One-month comparative efficacy of three topical ectoparasiticides against adult brown dog ticks (Rhipicephalus sanguineus sensu lato) on mixed-bred dogs in controlled environment

This study was designed to compare the therapeutic and residual efficacy for 1 month of three topical ectoparasiticides on mixed-bred dogs against the brown dog tick, Rhipicephalus sanguineus. Adult dogs (n = 32, 10.8–18.4 kg BW) were allocated to 4 groups (n = 8) and infested with 50 adult ticks on days −8, −2, 7, 14, 21, and 28. Within each group, dogs were treated topically on day 0 with a control solution (CS), Vectra® 3D (DPP), Frontline® Plus (FM), or K9 Advantix® (IP). Ticks were enumerated on dogs 24 h after treatment and each subsequent tick infestation by in situ thumb count assessment without removal and at 48 h by combing and removal. Acaricidal efficacy was calculated using arithmetic means for all 24 and 48 h tick count assessments. From 42 to 56 % of the total, infested ticks were found on dogs 48 h post-challenge in the CS group. Therapeutic efficacy for all treatments ranged from 45.5 to 64.6 % after 48 h of infestation. Residual efficacy after FM treatment was consistently lower compared to DPP or IP treatments at the 24 h assessments on days 8, 22, 23, and 29. Residual efficacy measured at this last time point was 94.8 % for DPP, 83.1 % for IP, and 46.9 % for FM. This study demonstrates that permethrin-based formulations (DPP and IP) provided a quicker onset of residual protection against brown dog ticks compared to FM. Although DPP and IP are both permethrin-based formulations, DPP exhibited consistently higher residual acaricidal efficacies and was the only treatment that provided >90 % protection for 1 month at 24 h post challenge.