Histopathological changes assoicated with the infection of viral deformity virus (VDV) were described in yellowtail fingerlings, Seriola quinqueradiata, from a hatchery in Nagasaki Prefecture. Advanced congestion in the liver, edema and anemia in the kidney, anemia in the spleen and congestion in the various parts of the brain were observed in naturally diseased fish. Experimentally infected fish showed congestion and focal necrosis in the liver, vacuolar degeneration in tubular epithelial

more »

... and edematous changes in the hematopoietic tissue of kidney, and extensive anemia and necrosis of the splenic tissues. In the brain of fish showing abnormal swimming behavior and deformity, advanced congestion and hemorrhage were found in all fish examined. Histopathological features in experimentally infected fish closely resembled those in naturally diseased fish. These findings suggest that lesions in the brain are related to abnormal swimming behavior and deformity of the diseased fish.