The efficacy of the pour-on formulation of eprinomectin, at a dose rate of 0.5 mg/kg bodyweight, was assessed in sheep against three main species of gastrointestinal nematodes and against the nasal bot fly, Oestrus ovis, and some pharmacokinetic parameters were determined for 21 days after the treatment. By comparison with untreated control sheep, infected experimentally with Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus colubriformis, eprinomectin was 100 per cent effective against the two abomasal species and 99-5 per cent effective against Tcolubriformis. In ewes naturally infected with the nasal bot fly, the efficacy of the drug against 0 ovis was 97.7 per cent. The mean (se) systemic area under the curve (Auc) was 56.0 (26.2) ng/day/ml and the mean residence time was 5.3 (1.0) days, but there were wide variations between individual sheep.
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