Date Thesis Awarded

12-2021

Access Type

Honors Thesis -- Access Restricted On-Campus Only

Degree Name

Bachelors of Science (BS)

Department

Biology

Advisor

Matthias Leu

Committee Members

Orissa Moulton

Ronald Smith

Abstract

As a result of anthropogenic change, humans are at increased risk of zoonotic disease exposure. Perhaps one of the most recognizable of these infections is Lyme disease, whose bacterial causative agent (Borrelia burgdorferi) is transmitted by Ixodes scapularis, the blacklegged tick. To understand the risk of encountering tick disease vectors and tick-borne disease, we should attempt to tease out what variables drive changes in tick populations over time and across space. The phenology of the black-legged tick suggests that landscape variables, which affect host movement, and weather variables, which affect tick physiology and survival, could be important factors in governing its population dynamics. As such, we developed an occupancy model incorporating these two broad variable classes to understand potential explanations for variation in tick populations in eastern Virginia. Using a year-stratified (“stacked”) model, we found that nymph occupancy was best explained by the average diameter of oaks at a plot, but adult occupancy was best explained by average humidity of the summer two years prior to sampling. Likewise, the detection process for nymphs was most strongly associated with Julian date, whereas maximum temperature for the sampling day performed best for adults. This suggests that both landscape and weather are key drivers for tick habitat suitability, but not necessarily for both life stages. Although further work can be done untangle these ecological relationships, our model provides key insights into this complex study system and challenges previous paradigms of thinking about tick populations and tick-borne disease.

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