Experimental model in rats for study on transmission dynamics and evaluation of Clonorchis sinensis infection immunologically, morphologically, and pathologically.

This study aims to gain a better insight into the transmission patterns and immunologic profile of Clonorchis sinensis infection and make a headway on the pathogenesis regarding cholangiocarcinoma and hepatic lesions. Experimental models orally infected by C . sinensis metacercariae were constructed in rats. Immunological assays were performed to measure serum level of IgA, IgE, IgG1, IgG2a, IFN-gamma, and IL-4. Infection parameters were assessed by worm recovery rate, eggs per gram faece and worm size. Pathological sections with livers were managed with immunofluorescence, hematoxylin, eosin, and Masson's trichrome staining to evaluate the hepatic pathological changes. Interestingly, rats infected with only one C . sinensis metacercariae even gained a high worm recovery rate of 83.3% compared with rats infected with more metacercariae. Serological changes according to different infection doses indicated that immune response presented a tendency to Th2 type by expressing transient high level of IgG1, IL-4, and IgE. Hepatic tissues appeared inflammatory and fibrotic, revealed by different stainings. Intrahepatic bile ducts displayed cholangiectasis and proliferation with excreted/secreted antigen histologically located. C . sinensis, as a fish-borne zoonosis, presented novel transmission patterns which explained high infection rate in endemic areas; infection rate of C . sinensis was frequency-dependent and dose-related. Humoral immunity played a prevalent role in resisting to C . sinensis based on the rat models. C . sinensis infection played an undoubted role in biliary and hepatic diseases.