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. 2010 Jun 16:10:173.
doi: 10.1186/1471-2334-10-173.

Geographical and environmental approaches to urban malaria in Antananarivo (Madagascar)

Fanjasoa Rakotomanana  1 , Jocelyn Ratovonjato, Rindra V Randremanana, Laurence Randrianasolo, Rogelin Raherinjafy, Jean-Paul Rudant, Vincent Richard
Affiliations

Geographical and environmental approaches to urban malaria in Antananarivo (Madagascar)

Fanjasoa Rakotomanana et al. BMC Infect Dis. .

Abstract

Background: Previous 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.

Methods: Remote 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.

Results: Polymerase 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.

Conclusion: Geographical 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.

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Figures

Figure 1
Figure 1
Location of study sites related to distance from the city centre (epidemiological and entomological sites).
Figure 2
Figure 2
Evolution of backscatter coefficient between ASAR_IMP_1P of January and July 2004. The backscatter coefficient of rice field increased, open water decreased and urban backscatter coefficient remained relatively unchanged.
Figure 3
Figure 3
ASAR_IMP_1P images illustrating changes between January and July 2004. Difference between images acquired in January and July 2004.
Figure 4
Figure 4
Neighbourhood distribution of malaria cases; each symbol represents one or two confirmed malaria cases.
Figure 5
Figure 5
Distribution of confirmed malaria cases at fifteen day intervals.
Figure 6
Figure 6
Minimum temperature and confirmed malaria cases during the study period.
Figure 7
Figure 7
Maximum temperature and confirmed malaria cases during the study period.
Figure 8
Figure 8
Rainfall and confirmed malaria cases during the study period.
See this image and copyright information in PMC

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