Abstract

Trichostrongylus colubriformis is an important cause of parasitic gastroenteritis in small ruminants which causes diarrhea, weakness, loss of production and death. The in vitro efficacy of tannins of Newbouldia laevis and Zanthoxylum zanthoxyloides was determined against this parasitic nematode. Larvae of T. colubriformis were incubated at 23°C in the leaf extracts of N. laevis and Z. zanthoxyloides at concentrations of 150, 300, 600 and 1200 µg ml^-1 for three hours, respectively. Phosphate buffered saline (PBS) was used as negative controls. Inhibition of larval migration was significantly (P < 0.05) observed with increasing concentrations of the extracts. In the range of concentration examined, the results were dose-dependent for N. laevis but not for Z. zanthoxyloides. The addition of Polyvinyl polypyrrolidone (PVPP) inhibited total or part of the anthelmintic effect. These results suggest that the larval migration is at least in part due to the action of tannins and supports the traditional use of N. laevis and Z. zanthoxyloides against parasites nematodes. Further research is required to isolate and structurally identify the active anthelmintic compounds, and to improve methods of plant extraction of the effective anthelmintic components that will be readily adaptable for use by rural communities against helminthiasis.

Key words: Larval migration, tannins, Trichostrongylus colubriformis, Newbouldia laevis, Zanthoxylum zanthoxyloides, Benin.