Graduate Thesis Or Dissertation
 

The Identification of Common Environmental and Demographic Associations for Tick-Borne Disease Risk and Surveillance Efforts in the United States

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  • Ixodes scapularis (e.g. blacklegged tick) is a hard-bodied tick considered endemic to certain regions within the United States. This species is considered a primary vector of Lyme disease (Borrelia burgdorferi), anaplasmosis (Anaplasma phagocytophilum) and babesiosis (Babesia microti). Each of these tick-borne diseases represent a growing health concern within the nation due to a combination of alternative transmission routes, case underreporting, and the emergence of the vector in new locations. As with other organisms, Ixodes scapularis is inexorably influenced by its surrounding environment. As such it is no surprise that prior work has focused on how certain factors, albeit from the physical environment or local demographics, may impact the risk from both the vector and its associated diseases. While providing valuable insight, these findings have limited generalizability due to a combination of differences between study locations and a topical focus on single diseases. Therefore, in order to expand upon this work, the goal of this research was to evaluate the impact of both environmental and socio-demographic predictors on the reported incidence and surveillance efforts of three separate tick-borne diseases to determine probable common associations. First with the aid of the NIH translational research framework, the initial study sought to organize the existing literature on babesiosis prevention in order to identify areas of strength and consensus, as well as gaps for future research to address. The results of this review indicated that nearly half of the 152 publications (47.3%) were found to contribute to the descriptive epidemiology or identification of potential intervention points of disease prevention. Among the identified gaps, a disparity surrounding the characterization of potential intervention points and candidate interventions to all recognized vectors and species of the disease was noted in the literature, which supports a need for future work in this field. The second study evaluated the association between select environmental and demographic factors and the annual reported incidence of Lyme disease, babesiosis, and anaplasmosis in eleven states to determine probable common associations. For the common predictors, nonmetropolitan counties and median income were found to report the largest positive associations for aggregate disease models while median income reported the largest positive association for each native disease model. The majority of covariates within the aggregate (86%) and native (53%-90%) models were found to share a common significant association with the reported incidence of each disease. These results suggest that common environmental and demographic associations may exist across the reported incidence of three tick borne diseases from multiple states. In addition, the modeling of covariates on different spatial scales allow for a better understanding of which native or seasonal component may ultimately influence the association between a given aggregate predictor and the reported incidence of each disease. Finally, the last study evaluated the association between select environmental and demographic factors and the total submission rate of Ixodes scapularis samples tested for Borrelia burgdorferi, Anaplasma phagocytophilum, and Babesia microti from Massachusetts to determine the probable common associations between each model. Some of the major associations of tick submission rates included percent grassland cover and the estimated population 65 and over, which reported the largest positive and inverse association in each model respectively. Overall the majority of covariates in each proposed (77%-100%) and complete (86%-93%) model reported a consistent significant association with tick submission rates. The findings from this study suggest that common environmental and demographic factors may exist in regard to the tick submission rates of different pathogen tests submitted by individuals. Identifying and understanding common associations between such models is essential because it may serve as a basis for understanding how to increase participation in citizen-driven passive surveillance efforts. These results provide evidence that common environmental and demographic factors are associated with both the reported incidence and passive surveillance efforts of related tick-borne diseases. Future studies should continue to evaluate potential relationships within the local environment to gain a better understanding of associations that may influence the risk and surveillance efforts of different tick-borne diseases. With such knowledge, interventions could be developed to address multiple tick-borne diseases providing an opportunity to combat a growing public health concern. Overall, these results will provide a foundation to help guide future research and prevention efforts to reduce the burden of Lyme disease, anaplasmosis, and babesiosis.  
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  • Intellectual Property (patent, etc.)
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  • 2020-06-14 to 2021-07-14

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