Evaluation of the speed-of-kill of Simparica Trio® against Ixodes ricinus in dogs

BACKGROUND: Rapid and high efficacy against ticks after attachment has the potential to aid in the prevention of tick-borne pathogen transmission. The objective of the study was to assess the speed-of-kill of Simparica Trio® against Ixodes ricinus. METHODS: On Study Day 0, sixteen Beagle dogs were treated with placebo or Simparica Trio at the minimum approved dose (1.24 mg/kg sarolaner, 0.024 mg/kg moxidectin, 5 mg/kg pyrantel). Each dog was infested with 50 unfed viable adult I. ricinus. Efficacy was assessed by in situ tick counts at 12 hours and by counts with removal of the ticks at 24 hours after treatment (Study Day 1) or re-infestation (Study Days 7, 14, 21, 28 and 35 after treatment). Efficacy was evaluated based on reduction of mean live tick counts in the treated versus the placebo group. RESULTS: Against a pre-existing infestation, treatment provided significant reduction in live tick counts (96.2%) within 24 hours after treatment. For subsequent re-infestations, live tick counts were also significantly reduced with efficacy >90% at 24 hours, for at least 36 days. At 12 hours, the number of tick counts was significantly lower in the treated group compared to the placebo group for two weeks, without achieving 90% reduction. CONCLUSIONS: A single treatment with Simparica Trio at the minimum approved dose (1.24 mg/kg sarolaner, 0.024 mg/kg moxidectin, 5 mg/kg pyrantel) is efficacious against I. ricinus within 24 hours after treatment and subsequent re-infestations for 36 days.