We have been studying the ecology, epidemiology and prevention of tick-borne diseases, particularly the spirochete (bacterium) that causes Lyme disease (LD). LD currently is the most commonly reported vector-borne infection in California, the United States, and in other temperate regions of the Northern Hemisphere. The broad objectives of this research are intended to clarify the transmission cycles of the LD spirochete and other emerging bacterial disease agents; to determine what behavioral and environmental factors place people at elevated risk for acquiring the LDS and other tick-borne infections; and to evaluate control methodologies for reducing such risk.
Several ongoing projects are aimed at expanding our knowledge of the relationship of LD spirochetes to their tick vectors and vertebrate hosts. Spirochetes detected in or isolated from ticks and wildlife are being characterized antigenically and genetically, and the infectivity of selected isolates for vertebrates and ticks evaluated. The ability of human and nonhuman-biting ticks to acquire, maintain and transmit LD spirochetes, and the role of lizards, birds and mammals in perpetuating them have been and still are being assessed both experimentally and in the field. Intrinsic and extrinsic factors that contribute to the vector efficiency of different ticks and to the reservoir competence of mammals also are being studied.
Another current focus is to elucidate biotic and abiotic factors that elevate the risk of human exposure to vector ticks in endemic areas of California, particularly in dense woodlands and mixed hardwood forests. These studies are being conducted in both wildland and recreational areas, and in peri-domestic settings in both rural and semi-rural communities endemic for LD. It is anticipated that these investigations will clarify various ecologic and epidemiologic factors that place humans at heightened risk of exposure to spirochetes at different spatial scales, and facilitate the development of predictive models to assess LD risk at both the community and county levels by means of remote sensing and ground-truthing ecologic studies.
The ultimate goal of this research is to use the basic knowledge gleaned from the foregoing projects to develop and implement strategies for reducing human exposure to tick-borne disease agents. To this end, several personal-protective measures and host-targeted methods for disseminating environmentally safe pesticides to rodent reservoir hosts of the LD spirochete already have been assessed. One method, the delivery of an oil-based formulation of permethrin to wood rats, has shown considerable promise for reducing populations of both vector ticks and fleas.
In the News
A new UC Berkeley-led study has found that birds are more important than previously recognized as hosts for Lyme disease-causing bacteria in California.
The Western fence lizard’s reputation for helping to reduce the threat of Lyme disease is in jeopardy. A new study led by UC Berkeley researchers found that areas where the lizard had been removed saw a subsequent drop in the population of the ticks that transmit Lyme disease. The decline in tick numbers seems to suggest a decreased risk of human exposure to Lyme disease when the lizard is gone.