Assessment of afoxolaner efficacy against Otodectes cynotis infestations of dogs

Doug Carithers, Jordan Crawford, Christa de Vos, Alta Lotriet, Josephus Fourie

The efficacy of a single 2.5 mg/kg dose of afoxolaner (NexGard®, Merial) against induced Otodectes cynotis infestations was assessed in eight afoxolaner-treated dogs, compared to eight untreated dogs. After O. cynotis infestations were established and confirmed by otoscopic assessments in 16 dogs, all of the dogs were included in the study and allocated to two separate treatment groups. The first group of eight ear mite-infested dogs remained untreated, while afoxolaner was administered orally to the second group of dogs at the minimum recommended dose once on Day 0. Otoscopic assessments performed on all dogs (Days -7, -2, 14 and 28) confirmed the presence or absence of live mites throughout the study. No serious adverse events were recorded throughout the study, and no adverse events were likely related to the administration of NexGard. By Day 28, seven out of eight untreated dogs were still infested with ear mites, while only two out of eight afoxolaner-treated dogs were infested, with one and four ear mites, respectively. On Day 28, the reductions of mite counts in the afoxolaner-treated group versus those of the control dogs were 98.5% based on geometric means, and 99.4% based on arithmetic means. Significantly fewer (P < 0.05) live mites were present in the afoxolaner-treated group than the untreated group on Day 28. The results of this study demonstrated that a single oral administration of afoxolaner at the minimum recommended dose is highly effective (>98%) in treating dogs with induced O. cynotis infestations.