Viral encephalopathy and retinopathy in hatchery-reared juvenile thread-sail filefish (Stephanolepis cirrhifer)

The present study characterizes the clinical picture of viral encephalopathy and retinopathy associated with betanodavirus infection in hatchery-reared juvenile thread-sail filefish. Necrotic encephalomyelitis was clearly evident in the spinal cord, the medulla oblongata, and the cerebellum. Necrotic retinitis and gastroenteritis were also noted. Immunohistochemistry using an anti-betanodavirus rabbit serum revealed that the viral antigens were present in the gastrointestinal tract, the spinal cord, the brain and the retina correlating with the histopathological changes. Strong positive immunohistochemical reactions in the stomach and intestine suggest that the gastrointestinal tract was a possible portal of entry into fish.