Effectiveness of Fluralaner and Afoxolaner Against Flea Infestations in Dogs

Both fluralaner and afoxolaner completely eliminated flea infestations on dogs in a field trial in Florida during the summer of 2015, according to a report recently published in Parasites & Vectors. Both treatments also significantly reduced or eliminated premises infestations and reduced dermatitis lesions and pruritus scores in infested dogs.

Fluralaner (Bravecto; Merck Animal Health) and afoxolaner (Nexgard; Merial, Inc) are isoxazoline paraciticides available as chewable tablets and marketed to kill fleas and ticks on dogs. Fluralaner is given once every 3 months and afoxolaner is given once every month.

The 3-month study included 61 dogs in 34 homes in west central Florida. All had natural flea infestations, as determined by flea counts on dogs and in flea traps placed in homes. Owners agreed to use no other flea control methods and to introduce no new mammals into the household during the course of the study. All dogs in each household were treated.

Dogs in the fluralaner group received a single oral dose on day 0; those in the afoxolaner group received 3 oral doses (day 0, between days 28 and 30, and between days 54 and 60). The study included no control group because of concerns for the welfare of heavily flea-infested dogs remaining untreated. Members of the research group administered the products to avoid client adherence problems.

By day 7, the mean flea counts on dogs were reduced by 99.0% in the fluralaner group and by 99.3% in the afoxolaner group. By days 28 to 30, the dogs’ mean flea counts were reduced by 100% in the fluralaner group and by 99.9% in the afoxolaner group. Mean flea counts on dogs in both groups were still reduced by 99.9% to 100% at the end of the 12-week study.

By day 14, 88.2% of the fluralaner-treated dogs and 81.5% of the afoxolaner-treated dogs were free of fleas. By the end of the study, all dogs in both groups were entirely free of fleas. The differences in mean flea counts and numbers of flea-free dogs were not significantly different between the 2 groups. Flea bite hypersensitivity severity scores, canine atopic dermatitis scores, and pruritus scores were also significantly reduced in both treatment groups, with no significant differences between the 2 treatments.

In the fluralaner group, 88.2% of premises were free of fleas by the end of the first month, and 100% were cleared of fleas by the end of the third month. In the afoxolaner group, 70.6% of households were free of fleas by the end of the first month, and 80% were free of fleas by the end of the third. These differences were not statistically significant.

The study was partly funded by Merck Animal Health. Both Merck Animal Health and Merial have funded research projects by the study’s first author and have sponsored lectures by the first and second authors. Four study authors are employees of Merck Animal Health.

Dr. Laurie Anne Walden received her doctorate in veterinary medicine from North Carolina State University. After an internship in small animal medicine and surgery at Auburn University, she returned to North Carolina, where she has been in small animal primary care practice for over 20 years. Dr. Walden is also a board-certified editor in the life sciences and owner of Walden Medical Writing, LLC.