Landscape Epidemiology and Integrated Mgmt of Tick-Borne DiseasesEPA Grant Number: R834897
Title: Landscape Epidemiology and Integrated Mgmt of Tick-Borne Diseases
Investigators: Ostfeld, Richard S.
Institution: Cary Institute of Ecosystem Studies
EPA Project Officer: Hahn, Intaek
Project Period: February 24, 2011 through February 23, 2013
Project Amount: $299,998
RFA: Pesticide Registration Improvement Renewal Act (PRIA 2) Partnership Grants (2010) RFA Text | Recipients Lists
Research Category: Biodiversity
Lyme disease (LD) is a tick-borne bacterial zoonosis that is embedded within both natural and built components of landscapes throughout the northeastern and midwestern United States. The causative agent, Borrelia hurgdorferi, is maintained largely in populations of small mammals, most prominently the white-footed mouse (Peromyscus leucopus). Larval blacklegged ticks (Ixodes scapularis) are extreme host generalists and will feed from virtually all terrestrial mammals and birds available. The infected nymphs that arise from those larval blood meals are responsible for almost all human cases of LD. Two other tick-borne diseases are emerging rapidly in the eastern and midwestern United States: human granulocytic anaplasmosis (1-IGA) and human babesiosis (HU), caused respectively by a bacterium (Anaplasmaphagocytophilum) and a protozoan (Babesia microti).
Current research by our group demonstrates that not only do different vertebrates vary in their probability of infecting ticks with zoonotic pathogens (reservoir competence), they also differ dramatically in their ability to support feeding and overwinter survival by blacklegged ticks. Empirically-based models suggest that both the abundance and pathogen infection prevalence of nymphal blacklegged ticks are influenced strongly by the species composition (diversity and specific identities) of the host community. In species-poor vertebrate communities, white-footed mice predominate, and larval ticks frequently encounter mice, resulting in high survival to the nymph stage and high infection prevalence. In more diverse vertebrate communities, larval ticks more frequently encounter non-mouse hosts, on which their survival and infection probabilities are lower.
The most potent cause of reduced vertebrate biodiversity in areas where Lyme disease occurs is fragmentation of forest habitats. As forests become fragmented some species become rare or absent whereas others increase in abundance. Species that tend to amplify ticks or tick-borne pathogens tend to increase with fragmentation, whereas those that dilute ticks or their pathogens decline. However, although several studies suggest that fragmentation increases ecological risk of tick-borne disease, the landscape features that most strongly affect risk are not well understood, In addition, the degree to which ecological risk (density and infection prevalence of ticks) predicts human incidence rates of tick-borne disease is largely unknown, Human incidence could be decoupled from risk if people tend to use portions of the landscape with low intrinsic risk. Our three objectives are to: (1): Develop predictive models of landscape-level variation in ecological risk of human exposure to Lyme disease, human anaplasmosis, and human babesiosis. (2): Test how strongly ecological metrics of disease risk correlate with actual human incidence of tick-borne diseases. (3): Use the landscape variables identified in Objectives (I) and (2) to assess the likely impacts of specific development scenarios on tick-borne disease risk and incidence. We will estimate densities and infection rates of ticks at 210 sites in a representative area, Dutchess County, NY and use inverse modeling to explore how local and landscape variables influence spatial variation in the key ecological risk factors for each tick-borne disease. If spatial patterns of human incidence are strongly correlated with those of ecological risk, then management of landscapes to reduce risk will be prescribed. If human incidence and risk are decoupled, then educational efforts to reduce risky behaviors, as well as localized interventions, will be more effective. Our statistical models of landscape effects will produce a GIS product designed to ask how future changes in landscape composition and configuration will affect risk and incidence of tick-borne diseases. Development plans that are projected to increase risk or incidence can be altered or replaced-based on quantitative assessments-using guidelines designed to protect health.
By determining how changes in land use affect disease transmission, this effort would provide the foundation for integrated management of ecological communities within which disease vectors (pests) are embedded. The data-based models can lead to the design of environmentally sound (non-chemical) strategies to reduce infectious-disease incidence. For example, sound land-use practices (e.g. specific landscape configurations of remnant forests) can be part of an 1PM strategy to minimize the use of pesticides as a control method of tick-borne disease, resulting in less pollution to land, air and water. Furthermore, project results are expected to assist in the development of methods of forest ecosystem valuation and to facilitate federal, state, and local management of forested landscapes to provide clear societal benefits.