Efficacy of sarolaner (Simparica) against induced infestations of Haemaphysalis longicornis on dogs.

Abstract

BACKGROUND: Haemaphysalis longicornis is the major tick affecting dogs in most of the East Asia/Pacific region and has recently been detected in a number of areas of the USA. This tick is a vector for a number of pathogens of dogs, other mammals and humans. In this study, the efficacy of a single oral administration of sarolaner (Simparica, Zoetis) at the minimum label dosage (2&#xa0;mg/kg) was evaluated against an existing infestation of H. longicornis and subsequent weekly reinfestations for 5&#xa0;weeks after treatment. METHODS: Sixteen dogs were ranked on pretreatment tick counts and randomly allocated to treatment on Day 0 with sarolaner at 2&#xa0;mg/kg or a placebo. The dogs were infested with H. longicornis nymphs on Days -&#x2009;2, 5, 12, 19, 26 and 33. Efficacy was determined at 48&#xa0;hours after treatment and subsequent re-infestations based on live tick counts relative to placebo-treated dogs. RESULTS: There were no adverse reactions to treatment. A single dose of sarolaner provided 100% efficacy on Days 2, 7, 14 and 21; and &#x2265;&#x2009;97.4% efficacy on Days 28 and 35. Considering only attached, live ticks, efficacy was 100% for the entire 35&#xa0;days of the study. Geometric mean live tick counts for sarolaner were significantly lower than those for placebo on all days (11.62&#x2009;&#x2264;&#x2009;t&#x2009;&#x2264;&#x2009;59.99, where 13.0&#x2009;&#x2264;&#x2009;df&#x2009;&#x2264;&#x2009;14.1, P&#x2009;<&#x2009;0.0001). CONCLUSIONS: In this study, a single oral administration of sarolaner at 2&#xa0;mg/kg provided 100% efficacy against an existing infestation of H. longicornis nymphs and &#x2265;&#x2009;97.4% efficacy (100% against attached ticks) against weekly reinfestation for at least 35&#xa0;days after treatment.