Abstract:Eels were experimentally infected with Aeromonas hydrophila which was isolated from European eel (Anguilla anguilla) in order to evaluate the pathological changes and distribution of the bacteria in the organs at different time after the infection.First,we injected Aeromonas hydrophila into the eel muscle in five doses to determine the LD50 of this bacteria.The result showed the LD50 was 5×104 cfu/g of the eel’s body weight.Then eels were injected the bacteria in the dose of 1×107 cfu per fish into the eel muscle.We collected liver,kidney and intestine of the moribund eels at 6,24 and 48 h after the injection,and we studied the pathological symptoms and immunohistochemistry distribution of the bacteria.The result indicated that clinical signs and pathological findings were in accordance with the blood poisoning of eels.Kidney showed more pronounced lesions including necrosis in sinusoids and peritubular capillaries in the kidney compared with the other organs.Liver lesions were hyperaemia,and abiogenetic desquamation of the plasma was in intestine.The most primary distribution of the bacteria in internal organs was kidney.The challenged bacteria were also found in liver and intestine of the eels.