The development of host resistance to anthelmintics and the increasing cost of commercial anthelmintics have encouraged the need for the in vitro anthelmintic evaluation of crude extract and fractions of Hymenodictyon pachyanta plant as alternative drugs against Haemonchus contortus. H. contortus is one of the most prevalent and highly pathogenic parasitic nematodes in small ruminant farming globally. H. pachyanta stem bark is a prospective plant used by the local and indigenous farmers of Nsukka, Enugu state, Nigeria. The stem bark of H. pachyanta were collected, dried, pulverized and extracted with 80 % methanol. The purpose of this study was to investigate the in vitro anthelmintic effects of these crude extract and fractions against H. contortus in sheep and goats. The two extracts (crude and fractions) of H. pachyanta were tested by the egg hatch assay (EHA) and the larval development inhibition assays (LDIA) and to compared the results with albendazole (as the positive control). The concentrations for the crude extract and albendazole used for this study were 0.78, 1.56, 3.125, 6.25 and 12.5 mg.ml−1. The results demonstrated that the crude extracts, fractions and albendazole all at the concentration doses of 12.5 mg.ml−1 produced 100 % inhibition of egg hatching and larval development. Statistically, there was no significant difference (P > 0.05) in the mean percentage inhibition of egg hatching and larval development inhibition of the crude extracts and fractions when compared with albendazole. However, a significant difference (P < 0.05) was observed with n-butanol fraction which inhibited 96.17 % of egg hatchability. All of the extracts and albendazole showed ovicidal and larvicidal effects and were able to induce over 50 % of the egg hatching and mortality of larvae at the concentration ranges of 0.78—12.5 mg.ml−1. The results obtained from our study suggest that H. pachyanta had ovicidal and larvicidal activity against H. contortus and that the bioactive plants compounds responsible for this effect could be attributed to the presence of tannins, alkaloids and the saponins contained in the crude extracts.
