Project Team: Southeast Health and Air Quality Team
Team Location: Mobile County Health Department (MCHD), Mobile, Alabama
James Pickett, Project Lead (University of South Alabama)
Shikher Mishra (University of South Alabama)
Brandi Stewart (University of South Alabama)
Dr. Kenton Ross (NASA DEVELOP National Science Advisor)
Joe Spruce (Senior Research Scientist, Computer Sciences Corp.; Science Advisor)
Dr. Bernard Eichold (Mobile County Public Health Officer)
Sid King (Fall 2013 DEVELOP Team Member)
Walt Clark (MCHD Center Lead)
Amber Jones (MCHD Assistant Center Lead)
Chagas disease is caused by the parasitic protozoa Trypanosoma cruzi, and is transmitted by Triatoma members of the Reduviidae family of insects, commonly known as ÛÏkissing bugs.Û Triatomines transmit the protozoa to hosts when they defecate after taking a blood meal. Long-term symptoms of the disease are primarily characterized by afflictions of the cardiovascular and gastrointestinal systems where the protozoa reproduce, resulting in the accumulation of internal scar tissue at these sites. Until recently, both vectors and parasites associated with Chagas disease were considered endemic only to Latin America. However, since the 1960s, Chagas disease insect vectors and infected reservoirs have been documented in the Southern United States. Triatoma sanguisuga is the most-adaptable vector species inhabiting the U.S., has become increasingly widespread throughout Louisiana and has been documented extensively in the southern portion of the state. Despite this, little attention is given to Chagas disease in the U.S.
Because of the confirmed presence of vectors in Louisiana and a suspected case of infection in a neighboring community, the Mobile DEVELOP node conducted ecological niche modeling on T. sanguisuga to determine the likelihood of its presence in Alabama, and to aid in possible collection of the vector for testing of the disease. The Genetic Algorithm for Rule-set Production (GARP) was implemented to produce habitat suitability maps of T. sanguisuga with the input of data provided from NASA remote-sensing satellites. For this study, Landsat 8 and Aqua/Terra platforms were primarily used.åÊ Shuttle Radar Topography Mission (SRTM) data were used for deriving terrain elevation and slope maps and to discriminate between deciduous and evergreen vegetation. Total Rainfall Measuring Mission (TRMM) data were used to calculate rainfall accumulations on a seasonal basis. Along with these bioclimatic parameters, data such as Land Surface Temperature (LST), Normalized Difference Vegetation and Water Indices (NDVI, and NDWI) were implemented as well. LST, NDVI, and NDWI were calculated from observations made by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard Aqua and Terra.
Model outputs indicated that large portions of the county exceeded 96 percent habitat suitability with more than half of this extent crossing the 99 percent suitability threshold. A secondary study was conducted to assess which locations within these regions would be most ideal for trapping sites, as well as which populations within the county are at greatest risk of encountering T. sanguisuga. For this purpose, a map consisting of wildland-urban interface and socio-economic data was constructed. To prioritize trap sites, the intersections between the various high percentiles, poorer housing structures, and both the wildland-urban interface and intermix regions were mapped.
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