Knock-down and speed of kill of a combination of fipronil and permethrin for the prevention of Ctenocephalides felis flea infestation in dogs A new combination of fipronil and permethrin for the control of ectoparasites of dogs Luis Cardosa

Background: a topical combination of fipronil + permethrin (frontline tri-act®/frontect®,merial) has recently been developed to control fleas,ticks,mosquitoes,sandflies and stable flies on dogs. two studies were conducted to assess its speed of kill and knock-down effect on ctenocephalides felis fleas. the combination was compared to either fipronil alone or to a combination of permethrin,dinotefuran,and pyriproxyfen,methods: in each study,18 dogs were randomly allocated to one of three groups: (group 1: untreated dog; group 2: treated once on d0 with the combination of fipronil and permethrin; group 3: treated once on d0 either with fipronil alone (study 1) or with a combination of permethrin,dinetofuran and pyriproxyfen (study 2)). each dog was infested with 100 unfed adult c. felis fleas on days 2 (study 2),7,14,21 and 28. fleas were collected from dogs at 1 h and 12 h post- infestations (pi) (study 1) or at 2 h and 6 h pi (study 2) to assess efficacy and from collection pans underneath cages 1 h (study 1) or 5 min (study 2) pi to assess knock-down effect. results: all treated dogs had significantly (p ≤ 0.01) lower flea counts than untreated dogs at every time point in both studies. for a whole month,a significant knock-down effect against infesting fleas is obtained in five minutes pi with the combination of permethrin and fipronil. complete efficacy (>95 %) was achieved in 1 h (study 1) or 2 h (study 2) pi for 14 days and by 6 h pi for all challenges conducted throughout the month. efficacy remains >85 % at 2 h pi for the whole month. a significantly higher efficacy of the fipronil + permethrin combination compared to other treatments was demonstrated at the earliest time points for the month (1 h knock-down effect and insecticidal efficacy compared to fipronil alone; 5 min knock-down effect compared to the combination of permethrin + dinetofuran + pyriproxyfen). conclusions: the rapid flea knock-down effect and speed of kill demonstrated by the spot on combination of fipronil + permethrin provide a reliable strategy against flea infestations in dogs. © 2016 halos et al.