Evaluation of the efficacy of moxidectin in a herd of goats after long-standing consistent use

Two trials were carried out in a herd of goats, where moxidectin had been consistently used for a long-standing period, in order to monitor its field efficacy. Trial I was carried out after the drug had been used for 4 years/13 times and trial II after it had been used for 7 years/23 times. In each trial, 90 goats naturally infested with gastrointestinal nematodes were divided into three groups (n = 30) and treated as follows: groups I-A and II-A with moxidectin 1% injectable solution at a dose rate of 0.2 mg kg−1 bodyweight, groups I-B and II-B with moxidectin 0.1% oral drench at a dose rate of 0.2 mg kg−1 bodyweight, groups I-C and II-C were kept as untreated controls. Before treatment, mean faecal epg counts were >350.0 for all groups, whilst 14 days later, mean faecal epg counts were 0.0 for groups I-A, II-A, I-B and II-B (percentage reduction after moxidectin administration 100%); 56 days after treatment, mean faecal epg counts were <30.0 for groups I-A, II-A, I-B and II-B (percentage reduction after moxidectin administration >93.5%). Coprocultures revealed the following genera of nematodes in faecal samples Trichostrongylus spp., Teladorsagia spp., Haemonchus contortus, Chabertia ovina, Oesophagostomum spp. and Bunostomum spp. It is concluded that injectable and oral moxidectin are effective against gastrointestinal nematodes in goats at the dose rate of 0.2 mg kg−1 bodyweight.