Recorded presentation

Tracy L. Lambert Jack, MPH¹, Lance A. Waller, PhD², Ruth L. Berkelman, MD¹, and Leslie A. Real, PhD³. (1) Department of Epidemiology, Rollins School of Public Health, Emory University, 1518 Clifton Road NE, Atlanta, GA 30322, (404) 727-9516, tllambe@sph.emory.edu, (2) Department of Biostatistics, Rollins School of Public Health, Emory University, 1518 Clifton Road NE, Atlanta, GA 30322, (3) Department of Biology, Emory University, 1510 Clifton Road NE, Atlanta, GA 30322

Human monocytic ehrlichiosis, a potentially fatal febrile illness caused by the organism Ehrlichia chaffeensis, is an emerging tick-borne infectious disease primarily found in the eastern United States. E. chaffeensis, along with several other human pathogens, is transmitted by an arthropod vector, Amblyomma americanum. Ticks have preferred environmental conditions that may be species specific and that determine their geographic distribution. Any insight into those factors that influence tick presence and abundance will be instrumental in constructing predictive theories of human disease risk. We studied the distribution, abundance, and infection status of A. americanum across the varied habitats of Georgia. We collected ticks in state wildlife management areas, state parks, and national wildlife refuges over two seasons (2003-2004) and partitioned across the 24 identifiable geographic districts within the state. We characterized the habitat preferences of A. americanum using digitized coverages of environmental data, including geology, soil, landcover, elevation, and climate variables, and field data integrated into a geographic information system. We performed regression analyses to determine which environmental variables explain variability between positive and negative sites and in tick abundance. Using a GIS, we overlaid the environmental coverages determined to be significant by regression onto a grid of the state to develop a risk map indicating current areas of high tick presence and predicting areas of high tick probability. The coupling of statistics and mapping in this manner allows for a quantitative visualization of potential human disease risk. Analysis indicates that elevation, landcover and soil type all contribute to tick presence/absence.

Learning Objectives: At the conclusion of the session, the participants will be able to

• identify how a GIS can facilitate epidemiologic investigations of zoonoses and vector-borne diseases
• describe the relationship between environmental elements, vector prevalence and infection rate, and potential human disease risk

Keywords: Epidemiology, Geographic Information Systems

Presenting author's disclosure statement:
I do not have any significant financial interest/arrangement or affiliation with any organization/institution whose products or services are being discussed in this session.

Recorded presentation