosis—is why the statement describing those signs best fits Infectious Salmon Anaemia. Other patterns like mild fever with only skin lesions, isolated respiratory signs, or neurological signs without anemia do not align with the characteristic systemic anemia and multi-organ hemorrhage of ISA.

Infectious Salmon Anaemia is a systemic viral infection that causes widespread damage to blood vessels and red blood cells. The hallmark is severe anemia, which, together with vascular injury, leads to variable hemorrhages and necrosis in multiple organs such as the spleen, kidney, liver, and heart. Clinically, affected fish are often pale, lethargic, and may show signs of poor feeding with abdominal swelling or edema from vascular leakage and ascites. Autopsy typically reveals pale gills and pale, hemorrhagic, necrotic organs, reflecting the extensive systemic involvement.

This pattern—severe anemia with multisystem hemorrhages and necrosis—is why the statement describing those signs best fits Infectious Salmon Anaemia. Other patterns like mild fever with only skin lesions, isolated respiratory signs, or neurological signs without anemia do not align with the characteristic systemic anemia and multi-organ hemorrhage of ISA.

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