Grantee Research Project Results

The Effects of Forestry Practices on Human Risk of Tick-Borne Diseases in the Missouri Ozarks

EPA Grant Number: F6F21329
Title: The Effects of Forestry Practices on Human Risk of Tick-Borne Diseases in the Missouri Ozarks
Investigators: Allan, Brian F
Institution: Washington University
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2006 through September 1, 2008
Project Amount: $86,272
RFA: STAR Graduate Fellowships (2006) RFA Text |  Recipients Lists
Research Category: Fellowship - Ecology , Academic Fellowships , Human Health

Objective:

I am working in a large-scale forestry experiment called the Missouri Ozark Forest Ecosystem Project (MOFEP), the goal of which is to assess the impacts of different forestry practices on the wide diversity of organisms that inhabit the Ozark ecosystem. For my dissertation research I am investigating the impacts of these different forestry practices on human risk of exposure to tick-borne diseases.

The objective of my proposed research is to determine if different timber harvesting practices influence human risk of infection by tick-borne diseases through changes in the abundance of ticks and/or their hosts. Multiple species in the bacteria genus Ehrlichia occur in Missouri, and several of these cause disease in humans, their pets, and wildlife. One common species is Ehrlichia chaffeensis, which causes Human Monocytic Ehrlichiosis (HME), an emergent zoonotic disease in North America. This pathogen is primarily transmitted to ticks via blood meals taken from white-tailed deer, the preeminent tick-host in this region. Since deer are known to respond strongly to certain forestry practices, I expect to find changes in both the abundance of ticks and their infections rates with pathogens such as E. chaffeensis. The area of highest incidence of HME occurs in southeastern Missouri, making MOFEP an ideal location to study the ecology of this pathogenic organism.

Approach:

Tick abundance will be estimated using two survey techniques: drag-sampling and CO₂ baited traps. Drag-sampling involves dragging a 1m² cloth along the ground and removing ticks that become attached. CO₂-baited traps are small traps consisting of an igloo cooler affixed to a board – a block of dry ice is placed inside the cooler and as it evaporates, the released CO₂ attracts ticks which become attached to the double-sided tape placed over the trap. Deer abundance will be estimated by performing dung cluster surveys and through the use of camera traps. Abiotic variation among habitats will be measured using remote data loggers. Tick infection rates and host selection will be determined through a combination of PCR and reverse line blot hybridization analyses performed at Washington University.

Expected Results:

Two field seasons of research in the MOFEP experiment indicate that white-tailed deer increase in abundance under a forestry practice known as even-aged management, a form of logging that involves generating clear- and intermediate cuts. This appears to generate significantly higher abundances of Lone Star ticks, the primary vector of HME and several other emerging diseases, which may lead to higher human risk of exposure to one of these pathogens. I am currently testing ticks collected from this experiment for a variety of emerging pathogens. I expect to find higher prevalence of pathogens such as E. chaffeensis in ticks collected from forestry treatments that increase deer abundance.

Supplemental Keywords:

disease ecology, ticks, pathogens, forestry, landscape management,, Health, Scientific Discipline, ENVIRONMENTAL MANAGEMENT, Health Risk Assessment, Risk Assessments, Ecology and Ecosystems, Risk Assessment, tick borne disease, forestry, human exposure, biological pathways, pathogens, land use, human health risk, disease potential

Progress and Final Reports:

2007

Final