1995 Volume 30 Issue 1 Pages 7-14
Hematological and histological studies were carried out on yellowtail, Seriola quinqueradiata, experimentally infected by intravenous injection of the bacterium causing jaundice of cultured yellowtail.
Hematocrit values and blood hemoglobin concentrations of the experimentally infected fish steadily decreased during 5 days after inoculation. In contrast, plasma hemoglobin and total bilirubin concentrations were maintained at a normal level during 3 days, but rapidly increased on the fifth day after inoculation. Histopathologically, the liver showed moderate focal necrosis and destruction of the endothelium of veins in moribund fish. The most extensive changes were observed in the spleen and kidney : severe anemia and necrosis in the splenic hematopoietic tissue, and degeneration and necrosis in the renal tubules and hematopoietic tissue were found. These pathological changes were similar to those observed in naturally infected fish. By indirect fluorescent antibody technique the bacteria causing jaundice were frequently detected in the spleen and kidney, but not in the hepatic parenchyma.
These findings suggest that in jaundiced yellowtail destruction of red blood cells by the causative bacteria resulted in increases in serum hemoglobin and bilirubin concentrations.
