Efficacy of oral afoxolaner against <i>Amblyomma maculatum</i> infestations in dogs

Amblyomma maculatum, the Gulf Coast tick, is a species of significant veterinary and public health importance, especially because it is a vector of important diseases, such as American canine hepatozoonosis and tidewater spotted fever. Amblyomma maculatum infests a wide range of vertebrates including livestock, dogs, cats, and humans. Two experimental studies were conducted to evaluate the efficacy of afoxolaner formulated in an oral tablet (NexGard^®) against induced infestations of A. maculatum in dogs. These Good Clinical Practice (GCP) studies used a randomized, negative controlled and masked design. In each study, 10 dogs were allocated to an untreated group and 10 dogs to a treated group, dosed once on Day 0 with a combination of tablets targeting the minimum therapeutic dose (2.5 mg/kg afoxolaner). Dogs were infested with 50 unfed adult A. maculatum on Days -2, 7, 14, 21, 28, and 35 (Study #1), or on Days -1, 14, and 28 (Study #2). Seventy-two (72) hours after treatment and subsequent infestations, ticks were removed and the numbers of live ticks in each group were used for efficacy calculations. At each time-point, all untreated dogs were adequately infested (i.e., with more than 12 live ticks), demonstrating a vigorous tick population and an adequate study model. The curative efficacy against established infestations, 72 hours after treatment, was 100% in Study #1 and 99.5% in Study #2. The preventive efficacy, 72 hours after the post-treatment infestations, ranged from 94.6% to 98.9% for five weeks in Study #1, and was ≥98.8% for four weeks in Study #2.