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This study was performed to observe the influence of host immune response on the chemotherapy of mice experimentally infected with Fasciola hepatica. Following immunosuppression with prednisolone or immunoenhancement with Freund´s complete adjuvant(FCA), mice were experimentally infected with 3 Fasciola hepatica metacercariae and treated with closantel at 1 week post infection. In the group of mice infected with metacercariae alone, 2 mice of 10 were dead at 10 weeks post infection(20% mortality), and adult flukes were recovered from the liver and the peritoneal cavity of the remaining 8 mice(100% infectivity). In the group of mice treated with prednisolone and infected with metacercariae, 8 of 10 mice died before euthanasia with a mean time of death earlier than the control group (p<0.05). In the group of immunosuppressed mice infected with metacercariae and treated with closantel 20㎎/㎏, 4 of 10 mice died before sacrifice. In the group of mice infected and treated with closantel 20㎎/㎏, mortality and infectivity was 10% and 30%, respectively. Similar results were observed in mice infected and treated with closantel 5㎎/㎏ which resulted in 10% and 50% mortality and infectivity, respectively. These results indicated that the efficacy of closantel treatment was decreased in immunosuppressed mice, while the pathogenicity was increased. In immunoenhanced mice infected with metacercariae, on the other hand, the efficacy of chemotherapy with both 5㎎/㎏ or 20㎎/㎏ closantel resulted in only 10% infectivity. The results shown in this study strongly suggest that a close interaction between chemotherapy against F hepatica with closantel and the host immune system exists. Considering that fascioliasis is a zoonosis, treatment regimen against the infection to immunosuppressed patients may require a concurrent prescription of an appro-priate immuno-enhancing adjuvant.
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