Efficacy of a new spot-on formulation of selamectin plus sarolaner against four common tick species infesting cats in Europe.

Abstract

A single application of a new spot-on formulation of selamectin plus sarolaner (StrongholdPlus, Zoetis) was evaluated for efficacy against the most common tick species infesting cats in Europe. In each of the seven laboratory studies, 16 adult and purpose-bred cats were randomly allocated to one of two treatment groups based on pre-treatment tick counts. Weekly infestations with 50 unfed adult Ixodes ricinus (2 studies), Ixodes hexagonus (1 study), Dermacentor reticulatus (2 studies), or Rhipicephalus sanguineus (2 studies) were scheduled on Days -2, 5, 12, 19, 26 and 33. Cats were treated on Day 0 with the spot-on formulation at the minimum recommended label dose of 6.0mg selamectin and 1.0mg sarolaner per kg bodyweight or with a placebo. Ticks were counted 48h after treatment and after each re-infestation. No treatment-related adverse reactions were recorded in any of the studies. Geometric mean live tick counts were significantly (P≤0.0012) lower in the selamectin/sarolaner-treated group compared to the placebo-treated group at all time-points. Against I. ricinus and I. hexagonus, efficacy was ≥97.2% against existing infestations and ≥97.4% against weekly re-infestations for at least 5 weeks. Treatment was 100% effective against existing R. sanguineus infestations and was ≥95.8% for at least 4 weeks. Against D. reticulatus treatment resulted in ≥94.4% efficacy for at least 4 weeks. Thus, a single application of the new spot-on formulation of selamectin plus sarolaner at the minimum dose provides rapid treatment of existing infestations and is at least one month effective against re-infestation by all relevant European tick species in cats.