Abstract
BackgroundFleas are a ubiquitous ectoparasite infesting dogs and cause direct discomfort, allergic reactions and are responsible for the transmission of several pathogens. The rapid speed of kill of a parasiticide is important to alleviate the direct deleterious effects of fleas, reduce the impact of allergic responses, and break the flea life cycle. In this study, the speed of kill of a novel orally administered isoxazoline parasiticide, sarolaner (Simparica™) against fleas on dogs was evaluated and compared with spinosad in combination with milbemycin oxime (Trifexis®) for 5 weeks after a single oral dose.MethodsTwenty-four dogs were randomly allocated to treatment with a single oral dose per product label of sarolaner (2 to 4 mg/kg), spinosad/milbemycin oxime (30 to 60 mg/kg / 0.2 to 0.4 mg/kg), or placebo based on pretreatment flea counts. Dogs were combed and live fleas counted at 8, 12, and 24 h after treatment and subsequent re-infestations on Days 7, 14, 21, 28, and 35. Efficacy (reduction in live flea counts) of each treatment was determined at each time point relative to counts for placebo dogs.ResultsThere were no adverse reactions to treatment. A single oral dose of sarolaner provided ≥94.0 % efficacy (based on geometric means) within 8 h of treatment or subsequent weekly re-infestations of fleas to Day 35. By 12 h, fleas were eradicated from all dogs and they remained flea free at 24 h. Significantly greater numbers of live fleas were recovered from spinosad/milbemycin oxime-treated dogs at 8 h from Day 21 to Day 35 (P ≤ 0.0085), and at 12 and 24 h on Day 35 (P ≤ 0.0002).ConclusionsIn this controlled laboratory evaluation, dogs treated with sarolaner had significantly fewer live fleas than spinosad/milbemycin oxime- treated dogs at 8 h after re-infestation from Day 21 after a single oral dose. The rapid and consistent kill of fleas after a single oral dose of sarolaner over 35 days indicates that this treatment should provide highly effective control of flea infestations, relief for dogs afflicted with flea allergy dermatitis, and also reduce the risk of transmission of flea-borne pathogens.
Highlights
Fleas are a ubiquitous ectoparasite infesting dogs and cause direct discomfort, allergic reactions and are responsible for the transmission of several pathogens
Treatment with sarolaner resulted in significantly lower flea counts than spinosad/milbemycin oxime at 8 h on Days 21, 28, and 35 (P < 0.0085)
A single oral treatment of sarolaner at the proposed commercial dose of 2 to 4 mg/kg resulted in the rapid reduction of an existing flea infestation as well as rapid kill of newly infested fleas for at least 35 days, and efficacy was more consistent over the full month with significantly faster kill of fleas than spinosad/milbemycin oxime from Day 21 onwards. Both products resulted in rapid control of an existing flea infestation
Summary
Fleas are a ubiquitous ectoparasite infesting dogs and cause direct discomfort, allergic reactions and are responsible for the transmission of several pathogens. The rapid kill of fleas is desirable to alleviate both the immediate irritation caused by fleas as well as to reduce associated allergenic responses and the risk of flea-borne pathogen transmission; this may include on-host flea treatment as well as environmental treatment to reduce the household infestation [2]. The speed of kill of adult fleas on the host is an important factor in the control of infestations, as female fleas do not begin producing eggs until 24 to 48 h after they start feeding [12]. Killing fleas before they lay eggs will, over time, effectively control the environmental infestation
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