Co‐occurrence of East and West African kdr mutations suggests high levels of resistance to pyrethroid insecticides in Anopheles gambiae from Libreville, Gabon

Abstract

Point mutations in the voltage-gated sodium channel gene involved in knockdown resistance to DDT and pyrethroid insecticides have been described in several insect species. In the malaria vector Anopheles gambiae Giles sensu stricto (Diptera: Culicidae) two mutations have been identified. The first, consisting of a leucine-phenylalanine substitution at amino acid position 1014, is widespread in West Africa. The second, a leucine-serine substitution at the same position, has to date only been detected in western Kenya. Analysis of the kdr polymorphism in a sample of 106 An. gambiae s.s. of the rDNA S-form/Type I collected in Libreville (Gabon) surprisingly revealed the presence of both East and West African kdr mutations with frequencies of 63% and 37%, respectively. No wild-type alleles were detected and there was an excess of heterozygous genotypes (P = 0.04). In addition, an inconsistency was found during the kdr genotyping procedures by polymerase chain reaction, which could have lead to an underestimation of resistance alleles. The implications of these findings are discussed.

Insecticide Resistance Allele Frequencies in Anopheles gambiae before and after Anti-Vector Interventions in Continental Equatorial Guinea

“…30 These villages were sampled across a diverse landscape of urban and agroindustrial settings in which pyrethroids and other insecticides are commonly used for agricultural, household nuisance reduction and public health uses, and L1014F increased substantially In Gabon, which borders Equatorial Guinea to the south, Pinto and others observed a much higher frequency of L1014S (63.0%) than L1014F (37.0%) in an S form population only approximately 100 km from the southern border of Equatorial Guinea. 8 Therefore, Gabon provides another possible entry route for L1014F and/or L1014S. However, the pre-intervention frequencies of kdr alleles in continental Equatorial Guinea are much higher than can be explained by mosquito migration and several years of genetic drift.…”

First Evidence of High Knockdown Resistance Frequency in Anopheles arabiensis (Diptera: Culicidae) from Ethiopia

“…gambiae s.s. populations has been reported from different countries in Africa. 10,11 The geographic restriction of both mutations is less definite than previously thought. 12 The two mutations, West and East African kdr in the major malaria vector An.…”

Differential resistance of insect sodium channels with kdr mutations to deltamethrin, permethrin and DDT

“…In West Africa L1014F predominates whereas in East Africa L1014S is mainly responsible for the kdr phenotype. However, these mutations are no longer unique to these geographic regions (Etang et al, 2006;Pinto et al, 2006;Santolamazza et al, 2008). There are also reports of kdr mutations co-occurring in A. gambiae (Verhaeghen et al, 2006).…”