Metabolic changes in some helminths from sheep treated with mebendazole

Summary

Three parasites (Moniezia expansa, Haemonchus contortus, and Fasciola hepatica), removed from mebendazole-treated sheep at arbitrarily chosen times after treatment, showed detrimental changes in energy metabolism. The changes produced in M. expansa included a reduction in total nucleotides, ATP levels and ATP/ADP ratios, that matched observations made in vitro. Scoleces were found to be more acutely stressed than gravid segments and there was no destrobilation. Similar changes were recorded in H. contortus, though it was evident that neither of the times chosen for assays coincided with maximum drug effect. In F. hepatica the total nucleotide concentration and ATP/ADP ratio increased up to 18 hours after treatment, but after 30 hours both values were significantly depressed.

All three parasites became detached from host tissue while physically and metabolically intact. In the case of H. contortus and M. expansa, detachment did not diminish contact with the drug contained in gastric and intestinal contents. F. hepatica, however, was apparently able to escape further contact with mebendazole, which was considered to be the reason for the ability of some flukes to survive treatment.