In vitro activities of itraconazole, methiazole, and nitazoxanide versus Echinococcus multilocularis larvae

Albendazole (ABZ) and mebendazole are the only drugs licensed for treatment of human alveolar echinococcosis. In order to augment the armamentarium against this deadly disease, we tested a series of drugs for their efficacy against Echinococcus multilocularis larvae. E. multilocularis larvae grown intraperitoneally in Mongolian gerbils were transferred into tissue culture. Vesicles budded from the tissue blocks and after 6 weeks, drugs were added, and the effect on the vesicles was observed. We tested the following drugs at various concentrations: ABZ, artemether, caspofungin, itraconazole (ITZ), ivermectin, methiazole (MTZ), miltefosine, nitazoxanide (NTZ), rifampin, and trimethoprim-sulfamethoxazole. ABZ, ITZ, MTZ, and NTZ effectively destroyed parasite vesicles in this in vitro culture system. At high NTZ doses of 10 microg/ml, disintegration of all vesicles was observed after 7 days and was significantly more rapid than with ABZ at equal concentrations (21 days). After drug discontinuation, regrowth of vesicles occurred between 7 and 14 days for all four drugs, indicating a parasitostatic effect. Combination treatment with NTZ-ABZ at concentrations between 1 and 10 microg/ml for either 3 weeks, 3 months, or 6 months yielded no vesicle regrowth during 8 months after drug discontinuation. The treated larval tissue was injected intraperitoneally into gerbils, and no regrowth of larval tissue was observed, suggesting a parasitocidal effect after combined treatment. ITZ, MTZ, and NTZ are potent inhibitors of larval growth, although they proved to be parasitostatic only. The combination of NTZ plus ABZ was parasitocidal in vitro. Animal experiments are warranted for studies of dose, toxicity, and drug interactions.