Anogeissus leiocarpus extract on the parasite nematode Onchocerca ochengi and on drug resistant mutant strains of the free-living nematode Caenorhabditis elegans

The ethanolic extract of Anogeissus leiocarpus was assessed for the in vitro anthelmintic activity by using the cattle parasite nematode Onchocerca ochengi as well as levamisole-, ivermectin- and albendazole-resistant mutant strains of the free-living nematode Caenorhabditis elegans, a model organism for research on nematode parasites. Worms were incubated in the presence of different concentrations of the plant extract and effects on survival were monitored after each 12 h to 96 h. The A. leiocarpus extract affected O. ochengi microfilaria, adults, and C. elegans wild-type worms with LC50 values of 0.06 mg/ml, 0.09 mg/ml after 24 h and 0.44 mg/ml after 48 h, respectively. Remarkably, the efficacy of the plant extract was not significantly altered in the ivermectin- and levamisole-resistant C. elegans mutant strains lev-1(e211), glc-2(ok1047), lev-9(x16) and avr-14(ad1302), avr-15(ad1051), glc-1(pk54). The albendazole resistant strain ben-1(e1880) exhibited a moderate increase of the LC50 value to 1.5 mg/ml after 48 h. These results are in good accordance with the use of A. leiocarpus extract against nematode infections by traditional healers, herdsmen and pastoralists. Moreover, the data indicate that the plant extract could be used to treat nematode infections even in cases of drug resistance towards established anthelmintic drugs.