Efficacy of a single dose of an otic ivermectin preparation or selamectin for the treatment of Otodectes cynotis infestation in naturally infected cats.

Otodectes cynotis infestation is common in kittens housed in crowded environments like animal shelters. It is unknown how rapidly O cynotis is killed within the first 72h of treatment with currently available products. Kittens ≥4 weeks of age with live O cynotis in both ears (AU) were administered 0.5ml of 0.01% ivermectin otic suspension (Acarexx; Idexx Pharmaceuticals) once, AU or selamectin (Revolution; Pfizer Animal Health) once, on the skin following the manufacturer's instructions. Repeat microscopic examination was performed on individual ears based on a randomization schedule during the 72h after treatment. There was no evidence of toxicity with either drug and administration of 0.01% ivermectin significantly reduced the time to live mite-free status compared to selamectin. Both drugs have an effect against O cynotis as early as 10-12h after administration with an increasing effect over time.