Comparative speed of kill of oral treatments with Simparica™(sarolaner) and Bravecto®(fluralaner) against induced infestations of Rhipicephalus sanguineus on dogs

Background: Rhipicephalus sanguineus is the most widely distributed tick species infesting dogs worldwide, which may cause discomfort to the host and transmit diseases. Acaricides with a rapid and sustained speed of kill are thus important to prevent infestation and to reduce the risk of disease transmission. In this study, the speed of kill of a monthly administered Simparica (TM)(sarolaner) treatment against induced infestations with R. sanguineus on dogs was evaluated and compared with a single dose of Bravecto (R)(fluralaner) for 95 days after the initial treatment. Methods: Twenty four dogs were randomly allocated to treatment and were treated with either placebo or sarolaner (at 2 to 4 mg/kg) on Days 0, 30 and 60 or with fluralaner (at 25 to 56 mg/kg) once on Day 0. Tick counts were performed in situ 8 and 12 h and with removal of the ticks 24 h after treatment and subsequent re-infestations on Days 14, 28, 44, 56, 74, 90 and 95. Acaricidal efficacy was determined at each time point relative to the placebo group. Results: Both products significantly reduced live ticks within 8 h after treatment against an existing infestation with R. sanguineus, and killed all ticks on all dogs within 24 h. After re-infestation, sarolaner provided >= 98.5 % reduction within 24 h on all days except Days 74 and 95 (P < 0.0001), compared to fluralaner which provided >= 95.5 % reduction until Day 44. Geometric mean live tick counts for sarolaner were significantly lower (P <= 0.0415) at 24 h than those for fluralaner on all days, except on Days 0, 14 and 28 (P >= 0.0678). There were no treatment-related adverse reactions observed during the study. Conclusions: When dosed at monthly intervals for 3 consecutive months, Simparica (TM) has a faster and more consistent speed of kill against R. sanguineus than a single oral dose of Bravecto (R) for which efficacy decreased after Day 44.