BACKGROUND: Simparica Trio METHODS: Two groups of eight dogs each were ranked based on pretreatment tick counts and then allocated through randomization to treatment on Day 0 with a single dose of either placebo or Simparica Trio at the minimum label dose of 1.2 mg/kg sarolaner, 24 µg/kg moxidectin and 5 mg/kg pyrantel (as pamoate salt). Dogs were infested with 50 viable adult H. longicornis on Days -2, 5, 12, 19, 26 and 33. Tick counts were conducted for all dogs 48 h after treatment and subsequent re-infestations. RESULTS: Simparica Trio was 98.9% effective in treating existing H. longicornis infestation when considering live attached (feeding) ticks. Efficacy remained >
98% in preventing re-infestation for at least 35 days, and the geometric mean live attached tick counts for Simparica Trio-treated dogs were significantly lower than for placebo-treated dogs (P <
0.0002) at all timepoints assessed in the study. Dogs treated with Simparica Trio also had significantly lower (P <
0.0002) geometric mean total live (attached and free) tick counts than placebo-treated dogs at all times. No adverse events were reported for any dogs throughout the duration of the study. CONCLUSIONS: A single administration of Simparica Trio at minimum label dose was efficacious in treating and controlling adult H. longicornis in dogs for more than one month.