Isoxazolines are a potent new class of ectoparasiticides that exhibit their anitparasitic activity through specific blockade of insect GABA- and glutamate-gated chloride channels. Fluralaner (Bravecto®, Merck Animal Heath), afoxolaner (NexGard®, Merial), and sarolaner (Simparica®, Zoetis) are oral isoxazolines approved for the prevention of fleas and ticks in dogs. Mounting clinical experience and several recent studies have illustrated the efficacy of isoxazoline parasiticides for canine demodicosis. Given their ease of use, safety, relative low cost and the potential side effects of other available treatments, many veterinarians and veterinary dermatologists are now reaching for these newer products when treating generalized demodicosis in dogs. Regardless of the selected treatment, miticidal therapy should be continued until at least two consecutive negative skin scrapings are obtained at monthly intervals. Below are brief summaries of the recently published studies.
A recent study of 16 dogs with generalized demodicosis compared the efficacy of Bravecto® given as a single oral dose with three monthly treatments of topical imidacloprid/moxidectin (Advocate®, Bayer) (Fourie et al. 2015). After a single oral administration of Bravecto®, mite numbers in skin scrapings were reduced by 99.8% on Day 28 and by 100% on days 56 and 84; significantly fewer mites were found on Days 56 and 84 on Bravecto® treated dogs compared to Advocate® treated dogs.
In a recent study by Beugnet et al. (2016), eight dogs with generalized demodicosis were treated with NexGard® at the label dose on days 0, 14, 28 and 56. Efficacy was compared with eight dogs on topical imidacloprid/moxidectin (Advocate®, Bayer) applied at the same intervals. The percentage reduction of mite counts in the afoxolaner-treated group were 99.2%, 99.9% and 100% on Days 28, 56 and 84, respectively. Mite reductions were significantly higher on Days 28, 56 and 84 in the afoxolaner-treated group compared to the imidacloprid/moxidectin-treated group. Afoxolaner has also been found to be effective at the label dose when given every 30 days for 3 treatments in 4 dogs with generalized demodicosis (Chavez 2016).
Six et al. (2016) compared the efficacy of sarolaner and imidacloprid/moxidectin (Advocate®, Bayer) in sixteen dogs with generalized demodicosis. Eight dogs were treated with sarolaner (2 mg/kg) orally on days 0, 30, and 60 and eight were treated with topical imidacloprid/moxidectin every seven days from day 0 to day 81. In the dogs treated with sarolaner, pretreatment mite counts were reduced by 97.1% at 14 days and 99.8% by 29 days after the first dose. No live mites were detected after day 29.
Submitted by Brian Palmeiro, VMD, Diplomate ACVD
Chavez F. Case report of afoxolaner treatment for canine demodicosis in four dogs naturally infected with Demodex canis. Int J Appl Res Vet Med. 2016;14(2):123-127. http://www.vin.com/doc/?id=7444684
Fourie JJ, Liebenberg JE, Horak IG. Efficacy of orally administered fluralaner (Bravecto™) or topically applied imidacloprid/moxidectin (Advocate®) against generalized demodicosis in dogs. Parasit Vectors. 2015 Mar 28;8:187.