Spatial approach of the production of Aedes aegypti pupae using GIS and remote sensing

DHF is a permanent challenge for Public Health authorities in Thailand, as epidemics in 1997–1998 and 2001, spread over most of the country. Wide variations of level of incidence over areas mean that to be efficient the control strategy needs the delineation of risk areas. Classical entomological indices are used by public health authorities to launch local vector control activities but their reliability to identify areas with higher incidence and to reduce it, is limited. In the frame of a WHO-TDR program to develop new entomological indices based on pupae counts, an exhaustive survey of potential breeding sites has been untertaken in areas with different types of urbanization in Thailand. A GIS database has been set up and includes the GPS location of every surveyed houses. The characterization of the most productive breeding sites in terms of pupae, the density of human population and socio economic indicators, such as the field description of the type of dwellings were additional layers of information. Most productive BS were similar in the different areas. Spatial patterns in the distribution of pupae allows to identify areas where targeted vector control should be easier and more efficient. This method, combining field survey for the characterization of productive breeding sites and GIS technology to delineate areas with a specific type of urbanization, will help to identify similar environments likely to evolve simultaneously in response to the emergence of epidemic phenomena.