Global Forum for Health Research Forum 8, Mexico, November 2004 An ecosystem approach study of malaria transmission and control interventions in southern Mexico. Mario H. Rodriguez 1 , Juan E. Hernández-Avila 2 , Angel Francisco Betanzos-Reyes 3 , Rogelio Danis-Lozano 3 , Lilia González-Cerón 3 , Luis G. Durán-Arenas 4 , Jorge Fernando Méndez- Galván 5 , Rosa María Vázquez-Mellado 6 , Oscar J. Velásquez-Monroy 5 , Héctor Holguín-Bernal 5 and Roberto Tapia-Coyner 7 1 Center for Research on infectious Diseases, National institute of Public Health, Mexico; 2 Department of Informatics and Geographic Medicine, National institute of Public Health, Mexico, 3 Center for Malaria Research, National institute of Public Health, Mexico, 4 Medical Benefits Head Office, Social Security Institute, Mexico, 5 National Coordination of Epidemiological Surveillance, Ministry of Health, Mexico, 6 Comunicación Investigación y Capacitación, A. C., 7 Underministry of Health and Prevention, Ministry of Health, Mexico Introduction Malaria remains a public health problem in Mexico, (Rodriguez and Loyola 1989). It is estimated that 33.1% of all Mexicans live in areas where transmission can occur. Malaria is currently under control in most endemic areas but residual foci, where transmission persists, remain on the Pacific Ocean coast. These foci are traditionally the origin of outbreaks when malaria control activities are reduced. The average parasite incidence in these areas could reach levels fivefold higher than that of the rest of the malariogenic areas in the country. In most malarious areas of Mexico, control measures are usually successful in interrupting the transmission of the disease, but as the conditions determining its reappearance are not eliminated, the potential for transmission remains. Control activities are currently decentralized in Mexico, although the coordination of policy and planning of activities are still conducted by the National Vector Control Program. Indoor DDT spraying was the main weapon for malaria control but its use was rapidly reduced and completely suspended by the year 2000. It is remarkable that the last malaria outbreak, occurring in 1998 in the residual foci located in the state of Oaxaca, was controlled without the use of DDT. Malaria control is currently conducted by an integrated approach that includes improvement of sanitation, surveillance and the reduction of parasite sources. The main activity consists of mosquito larval breeding elimination by removal of filamentous algae in water ponds formed along shrinking river edges during the dry season. This is carried out every two weeks during the dry season by members of the community. Focal interventions, based on selective spraying and prophylactic treatment to people with a history of malaria are conducted only in the case of an increase of cases in the locality (Chanon et al. 2003). Indoor insecticide spraying is conducted using pyrethroids in low volume. This new technique allows the spraying of very low amounts of insecticide at a very speedy coverage (Arredondo et al. 1993). At the beginning of this project, it was thus recognized that in order to design specific anti- malaria control activities, reduce pesticide dependence and promote community based interventions