Efficacy of fluralaner chewable tablets (Bravecto®) against Asian longhorned tick (Haemaphysalis longicornis) infestations of dogs

Abstract

Background The parthenogenic reproductive ability of Haemaphysalislongicornis, facilitating quick life cycle completion and rapid geographic spread and its pathogen vector potential make infestations a risk to human and canine health. Two 90-day studies were initiated to evaluate the efficacy of a single fluralaner administration for the treatment and prevention of H.longicornis infestations on dogs. Methods Dogs were randomly assigned (10 dogs/group) to either an untreated control group or a group treated once (Day 0) with 13.64% w/w fluralaner chewable tablets (Bravecto®) at the minimum label dose rate of 25 mg/kg. Each dog was infested with approximately 50 H.longicornis ticks on Days -9 or -6 and on Days -2, 28, 58 and 88. A different US tick isolate was used in each study. Tick counts were completed on Days -7 or -4, 2, 30, 60 and 90. The primary efficacy criterion was a 90% reduction in arithmetic mean tick counts between the treated and control groups. For between-group comparisons at any assessment, at least six control dogs were required to retain at least 25% of the infestation dose (13 live ticks). Results Pre-study infestations demonstrated susceptibility of all study dogs to challenge with H.longicornis. At each subsequent assessment in both studies, at least seven untreated control dogs retained ≥ 25% of the challenge, demonstrating adequate infestations for each efficacy calculation. On Days 2, 30, 60 and 90 the mean live tick infestation rate (number of ticks recovered from each dog/infesting challenge of each dog) of untreated control dogs ranged from 27.8 to 60.8%. No live ticks, free or attached, were found on any fluralaner-treated dog in either study. Between-group differences were statistically significant (P ≤ 0.0002) at each assessment. Conclusion At the minimum recommended label dose rate of 25 mg/kg, fluralaner chewable tablets were 100% effective in eliminating H.longicornis ticks from dogs infested at the time of treatment. Complete efficacy against both US isolates of this tick was maintained through 90 days following a single treatment. Therefore, fluralaner is a treatment of choice for protecting dogs against this invasive tick species. Graphical abstract