It has been demonstrated that larval para-sites, at the early stages of infection, were more susceptible to immunological killing [28]. Fur-thermore, in AE infection mice, it has been reported that during 1-2months infection, the hepatocyte proliferation occurred, and might play an important role in fighting against para-sites [23]. Therefore, we hypothesized that critical host immune response might occurred at this time, and we expected that effector mechanisms responsible for elimination of the E. gran-ulosus to be apparent at this stage in sheep with CE infection.