The speed of kill of fluralaner (Bravecto™) against Ixodes ricinus ticks on dogs

BACKGROUND: Pathogens that are transmitted by ticks to dogs, such as Anaplasma phagocytophilum, Babesia spp., Borrelia burgdorferi sensu latu, and Ehrlichia canis, are an increasing problem in the world. One method to prevent pathogen transmission to dogs is to kill the ticks before transmission occurs. Fluralaner (Bravecto™) is a novel isoxazoline insecticide and acaricide that provides long persistent antiparasitic activity following systemic administration. This study investigated the speed of kill of fluralaner against Ixodes ricinus ticks on dogs. METHODS: A total of 48 dogs were randomized to 8 groups of 6 dogs and each dog was infested with 50 female and 10 male I. ricinus ticks. Two days later (day 0), 4 groups received a single treatment of 25 mg fluralaner/kg body weight as Bravecto™ chewable tablets; the dogs in the other 4 groups were left untreated. Separate control and treatment groups were paired at each time point (4, 8, 12, or 24 hours after treatment) for assessment of tick-killing efficacy. At 4, 8, and 12 weeks after treatment, all dogs were re-infested with 50 female I. ricinus ticks and subsequently assessed for live or dead ticks at either 4, 8, 12, or 24 hours after re-infestation. Efficacy was calculated for each assessment time point by comparison of the treatment group with the respective control group. RESULTS: Tick-killing efficacy was 89.6% at 4 hours, 97.9% at 8 hours, and 100% at 12 and 24 hours after treatment. Eight hours after re-infestation, efficacy was 96.8%, 83.5%, and 45.8% at 4, 8, and 12 weeks after treatment, respectively. At least 98.1% tick-killing efficacy was demonstrated 12 and 24 hours after re-infestation over the entire 12 week study period. CONCLUSIONS: Fluralaner kills ticks rapidly after treatment at 4 hours, and over its entire 12-week period of efficacy, it achieves an almost complete killing effect within 12 hours after tick infestation. The rapid tick-killing effect together with the long duration of efficacy enables fluralaner to aid in the prevention of tick borne diseases.