Efficacy of selamectin and fipronil-(S)-methoprene spot-on formulations applied to cats against adult cat fleas (Ctenocephalides felis), flea eggs, and adult flea emergence.

A study was conducted to evaluate the efficacy of selamectin and fipronil-(S)-methoprene against adult cat fleas (Ctenocephalides felis), flea egg production, and the viability of flea eggs collected from treated cats. Cats were infested with approximately 50 adult fleas 2 days before treatment and weekly thereafter; flea eggs were collected and counted on days 0, 1, 2, and 3 and 48 and 72 hours after each weekly flea infestation. Live fleas were collected approximately 72 hours after treatment or infestation. Compared with fipronil-(S)-methoprene, selamectin provided significantly greater control of adult fleas from days 24 to 31 and significantly greater reduction in egg production from days 16 to 45. For the most part, both products significantly impacted larval and adult emergence for the entire 6-week study, with fipronil-(S)-methoprene providing significantly greater reduction in larval and adult emergence at week 6.