Effect of mebendazole against Echinococcus granulosus and Taenia hydatigena cysts in naturally infected sheep and relevance to larval tapeworm infections in man.

The ability of three treatment schedules of mebendazole to kill well-established hydatid cysts was studied. Pregnant sheep, naturally infected with Echinococcus granulosus and/or Taenia hydatigena, were treated daily with mebendazole at a dose rate of 50 mg/kg body weight for either five days, one month, or three months. At autopsy, seven months after the commencement of treatment, no evidence was found that the 5-day treatment schedule had any damaging effect on E. granulosus cysts. The effects of the one month treatment were equivocal. There was evidence of a damaging effect from the 3-month treatment schedule and protoscoleces were not infective to dogs. No T. hydatigena cysts survived the 1- and 3-month treatments, but organisms from the 5-day treatment were infective to dogs. These results for E. granulosus in sheep suggest that long-term treatment with mebendazole may be required in hydatid disease in man. The results obtained for T. hydatigena in sheep are discussed in relation to the treatment of cysticercosis from T. solium in man. Mebendazole showed no untoward effect on the sheep or their lambs.