The flea counts for both studies are summarized in DNA Synthesis inhibitor Table 1. In both studies, the flea counts of untreated dogs were consistently high, with geometric means ranging from 58.9 to 93.8. For live flea counts performed 12 h after treatment or challenge infestations, the percent efficacy was ≥95.2% for the first four infestations through Day 21, was 81.1% on Day 28, and was 93% on Day 35 in Study 1. Efficacy at 12 h was ≥98.5% through Day 28 and 89.7% on Day 35 for Study 2. For live

flea counts performed 24 h after treatment or challenge infestations, percent efficacy was 100% for all time points until Day 35, with the exception of one time point (99.9% on Day 22) for Study 2. The flea counts were significantly different between treated and control dogs at all time-points for both 12 and 24 h counts in both studies (p = 0.003 Study 1, p = 0.0006 Study 2). The flea egg counts for Study 1 are summarized in Table 2. For egg counts performed 12 h after treatment, meaning 36 h after flea infestations, 22 eggs were found from treated dogs (Groups 2, 0–11 eggs per dog) and a total of 183 eggs from control dogs (Groups 1, 4–90 eggs per dog)

(efficacy of 88.8%, p < 0.004). For egg count performed 24 h after treatment, meaning 48 h after flea infestations, 43 eggs were found from treated dogs (Groups 4, 1–17 eggs per dog) and a total of 431 eggs from control dogs (0–118 eggs per dog) (efficacy Enzalutamide in vivo of 85.8%, p = 0.028). For egg counts performed 12 h after infestation at or beyond Day 7, two treated animals had a single egg collected on Day 14, compared to 216 eggs collected in Group 1 dogs (9–62 eggs per dog), resulting in 99.1% efficacy. One treated animal had a single egg collected on Day 21,

compared to 213 eggs collected in Group 1 dogs (3–81 next eggs per dog) resulting in 99.5% efficacy. No eggs were collected on treated dogs at Days 7, 28 or 35, when 150, 194 and 112 eggs were collected from control dogs at Days 7, 28 and 35, respectively. For C. felis egg counts performed 24 h after challenge infestation at or beyond Day 7, only one treated animal had a single egg collected on Day 15, compared to 438 eggs collected from control dogs (8–113 eggs per dog), resulting in 99.8% efficacy. For all other time points at 24 h post-infestation, the efficacy was 100% as no eggs were found in the treated Group. In the control group, 297, 421, 253 and 357 eggs were collected at Days 8, 22, 29 and 36, respectively. There was no observed adverse event based on hourly post-treatment observations for 4 h and daily observations thereafter. Oral treatment of dogs with the new insecticide afoxolaner at the minimum effective dose of 2.5 mg/kg provided ≥99.9% efficacy against adult fleas at 24 h count for 5 weeks after a single administration. The present study also demonstrated a sustained 12 h efficacy against adult fleas for a full month.