Speed of kill of a new spot-on formulation of selamectin plus sarolaner for cats against induced infestations with Ixodes ricinus

There were no treatment-related adverse reactions during the study. Placebo-treated cats maintained infestations with mean tick counts ranging from 10.3 to 21.9 throughout the study. The new spot-on formulation of selamectin plus sarolaner demonstrated 99.3% efficacy (P < 0.0001) within 24 h after treatment against pre-existing infestations. For subsequent re-infestations, efficacy was >97.9% for at least 3 weeks and was 89.0% after the re-infestation on Day 28. Mean live tick counts were significantly reduced by 12 h after re-infestation for at least 28 days (P < 0.0338). Thus, a single application of the new spot-on formulation of selamectin plus sarolaner at the minimum label dose started killing ticks within 24 h after treatment and within 12 h after re-infestations for 4 weeks. High acaricidal efficacy was achieved within 24 h after treatment and this persisted following subsequent re-infestations for a month.