Abstract
BackgroundPrevious studies, conducted in the urban of Antananarivo, showed low rate of confirmed malaria cases. We used a geographical and environmental approach to investigate the contribution of environmental factors to urban malaria in Antananarivo.MethodsRemote sensing data were used to locate rice fields, which were considered to be the principal mosquito breeding sites. We carried out supervised classification by the maximum likelihood method. Entomological study allowed vector species determination from collected larval and adult mosquitoes. Mosquito infectivity was studied, to assess the risk of transmission, and the type of mosquito breeding site was determined. Epidemiological data were collected from November 2006 to December 2007, from public health centres, to determine malaria incidence. Polymerase chain reaction was carried out on dried blood spots from patients, to detect cases of malaria. Rapid diagnostic tests were used to confirm malaria cases among febrile school children in a school survey.A geographical information system was constructed for data integration. Altitude, temperature, rainfall, population density and rice field surface area were analysed and the effects of these factors on the occurrence of confirmed malaria cases were studied.ResultsPolymerase chain reaction confirmed malaria in 5.1% of the presumed cases. Entomological studies showed An. arabiensis as potential vector. Rice fields remained to be the principal breeding sites. Travel report was considered as related to the occurrence of P. falciparum malaria cases.ConclusionGeographical and environmental factors did not show direct relationship with malaria incidence but they seem ensuring suitability of vector development. Absence of relationship may be due to a lack of statistical power. Despite the presence of An. arabiensis, scarce parasitic reservoir and rapid access to health care do not constitute optimal conditions to a threatening malaria transmission. However, imported malaria case is suggestive to sustain the pocket transmission in Antananarivo.
Highlights
Previous studies, conducted in the urban of Antananarivo, showed low rate of confirmed malaria cases
Travel report was considered as related to the occurrence of P. falciparum malaria cases
We found that the presence or absence of confirmed malaria cases was not affected by the altitude of the neighbourhood, population density or the area of the rice fields
Summary
Previous studies, conducted in the urban of Antananarivo, showed low rate of confirmed malaria cases. All countries are faced with the reality that, between and 2050, three billion people are likely to settle in urban areas, principally cities. This rapid growth of urban populations is due to an exodus from rural areas and the progressive urbanisation of the rural areas around existing. Several studies in Africa have investigated the factors contributing to the maintenance of anopheline mosquito populations in urban areas. A study carried out in two urban areas of Kenya showed that 65% (Kisumu) and 93% (Malindi) of the aquatic mosquito habitats were created by humans and that 39% and 65% of these habitats harboured anopheline larvae. Omumbo et al (1998) used a GIS to quantify the relationship between the occurrence of anopheline mosquitoes and environmental variables [12]
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