Evaluation of the anthelmintic efficacy of an ivermectin controlled-release capsule in lambs under field conditions in Europe

Three field trials were conducted in Germany, Slovakia and UK to evaluate the anthelmintic efficacy and productivity responses attributable to treatment of lambs with an intra-ruminal controlled-release capsule which is designed to deliver ivermectin at 0.8 mg/day for 100 days to lambs weighing 20-40 kg at treatment. Sixty Merino Landrace, 60 Valaska or 52 Suffolk cross lambs weighing between 24.0 and 40.0 kg at the time of treatment were used. Lambs were either untreated (or subjected to salvage treatment) or they received an ivermectin controlled-release capsule. Faecal egg and larval counts of various nematodes, body weights and scores of the faecal soiling of the breech area (formation of dags) were determined before treatment and at 28, 56, 84, 98 and 112 days after treatment. Before treatment, faecal strongyle, Nematodirus and Trichuris egg counts and Dictyocaulus filaria larval counts were not significantly different (P > 0.05 or P > 0.1) between groups, but at each point of time thereafter, egg and larval counts of the ivermectin controlled-capsule treated lambs were significantly reduced compared to the untreated controls. Lambs treated with the ivermectin controlled-release capsule gained significantly more weight (10.9, 11.1 or 11.1 kg, respectively) over the 112 days of the trials compared to untreated lambs (8.2, 9.7 or 5.5 kg, respectively). The mean scores of faecal soiling were not different at the start of the trials (P > 0.05 or P > 0.1), but at the end of the trials, the ivermectin controlled-release capsule treated lambs had significantly lower scores of faecal soiling than the controls. (C) 1999 Elsevier Science B.V. All rights reserved.