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

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 LD 50 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 LD 50 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. LD 50 values for tetrachlorvinphos ranged from 20.0 to 420.0 ng/flea. The rdl mutation (conferring target-site resistance Parasitol Res (2015) 114 (Suppl 1):S7-S18 DOI 10.1007/s00436-015-4512-1 S7Ectopar asitEs 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.

Insecticide Resistance in Fleas

“…No isolates had an observed slope, LC 50 or LC 95 significantly different from the susceptible laboratory strains. Baseline values against adult cat fleas for imidacloprid were consistent with previously published data [ 33 ].…”

“…Susceptibility was correlated to latitude, but not to longitude, insecticide used, or the date of sampling. Most of the 12 field-collected isolates of C. felis were significantly less susceptible to deltamethrin and permethrin compared with a DPIL strain tested in 2001 [ 33 ].…”

“…One of the major goals of monitoring flea populations is to detect insecticide resistance early, allowing for alternative treatments. The long-term goal of resistance management is to extend the longevity of the current host-targeted therapies [ 33 ]. Understanding and preventing the development of insecticide resistance will ensure a broad selection of veterinary products.…”

Efficacy of a fipronil bait in reducing the number of fleas (Oropsylla spp.) infesting wild black-tailed prairie dogs

“…Potential resistance of flea populations is of concern when applying insecticides in the field. However, topical applications of fipronil and imidacloprid have suggested no resistance in strains of cat fleas ( Ctenocephalides felis ) (Rust et al ), the flea species historically most associated with resistance (Bossard et al ) and known to show resistance to multiple insecticides (Coles and Dryden ). Due to the relative infrequency of the proposed method of field application, we predict that insecticide resistance will be of minimal concern.…”

Visceral leishmaniasis on the Indian Subcontinent: Efficacy of fipronil-based cattle treatment in controlling sand fly populations is dependent on specific aspects of sand fly ecology

“…However, there is little direct evidence suggesting that resistance to fipronil occurs [22,71]. Research involving other arthropod vectors, such as the cat flea (Ctenocephalides felis), suggest no fipronil resistance in laboratory and field strains [72,73]. The relative infrequency of treatment application, in conjunction with the fact that this treatment targets two life stages, should limit the relative risk of resistance occurring.…”