Spatial analysis of the distributions of two tick-borne bacteria, Anaplasma phagocytophilum and Ehrlichia chaffeensis, in the Mississippi Alluvial Valley
Manangan, Jamie Sara
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Human monocytotropic ehrlichiosis (HME), caused by the bacterium Ehrlichia chaffeensis, and human granulocytic anaplasmosis (HGA), caused by the bacterium Anaplasma phagocytophilum, are two emerging tick-borne zoonoses of concern. The primary objective of this research was to determine the influences of the physical environment, land cover composition, and landscape heterogeneity on the spatial distributions of E. chaffeensis and A. phagocytophilum at multiple spatial scales in the Mississippi Alluvial Valley. Logistic regression models were developed using three different strategies (a priori, exploratory, and spatial extent). Ecological predictor variables used to develop models included deer density, elevation, land cover, normalized difference vegetation indices, hydrology, and soil moisture. Presence or absence of bacteria was measured using white-tailed deer (Odocoileus virginianus) serology samples collected in the period of 1981-2005. This research indicates that land cover composition and configuration (measures of habitat availability and connectivity for vector or host species) and probability of flooding (because of impacts on vector populations) influence pathogen distributions in the MAV.