SPATIAL-ANALYSIS OF THE DISTRIBUTION OF TSETSE-FLIES IN THE LAMBWE VALLEY, KENYA, USING LANDSAT TM SATELLITE IMAGERY AND GIS

1. Satellite imagery, geographic information systems (GIS) and spatial statistics provide tools for studies of population dynamics of diseas e vectors in association with habitat features on multiple spatial sca les. 2. Tsetse flies were collected during 1988-90 in biconical traps located along transects in Ruma National Park in the Lambwe Valley, we stern Kenya. Fine spatial resolution data collected by Landsat Themati c Mapper (TM) satellite and reference ground environmental data were i ntegrated in a GIS to identify factors associated with local variation s of fly density. 3. Statistical methods of spatial autocorrelation an d spatial filtering were applied to determine spatial components of th ese associations. Strong positive spatial associations among traps occ urred within transects and within the two ends of the park. 4. From sa tellite data, TM band 7, which is associated with moisture content of soil and vegetation, emerged as being consistently highly correlated w ith fly density. Using several spectral bands in a multiple regression , as much as 87% of the variance in fly catch values could be explaine d. 5. When spatial filtering was applied, a large component of the ass ociation between fly density and spectral data was shown to be the res ult of other determinants underlying the spatial distributions of both fly density and spectral values. Further field studies are needed to identify these determinants. 6. The incorporation of remotely sensed d ata imagery into a GIS with ground data on fly density and environnmen tal conditions can be used to predict favourable fly habitats in inacc essible sites, and to determine number and location of fly suppression traps in a local control programme.