Abstract
BackgroundThe rapid and unplanned urbanization of African cities is considered to increase the risk of urban malaria transmission. The present study objective was to assess factors influencing the spatio-temporal distribution of Anopheles gambiae s.l. larvae in the city of Yaoundé, Cameroon.MethodsAll water bodies were checked once every 2 months for the presence of mosquito larvae from March 2017 to May 2018 in 32 districts of Yaoundé. Physico-chemical characteristics including the size, depth, turbidity, pH, temperature, conductivity, sulfates, organophosphates, hydrogen peroxide (H2O2), conductivity, iron and calcium were recorded and analyzed according to anopheline larvae presence or absence. High resolution satellite images from landsat sentinel Enhanced Thematic Mapper were used for spatial mapping of both field and environmental variables. Bivariate and multivariate logistic regression models were used to identify variables closely associated with anopheline larvae distribution.ResultsA total of 18 696 aquatic habitats were checked and only 2942 sites (15.7%) contained anopheline larvae. A high number of sites with anopheline larvae (≥ 69%) presented late instar larvae (L3, L4 and pupae). Anopheline mosquito larvae were sampled from a variety of breeding sites including puddles (51.6%), tire prints (12.9%), wells (11.7%) and drains (11.3%). Bivariate logistic regression analyses associated anopheline larvae presence with the absence of predators, absence of algae, absence of vegetation and depth of less than 1 m. Conductivity, turbidity, organophosphates, H2O2 and temperature were significantly high in breeding sites with anopheline larvae than in breeding sites without these larvae (P < 0.1). Anopheline species collected included An. coluzzii (91.1%) and An. gambiae s.s. (8.9%). GIS mapping indicated a heterogeneous distribution of anopheline breeding habitats in the city of Yaoundé. Land cover analysis indicated high variability of the city of Yaoundé’s landscape.ConclusionsThe data confirms adaptation of An. gambiae s.l. to the urban domain in the city of Yaoundé and calls for urgent actions to improve malaria vector control.
Highlights
The rapid and unplanned urbanization of African cities is considered to increase the risk of urban malaria transmission
Logistic regression analysis between anopheline larval presence and breeding habitats characteristics Bivariate logistic regression analyses were conducted to assess any association between anopheline larvae presence and some breeding sites characteristics
It appears that anopheline larvae were frequent in the absence of predators (OR = 3.4, P < 0.0001), absence of algae (OR = 1.5, P = 0.06), and in breeding sites situated less than 10 m from living habitations (OR = 1.7, P = 0.002) (Table 2)
Summary
The rapid and unplanned urbanization of African cities is considered to increase the risk of urban malaria transmission. The rapid unplanned urbanization of sub-Saharan Africa cities, is significantly affecting the epidemiology of vector borne diseases [1,2,3,4,5,6,7,8]. Successful scale up of control tools such as long lasting insecticidal nets (LLINs) and indoor residual spraying permitted to reduce the global burden of the disease across the continent [13], the disease is still highly prevalent in most urban settings [2, 14,15,16,17]. The said conditions occurring at a large scale, create suitable breeding opportunities for mosquitoes increasing malaria transmission risk in urban settings. Understanding anopheline larvae dynamic in this changing environment becomes imperative for the implementation of successful control measures
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