Date of Award

January 2013

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Maria Diuk-Wasser

Abstract

Peridomestic exposure to infected Ixodes scapularis nymphs is considered the dominant means of infection with tick-borne pathogens in the eastern United States. Previous studies of risk of developing tick-borne infection established a positive association between the density of infected nymphs and Lyme disease cases at the population level. Studies examining the effectiveness of personal protective behaviors have not included measures of tick exposure. This study simultaneously assesses the effect of tick exposure and human behavior in Lyme disease infection risk using a longitudinal serosurvey study on Block Island, RI. Tick exposure risk at all Island properties was estimated by identifying remotely-sensed landscape proxies that most strongly correlated with tick density at the individual property level. Landscape metrics associated with lawn and shrub edge, patch density, percent land, class area, and the number of patches were found to be most associated with positive serology. Human behavior related risk factors included the average number of hours spent daily outside in tick habitat, and owning a cat that spends time both indoors and outdoors. Age at the time of test was also found to increase risk. Wearing protective clothing during outdoor exposure was protective. A multivariate model including peridomestic shrub patch density (decreased risk), wearing protective clothing (decreased risk), and owning a cat (increased risk) was determined to be the best model based on the lowest Akaike Information Criterion. Our findings emphasize that both environmental risk and human behavior contribute significantly to risk of tick-borne infection. They highlight the importance of accounting for environmental exposure to accurately ascertain the effectiveness of personal protective behaviors. A better understanding of the relative roles of environmental and behavioral risk factors in driving infection with tick-borne pathogens should guide future intervention studies to reduce the risk of these infections.

Comments

This is an Open Access Thesis.

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