Chemotherapy for larval echinococcosis in animals and humans: report of a workshop

Mebendazole, its fluorine analogue flubendazole, and other benzimidazole derivatives are active against many gastrointestinal and tissue-stage helminths. This article reviews the published literature and proceedings of a workshop on the use of benzimidazoles against larval echinococcosis (hydatid disease). Orally administered high doses (30-50 mg/kg body weight) of mebendazole given daily for 20-90 days to rodents or sheep infected with larval Echinococcus granulosus cause damage of destruction of the cyst wall, loss of cyst fluid, and death of protoscolices. Similar treatment of rodents infected with E. multilocularis with mebendazole, flubendazole, fenbendazole, and albendazole for 60-300 days leads to reduction of weight, inhibition of growth and the metastases formation of E. multilocularis tissue, and to prolonged host survival time although the metacestodes are not killed. Mebendazole or flubendazole treatment of human patients infected with E. granulosus is followed by subjective improvement in most, and evidence of regression of cysts in some; in other patients, cysts continue to grow or have been proven viable even after several months of high-dose mebendazole therapy. In patients infected with E. Multilocularis, the progressive course of the disease appeared to be arrested, but treatment apparently did not kill the parasite. Side effects of some patients have included allergic reactions, alopecia, and reversible neutropenia. Some possible reasons for different responses to treatment include inadequate plasma drug absorption from the gut and age, condition, and location of cysts. Many remaining questions concerning the risk versus benefits of mebendazole therapy can be answered only through controlled clinical trials.