Efficacy of moxidectin 0.5% pour-on against naturally acquired nematode infections in cattle in the Mexican tropics

The efficacy of 0.5% moxidectin pour-on in cows with naturally acquired nematode infections was evaluated. The study was carried out in a ranch in Veracruz, Mexico. Four groups of 15 cows were randomly allocated. Animals in the treated group received 0.5% moxidectin pour-on at a dose of 0.5 mg/kg body weight on a single occasion. The other two groups remained as untreated controls. Fecal samples from all cattle were taken on days 0 (pre-treatment), 7, 14, 28 and 60 (post-treatment, PT). Fecal egg-counts were determined using a modified McMaster technique and fecal cultures were performed to identify gastrointestinal nematodes infected larvae (L3). Treatment with moxidectin was associated with a significant reduction in fecal trichostrongyle egg-counts compared with the controls; efficacy was 100% at 28 days PT. Haemonchus spp. and Strongyloides spp. were the two genera identified from coprocultures.