Macro and microfilaricidal activities of extracts of Annona senegalensis and Milletia comosa against Onchocerca ochengi and Loa loa.

ABSTRACT

Despite the efforts employed for the control of onchocerciasis, the latter has remained a significant public health problem, due mainly to the lack of safe and effective adult worm drugs and/or microfilaricides that do not kill Loa loa microfilariae (mf). Serious adverse events have been encountered after administering ivermectin to some onchocerciasis patients coinfected with Loa loa. There is therefore, an urgent need for a macro and/or microfilaricidal drug which kills Onchocerca but not L. loa microfilariae. A total of 12 crude extracts from Milletia comosa and Annona senegalensis were prepared and screened in vitro against the bovine species of Onchocerca, O. ochengi, and L. loa mf from humans. Mf and male worm viabilities were determined by motility scoring using microscopy at 120 h of incubation with drug, while adult female worm viability and cytotoxicity were determined biochemically by MTT/formazan colorimetry after 120 h of incubation with drug. Out of the 12 extracts, all 6 from M. comosa and 4 from A. senegalensis were active against male, female and mf of O. ochengi. The hexane extract from M. comosa leaves (MCL hex) was the most active with IC50 values of 1.38, 0.86 and 17.74 µg/mL for O. ochengi adult males, adult female and the mf, respectively. About 58% of the extracts were more active against O. ochengi than L. loa mf. These results demonstrate that these extracts contain active principles that kill Onchocerca parasite and to a lesser extent L. loa, and suggest that they can be fractionated for isolation of lead molecules for the safe treatment of onchocerciasis.