[Malaria and schistosomiasis: 2 examples using systems of geographical information and teledetection in Madagascar].

Schistosomiasis and malaria constitute major health problems in Madagascar. The main objectives of the national schistosomiasis control programme--launched in 1998--are to improve knowledge about the modes of transmission of the disease and conduct mass treatment in hyperendemic areas, so as to lower incidence rates. A Geographic Information System (GIS) was established aiming to conduct a series of remote sensing studies based on digital image processing and analysis from Landsat TM and panchromatic Spot. The importance of local environmental and geographic characteristics in the Ihosy region such as proximity to roads and water were assessed by spatial analysis in order to construct a predictive model of Schistosoma mansoni endemicity. Unstable transmission in the Central Highlands of Madagascar caused severe outbreaks of malaria in the 1980s. Attempts to prevent such events reoccurring have been highlighted in the national malaria control programme. Thanks to intense vector control measures introduced in the area over a five-year period, a marked decrease in incidence of malaria was observed. This region borders on the Highlands as well as southern areas, allowing for vector control evaluation. The GIS and remote sensing system were applied to analyse ricefield areas, where the main vector are Anopheles funestus. Rice-field surfaces were statistically linked with abundance of vectors evaluated by entomological parametres.