Evaluation of the speed of kill of fleas and ticks with Frontline Top Spot in dogs.

The speed of kill of a spot-on formulation of fipronil (Frontline Top Spot, Merial Limited, Duluth, GA) against adult cat fleas (Ctenocephalides felis) and brown dog ticks (Rhipicephalus sanguineus) was evaluated in dogs in a commercial laboratory setting. Forty dogs were allocated to 20 replicates of two based on sex and pretreatment flea counts. Within each replicate, dogs were randomly allocated to an untreated control group or to treatment with fipronil, administered topically as a spot-on per label instructions. The technical staff performing the flea and tick counts were unaware of treatment group assignments. Each dog was infested with approximately 100 unfed adult fleas on Day -8 or -6 and on Day -1. Each dog also was infested with approximately 50 unfed adult ticks on Day -1. Treatments were administered on Day 0 according to body weight. Flea and tick counts were performed on four randomly selected dogs from each treatment group at approximately 6, 12, 18, 24, and 48 hours after treatment. Flea and tick count reductions for dogs treated with fipronil were significant (P < .05), as compared with untreated controls, at 18, 24, and 48 hours after treatment. Controlled efficacy of fipronil against C. felis and R. sanguineus ranged from 94% to 100% at these evaluation times. This study demonstrated that the speed of kill of fipronil, applied topically as a spot-on, was 100% against C. felis fleas on dogs within 12 to 18 hours after treatment and 100% against R. sanguineus ticks between 24 and 48 hours after treatment.