TANGLED IN TICKS: BREAKING DOWN THE COMPLEX WEB OF PARASITE, HOST, AND LANDSCAPE DYNAMICS

Abstract

Ticks and tick-borne diseases pose a significant public health concern in the United States, with common illnesses including Lyme disease, Anaplasmosis, Rocky Mountain Spotted Fever, Babesiosis, Tularemia, and Powassan virus. Lyme disease, caused by the bacterium Borrelia burgdorferi, remains the most reported in the U.S., with over 89,000 confirmed cases in 2023 and an estimated annual infection rate exceeding 470,000 people in 2022. As the geographic range of ticks expands and the risk of vector-borne diseases increases, it becomes increasingly important to understand the complex interactions among host species, tick abundance, and landscape features. This study aims to identify the key factors driving tick abundance and disease prevalence at the local level to improve management of high-risk areas in urban spaces. Over four years, we collected extensive data through small-mammal trapping, camera traps, and tick sampling across eight parks in Montgomery County, Maryland. In this dissertation, Chapter 1 explores the most effective modeling approaches for tick distribution and landscape patterns, finding that incorporating random continuous spatial fields can help identify tick microhabitats for more targeted management. Chapter 2 examines wildlife communities' occupancy in a heavily developed area of Montgomery County, Maryland. The overall wildlife community preferred areas with more core natural habitats, though some species thrived in regions with high human density and disturbance. Chapter 3 synthesizes these findings, analyzing correlations among landscape features, tick-borne disease incidence, and the occupancy and abundance of key host species. We found that modeling ticks using a continuous spatial field with true zeros provides a more realistic representation of fine-scale distributions, allowing for more accurate predictions of tick presence and potential disease risk, even within highly urbanized parks. Generalist wildlife species, such as red foxes and raccoons, readily use human-dominated areas, and connected or extensive green spaces support higher abundances of these hosts. This pattern may serve as an important driver of both host community structure and tick abundance. Additionally, our results indicate a relationship between overabundant host species, particularly white-tail deer, probability of tick presence and forest cover may increase disease risk at a specific site. This suggests that during peak nymphal season, unique ecological drivers may be influencing disease dynamics in Montgomery County, Maryland. Overall, landscape features and human activity are key determinants of high-risk areas, acting through their effects on host abundance and the availability of high-quality tick habitat.