Mechanisms Linking Host Biodiversity to Lyme Disease Risk: An Experimental ApproachEPA Grant Number: R833776
Title: Mechanisms Linking Host Biodiversity to Lyme Disease Risk: An Experimental Approach
Investigators: Ostfeld, Richard S. , Brunner, Jesse , Canham, Charles D. , Keesing, Felicia , Killilea, Mary
Institution: Cary Institute of Ecosystem Studies
EPA Project Officer: Pongsiri, Montira J.
Project Period: January 1, 2008 through December 31, 2010
Project Amount: $750,000
RFA: An Interdisciplinary Approach To Examining The Links Between Social Stressors, Biodiversity And Human Health (2007) RFA Text | Recipients Lists
Research Category: Biodiversity , Ecological Indicators/Assessment/Restoration
Vector-borne zoonoses pose threats to human health throughout the world. Both anticipation of disease outbreaks and intervention that is effective in reducing risk are crucial for protecting public health. Such anticipation and intervention require a robust understanding of ecological conditions responsible for variation in disease threats. The proposed study will examine the broad context of interactions between ecological systems and human health to better understand the complex life cycle of Lyme disease, the most frequently reported vector-borne disease in the United States. Research is needed that focuses on the interactions among ticks, bacterial pathogens, the community of vertebrate hosts, and the landscapes in which vectors, pathogens, hosts, and humans interact to affect exposure to Lyme disease (LD). Risk of exposure to LD in the northeastern USA is a function of the abundance and Borrelia burgdorferi-infection prevalence of nymphal Ixodes scapularis ticks. The objective is to understand the mechanism(s) by which host diversity and community composition, as affected by anthropogenic changes to the landscape and other social stressors, drive human risk of infection with zoonotic pathogens, using LD as a model system.
We conceive of this effort broadly as providing the foundation for Integrated Pest Management (IPM), applied to ecological communities within which disease vectors are embedded. This research is composed of intensive, well-replicated, experimental field manipulation of the vertebrate communities that supply blood meals and B. burgdorferi infections to the tick vectors, to explore the causes of variation in entomological LD risk. Both diversity and community composition of hosts will be manipulated by removing and translocating two competent reservoirs for B. burgdorferi: white-footed mice (Peromyscus leucopus), eastern chipmunks (Tamias striatus), and one incompetent reservoir: gray squirrels (Sciurus carolinensis) in forest fragments. Abundances of other hosts will be monitored. New statistical approaches will be used to evaluate the relative importance of the causes of variation in both tick abundances and infection prevalence. Evidence will be evaluated for three specific mechanism by which high host diversity might reduce disease risk: (1) reducing encounter rates between ticks and P. leucopus; (2) regulating abundance of P. leucopus; and (3) regulating abundance of I. scapularis. The studies will be conducted in Dutchess County, New York, which has among the highest numbers of cases and incidence rates of LD in the United States.
We expect that communities in which abundances of non-mouse hosts are increased will be characterized by: (1) lower average larval burdens on mice; (2) lower densities and survival rates of mice; (3) lower total larval populations that feed on mice; (4) lower survival of larvae to the nymphal stage; (5) lower nymphal densities; and (6) lower infection prevalences of nymphs with B. burgdorferi. This research, combined with related efforts to understand the anthropogenic causes of change in host diversity and community composition, will provide the basis for a workshop that will foster interdisciplinary interactions among ecologists, epidemiologists, geographers, urban/suburban planners, and members of local, county, and state government (e.g. planning boards, zoning boards). The expected result of this workshop is a tentative set of guidelines to reduce LD risk. By better understanding disease dynamics, we may be able to develop new, non-chemical, environmentally based strategies to ameliorate disease transmission, while at the same time relying less on the use of pesticides. These new strategies can be part of an IPM approach to manage pest-borne diseases.