Comparative efficacy of topical treatments with Revolution Plus (selamectin and sarolaner) and Bravecto for Cats (fluralaner) against Ixodes scapularis ticks on cats.

The efficacy of three consecutive monthly treatments with a novel topical product (Revolution Plus/Stronghold Plus, Zoetis) containing selamectin in combination with the isoxazoline, sarolaner, was compared with that of another topical isoxazoline, fluralaner [Bravecto (fluralaner topical solution) for Cats, Merck] against Ixodes scapularis ticks on cats. Twenty-four cats were ranked by pre-treatment tick counts to form groups of three and were randomly allocated to be treated with placebo, the minimum label dosage of Revolution Plus (6 mg/kg selamectin plus 1 mg/kg sarolaner) or the minimum label dosage of Bravecto for Cats (40 mg/kg fluralaner) within the groups. On Days 0, 30, and 60, each cat in the placebo and Revolution Plus-treated groups was treated topically, whereas cats in the Bravecto for Cats-treated group were treated topically once on Day 0 with fluralaner and, subsequently, these animals were treated with the placebo on Days 30 and 60 to maintain masking. Doses were calculated based on weight to provide the minimum label dosage for each product; the calculated volume of product to be administered was rounded off to the nearest 0.1 mL. The selamectin plus sarolaner-treated cats received effective dosages of 5.29-7.12 mg/kg selamectin and 0.88-1.19 mg/kg sarolaner, while the fluralaner cats received dosages of 35.21-43.16 mg/kg fluralaner. Cats were infested with approximately 50 unfed viable adult I. scapularis ticks on Days 5, 12, 26, 40, 54, 68, 82, and 88. Efficacy was assessed at 48 h after each infestation. There were no adverse reactions to any treatment during the study. The placebo-treated cats maintained adequate tick infestations throughout the study. Three monthly treatments with selamectin plus sarolaner (Revolution Plus) resulted in high and consistent efficacy against I. scapularis for up to 30 days after each treatment. Based on geometric means, efficacy was ≥99.1% at all time points assessed. Treatment with fluralaner (Bravecto for Cats) provided high and consistent efficacy of ≥99.3% up to Day 70. On Day 84, efficacy was 90.1%; however, cats from which ticks were recovered on Day 84 had received approximately 4%-12% less than the minimum dosage of 40 mg/kg fluralaner. Three consecutive monthly treatments with Revolution Plus or a single treatment with Bravecto for Cats provided >90% control of I. scapularis ticks over a 12-week time period.