Efficacy of lotilaner (Credelio™) against experimentally induced infestations of the adult cat flea, Ctenocephalides felis, and flea eggs following oral administration to cats

Background: Credelio (TM) (lotilaner; Elanco) is indicated for the treatment of flea and tick infestations on cats at a recommended lotilaner dose rate of 6-24 mg/kg. This study evaluated the efficacy and safety of lotilaner following a single oral administration to cats for the treatment and prevention of adult Ctenocephalides felis fleas and flea egg production under laboratory conditions. Methods: Two treatment groups of ten cats each were used in this study. One group was treated with lotilaner at a dose rate of 6-9 mg/kg on Day 0 and the other group served as the control group. Each cat was infested with 100 unfed adult fleas on days -1, 6, 13, 20 and 29. At 24 h post-treatment or post-infestation, each cat was combed to remove and count adult live fleas. At each time point, flea eggs were also collected and counted from under each cat cage. Results; Following a single oral administration of lotilaner at a minimum dose rate of 6 mg/kg (range 6.00-8.57 mg/kg), the lotilaner group displayed 100%, 100%, 99.9%, 99.9% and 99.8% efficacy against adult live flea counts as compared to the control group on Days 1, 7, 14, 21 and 30, respectively. At each time point, adult flea counts from the lotilaner-treated cats were significantly lower (P < 0.0001) than from the control group. A mean flea egg count of 22.6 in the lotilaner-treated cats (compared to 441.7 in the control animals) was observed 24 h post-treatment. No eggs were present from any of the treated cats on Days 7, 14 and 30 and a single egg was detected on a single treated cat on Day 21. One adverse event (regurgitated food) was observed during the study in one treated cat approximately 1 h after dosing. Conclusions: Lotilaner was well tolerated; only one adverse event was observed in the treated group. Virtually all adult fleas were killed within 24 h post-treatment or post-infestation in cats treated with a single dose of lotilaner as compared to the control group, thus significantly reducing the number of flea eggs being produced for 30 days after treatment.