Efficacy and safety of a new spot-on formulation of selamectin plus sarolaner in the treatment of naturally occurring flea and tick infestations in cats presented as veterinary patients in Europe.

Two randomised, blinded, multi-centre field studies were conducted in Europe (Germany, Italy, France, Hungary) to demonstrate the efficacy and safety of three monthly applications of a new spot-on formulation of selamectin plus sarolaner (Stronghold® Plus, Zoetis) against natural flea or tick infestations in cats presented as veterinary patients. The spot-on formulation was administered at the commercial dose range of 6.0-12.0mg selamectin and 1.0-2.0mg sarolaner per kg bodyweight. In the flea study, the improvement in clinical signs associated with flea allergy dermatitis (FAD) was also monitored. Imidacloprid plus moxidectin (Advocate® for Cats, Bayer) and fipronil (Frontline® Spot on, Merial) were used as positive control products in the flea and tick studies, respectively. Treatments were administered on Days 0, 30 and 60. Efficacy was calculated based on the mean percent reduction of live parasite counts on post-treatment days 14, 30, 60 and 90 versus the pre-treatment count on Day 0. Non-inferiority of selamectin/sarolaner to the control products was assessed at each time-point using a non-inferiority margin of 15% at the one-sided 0.025 significance level. Cats were enrolled in a 2:1 ratio (selamectin/sarolaner:comparator). In the flea study, 277 cats were assessed for efficacy and safety, and an additional 170 cats were assessed for safety only. On days 14, 30, 60 and 90, efficacy against fleas was 97.4%, 97.3%, 98.8% and 99.4% in the selamectin/sarolaner-treated group and was 90.0%, 83.6%, 87.7% and 96.3% in the imidacloprid/moxidectin-treated group, respectively. Selamectin/sarolaner was non-inferior to imidacloprid/moxidectin at all time-points. For the 16 cats identified as having FAD at enrolment, clinical signs related to FAD improved following treatment administration. In the tick study, 200 cats were assessed for efficacy and safety, and a further 70 cats were assessed for safety only. Four tick species were identified. Overall efficacy against ticks was 96.7%, 92.6%, 98.8% and 99.5% in the selamectin/sarolaner-treated group and was 90.2%, 74.6%, 83.0% and 93.4% in the fipronil-treated group on Days 14, 30, 60 and 90, respectively. Selamectin/sarolaner was non-inferior to fipronil at all time-points, and was superior on Days 30 and 60. There were no serious treatment-related adverse events in any study. Thus, the new spot-on formulation of selamectin plus sarolaner administered at monthly intervals was safe and highly effective against natural infestations of fleas and ticks on cats, and improved clinical signs of FAD.