Therapeutic and persistent efficacy of ivermectin, moxidectin and closantel against fenbendazole resistant Haemonchus contortus in sheep

Abstract

Sheep (40) naturally infected with fenbendazole resistarit Haemonchus contortlls were selected to study the therapeutic efficacies of 3 endectocides. On day 10 post-treatment of these sheep with ivermectin (@ 0.2 mg/kg. b.wt.s.c), moxidectin (@0.5 mg/kg. b.wt. pour-on) and closantel (@ (0 mg/kg. b:wL orally), faecal egg count reduction (FECR) was 96.3, 99.4 and 97.7% respectively. Similar results were obtained in 12 experimentally infected lambs where ivermectin, moxidectin and closantel reduced faecal egg counts and worm counts to >99%. The evaluation of persistent efficacies of these endectocides was studied in 80 lambing ewes naturally infected with fenbendazole resistant H. contortus at the same farm for 12 weeks i.e. 1 week before lambing till 11 weeks post-lambing. The effect (>95%) of ivermectin and closantel persisted in treated ewes up to 9 weeks post-lambing, whereas, it remained up to 11 weeks post-lambing in moxidectin treated ewes. Thus present study shows the prolonged persistent effect of endectocides which can be used successfully for the control of fenbendazole resistant H.contortus in sheep.