2026 Theses Doctoral

Ticks in the city: Socio-ecological dynamics of tick-borne disease across an urbanization gradient

Lilly, Marie V.

Tick-borne hazards in urban landscapes are increasing, yet critical gaps remain in understanding human tick-borne disease risk across urbanization gradients. With the loss of natural habitat globally, urban greening is underway. Urban greenspaces can provide critical habitat for wildlife as well as space for human recreation, with varying consequences for tick-borne disease emergence. In the United States, the Northeast is both highly urban and a hotspot for blacklegged ticks (Ixodes scapularis) and tick-borne disease emergence.

Using the New York City metropolitan area as a study system, this dissertation integrates landscape ecology, tick-host-pathogen relationships, and social science to evaluate how socio-ecological dynamics influence tick-borne hazards and disease risk across an urbanization gradient. To establish a landscape scale study design, (chapter 1) we developed a paired urban tick and wildlife surveillance system across an urbanization gradient from New York City through Long Island, NY in which we deployed wildlife camera traps and standardized tick collections.

Using these data collection methods, we evaluated landscape-host-tick interactions (chapter 2) by using circuit theory methods to model the impact of functional connectivity on white-tailed deer occupancy, blacklegged tick abundance, and pathogen infected ticks across an urbanization gradient. We found that functional connectivity significantly predicted deer occupancy with cascading effects on abundance of blacklegged nymphal ticks and Borrelia burgdorferi infection. We novelly identified a threshold of functional connectivity in urban areas necessary for deer occupancy, tick populations, and tick infection with B. burgdorferi, to emerge in urban environments.

To evaluate landscape-pathogen-host relationships (chapter 3), we surveyed host-seeking nymphal blacklegged ticks and live-trapped small mammals and meso-mammals at a subset of greenspaces with varying levels of surrounding functional connectivity. This work innovatively identified pathways by which functional connectivity interacts with host community composition to impact tick-borne hazards in urban landscapes.

Lastly, to understand how humans interface with ticks and wildlife and identify drivers of tick-borne disease risk (chapter 4), we conducted a survey of greenspace users across the urbanization gradient. We found that perceptions of cultural ecosystem services and human-wildlife coexistence in urban greenspaces are separate from perceptions of tick-borne hazards, but are dependent on the same ecological properties that increase tick-borne hazards. Collectively, these findings highlight the importance of examining multi-scale landscape drivers of host, tick, and pathogen interactions while integrating socio-ecological approaches to minimize tick-borne disease risk in urban areas.