Histopathological study of lesions caused by Yersinia ruckeri in rainbow trout

Yersinia ruckeri the causative agent of Enteric Red Mouth Disease leading to significant economic losses in salmonid aquaculture industry in Iran and all over the world. In this study sick and dying fish samples from several fish farms of Piranshahr were collected and sent to the microbiology and pathology laboratories. In the laboratory, the bacteria were collected from the intestine. Samples of internal organs were placed in formalin 10% and histological slides were prepared by H&E staining. Ulcers with decrease in mucous cells and columnar cells necrosis was observed in stomach. The lesions in the gills included lamellar edema and atrophy, proliferation of chloride cells, aneurysm in capillaries. Focal necrosis of the inflammatory invaded cells was also observed in liver and kidney.