Efficacy and safety of sarolaner (Simparica®) in the treatment and control of naturally occurring flea infestations in dogs presented as veterinary patients in Australia

Background: The efficacy and safety of a novel isoxazoline compound, sarolaner (Simparica (R), Zoetis) and spinosad (Comfortis (R), Elanco) as a positive control were evaluated for the treatment and control of natural flea infestations on dogs in two randomised, blinded, multi-centric clinical trials conducted in 11 veterinary clinics in northeastern and southeastern states of Australia. Methods: A total of 162 client-owned dogs (80 in northern study and 82 in southern study) from 105 households were enrolled. Each household was randomly allocated to receive either sarolaner (Simparica (R), Zoetis) or spinosad (Comfortis (R), Elanco). Dogs were dosed on Days 0, 30 and 60 and physical examinations and flea counts were conducted on Days 0, 14, 30, 60 and 90. Efficacy assessments were based on the percentage reduction in live flea counts post-treatment compared to Day 0. Results: In the northern study, at enrolment, primary dogs had flea counts ranging from 5 to 772. At the first efficacy assessment on Day 14, sarolaner resulted in 99.3% mean reduction in live flea counts relative to Day 0, compared to 94. 6% in the spinosad group. On Day 30, the sarolaner-treated group had mean efficacy of 99.2% compared to 95.7% in the spinosad-treated group, and on days 60 and 90, both groups had mean efficacies of >= 98.8%. In the southern study, at enrolment, primary dogs had flea counts ranging from 5 to 156. Both sarolaner and spinosad resulted in >= 96. 7% mean reduction in live flea counts on Day 14. On Day 30, the sarolaner-treated group had mean efficacy of 99.5% compared to 89.7% in the spinosad-treated group, and on days 60 and 90, both groups had mean efficacies of >= 98. 6%. No treatment-related adverse events were observed in either study. Conclusions: A single monthly dose of sarolaner (Simparica (R)) administered orally at 2-4 mg/kg for three consecutive months was well tolerated and provided excellent efficacy against natural infestations of fleas under a range of Australian field conditions including different climatic and housing conditions. Similar efficacy was observed with spinosad (Comfortis (R)) after the second and third monthly treatments.