Toxicity of fluralaner, a companion animal insecticide, relative to industry-leading agricultural insecticides against resistant and susceptible strains of filth flies

Edwin R Burgess,Christopher J Geden,Kimberly H Lohmeyer,B H King,Erika T Machtinger,Jeffrey G Scott

doi:10.1038/s41598-020-68121-z

Abstract

Filth flies cause billions of dollars of losses annually to the animal production industry. Fluralaner is a relatively new pesticide currently sold for control of fleas, ticks, and mites on companion animals and poultry. We examined the efficacy of fluralaner against three species of filth flies. Insecticide-susceptible horn flies and stable flies were tested topically. Fluralaner outperformed permethrin by > 2-fold for the horn flies but underperformed permethrin by > 45-fold for stable flies at 24 h. House flies were tested topically with fluralaner in comparison to permethrin at 48 h and orally with fluralaner in comparison to imidacloprid at 24 h. Topical fluralaner was 6- to 28-fold as toxic as permethrin in four pyrethroid-resistant strains and not significantly less toxic than permethrin in a susceptible strain and a mildly pyrethroid-resistant strain. There was slight cross-resistance between topically applied fluralaner and permethrin in all five insecticide-resistant strains tested. Oral fluralaner was more toxic than imidacloprid in all four house fly strains tested, 9- to 118-fold as toxic. Oral cross-resistance between imidacloprid and fluralaner was not detected, but imidacloprid resistance was not high in any of the tested strains. Fluralaner shows promise for control of horn flies and house flies.

Highlights

Filth flies cause billions of dollars of losses annually to the animal production industry
The house fly is a vector of many microorganisms of veterinary concern, including those that cause habronemiasis in e quines[10], mastitis in c attle[11], and necrotic enteritis in p oultry[12]
There was a dosedependent response to fluralaner at 24 h in both the horn flies and the stable flies (Table 2) and that response increased at 48 h, whereas response to permethrin was largely unchanged

Summary

Introduction

Filth flies cause billions of dollars of losses annually to the animal production industry. House flies were tested topically with fluralaner in comparison to permethrin at 48 h and orally with fluralaner in comparison to imidacloprid at 24 h. There was slight cross-resistance between topically applied fluralaner and permethrin in all five insecticide-resistant strains tested. Oral fluralaner was more toxic than imidacloprid in all four house fly strains tested, 9- to 118-fold as toxic. Filth flies (Diptera: Muscidae) are perhaps the greatest arthropod pest of animal production worldwide, causing billions of dollars (USD) in economic losses each year [e.g.1–3]. Chemical control historically has been employed for quick reduction of filth fly populations Pyrethroids and their natural counterpart, pyrethrins, have been widely used for decades and are still widely used as sprays, dusts, and pour-ons (topical applications of insecticide applied to an animal’s coat or skin)[18]. Insecticide-susceptible, based on sequencing (Results) and lack of exposure to pesticides Pyrethroid-resistant with mutations in the cytochrome P450 CYP6D1v1 gene, several acetylcholinesterase mutations known to confer pesticide resistance, and several kdr mutations[19] Pyrethroid-resistant with unknown mechanisms

Methods

Results

Conclusion