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M K Rust,
I Denholm,
M W Dryden,
P Payne,
B L Blagburn,
D E Jacobs, R Bond,
N Mencke,
I Schroeder,
S Weston,
M Vaughn,
G Coleman,
S Kopp
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ABSTRACT: Although on-animal topical treatment with compounds such as imidacloprid has revolutionized the control of the cat flea, Ctenocephalides felis (Bouché) (Siphonaptera: Pulicidae), the development of insecticide resistance is a continuing threat. As part of a highly co-ordinated and unprecedented resistance monitoring programme for C. felis, 1437 flea isolates were collected by veterinary clinics in Australia, Germany, France, the U.K. and 29 states in the U.S.A. from 2002 to 2009. About 65% of the collections were made from June to October each year and 71% of the collections were from cats. Collections of flea eggs were sent to one of five different laboratories, where they were tested with a diagnostic dose of imidacloprid (3 p.p.m.) applied to larval flea-rearing medium. Of the 1437 collections received, 1064 contained adequate numbers of eggs for testing. Of these isolates, untreated eggs failed to hatch in 22.7% and were not considered valid bioassays. Survival rates >5% and development of adult fleas (a threshold for further testing) occurred in only 22 isolates. They were re-tested with the same diagnostic dose and none produced >5% adult emergence. Complete dose-response bioassays were performed on three of the isolates that had triggered a second test and produced slopes, intercepts and LC(50) values similar to those for existing susceptible laboratory strains. Results confirmed sustained susceptibility of C. felis to imidacloprid, despite its widespread use for over a decade.
Medical and Veterinary Entomology 03/2011; 25(1):1-6. · 1.91 Impact Factor
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M Vobis,
J D'Haese,
H Mehlhorn,
N Mencke,
B L Blagburn, R Bond,
I Denholm,
M W Dryden,
P Payne,
M K Rust,
I Schroeder,
M B Vaughn,
D Bledsoe
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ABSTRACT: The phylogenetic relationships among 31 different flea isolates representing seven different species were studied by nucleotide sequence comparison of the internal transcribed spacer 1 (ITS1), internal transcribed spacer 2 (ITS2) and/or mitochondrial 16S ribosomal RNA gene (mt16S-rDNA) to examine the patterns of variation. Results show that all regions are useful in discriminating among flea species. In Ctenocephalides felis and Tunga penetrans, some differences in these gene regions occurred among different isolates within the same species. In the latter case, the differences are in the mt16S-rDNA region, with one isolate showing 48% divergence in nucleotide sequence. The taxonomic implications of this result are unclear at present. The gene regions revealed differences between C. felis isolates only after DNA sequencing the PCR products. Further differentiation among C. felis isolates was obtained using four different random binding primers (decamers) and primers for mammalian aldolase to amplify narrow differences in the genome. Using these primers we were able to discriminate between different C. felis isolates and determine that some of the genetic variation coincided with minor differences in response to the control agent imidacloprid. However, overall findings do not support the existence of subspecies of C. felis.
Parasitology Research 11/2004; 94(3):219-26. · 2.15 Impact Factor
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I Schroeder,
B L Blagburn,
D L Bledsoe, R Bond,
I Denholm,
M W Dryden,
D E Jacobs,
H Mehlhorn,
N Mencke,
P Payne,
M K Rust,
M B Vaughn
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ABSTRACT: The "Imidacloprid Flea Susceptibility Monitoring Team" has aim to develop and validate a bioassay to effectively monitor and document susceptibility of cat flea (Ctenocephalides felis) isolates to imidacloprid. A larval bioassay was developed, standardized and validated and agreed upon by the team as the reference diagnostic test kit as research has shown that the proposed WHO adult test was not reliable. The selected 3 ppm discriminating dose, determined from evaluating year 2000 field isolates, was approximately 2 times the highest LC95 of the control laboratory flea strains. In 2001 and 2002, this standardized bioassay was used to test more than 190 separate egg collections from individual flea isolates from USA, UK and Germany. If survivorship in the 3 ppm assay is confirmed, the LD50 values of this isolate and the laboratory strains will be determined by a dose-response study in the range of 0.005 to 3 ppm imidacloprid. By comparison of these LD50 values it can be estimated whether a shift in susceptibility to imidacloprid has occurred. In either case the flea isolate will be researched extensively. Currently an in-vivo test which will evaluate the on-host efficacy of Advantage is being established. None of the to date tested isolates revealed reduced susceptibility to imidacloprid.
Parasitology Research 08/2003; 90 Suppl 3:S127-8. · 2.15 Impact Factor
