Recovery of larval Hymenolepis diminuta and H. nana from the retardation produced by prolonged exposure to mebendazole in beetles.

Tribolium confusum infected with Hymenolepis diminuta or H. nana were fed continuously on a mixture of mebendazole and flour from day 1 (24 hr) to day 9, 18, 27, or 36 postinfection when they were dissected. In all cases, underdeveloped cysticercoids were recovered from these hosts, whereas all parasites grown simultaneously in beetles fed on flour only had reached full development. However, when infected beetles were fed on the drug-flour mixture for these periods of time and then on flour only for 9 days thereafter, the inhibiting effect of mebendazole was reversed. Parasites retarded by the drug recovered and developed into infective cysticercoids.