The efficacy of a Moxidectin subcutaneously injectable formulation in 0.1; 0.2, and 0.4mg Kg-1 body weight was evaluated compared with Ivermectin at 0.2 mg kg-1 and control group. Forty female Holstein yearling, randomly allocated in eight blocks, were artificially infested with 4,000 B. microplus larvae per day from 200mg of eggs in the 20; -17; -14; -7; -1; +5; +9 and +14 days (day 0= treatment day). The counts of semi-ingurged female ticks (4.5 to 8.0mm long) were carried out 21 days after each infestation. The average and the efficacy between the 4 to 20 count days were 982.8 for the control group, 160.3 (85.7%) for the Ivermectin treatment; 205.3 (81.8%), 94.1 (92.2%), and 58.7 (94.55%) for the Moxidectin treatment at 0.1; 0.2 and 0.4mg kg-1, respectively. Significant differences were found (P 0.05) between the control group and all treatments. No significant differences (P> 0.05) were found between Moxidectin 0.4mg kg-1 and Moxidectin and Ivermectin 0.2mg kg-1, respectively. The best treatments efficacy rates against larvae which infested 1 day before the treatments were 94.7% for Ivermectin 0.2mg kg-1 and 91.8%, 97.2%, and 99.7% for Moxidectin 0.1; 0.2 and 0.4mg kg-1, respectively. Infestations that occur 5 days after the treatments (counts on day +26) showed mean counts and efficacy of 165.5 for the control group; 174.5 (8.3%); 109.5 (45.9%), and 22.9 (87.8%) fo
Efficiency of Moxidectin in Boophilus microplus tick control in cattle artificially infested/ Eficiência do Moxidectin no controle do carrapato Boophilus microplus em bovinos artificialmente infestados