Evaluation of the curative and preventive efficacy of a single oral administration of afoxolaner against cat flea Ctenocephalides felis infestations on dogs

The efficacy of orally administered afoxolaner for treatment and prevention of repeated infestations with adult Ctenocephalides felis on dogs was evaluated in two studies after administration of a beef-flavored soft chew. In each study, 32 dogs were divided randomly into four equal groups. Dogs in Groups 1 and 3 were not treated and served as controls. Dogs in Groups 2 and 4 were treated on Day 0 with a combination of chewable tablets to be as close as possible to the minimum therapeutic dose of 2.5 mg/kg. All animals were infested experimentally with unfed C. felis (100 ± 5) on Days −1, 7, 14, 21, 28 and 35. Flea killing efficacy was evaluated in both studies while, efficacy against flea egg production was assessed in Study 1. Live fleas were counted at 12 (Groups 1 and 2) and 24 h (Groups 3 and 4), after treatment or after weekly infestations. In Study 1, flea eggs were collected and counted at either 12 or 24 h after each flea infestation on Days 7, 14, 21, 28 and 35. The results of both studies demonstrate the long lasting and rapid efficacy of afoxolaner against C. felis, when administered as a single oral dose to dogs. For flea counts conducted 24 h after treatment or infestation, efficacy was 100% for all time points up to Day 36 in both studies, except for one time point (99.9% on Day 22) for Study 2. For flea counts performed 12 h after treatment or infestation, efficacy was ≥95.2% until Day 21 in both studies. Efficacy at 12 h was ≥93.0% on Day 35 in Study 1 and ≥89.7% on Day 35 in Study 2. The treated groups had significantly fewer fleas than untreated control dogs in both studies for all flea counts (p = 0.003 Study 1, p = 0.0006 Study 2). In Study 1, for all egg counts performed at or beyond Day 7, efficacy in egg reduction was >99% for all time points between Days 7 and 35.