Detecting in vitro anthelmintic effects with a micromotility meter.

An in vitro target parasite anthelmintic assay utilizing a micromotility meter has been developed and validated. Haemonchus contortus, an economically important ruminant helminth with worldwide distribution, was the parasite used in the model. Four commercially available ruminant anthelmintics (albendazole, ivermectin, levamisole hydrochloride and coumaphos) were initially evaluated at concentrations of 200, 150, 100 and 50 micrograms ml-1. All four significantly affected helminth motor activity and were active at 200 and 150 micrograms ml-1, and three of the four were active at 100 and 50 micrograms ml-1. An Upjohn compound (p-toluoyl chloride phenylhydrazone) was also assayed and was significantly active at all four levels. In a subsequent titration study, albendazole, levamisole hydrochloride, ivermectin and the hydrazone were significantly active at 100 and 10 micrograms ml-1; only levamisole hydrochloride and the hydrazone were active at 1.0 microgram ml-1. None of the drugs were active at 0.1 microgram ml-1. The data indicate that the in vitro H. contortus assay utilizing the micromotility meter is sensitive, accurate, rapid, repeatable, and inexpensive. With additional effort, this model can be extended to incorporate other target helminth parasites and stages of development. This in vitro assay system should be a valuable addition to the battery of tests used to identify anthelmintic candidates, monitor drug resistance, and define the kinetics and mode of action of drugs.