Abstract
BackgroundUrban malaria is becoming a major health priority across Africa. A study was undertaken to assess the importance of urban pollution and agriculture practice on the distribution and susceptibility to insecticide of malaria vectors in the two main cities in Cameroon.MethodsAnopheline larval breeding sites were surveyed and water samples analysed monthly from October 2009 to December 2010. Parameters analysed included turbidity, pH, temperature, conductivity, sulfates, phosphates, nitrates, nitrites, ammonia, aluminium, alkalinity, iron, potassium, manganese, magnesium, magnesium hardness and total hardness. Characteristics of water bodies in urban areas were compared to rural areas and between urban sites. The level of susceptibility of Anopheles gambiae to 4% DDT, 0.75% permethrin, 0.05% deltamethrin, 0.1% bendiocarb and 5% malathion were compared between mosquitoes collected from polluted, non polluted and cultivated areas.ResultsA total of 1,546 breeding sites, 690 in Yaoundé and 856 in Douala, were sampled in the course of the study. Almost all measured parameters had a concentration of 2- to 100-fold higher in urban compare to rural breeding sites. No resistance to malathion was detected, but bendiocarb resistance was present in Yaounde. Very low mortality rates were observed following DDT or permethrin exposure, associated with high kdr frequencies. Mosquitoes collected in cultivated areas, exhibited the highest resistant levels. There was little difference in insecticide resistance or kdr allele frequency in mosquitoes collected from polluted versus non-polluted sites.ConclusionThe data confirm high selection pressure on mosquitoes originating from urban areas and suggest urban agriculture rather than pollution as the major factor driving resistance to insecticide.
Highlights
Urban malaria is becoming a major health priority across Africa
Malaria transmission rates still remain higher in the suburban areas compared to central districts, clinical malaria attacks and severe episodes are frequent in both areas [9,6,10]
Breeding sites in urban settings were classified as originating from cultivated areas, polluted and non-polluted sites and the vector susceptibility to insecticides was assessed in each type of site
Summary
A study was undertaken to assess the importance of urban pollution and agriculture practice on the distribution and susceptibility to insecticide of malaria vectors in the two main cities in Cameroon. The national malaria control programme has distributed over two millions impregnated bed nets since 2000, mainly to urban dwellers [10]. This has had a limited impact on the disease burden. There is a clear need for a thorough assessment of malaria transmission risks across ecological foci, and an evaluation of the efficacy of control measures targeting the aquatic stages of mosquitoes which could constitute an important component of the vector control strategy in urban areas as it is already the case in several African cities [14,15,16,17]. Breeding sites in urban settings were classified as originating from cultivated areas, polluted and non-polluted sites and the vector susceptibility to insecticides was assessed in each type of site
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