The control of inhibited fourth-stage larvae of Haemonchus contortus and Teladorsagia spp. in sheep in Australia with monepantel

Monepantel is the first molecule from the amino-acetonitrile derivatives to be developed for controlling gastro-intestinal nematodes in sheep. Two studies were undertaken to examine the drug's efficacy against inhibited fourth-stage larvae of Haemonchus contortus and Teladorsagia spp. in sheep when administered as an oral solution at 2.5 mg/kg bodyweight. In study 1, efficacy was 99.7% against H. contortus (p < 0.0001) and in study 2, 99.8% against Teladorsagia spp. (p < 0.0001). This population consisted of 93% T. circumcincta and 7% T. trifurcata. In conclusion, monepantel is a highly effective treatment against inhibited fourth-stage larvae of H. contortus and Teladorsagia spp. and the studies reported here provide the first published evidence of efficacy of this new anthelmintic against these parasites.