Abstract:Thirty rats were randomly divided into experimental and control groups in which 20 rats were chosen for the experimental group and 10 rats used as the control group. To the experimental group of rats, metacercariae of Pagumongonimus skrjabini were injected intraperitoneally, and the animals of each group were killed at various times after infection.The ultrastructural observation by transmission eletron microscopy of the liver tissues of these two groups of rats was made afterwards. It was found that all the livers showed different degrees of fibrosis 2 weeks after infection and the fibrosis aggravated 8 weeks after infection.In addition, inflammation, degeneration, necrosis and hemorrhage were also observed in the liver tissues. It concludes that the infection with P. skrjabini induces hepatic damages in rats, of which the most prominent changes in the ultrastructure of liver are progressive fibrosis.