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International Journal of Health Geographics BioMed Central Research Open Access Determining areas that require indoor insecticide spraying using Multi Criteria Evaluation, a decision-support tool for malaria vector control programmes in the Central Highlands of Madagascar Fanjasoa Rakotomanana*1, Rindra V Randremanana1, Léon P Rabarijaona1, Jean Bernard Duchemin2, Jocelyn Ratovonjato1, Frédéric Ariey3, Jean Paul Rudant4 and Isabelle Jeanne2 Address: 1Cellule Système d'Information Géographique, Unité Epidémiologie, BP1274, Tel 261 20 22 412 72 Institut Pasteur, Antananarivo, Madagascar, 2CERMES, BP 10887 Niamey, Niger, 3Institut Pasteur, Phnom Penh, Cambodia and 4Institut Francilien de Géosciences, Université Marne La Vallée, France Email: Fanjasoa Rakotomanana* - [email protected]; Rindra V Randremanana - [email protected]; Léon P Rabarijaona - [email protected]; Jean Bernard Duchemin - [email protected]; Jocelyn Ratovonjato - [email protected]; Frédéric Ariey - [email protected]; Jean Paul Rudant - [email protected]; Isabelle Jeanne - [email protected] * Corresponding author Published: 29 January 2007 Received: 19 September 2006 Accepted: 29 January 2007 International Journal of Health Geographics 2007, 6:2 doi:10.1186/1476-072X-6-2 This article is available from: http://www.ij-healthgeographics.com/content/6/1/2 © 2007 Rakotomanana et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Background: The highlands of Madagascar present an unstable transmission pattern of malaria. The population has no immunity, and the central highlands have been the sites of epidemics with particularly high fatality. The most recent epidemic occurred in the 1980s, and caused about 30,000 deaths. The fight against malaria epidemics in the highlands has been based on indoor insecticide spraying to control malaria vectors. Any preventive programme involving generalised cover in the highlands will require very substantial logistical support. We used multicriteria evaluation, by the method of weighted linear combination, as basis for improved targeting of actions by determining priority zones for intervention. Results: Image analysis and field validation showed the accuracy of mapping rice fields to be between 82.3% and 100%, and the Kappa coefficient was 0.86 to 0.99. A significant positive correlation was observed between the abundance of the vector Anopheles funestus and temperature; the correlation coefficient was 0.599 (p < 0.001). A significant negative correlation was observed between vector abundance and human population density: the correlation coefficient was -0.551 (p < 0.003). Factor weights were determined by pair-wise comparison and the consistency ratio was 0.04. Risk maps of the six study zones were obtained according to a gradient of risk. Nine of thirteen results of alert confirmed by the Epidemiological Surveillance Post were in concordance with the risk map. Conclusion: This study is particularly valuable for the management of vector control programmes, and particularly the reduction of the vector population with a view to preventing disease. The risk map obtained can be used to identify priority zones for the management of resources, and also help avoid systematic and generalised spraying throughout the highlands: such spraying is particularly difficult and expensive. The accuracy of the mapping, both as concerns time and space, is dependent on the availability of data. Continuous monitoring of malaria transmission factors must be undertaken to detect any changes. A regular case notification allows risk map to be verified. These actions should therefore be implemented so that risk maps can be satisfactorily assessed. Page 1 of 11 (page number not for citation purposes) International Journal of Health Geographics 2007, 6:2 http://www.ij-healthgeographics.com/content/6/1/2 Background Methods The highlands of Madagascar present an unstable pattern Study zones of transmission of malaria. The population has no immu- Six zones, numbered z1 to z6 (hatched surfaces in figure nity and there have been epidemics with large numbers of 1), were chosen according to their geographical location casualties [1,2]. The last epidemic occurred in the 1980s in the central highlands, the dominance of rice field typol- and killed about 30,000 people [3]. The epidemics in Mal- ogy, the parasite prevalence among schoolchildren as agasy highlands corresponded to the re-emergence of determined in 1998 [6] and the time of the last indoor malaria and spread after the vector control programme insecticide spraying campaign. was reduced or stopped [4]. The same phenomenon has been observed in Belize, Central America and highlands Mahatsinjo (zone 1): This zone is located on the Northern in Africa [1,4,5]. The malaria epidemic control strategy in margin of the Highlands. The rice fields occupy the small the Malagasy highlands has been based on indoor insecti- valley bottoms. This area had never been treated with cide spraying, to control the vectors. Anopheles funestus insecticide spraying. (An. funestus) is the main vector responsible for malaria epidemics in the Central Highlands of Madagascar [1]. Ambohibary (zone 2): This is a vast plain of rice fields on The success of the vector control programme was due to the North Eastern part of the mountain of Ankaratra, at the anthropophilic and endophilic behaviour of An. funes- more than 1600 m above the sea level. This area has been tus. treated with only the first cycle of insecticide spraying. During the first cycle of the vector control programme, the Ambositra (zone 3): This zone is in the Andina valley. Rice major criterion used for the inclusion of a village was sim- fields occupy broad valleys and the micro-basins managed ply being at an altitude between 1,000 m and 1,500 m [6]. in regular parcels. The lower closed slopes are managed This resulted in huge areas needing to be covered by for dry cultivation or in terraces around the hills for rice indoor insecticide spraying during each of the five cycles fields. This area has been treated with insecticide spraying. of the programme named "Opération de Pulvérisation IntraDomiciliaire" (OPID). This was followed by annual Ambalavao (zone 4): This zone is at the southern edge of selected indoor insecticide spraying named "Campagne the central highland. Long digitated rice fields cover the d'Aspersion IntraDomiciliaire" (CAID) based on alerts secondary valleys and the small tertiary valleys. This zone declared by Health Facility Centres and confirmed biolog- has been treated with insecticide spraying. ically by epidemiological surveillance centres, named "Poste Sentinelle de Surveillance Epidémiologique Fenoarivo (zone 5): In the district of Ambalavao, this (PSSE)". Complete coverage of the highlands by indoor zone includes the same types of rice fields found in zone insecticide spraying programmes would require a massive 4. In particular, rice fields occupy the small valleys and logistical effort: a single campaign may cost as much as US also pluvial micro-parcels. Most of this zone is at less than $3,500,000. Furthermore, the human resources are not 1,000 m altitude and has never been treated with insecti- available, some of the areas are inaccessible and to be cide spraying. effective, the programme must be implemented in a rela- tively short time window, immediately before the malaria Amborompotsy (zone 6): This zone is situated in the west transmission season. Thus, it would be extremely benefi- part of the central highlands. Smooth slopes to deep val- cial to select priority zones allowing action to be better leys are managed in terraces for rice cultivation but wider focused. Generalised spraying could be avoided, and valleys are only exploited at the bottom. Amborompotsy more selective, targeted treatment used. has never been treated with insecticide spraying. In Kenyan highlands, malaria is associated with ecological Data sources risk factors. Higher elevation, increased distance from the - A Digital Elevation Model (DEM) was obtained for all forest and swamp and increased population density were the highlands of Madagascar (between 45°26E and associated with decreased malaria risk [7]. 48°05E of longitude, 17°39S and 22°12S of latitude), from the Earth Observation Epidemioproject of the Euro- The objective of the study is to determine zones at risk of pean Spatial Agency (ESA). The horizontal ground resolu- malaria epidemic using Geographic Information System tion was 50 m and the map scale was 1: 200 000. and then to guide the vector control programmes. Finally, the results of this study could be used as a decision – sup- - Temperature distribution was determined with the Spa- port tool for the decision makers in resource manage- tial Characterization Tool (SCT) [8]. ment. Page 2 of 11 (page number not for citation purposes) International Journal of Health Geographics 2007, 6:2 http://www.ij-healthgeographics.com/content/6/1/2 Inter Pasteurienne (ACIP) project. Synthetic Aperture Radar (SAR) and Advanced Synthetic Aperture Radar (ASAR) images were used for Amborompotsy (z6). The image from ERS2 was acquired in May 2003 and that from Envisat was acquired in January 2004. Two ASAR images were used for Fenoarivo (z5): the first image was acquired in January 2004 and the second