Comparison of the initial and residual speed of Amblyomma americanum kill on dogs treated with a single dose of Bravecto® Chew (25 mg/kg fluralaner) or Simparica TRIO® (1.2 mg/kg sarolaner, 24 µg/kg moxidectin, 5 mg/kg pyrantel).

Background: To manage tick infestations and reduce tick-borne pathogen transmission risk to dogs, compliant administration of a fast-acting ectoparasiticide is necessary. Isoxazoline-containing ectoparasiticide products provide systemic whole-body coverage; however, differences in tick kill have been observed between products and these differences may be more pronounced when controlling common dose-limiting tick species such as Amblyomma americanum.

Methods: Dogs were ranked by tick carrying capacity, randomly allocated to one of three treatment groups, and administered Bravecto® Chews (minimum 25 mg/kg fluralaner), Simparica TRIO® (minimum 1.2 mg/kg sarolaner, 24 µg/kg moxidectin, 5 mg/kg pyrantel), or no treatment. Dogs were infested with approximately 50 unfed adult (25 female, 25 male) A. americanum on days -2, 21, 28, and 35. Live tick counts were performed at 8, 12, 24, 48, and 72 h post-treatment (day 0) and post-infestation on days 21, 28, and 35. At each tick count timepoint, product efficacy was determined by comparing geometric mean live tick counts for each product-treated group to the untreated group and a linear mixed model was used for between-group comparisons.

Results: Compared with untreated dogs, significant control of existing A. americanum infestations began by 8 h post-treatment (81.6%) and reached 98.0% control by 12-h for Bravecto®-treated dogs. In comparison, significant control for Simparica TRIO®-treated dogs began by 24 h post-treatment (97.7%). When reinfested on day 21, A. americanum infestations were controlled more quickly for Bravecto® compared with Simparica TRIO®-treated dogs at 12 h (efficacy 95.3% versus 25.5%, P < 0.001) and 24 h (efficacy 99.7% versus 70.9%, P < 0.001) post-infestation. Similarly, when reinfested on day 28, faster A. americanum control occurred for Bravecto® compared with Simparica TRIO®-treated dogs at 12 h (efficacy 87.9% versus 18.3%, P < 0.001) and at 24 h (99.2% versus 59.3%, P < 0.001) post-infestation. Finally, when reinfested on day 35, time to ≥ 90% efficacy was achieved by 48 h for Bravecto®-treated dogs compared with 72 h post-infestation for Simparica TRIO®-treated dogs. Both products performed within label indications and no treatment-related adverse reactions occurred during the study.

Conclusions: Amblyomma americanum infestations are controlled more quickly immediately upon treatment and at 21, 28, and 35 days post-treatment for Bravecto® compared with Simparica TRIO®-treated dogs.