Resistance of Abomasal Parasites to Common Anthelmintics in Small Ruminants in the Northeast

The abomasal worm of ruminants, Haemonchus contortus, is detrimental to Northeast sheep and goats. It is also often resistant to anthelmintics commonly used by sheep producers in Maine. We developed methods to assess response of these parasites to anthelmintics. Fecal samples from experimentally infected sheep in West Virginia and from two farms in Maine were used as sources of parasite ova and larvae in these experiments. Parasites were grown to the L3 stage, examined, and then studied using motility tests, Methylthiazol Tetrazolium (MTT) assays and spectrophotometry. Due to selection for resistance over time in Maine parasites, we expect anthelmintics to have a higher kill rate on parasites obtained from West Virginia than on parasites collected from Maine