Pathology of spontaneous cases of Lactococcus garvieae induced septicemic infection in cultured rainbow trouts in Iran

In the past five years, each year a septicemia took place in the rainbow trout farms in Ilam (Iran), and the agent was identified as Lactococcus garvieae on the basis of microbiological tests. Diseased fish showed clinical symptoms such as lethargie, erratic swimming, skin darkness and exophthalmia. Histopathological alternations were observed in the liver, kidney and spleen. Pathological changes in the liver included hepatocytes degeneration and necrosis, sinusoids dilation and hepatocytes with large lipid droplets, hemorrhages and lymphoid cell infiltrations. Thickening of the basement membrane of glomerulus capsule, narrowing of tubular lumen, tubular epithelial degeneration, hyaline droplets in tubular epithelial cells, marked congestion and hemorrhages were seen in the kidney.