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Polymorphism of intron-1 in the voltage-gated sodium channel gene of Anopheles gambiae s.s. populations from Cameroon with emphasis on insecticide knockdown resistance mutations

Authors

  • JOSIANE ETANG,

    1. Organisation de Coordination Pour la Lutte Contre les Endémies en Afrique Centrale, PO Box 288, Yaounde, Cameroon
    2. Faculty of Medicine and Pharmaceutical Sciences, University of Douala, PO Box 2701, Douala, Cameroon
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  • JOSE L. VICENTE,

    1. Centro de Malária e Outras Doenças Tropicais, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira 96, 1349-008 Lisbon, Portugal
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  • PHILIPPE NWANE,

    1. Organisation de Coordination Pour la Lutte Contre les Endémies en Afrique Centrale, PO Box 288, Yaounde, Cameroon
    2. Department of Animal Biology and Physiology, University of Yaoundé I, PO Box 812, Yaounde, Cameroon
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  • MOUHAMADOU CHOUAIBOU,

    1. Organisation de Coordination Pour la Lutte Contre les Endémies en Afrique Centrale, PO Box 288, Yaounde, Cameroon
    2. Department of Animal Biology and Physiology, University of Yaoundé I, PO Box 812, Yaounde, Cameroon
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  • ISABELLE MORLAIS,

    1. Organisation de Coordination Pour la Lutte Contre les Endémies en Afrique Centrale, PO Box 288, Yaounde, Cameroon
    2. UR016, Institut de Recherche Pour le Développement, 911 Avenue Agropolis, PO Box 64501, 34394 Montpellier Cedex 5, France
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  • VIRGILIO E. DO ROSARIO,

    1. Centro de Malária e Outras Doenças Tropicais, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira 96, 1349-008 Lisbon, Portugal
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  • FREDERIC SIMARD,

    1. UR016, Institut de Recherche Pour le Développement, 911 Avenue Agropolis, PO Box 64501, 34394 Montpellier Cedex 5, France
    2. Institut de Recherche Pour le Développement, PO Box 171, Bobo Dioulasso, Burkina Faso
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  • PARFAIT AWONO-AMBENE,

    1. Organisation de Coordination Pour la Lutte Contre les Endémies en Afrique Centrale, PO Box 288, Yaounde, Cameroon
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  • JEAN CLAUDE TOTO,

    1. Organisation de Coordination Pour la Lutte Contre les Endémies en Afrique Centrale, PO Box 288, Yaounde, Cameroon
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  • JOAO PINTO

    1. Centro de Malária e Outras Doenças Tropicais, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira 96, 1349-008 Lisbon, Portugal
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  • J.E., a medical entomologist overseeing vector control and insecticide resistance programmes at AOCEAC. J.L.V. is a research assistant at IHMT, with long-standing experience in molecular techniques. P.N. is a PhD student at OCEAC, working on insecticide resistance in malaria vectors. M.C. is a junior researcher at OCEAC, working on impact of insecticide resistance on vector control. I.M. is a senior researcher at OCEAC-IRD, working on molecular characterization of malaria parasite and vector. V.E.R. is a senior researcher leading the malaria group in IHMT. F.S. is a medical entomologist working on mosquito genetics and biology at IRD. P.A.-A. is a medical entomologist at OCEAC, with a good experience in field and laboratory mosquito processing. J.C.T. is a research assistant at OCEAC, with long-standing experience field techniques. J.P. is a medical entomologist working on mosquito genetics and biology at IHMT.

Josiane Etang, Fax: +237 22 23 00 61; E-mail: josyet@yahoo.fr

Abstract

Sequence variation at the intron-1 of the voltage-gated sodium channel gene in Anopheles gambiae M- and S-forms from Cameroon was assessed to explore the number of mutational events originating knockdown resistance (kdr) alleles. Mosquitoes were sampled between December 2005 and June 2006 from three geographical areas: (i) Magba in the western region; (ii) Loum, Tiko, Douala, Kribi, and Campo along the Atlantic coast; and (iii) Bertoua, in the eastern continental plateau. Both 1014S and 1014F kdr alleles were found in the S-form with overall frequencies of 14% and 42% respectively. Only the 1014F allele was found in the M-form at lower frequency (11%). Analysis of a 455 bp region of intron-1 upstream the kdr locus revealed four independent mutation events originating kdr alleles, here named MS1 -1014F, S1-1014S and S2-1014S kdr-intron-1 haplotypes in S-form and MS3-1014F kdr-intron-1 haplotype in the M-form. Furthermore, there was evidence for mutual introgression of kdr 1014F allele between the two molecular forms, MS1 and MS3 being widely shared by them. Although no M/S hybrid was observed in analysed samples, this wide distribution of haplotypes MS1 and MS3 suggests inter-form hybridizing at significant level and emphasizes the rapid diffusion of the kdr alleles in Africa. The mosaic of genetic events found in Cameroon is representative of the situation in the West–Central African region and highlights the importance of evaluating the spatial and temporal evolution of kdr alleles for a better management of insecticide resistance.

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