Identification of a point mutation in the voltage-gated sodium channel gene of Kenyan Anopheles gambiae associated with resistance to DDT and pyrethroids

doi:10.1046/j.1365-2583.2000.00209.x

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Wiley InterScience

Insect Molecular Biology

Volume 9 Issue 5, Pages 491 - 497

Published Online: 25 Dec 2001

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Identification of a point mutation in the voltage-gated sodium channel gene of Kenyan Anopheles gambiae associated with resistance to DDT and pyrethroids

H. Ranson, ¹ * B. Jensen, ¹ J. M. Vulule, ² X. Wang, ¹ J. Hemingway ³ and F. H. Collins ¹

¹ Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA, ² Vector Biology and Control Research Centre, Kenya Medical Research Institute, Kisumu, Kenya, and ³ School of Biosciences, Cardiff University, Main College, Cardiff, UK

Correspondence: H. Ranson, School of Biosciences, Cardiff University, Main College, Cardiff CF1 3TL, UK. Tel.: (44) 029 20874170; fax: (44) 029 20874305; e-mail: RansonHA@cardiff.ac.uk

*Present address: School of Biosciences, Cardiff University, Main College, Cardiff, UK.

KEYWORDS

pyrethroid resistance • DDT resistance • Anopheles gambiae • sodium channel • kdr

ABSTRACT

Abstract

A field trial of permethrin-impregnated bednets and curtains was initiated in Western Kenya in 1990, and a strain of Anopheles gambiae showing reduced susceptibility to permethrin was colonized from this site in 1992. A leucine–phenylalanine substitution at position 1014 of the voltage-gated sodium channel is associated with resistance to permethrin and DDT in many insect species, including Anopheles gambiae from West Africa. We cloned and sequenced a partial sodium channel cDNA from the Kenyan permethrin-resistant strain and we identified an alternative substitution (leucine to serine) at the same position, which is linked to the inheritance of permethrin resistance in the F₂ progeny of genetic crosses between susceptible and resistant individuals. The diagnostic polymerase chain reaction (PCR) developed by Martinez-Torres et al. [(1998) Insect Mol Biol 7: 179–184] to detect kdr alleles in field populations of An. gambiae will not detect the Kenyan allele and hence reliance on this assay may lead to an underestimate of the prevalence of pyrethroid resistance in this species. We adapted the diagnostic PCR to detect the leucine–serine mutation and with this diagnostic we were able to demonstrate that this kdr allele was present in individuals collected from the Kenyan trial site in 1986, prior to the introduction of pyrethroid-impregnated bednets. The An. gambiae sodium channel was physically mapped to chromosome 2L, division 20C. This position corresponds to the location of a major quantitative trait locus determining resistance to permethrin in the Kenyan strain of An. gambiae.