| dc.description.abstract | A geographic information system (GIS) was constructed using maps of regional agroclimatic features, vegetation
indices and earth surface temperature data from environmental satellites, together with Schistosoma mansoni
prevalence records from 270 municipalities including snail host distributions in Bahia, Brazil to study the spatial and
temporal dynamics of infection and to identify environmental factors that influence the distribution of schistosomiasis.
In an initial analysis, population density and duration (months) of the annual dry period were shown to be
important determinants of disease. In cooperation with the National Institute of Spatial Research in Brazil (INPE),
day and night imagery data covering the state of Bahia were selected at approximately bimonthly intervals in 1994
(six day–night pairs) from the data archives of the advanced very high resolution radiometer (AVHRR) sensor of the
National Oceanic and Atmospheric Administration (NOAA)-11 satellite. A composite mosaic of these images was
created to produce maps of: (1) average values between 0 and +1 of the normalized difference vegetation index
(NDVI); and (2) average diurnal temperature differences (dT) on a scale of values between 0 and 15°C. For each
municipality, NDVI and dT were calculated for a 3×3 pixel (9 km2 area) grid and analyzed for relationships to
prevalence of schistosomiasis. Results showed a statistically significant relationship of prevalence to dT (r=−0.218)
and NDVI (r=0.384) at the 95% level of confidence by the Spearman rank correlation coefficient. Results support
use of NDVI, dT, dry period climatic stress factors and human population density for development of a GIS
environmental risk assessment model for schistosomiasis in Brazil. © 2001 Elsevier Science B.V. All rights reserved | |
