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Evidence of increasing Leu-Phe knockdown resistance mutation in Anopheles gambiae from Niger following a nationwide long-lasting insecticide-treated nets implementation.

Czeher C, Labbo R, Arzika I, Duchemin JB - Malar. J. (2008)

Bottom Line: Higher kdr frequencies were repeatedly noticed within host-seeking females compared to resting ones in indoor collections.In addition, preliminary results in M form urban populations from Niamey showed far higher kdr frequencies than in all of the rural sites studied.While the kdr mutation is still found at a low level, this rapid increase could potentially lead to high kdr frequencies within a few years.

View Article: PubMed Central - HTML - PubMed

Affiliation: Parasitology Unit, Centre de Recherche Médicale et Sanitaire, Institut Pasteur International Network, Niamey, Niger. cyril_czeher@yahoo.fr

ABSTRACT

Background: At the end of 2005, a nationwide long-lasting insecticide-treated net (LLIN) distribution targeting the most vulnerable populations was implemented throughout Niger. A large number of studies in Africa have reported the existence of anopheline populations resistant to various insecticides, partly due to knockdown resistance (kdr) mutations, but few operational wide-scale control programmes were coupled with the monitoring of such mutations. The distribution of the kdr-west (kdr-w) Leu-Phe mutation was studied in Anopheles gambiae s.l. populations from Niger and temporal variations were monitored following the nationwide LLIN implementation.

Methods: Mosquitoes were collected from 14 localities during the wet seasons of 2005, 2006 and 2007 with additional sampling in the capital city, Niamey. After morphological identification of Anopheles gambiae s.l. specimens, DNA extracts were used for the determination of species and molecular forms of the Anopheles gambiae complex and for the detection of the kdr-w mutation.

Results: Around 1,500 specimens collected in the three consecutive years were analysed. All Anopheles arabiensis specimens analysed were homozygous susceptible, whereas the few Anopheles gambiae S forms exhibited a high overall kdr-w frequency. The M form samples exhibited a low overall kdr-w frequency before the LLIN distribution, that increased significantly in the two wet season collections following the LLIN distribution. Higher kdr frequencies were repeatedly noticed within host-seeking females compared to resting ones in indoor collections. In addition, preliminary results in M form urban populations from Niamey showed far higher kdr frequencies than in all of the rural sites studied.

Discussion: This study describes the first case of kdr mutation in Anopheles gambiae populations from Niger. It is suspected that the LLIN have caused the important temporal increase of kdr-w mutation observed during this study. While the kdr mutation is still found at a low level, this rapid increase could potentially lead to high kdr frequencies within a few years.

Conclusion: These results are of prime importance in the effort to document multiple effects of operational control programmes on mosquito vectors, and to conceive sustainable control strategies for future malaria control programmes.

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Related in: MedlinePlus

Map of the study area and collection sites.
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Figure 1: Map of the study area and collection sites.

Mentions: Mosquitoes were collected from 14 localities situated in the sahelian zone during the wet season (between July and September) of 2005, 2006 and 2007 (Figure 1). The 2007 collections were made in eight of the 14 initial study sites because of logistical constraints. This sampling scheme allowed us to collect specimens from West to East over a distance of around 1,700 km. In each village, landing catches on human adult male volunteers and indoor spray catches with pyrethroids (Mobil insecticide, Mobil Oil Nigeria, Lagos, Nigeria) were employed following standardized procedures and with agreement of the National Ethics Committee. The 2005 collections were made before the implementation of the nationwide LLIN coverage to provide baseline kdr mutation frequency data, whereas the 2006 and 2007 collections were made approximately 7–8 months and 19–20 months after the LLIN distribution, respectively. Additionally, some larval samples collected in Niamey (the capital city) during the 2003 and 2007 wet seasons were included in the study.


Evidence of increasing Leu-Phe knockdown resistance mutation in Anopheles gambiae from Niger following a nationwide long-lasting insecticide-treated nets implementation.

Czeher C, Labbo R, Arzika I, Duchemin JB - Malar. J. (2008)

Map of the study area and collection sites.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2562389&req=5

Figure 1: Map of the study area and collection sites.
Mentions: Mosquitoes were collected from 14 localities situated in the sahelian zone during the wet season (between July and September) of 2005, 2006 and 2007 (Figure 1). The 2007 collections were made in eight of the 14 initial study sites because of logistical constraints. This sampling scheme allowed us to collect specimens from West to East over a distance of around 1,700 km. In each village, landing catches on human adult male volunteers and indoor spray catches with pyrethroids (Mobil insecticide, Mobil Oil Nigeria, Lagos, Nigeria) were employed following standardized procedures and with agreement of the National Ethics Committee. The 2005 collections were made before the implementation of the nationwide LLIN coverage to provide baseline kdr mutation frequency data, whereas the 2006 and 2007 collections were made approximately 7–8 months and 19–20 months after the LLIN distribution, respectively. Additionally, some larval samples collected in Niamey (the capital city) during the 2003 and 2007 wet seasons were included in the study.

Bottom Line: Higher kdr frequencies were repeatedly noticed within host-seeking females compared to resting ones in indoor collections.In addition, preliminary results in M form urban populations from Niamey showed far higher kdr frequencies than in all of the rural sites studied.While the kdr mutation is still found at a low level, this rapid increase could potentially lead to high kdr frequencies within a few years.

View Article: PubMed Central - HTML - PubMed

Affiliation: Parasitology Unit, Centre de Recherche Médicale et Sanitaire, Institut Pasteur International Network, Niamey, Niger. cyril_czeher@yahoo.fr

ABSTRACT

Background: At the end of 2005, a nationwide long-lasting insecticide-treated net (LLIN) distribution targeting the most vulnerable populations was implemented throughout Niger. A large number of studies in Africa have reported the existence of anopheline populations resistant to various insecticides, partly due to knockdown resistance (kdr) mutations, but few operational wide-scale control programmes were coupled with the monitoring of such mutations. The distribution of the kdr-west (kdr-w) Leu-Phe mutation was studied in Anopheles gambiae s.l. populations from Niger and temporal variations were monitored following the nationwide LLIN implementation.

Methods: Mosquitoes were collected from 14 localities during the wet seasons of 2005, 2006 and 2007 with additional sampling in the capital city, Niamey. After morphological identification of Anopheles gambiae s.l. specimens, DNA extracts were used for the determination of species and molecular forms of the Anopheles gambiae complex and for the detection of the kdr-w mutation.

Results: Around 1,500 specimens collected in the three consecutive years were analysed. All Anopheles arabiensis specimens analysed were homozygous susceptible, whereas the few Anopheles gambiae S forms exhibited a high overall kdr-w frequency. The M form samples exhibited a low overall kdr-w frequency before the LLIN distribution, that increased significantly in the two wet season collections following the LLIN distribution. Higher kdr frequencies were repeatedly noticed within host-seeking females compared to resting ones in indoor collections. In addition, preliminary results in M form urban populations from Niamey showed far higher kdr frequencies than in all of the rural sites studied.

Discussion: This study describes the first case of kdr mutation in Anopheles gambiae populations from Niger. It is suspected that the LLIN have caused the important temporal increase of kdr-w mutation observed during this study. While the kdr mutation is still found at a low level, this rapid increase could potentially lead to high kdr frequencies within a few years.

Conclusion: These results are of prime importance in the effort to document multiple effects of operational control programmes on mosquito vectors, and to conceive sustainable control strategies for future malaria control programmes.

Show MeSH
Related in: MedlinePlus