Susceptibility of Adult Cat Fleas (Siphonaptera: Pulicidae) to Insecticides and Status of Insecticide Resistance Mutations at the Rdl and Knockdown Resistance Loci

Michael K Rust,Claudia Böhm,Byron Blagburn,Glen Coleman,Steven Kopp,Ian Denholm,Joe Hostetler,Wendell Davis,Sabrina Foit,Martin S Williamson,Norbert Mencke,Robert Rees,Kathrin Tetzner,Richard Vetter

doi:10.1007/s00436-015-4512-1

Abstract

The susceptibility of 12 field-collected isolates and 4 laboratory strains of cat fleas, Ctenocephalides felis was determined by topical application of some of the insecticides used as on-animal therapies to control them. In the tested field-collected flea isolates the LD50 values for fipronil and imidacloprid ranged from 0.09 to 0.35 ng/flea and 0.02 to 0.19 ng/flea, respectively, and were consistent with baseline figures published previously. The extent of variation in response to four pyrethroid insecticides differed between compounds with the LD50 values for deltamethrin ranging from 2.3 to 28.2 ng/flea, etofenprox ranging from 26.7 to 86.7 ng/flea, permethrin ranging from 17.5 to 85.6 ng/flea, and d-phenothrin ranging from 14.5 to 130 ng/flea. A comparison with earlier data for permethrin and deltamethrin implied a level of pyrethroid resistance in all isolates and strains. LD50 values for tetrachlorvinphos ranged from 20.0 to 420.0 ng/flea. The rdl mutation (conferring target-site resistance to cyclodiene insecticides) was present in most field-collected and laboratory strains, but had no discernible effect on responses to fipronil, which acts on the same receptor protein as cyclodienes. The kdr and skdr mutations conferring target-site resistance to pyrethroids but segregated in opposition to one another, precluding the formation of genotypes homozygous for both mutations.

Highlights

The development of resistance by pest organisms poses a constant threat to the performance of onanimal applied insecticides registered as veterinary medicinal products
A larval bioassay with imidacloprid and fipronil has provided consistent results (Rust et al 2002, 2014), and topical application of insecticides on the cuticle of adult fleas, which enables the testing of individual fleas, has provided reliable levels of sensitivity (Moyses 1995)
Bioassays with pyrethroid insecticides Of the laboratory strains maintained at University of California Riverside (UCR), Auburn was the most susceptible to deltamethrin (Table 2)

Summary

Introduction

The development of resistance by pest organisms poses a constant threat to the performance of onanimal applied insecticides registered as veterinary medicinal products. To provide scientifically sound data on responses of the cat flea (Ctenocephalides felis) to the insecticide imidacloprid, a larval bioassay was developed and evaluated, and field-collected isolates from three continents have been tested since 2002 (Blagburn et al 2006; Rust et al 2002, 2005, 2011). A larval bioassay with imidacloprid and fipronil has provided consistent results (Rust et al 2002, 2014), and topical application of insecticides on the cuticle of adult fleas, which enables the testing of individual fleas, has provided reliable levels of sensitivity (Moyses 1995). Topical application bioassays of 13 insecticides to individuals of a single flea strain were reported by Moyses and Gfellar (2001)

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Conclusion