The speed of kill of a topical combination of selamectin plus sarolaner against induced infestations of Ixodes scapularis ticks on cats

•Speed of kill of selamectin plus sarolaner was evaluated against Ixodes scapularis in cats.•Selamectin plus sarolaner started to kill ticks within 12 h after treatment.•Efficacy of 100% was observed within 24 h after treatment.•The product started to kill ticks within 24 h after weekly re-infestations, for 5 weeks.•Efficacy observed at 24 h after re-infestation was >94% at 1–3 weeks and >56% at 4–5 weeks.•There were no treatment-related adverse reactions. The speed of kill of a novel, topical product containing selamectin in combination with sarolaner (selamectin/sarolaner; Revolution® Plus/Stronghold® Plus) was evaluated against Ixodes scapularis ticks on cats. Sixteen cats were randomly allocated to a treatment group and treated topically on Day 0 with either placebo (vehicle control) or 6 mg/kg selamectin plus 1 mg/kg sarolaner. Cats were infested with approximately 50 unfed viable adult I. scapularis ticks on Days -2, 7, 14, 21, 28 and 35. Efficacy was assessed at 4, 8, 12, 24, 48 and 72 h after treatment on Day 0 and at 4, 8, 12 and 24 h after post-treatment re-infestations. There were no adverse reactions to the topical treatment with selamectin/sarolaner. Placebo-treated cats maintained tick infestations throughout the study. Treatment with selamectin/sarolaner significantly reduced tick counts within 12 h (P