Comparative speed of efficacy against Ctenocephalides felis of two oral treatments for dogs containing either afoxolaner or fluralaner

A study was designed to compare the efficacy of NexGard® and Bravecto™, 2 recently introduced oral ectoparasiticides containing isoxazolines, against fleas (Ctenocephalides felis) on dogs. Twenty-four healthy dogs, weighing 9.2kg to 28.6kg, were included in this parallel group design, randomized, and controlled efficacy study. On Day −1, the 24 dogs were allocated to 3 study groups: untreated control; Nexgard® treated and Bravecto™ treated. The treatments were administered on Days 0, 28 and 56 for Nexgard® (labelled for monthly administration), and once on Day 0 for Bravecto™ (labelled for a 12 week use). Flea infestations were performed weekly with 100 adult unfed C. felis on each dog from Days 42 to 84. Fleas were counted and re-applied at 6 and 12h post-infestation and removed and counted 24h post-infestation. The arithmetic mean flea count for the untreated group ranged from 62.9 to 77.6 at 24h post-infestation, indicating vigorous flea challenges on all assessment days. Both the Nexgard® and Bravecto™ treated groups had statistically significantly (p<0.05) less fleas compared to the untreated group on all assessment time points and days. Significantly fewer fleas were recorded for NexGard® treated dogs compared to Bravecto™ treated dogs at 6h post-infestation on Day 56, 63, 70, 77 and 84 and at 12h post-infestation on Days 70 and 84. No statistically significant (p<0.05) differences were recorded between the treated groups at 24h post-infestation. Efficacies recorded 6h post-infestation for Nexgard® ranged from 62.8% (Day 49) to 97.3% (Day 56), and efficacies ranged from 94.1% (Day 49) to 100% (Days 42, 56, 70 and 84) at 12h post-infestation. Efficacies recorded for Bravecto™ ranged from 45.1% (Day 84) to 97.8% (Day 42) at 6h post-infestation, and from 64.7% (Day 84) to 100% (Days 42 and 56) at 12h post-infestation. Efficacies observed at 24h were 100% for both products during the study except 99.6% on Day 84 for Bravecto™.