Evaluation of the speed of kill of sarolaner (Simparica™) against induced infestations of three species of ticks (Amblyomma maculatum, Ixodes scapularis, Ixodes ricinus) on dogs.

The rapid speed of kill of sarolaner (Simparica™, Zoetis), a novel isoxazoline compound, was demonstrated against three tick species known to infest dogs in Europe or the United States. Efficacy was measured against an existing infestation and against subsequent weekly re-infestations for 35 days after treatment. Dogs were randomly allocated to treatment with a single oral dose of either placebo or sarolaner (2mg/kg) based on pre-treatment host-suitability tick counts. Dogs were infested with approximately 50 unfed adult Ixodes scapularis, Ixodes ricinus or Amblyomma maculatum ticks on Days-2, 7, 14, 21, 28 and 35. Tick counts were conducted at 4 (I. scapularis only), 8, 12 and 24h after treatment on Day 0 and after each subsequent re-infestation. No treatment-related adverse reactions occurred during any of these studies. Dogs in the placebo-treated groups maintained adequate tick infestations (recovery of 20-70% of applied ticks) throughout the duration of the studies. Following treatment, live tick counts were significantly reduced relative to placebo at the 8h post treatment counts indicating that sarolaner started killing existing infestations of ticks rapidly after treatment. Efficacy was 90.1% against I. ricinus, 98.8% against I. scapularis, and 99.2% against A. maculatum within 12h, and 100% efficacy was achieved at 24h after treatment against all three tick species. This speed of kill was maintained throughout the month with ≥95.7%, ≥98.7% and ≥89.6% efficacy against I. scapularis, I. ricinus, and A. maculatum, respectively, at 24h after re-infestation at least through Day 28.