Response of pre-adult and adult stages of Trichuris muris to common anthelmintics in mice

The common anthelmintics, oxantel, mebendazole, albendazole and pyrantel were assessed for their comparative activity against Trichuris muris in mice. Mice were infected with T. muris and the infection was maintained by a brief cortisone administration during the second week of infection. Mice carrying the infection with different life cycle stages, viz. fourth stage larvae (L4), pre-adult and adult stages were dosed with anthelmintics. The worm burdens in control infection groups varied although infection dose and other conditions were uniformly followed. With various dose regimens tested, oxantel was highly potent; it eliminated completely pre-adult and adult stages, respectively at 25 and 12.5 mg kg −1 dose levels with significant activity also against adult worms at a 1.56 mg kg −1 dose level and against preadults at a 6.25 mg kg −1 level. Pre-adults required twice the dose given to that of adults for complete (100%) activity. Mebendazole was the next most active; a dosage of 37.5 mg kg −1 was completely active against preadults whereas a dosage of 2 × 50 mg kg −1 was required for complete elimination of adult worms. In addition, about 90% of the worms were eliminated with a single dose of 150 mg kg −1. However, a significant activity was seen against adults at a 25 mg kg −1 level and pre-adults at 37.5 mg kg −1, the lowest level tested. In comparison, albendazole did not induce complete clearance of pre-adult and adult stages even when tested at dose levels as high as 150 and 2 × 75 mg kg −1, respectively. All anthelmintics were completely effective (100% activity) against L4 even with the lowest dose (oxantel 6.25 mg kg −1; mebendazole and albendazole 37.5 mg kg −1) tested. Pyrantel showed a very insignificant activity. Experimental data show that the conditions prevailing in the infected host are important for exerting anti-parasite activity.