For counts performed 12 h after treatment or infestation, the percent efficacy was ≥94.1% until Day 21 ( Table 1). The afoxolaner group had a significantly lower mean flea counts than the untreated control group for all counts at both 12 and 24 h after either infestation or treatment (P ≤ 0.008 for all comparisons). Geometric mean flea counts for untreated control dogs ranged from 65.3 to 87.8 ( Table 1). Twenty four hours after treatment corresponding to 48 h after flea infestations, an average of 58.8 eggs (533 eggs, 26–138 per dog) were collected from the control group dogs, whereas an average

of 1.5 egg (24 eggs, 0–12 per dog) were collected from the learn more treated dogs. After Day 1, no egg was collected from any treated dog following the weekly infestations up to Day 35, whereas a total of 489, 570, 524, 341 and 188 eggs were collected, respectively, at Day 8, 15, 22, 29 and 36 from the control group (Table 2). The treatment of dogs with the proposed minimum effective dose of 2.5 mg/kg of orally administered afoxolaner provided effective control (≥99%) of the dog fleas for at least 5 weeks after treatment. These results are similar to those obtained with fipronil where

99.6% and 100% efficacies were observed for 37 days after treatment (Cadiergues et al., 2001 and Bouhsira et al., 2011). Spinosad administered orally following US labeling (at doses ranging from 31.65 to 54.85 mg/kg) has been shown to provide good efficacy against C. canis for 3 weeks only at 24 h counts ( Franc and Bouhsira, 2009). The results of the present study highlight selleck compound the sustained speed of kill provided by afoxolaner.

The speed of kill is generally evaluated as a curative efficacy on existing unless flea infestations within the hours immediately following the treatment on Day 0 when the concentration of the insecticide is the highest. In the present study, efficacy was ≥94.1% at 12 h after infestation until Day 21. In addition, the results of the flea egg counts demonstrated that afoxolaner completely prevented egg production for at least 5 weeks (from Days 8 to 36). A small numbers of eggs (24 eggs in total) were recovered from some treated dogs at the first egg count performed 24 h after treatment. As fleas were present on the dogs for one day before treatment and as it takes around 2–8 h to an egg to fall from the host fur (Dryden and Rust, 1994), those eggs were most likely related to eggs produced prior to treatment. This hypothesis is strongly supported by the fact that no additional egg was recovered from the treated group 24 h after each flea infestation during the following weeks. Noteworthy, according to the design of the present study, the availability of flea eggs in the control group was uncertain since it is usually accepted that female fleas start laying eggs in average 36 h after the host infestation (Dryden and Rust, 1994).