Risk factors forAnophelesmosquitoes in rural and urban areas of Blantyre District, southern Malawi.
Although urban malaria transmission is low and seasonal, it remains a major public health problem. This study aimed at demonstrating the presence ofAnophelesmosquitoes and their potential to transmit malaria in urban settings.



Two cross-sectional surveys were carried out in Blantyre District, Malawi, during the dry and wet seasons of 2008 and 2010, respectively. A map of Blantyre was divided into a grid of 400 cells, of which 60 cells were randomly selected. Five households located within 100 m from the centre of each selected cell were enrolled, a standard questionnaire was administered, and indoor resting mosquitoes were sampled.



In 2008 and 2010, a total of 960 and 1045 mosquitoes were collected, respectively.Anopheles funestuscomprised 9.9% (n = 95) and 10.3% (n = 108) during the two surveys, respectively.Anopheles gambiae sensu lato (s.l.)was rarely detected during the second survey (n = 6; 0.6%). Molecular identification was performed on samples collected during the first survey, andAn. funestus sensu stricto (s.s.)was the only sibling species detected. All theAnophelesmosquitoes were collected from households located in rural areas of Blantyre and none from urban areas. In univariate analysis, the presence of open eaves was associated with increasedAnophelesprevalence, both during the dry (incidence rate ratio, IRR = 4.3; 95% CI 2.4 - 7.6) and wet (IRR = 2.47; 95% CI 1.7 - 3.59) seasons. Chances of detectingAnophelesspp. decreased with increasing altitude (IRR = 0.996; 95% CI 0.995 - 0.997) and during the dry season, but increased during the wet season (IRR = 1.0017; 95% CI 1.0012 - 1.0023). These factors remained significant following a multiple Poisson regression analysis. No association was found between insecticide-treated bednet ownership and the number ofAnophelesmosquitoes detected.



The presence ofAn. funestuss.s andAn. gambiae s.l.in the periphery of Blantyre city was an indication that malaria transmission was potentially taking place in these areas.
Malaria Alert Centre, College of Medicine, University of Malawi, Blantyre, Malawi.
Themba
T
Mzilahowa
Malaria Alert Centre, College of Medicine, University of Malawi, Blantyre, Malawi.
Madalitso
M
Luka-Banda
Malaria Alert Centre, College of Medicine, University of Malawi, Blantyre, Malawi.
Veronica
V
Uzalili
Malaria Alert Centre, College of Medicine, University of Malawi, Blantyre, Malawi.
Don P
DP
Mathanga
Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, USA.
Carl H
CH
Campbell
Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi.
Mavuto
M
Mukaka
Entomology Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
John E
JE
Gimnig
D000818:Animals; D000852:Anopheles / Q000469:parasitology; D003430:Cross-Sectional Studies; D006801:Humans; D007303:Insect Vectors / Q000469:parasitology; D008288:Malaria / Q000635:transmission*; D008295:Malawi; D012307:Risk Factors; D012424:Rural Population; D012621:Seasons; D014505:Urban Population