Fluralaner activity against life stages of ticks using Rhipicephalus sanguineus and Ornithodoros moubata IN in vitro contact and feeding assays

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.

Comparative in vitro evaluation of contact activity of fluralaner, spinosad, phoxim, propoxur, permethrin and deltamethrin against the northern fowl mite, Ornithonyssus sylviarum

“…A study by Williams et al [ 34 ], showed likely in vitro contact activity of fluralaner against larvae of the brown dog tick Rhipicephalus sanguineus , but that was by immersion, which also could result in some small amount of oral/internal exposure. In the present study the mites should not have ingested any residues of fluralaner, except perhaps by grooming appendages that came into contact with it on the filter paper.…”

Midgut proteome of an argasid tick, Ornithodoros erraticus: a comparison between unfed and engorged females

“…It has also been demonstrated that the ingestion of drugs present in blood may have a deleterious effect on ticks. An example of this is the effect of the recently commercialized drug Fluralaner (Bravecto™), although it does not target intestinal proteins, its oral administration has proved to be effective against several tick species, causing their death a few hours after feeding [ 37 – 39 ].…”

Efficacy of sarolaner (Simparic™) against induced infestations of Amblyomma cajennense on dogs

“…The studies reported by Six et al [ 18 – 22 ] and Geurden et al [ 22 , 23 ] evaluated efficacy against adult ticks. It is interesting to note that the efficacy of sarolaner demonstrated against adult ticks was similar to that observed against nymphal A. cajennense , given that the immature stages are generally considered to be more susceptible than adults [ 26 ].…”