Dissertation/Thesis Abstract

Black-Legged Tick Distributions, Small Mammal Abundances, Mast Production, and Vegetative Influences on Lyme Disease Apparent Prevalence on Fort Drum Military Installation, New York
by Fino, Samantha R., M.S., West Virginia University, 2017, 246; 10637853
Abstract (Summary)

Lyme disease is the most common infectious disease spread by black-legged ticks in the Northern Hemisphere. Lyme disease is a vector-borne zoonotic disease typically caused by bacterial spirochetes of the species Borrelia burgdorferi. The primary vector of Lyme disease in the Midwestern and eastern United States is Ixodes scapularis, the deer or black-legged tick. Although there are several preventative measures against ticks that carry Lyme disease, such as public education regarding personal protection (e.g., wearing light colored clothing, tucking pants into socks, wearing repellent, promptly inspecting oneself to remove ticks, getting pets vaccinated) and recommended control measures, it is important to understand how the disease is transmitted and which factors increase the potential risk of contracting the disease. Even with these preventative measures, which are not necessarily available worldwide, tick-borne diseases are increasing both in numbers and impact to the overall human population, and there are still several knowledge gaps and conflicting findings that need to be elucidated. For these reasons, there exists a need for further research on Lyme disease ecology to identify steps necessary to decrease disease prevalence and reduce human exposure. I conducted a field study on the Cantonment Area of Fort Drum Military Installation, New York, which is representative of a suburban community with multiple cover types. From May 2015–November 2016 I surveyed the Cantonment Area to evaluate the basic distributions of Ixodes scapularis and small mammal host species, their relationships with vegetative characteristics, and associated Lyme disease apparent prevalence. This will allow resource managers to assess and communicate the likelihood of encountering a Lyme-positive tick and to take necessary actions to minimize that risk. Specifically, our objective was to assess the apparent prevalence of Lyme disease based on the distributions and indice of abundance of the vector and host populations on Fort Drum.

I used tick drags to evaluate black-legged tick temporal and spatial distributions in six different cover types discriminated by developmental stage. Total index of tick abundance was related to (1) temperature, (2) humidity, (3) coarse woody debris, (4) leaf litter depth, (5) tree species richness (6) average tree dbh, and (7) patch size. Adult index of abundance was greatest in the spring and fall, while nymph index of abundance was greatest in early summer and larval index of abundance was greatest at the end of summer. Tick and Lyme-positive tick indices of abundance were greatest in the coniferous and mixed cover type and lowest in the shrub and deciduous cover type. Overall Lyme disease apparent prevalence on the Cantonment Area of Fort Drum was 35% (434/1246). These results provide objective criteria for understanding a baseline of tick distributions on a temporal and spatial scale, and assist in developing management recommendations to decrease Lyme disease apparent prevalence on the landscape.

I used Sherman and Tomahawk traps to capture individuals from the overall small mammal host community during June–August. The small mammal community was composed mostly of Peromyscus sp. (n = 79; 38%), chipmunk (n = 59; 28%), red squirrel (n = 33; 16%), gray squirrel (n = 18; 9%). Trapping success, as well as Simpson’s and Shannon’s indices of diversity were greatest in the developed and coniferous forest cover types. Indices of abundance of small mammals were greatest in the developed cover type, followed by coniferous forest. We modeled the relation between estimated index of abundance of ticks with the estimated index of abundance of all small mammal host species, as well as the relationship between estimated index of abundance of Lyme-positive ticks and small mammal host Simpson’s and Shannon’s indices of diversity. Although Peromyscus sp. had a greater number of individuals with tick burdens, there was significantly greater estimated index of abundance of Lyme-positive tick burdens on chipmunks. Furthermore, a significantly greater proportion of sampled chipmunks (58%) had Lyme-positive ear punches.

My results suggest that habitat management in the coniferous and mixed forest that target vector and host habitat is necessary in order to decrease Lyme disease prevalence and reduce risk of human exposure. Recommendations such as removal of the leaf/pine litter and coarse woody debris, which provide stable microhabitat for ticks and small mammals alike, a selective cut of large conifer trees, allowing sunlight and wind penetration that encourages tick desiccation, and creating and mowing grassland barrier habitat between human developed areas and forested areas are possible solutions for decreasing Lyme disease prevalence and human risk of exposure on the landscape. Public education seminars regarding black-legged tick spatial and temporal distributions, as well as explaining recommended control measures for personal property should also be developed in order to communicate Lyme disease risk to residents on Fort Drum Military Installation.

Indexing (document details)
Advisor: Edwards, John W.
Commitee: Owen, Sheldon F., Rainbolt, Raymond E., Wimsatt, Jeffrey
School: West Virginia University
Department: Argriculture, Natural Resources, & Design
School Location: United States -- West Virginia
Source: MAI 57/01M(E), Masters Abstracts International
Source Type: DISSERTATION
Subjects: Wildlife Management, Entomology, Parasitology, Epidemiology
Keywords: Black-legged tick, Borrelia burgdorferi, Cover type, Ixodes scapularis, Lyme disease, New York, Small mammals
Publication Number: 10637853
ISBN: 9780355516746
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