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Insecticide resistance in Anopheles gambiae from south-western Chad, Central Africa
BACKGROUND: Indoor residual spraying and insecticide-treated nets (ITN) are essential components of malaria vector control in Africa. Pyrethroids are the only recommended compounds for nets treatment because they are fast-acting insecticides with low mammalian toxicity. However, there is growing con...
Autores principales: | , , , , , , |
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Formato: | Texto |
Lenguaje: | English |
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BioMed Central
2008
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2566574/ https://www.ncbi.nlm.nih.gov/pubmed/18823537 http://dx.doi.org/10.1186/1475-2875-7-192 |
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author | Kerah-Hinzoumbé, Clément Péka, Mallaye Nwane, Philippe Donan-Gouni, Issa Etang, Josiane Samè-Ekobo, Albert Simard, Frédéric |
author_facet | Kerah-Hinzoumbé, Clément Péka, Mallaye Nwane, Philippe Donan-Gouni, Issa Etang, Josiane Samè-Ekobo, Albert Simard, Frédéric |
author_sort | Kerah-Hinzoumbé, Clément |
collection | PubMed |
description | BACKGROUND: Indoor residual spraying and insecticide-treated nets (ITN) are essential components of malaria vector control in Africa. Pyrethroids are the only recommended compounds for nets treatment because they are fast-acting insecticides with low mammalian toxicity. However, there is growing concern that pyrethroid resistance may threaten the sustainability of ITN scaling-up programmes. Here, insecticide susceptibility was investigated in Anopheles gambiae sensu lato from an area of large scale ITN distribution programme in south-western Chad. METHODS: Susceptibility to 4% DDT, 0.05% deltamethrin, 0.75% permethrin, 0.1% bendiocarb and 5% malathion was assessed using the WHO standard procedures for adult mosquitoes. Tests were carried out with two to four days-old, non-engorged female mosquitoes. The An. gambiae Kisumu strain was used as a reference. Knockdown effect was recorded every 5 min and mortality scored 24 h after exposure. Mosquitoes were identified to species and molecular form by PCR-RFLP and genotypes at the kdr locus were determined in surviving specimens by Hot Oligonucleotide Ligation Assay (HOLA). RESULTS: During this survey, full susceptibility to malathion was recorded in all samples. Reduced susceptibility to bendiocarb (mortality rate of 96.1%) was found in one sample out of nine assayed. Increased tolerance to pyrethroids was detected in most samples (8/9) with mortality rates ranging from 70.2 to 96.6% for deltamethrin and from 26.7 to 96.3% for permethrin. Pyrethroid tolerance was not associated with a significant increase of knock-down times. Anopheles arabiensis was the predominant species of the An. gambiae complex in the study area, representing 75 to 100% of the samples. Screening for kdr mutations detected the L1014F mutation in 88.6% (N = 35) of surviving An. gambiae sensu stricto S form mosquitoes. All surviving An. arabiensis (N = 49) and M form An. gambiae s.s. (N = 1) carried the susceptible allele. CONCLUSION: This first investigation of malaria vector susceptibility to insecticides in Chad revealed variable levels of resistance to pyrethroid insecticides (permethrin and deltamethrin) in most An. gambiae s.l. populations. Resistance was associated with the L1014F kdr mutation in the S form of An. gambiae s.s.. Alternative mechanisms, probably of metabolic origin are involved in An. arabiensis. These results emphasize the crucial need for insecticide resistance monitoring and in-depth investigation of resistance mechanisms in malaria vectors in Chad. The impact of reduced susceptibility to pyrethroids on ITN efficacy should be further assessed. |
format | Text |
id | pubmed-2566574 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2008 |
publisher | BioMed Central |
record_format | MEDLINE/PubMed |
spelling | pubmed-25665742008-10-11 Insecticide resistance in Anopheles gambiae from south-western Chad, Central Africa Kerah-Hinzoumbé, Clément Péka, Mallaye Nwane, Philippe Donan-Gouni, Issa Etang, Josiane Samè-Ekobo, Albert Simard, Frédéric Malar J Research BACKGROUND: Indoor residual spraying and insecticide-treated nets (ITN) are essential components of malaria vector control in Africa. Pyrethroids are the only recommended compounds for nets treatment because they are fast-acting insecticides with low mammalian toxicity. However, there is growing concern that pyrethroid resistance may threaten the sustainability of ITN scaling-up programmes. Here, insecticide susceptibility was investigated in Anopheles gambiae sensu lato from an area of large scale ITN distribution programme in south-western Chad. METHODS: Susceptibility to 4% DDT, 0.05% deltamethrin, 0.75% permethrin, 0.1% bendiocarb and 5% malathion was assessed using the WHO standard procedures for adult mosquitoes. Tests were carried out with two to four days-old, non-engorged female mosquitoes. The An. gambiae Kisumu strain was used as a reference. Knockdown effect was recorded every 5 min and mortality scored 24 h after exposure. Mosquitoes were identified to species and molecular form by PCR-RFLP and genotypes at the kdr locus were determined in surviving specimens by Hot Oligonucleotide Ligation Assay (HOLA). RESULTS: During this survey, full susceptibility to malathion was recorded in all samples. Reduced susceptibility to bendiocarb (mortality rate of 96.1%) was found in one sample out of nine assayed. Increased tolerance to pyrethroids was detected in most samples (8/9) with mortality rates ranging from 70.2 to 96.6% for deltamethrin and from 26.7 to 96.3% for permethrin. Pyrethroid tolerance was not associated with a significant increase of knock-down times. Anopheles arabiensis was the predominant species of the An. gambiae complex in the study area, representing 75 to 100% of the samples. Screening for kdr mutations detected the L1014F mutation in 88.6% (N = 35) of surviving An. gambiae sensu stricto S form mosquitoes. All surviving An. arabiensis (N = 49) and M form An. gambiae s.s. (N = 1) carried the susceptible allele. CONCLUSION: This first investigation of malaria vector susceptibility to insecticides in Chad revealed variable levels of resistance to pyrethroid insecticides (permethrin and deltamethrin) in most An. gambiae s.l. populations. Resistance was associated with the L1014F kdr mutation in the S form of An. gambiae s.s.. Alternative mechanisms, probably of metabolic origin are involved in An. arabiensis. These results emphasize the crucial need for insecticide resistance monitoring and in-depth investigation of resistance mechanisms in malaria vectors in Chad. The impact of reduced susceptibility to pyrethroids on ITN efficacy should be further assessed. BioMed Central 2008-09-29 /pmc/articles/PMC2566574/ /pubmed/18823537 http://dx.doi.org/10.1186/1475-2875-7-192 Text en Copyright © 2008 Kerah-Hinzoumbé et al; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( (http://creativecommons.org/licenses/by/2.0) ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Research Kerah-Hinzoumbé, Clément Péka, Mallaye Nwane, Philippe Donan-Gouni, Issa Etang, Josiane Samè-Ekobo, Albert Simard, Frédéric Insecticide resistance in Anopheles gambiae from south-western Chad, Central Africa |
title | Insecticide resistance in Anopheles gambiae from south-western Chad, Central Africa |
title_full | Insecticide resistance in Anopheles gambiae from south-western Chad, Central Africa |
title_fullStr | Insecticide resistance in Anopheles gambiae from south-western Chad, Central Africa |
title_full_unstemmed | Insecticide resistance in Anopheles gambiae from south-western Chad, Central Africa |
title_short | Insecticide resistance in Anopheles gambiae from south-western Chad, Central Africa |
title_sort | insecticide resistance in anopheles gambiae from south-western chad, central africa |
topic | Research |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2566574/ https://www.ncbi.nlm.nih.gov/pubmed/18823537 http://dx.doi.org/10.1186/1475-2875-7-192 |
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