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Insecticide resistance in Anopheles gambiae from the northern Democratic Republic of Congo, with extreme knockdown resistance (kdr) mutation frequencies revealed by a new diagnostic assay

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Lynd, Amy, Oruni, Ambrose, Van 't Hof, Arjen, Morgan, John, Naego, Leon Bwazumo, Pipini, Dimitra, O'Kines, Kevin A, Bobanga, Thierry L, Donnelly, Martin ORCID: https://orcid.org/0000-0001-5218-1497 and Weetman, David ORCID: https://orcid.org/0000-0002-5820-1388 (2018) 'Insecticide resistance in Anopheles gambiae from the northern Democratic Republic of Congo, with extreme knockdown resistance (kdr) mutation frequencies revealed by a new diagnostic assay'. Malaria Journal, Vol 17, Issue 412.

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Abstract

Background: Mutations in the voltage-gated sodium channel at codon 1014 confer knock-down resistance (kdr) to pyrethroids in a wide range of insects. Anopheles gambiae exhibits two mutant alleles at codon 1014, serine and phenylalanine; and both are now widespread across Africa. Existing screening methods only allow for one resistant allele to be detected per assay. A new locked nucleic acid (LNA) qPCR assay was developed for the simultaneous detection of both mutant alleles and the wild type allele in a single assay. This tri-allelic detection assay was assessed as part of a study of the insecticide resistance in An. gambiae sensu stricto (s.s.) in the previously un-sampled area of Nord Ubangi,
Democratic Republic of the Congo.

Methods: Samples from three sites were tested for insecticide susceptibility using WHO bioassays, with and without the synergist PBO preceding pyrethroid exposures, and were subsequently analysed for frequency and resistance association of the Vgsc-1014 and Vgsc-N1575Y mutations. Results from the LNA-kdr 1014 assay were compared to results from standard TaqMan-kdr assays.

Results: Anopheles gambiae sensu lato (s.l.) was by far the predominant vector captured (84%), with only low frequencies of Anopheles funestus s.l. (9%) detected in Nord Ubangi. Molecular identification found An. gambiae s.s. to be the principal vector (99%) although Anopheles coluzzii was detected at very low frequency. Anopheles gambiae were
susceptible to the carbamate insecticide bendiocarb, but resistant to DDT and to the pyrethroids permethrin and deltamethrin. Susceptibility to both pyrethroids was partially restored with prior exposure to PBO suggesting likely involvement of metabolic resistance. Anopheles gambiae s.s. was homozygous for kdr resistant alleles with both the
L1014F and L1014S mutations present, and the N1575Y polymorphism was present at low frequency. The LNA-kdr assay simultaneously detected both resistant alleles and gave results entirely consistent with those from the two TaqMan-kdr assays.

Conclusion: This study provides rare data on insecticide resistance and mechanisms in Anopheles from the centre of Africa, with the first detection of N1575Y. Nord Ubangi populations of An. gambiae s.s. show insecticide resistance mediated by both metabolic mechanisms and Vgsc mutations. The LNA-kdr assay is particularly suitable for use in populations in which both 1014S and 1014F kdr alleles co-occur and provides robust results, with higher throughput and at a quarter of the cost of TaqMan assays.

Item Type: Article
Subjects: QV Pharmacology > Drug Standardization. Pharmacognosy. Medicinal Plants > QV 771 Standardization and evaluation of drugs
QX Parasitology > Insects. Other Parasites > QX 510 Mosquitoes
QX Parasitology > Insects. Other Parasites > QX 515 Anopheles
QX Parasitology > Insects. Other Parasites > QX 600 Insect control. Tick control
WA Public Health > Health Problems of Special Population Groups > WA 395 Health in developing countries
Faculty: Department: Biological Sciences > Vector Biology Department
Digital Object Identifer (DOI): https://doi.org/10.1186/s12936-018-2561-5
Depositing User: Stacy Murtagh
Date Deposited: 29 Nov 2018 16:21
Last Modified: 30 Nov 2018 11:43
URI: https://archive.lstmed.ac.uk/id/eprint/9703

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