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Open Access Highly Accessed Research article

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

Fanjasoa Rakotomanana1*, Jocelyn Ratovonjato2, Rindra V Randremanana1, Laurence Randrianasolo1, Rogelin Raherinjafy3, Jean-Paul Rudant4 and Vincent Richard1

Author Affiliations

1 Unité Epidémiologie, Institut Pasteur, BP 1274, Antananarivo, Madagascar

2 Unité d'Entomologie médicale, Institut Pasteur, BP 1274, Antananarivo, Madagascar

3 Unité de Recherche sur le Paludisme, Institut Pasteur, BP1274, Antananarivo, Madagascar

4 Institut Francilien de Géosciences, Université Paris-Est, Marne La Vallée, France

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BMC Infectious Diseases 2010, 10:173  doi:10.1186/1471-2334-10-173

Published: 16 June 2010

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.