Ecology of urban malaria vectors in Niamey, Republic of Niger.
Urbanization in African cities has major impact on malaria risk. Niamey, the capital of the Republic of Niger, is situated in the West African Sahel zone. The short rainy season and human activities linked with the Niger River influence mosquito abundance. This study aimed at deciphering the factors of distribution of urban malaria vectors in Niamey.



The distribution of mosquito aquatic stages was investigated monthly from December 2002 to November 2003, at up to 84 breeding sites, throughout Niamey. An exploratory analysis of association between mosquito abundance and environmental factors was performed by a Principal Component Analysis and confirmed by Kruskall-Wallis non-parametric test. To assess the relative importance of significant factors, models were built for Anopheles and Culicinae. In a second capture session, adult mosquitoes were collected weekly with pyrethrum sprays and CDC light-traps from June 2008 to June 2009 in two differentiated urban areas chosen after the study's first step. Members of the Anopheles gambiae complex were genotyped and Anopheles females were tested for the presence of Plasmodium falciparum circumsporozoite antigens using ELISA.



In 2003, 29 % of 8420 mosquitoes collected as aquatic stages were Anopheles. They were significantly more likely to be found upstream, relatively close to the river and highly productive in ponds. These factors remained significant in regression and generalized linear models. The Culicinae were found significantly more likely close to the river, and in the main temporary affluent stream. In 2009, Anopheles specimens, including Anopheles gambiae s.l. (95 %), but also Anopheles funestus (0.6 %) accounted for 18 % of the adult mosquito fauna, with a large difference between the two sampled zones. Three members of the An. gambiae complex were found: Anopheles arabiensis, Anopheles coluzzii, and An. gambiae. Nineteen (1.3 %) out of 1467 females tested for P. falciparum antigen were found positive.



The study provides valuable update knowledge on malaria vector ecology and distribution in Niamey. The identification of spatial and environmental risk factors could pave the way to larval source management strategy and allow malaria vector control to focus on key zones for the benefit of the community.
Centre de Recherche Médicale et Sanitaire (CERMES), Institut Pasteur International Network, 634 Bd de la Nation, BP 10887, Niamey, Niger. rabiou@cermes.org.
Rabiou
0000-0002-4373-4974
R
Labbo
Centre de Recherche Médicale et Sanitaire (CERMES), Institut Pasteur International Network, 634 Bd de la Nation, BP 10887, Niamey, Niger.
Thierry
T
Fandeur
Centre de Recherche Médicale et Sanitaire (CERMES), Institut Pasteur International Network, 634 Bd de la Nation, BP 10887, Niamey, Niger.|School of Medicine, Deakin University, 75 Pigdons Road, Waurn Ponds, VIC, 3216, Australia.
Isabelle
I
Jeanne
Centre de Recherche Médicale et Sanitaire (CERMES), Institut Pasteur International Network, 634 Bd de la Nation, BP 10887, Niamey, Niger.|World Health Organization Representative Offices for Solomon Islands, Honiara, Solomon Islands.
Cyril
C
Czeher
Parsons Laboratory, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA.
Earle
E
Williams
Centre de Recherche Médicale et Sanitaire (CERMES), Institut Pasteur International Network, 634 Bd de la Nation, BP 10887, Niamey, Niger.
Ibrahim
I
Arzika
Centre de Recherche Médicale et Sanitaire (CERMES), Institut Pasteur International Network, 634 Bd de la Nation, BP 10887, Niamey, Niger.
Amadou
A
Soumana
Centre de Recherche Médicale et Sanitaire (CERMES), Institut Pasteur International Network, 634 Bd de la Nation, BP 10887, Niamey, Niger.|Hôpital National de Niamey, Niamey, Niger.
Ramatoulaye
R
Lazoumar
Centre de Recherche Médicale et Sanitaire (CERMES), Institut Pasteur International Network, 634 Bd de la Nation, BP 10887, Niamey, Niger.|Australian Animal Health Laboratory (AAHL), Health and Biosecurity CSIRO, 5 Portarlington Road East, Geelong, VIC, 3220, Australia.
Jean-Bernard
JB
Duchemin
D000818:Animals; D000852:Anopheles / Q000254:growth & development* / Q000469:parasitology*; D004463:Ecology; D017753:Ecosystem; D004777:Environment; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D016778:Malaria, Falciparum; D000072138:Mosquito Vectors / Q000254:growth & development* / Q000469:parasitology*; D009548:Niger; D010963:Plasmodium falciparum / Q000302:isolation & purification; D011156:Population Density; D015800:Protozoan Proteins / Q000032:analysis
D015800:Protozoan Proteins; C041595:circumsporozoite protein, Protozoan
Anopheles; Anopheles gambiae; Malaria; Niamey; Niger; Sahel; Urban; Vector ecology