Efficacy of RevolutionPlus (selamectin plus sarolaner) for the prevention of transmission of Borrelia burgdorferi from infected Ixodes scapularis to cats.

Abstract

BACKGROUND: Borrelia burgdorferi and Anaplasma phagocytophilum are transmitted by Ixodes spp., with antibodies having been detected in cats in endemic areas. The combination of selamectin plus sarolaner (RevolutionPlus/StrongholdPlus; Zoetis; RP) is effective against Ixodes spp. for 1 month. The objective of this study was to determine whether RP protects cats against transmission of B. burgdorferi from Ixodes scapularis by killing the ticks before transmission occurs. Transmission of A. phagocytophilum was also monitored. METHODS: Ten cats per group were treated once topically either with placebo solution (0.1 ml/kg) or with the minimum label dose of RP (6.0 mg/kg selamectin plus 1.0 mg/kg sarolaner). Thirty days post-treatment, cats were infested with 50 wild-caught adult I. scapularis. Ticks were counted, categorized, and removed on day 35. Blood collections for serology occurred on days -6, 30 (prior to infestation), 49, 63, 77, 91, and 104. Serum antibody assay results (B. burgdorferi and A. phagocytophilum) and polymerase chain reaction (PCR) of skin biopsies (B. burgdorferi) were used to define infection rates in the cats. RESULTS: Treatment with RP resulted in a 100% reduction of I. scapularis ticks compared with placebo-treated cats. In placebo-treated cats, antibodies against B. burgdorferi, A. phagocytophilum, both agents, and B. burgdorferi DNA in skin (five, nine, six, and three cats, respectively) were detected by day 104. In contrast, none of the RP-treated cats developed B. burgdorferi antibodies or DNA in skin biopsies, and A. phagocytophilum antibodies were detected in only two cats, significantly lower than in placebo-treated cats. CONCLUSIONS: Results suggest that a single application of RP at the minimum label dose reduces the risk of infection by both B. burgdorferi and A. phagocytophilum, when infected at the end of the dosing interval.