Abstract
BackgroundFluralaner is a novel isoxazoline eliciting both acaricidal and insecticidal activity through potent blockage of GABA- and glutamate-gated chloride channels. The aim of the study was to investigate the susceptibility of juvenile stages of common tick species exposed to fluralaner through either contact (Rhipicephalus sanguineus) or contact and feeding routes (Ornithodoros moubata).MethodsFluralaner acaricidal activity through both contact and feeding exposure was measured in vitro using two separate testing protocols. Acaricidal contact activity against Rhipicephalus sanguineus life stages was assessed using three minute immersion in fluralaner concentrations between 50 and 0.05 μg/mL (larvae) or between 1000 and 0.2 μg/mL (nymphs and adults). Contact and feeding activity against Ornithodoros moubata nymphs was assessed using fluralaner concentrations between 1000 to 10−4 μg/mL (contact test) and 0.1 to 10−10 μg/mL (feeding test). Activity was assessed 48 hours after exposure and all tests included vehicle and untreated negative control groups.ResultsFluralaner lethal concentrations (LC50, LC90/95) were defined as concentrations with either 50%, 90% or 95% killing effect in the tested sample population. After contact exposure of R. sanguineus life stages lethal concentrations were (μg/mL): larvae - LC50 0.7, LC90 2.4; nymphs - LC50 1.4, LC90 2.6; and adults - LC50 278, LC90 1973. After exposure of O. moubata nymphs to fluralaner lethal concentrations were (μg/mL): contact exposure - LC50 720, LC95 1133; and feeding exposure- LC50 0.00007, LC95 0.09.ConclusionsFluralaner demonstrates potent in vitro acaricidal activity against all life stages of the brown dog tick, R.sanguineus. The testing of fluralaner contact and feeding routes using O. moubata nymphs demonstrates a high acaricidal activity in both exposure routes.
Highlights
Fluralaner is a novel isoxazoline eliciting both acaricidal and insecticidal activity through potent blockage of GABA- and glutamate-gated chloride channels
Tick contact exposure of R. sanguineus life stages The arithmetic mean mortality obtained from vehicle control and untreated control was 3.1%, 0.7% and 0%
Tick contact and membrane feeding exposure of O. moubata The arithmetic mean mortality obtained from vehicle control and untreated control was 0% after contact exposure and 2.5% after feeding exposure
Summary
Fluralaner is a novel isoxazoline eliciting both acaricidal and insecticidal activity through potent blockage of GABA- and glutamate-gated chloride channels. Fluralaner is a new molecular entity of the isoxazoline class and provides potent acaricidal and insecticidal activity through a dual mechanism of binding to both neuronal GABA and glutamate channels in susceptible invertebrates [1,2]. A short period of time is needed to effectively kill fleas (8 hours) and ticks (12 hours) on orally treated dogs [5,6]. It was shown that concurrent treatments of oral fluralaner with milbemycin oxime – praziquantel
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