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Browsing by Author "Bachand, Annette M., advisor"

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    Epidemiologic studies of hard tick-associated illness in the United States
    (Colorado State University. Libraries, 2009) Murphree, Rendi, author; Bachand, Annette M., advisor
    This dissertation describes three epidemiologic studies of hard tick-associated illness in the United States. The first is the prospective health assessment of Fort Campbell, Kentucky patrons bitten by ticks during 2004-2006. The study was designed to determine the frequency, clinical characteristics, and etiology of Amblyomma americanum-associated illness and to identify associated risk factors. Amblyomma americanum is an aggressive human biting tick associated with a Lyme disease-like illness of unknown etiology. Study findings suggested that a variety of symptoms were temporally associated with tick bite but data provided no clear evidence that symptoms were caused by an infectious process. Removing ticks by hand or being bitten on a limb may have been risk factors for illness. The second examines 248,074 cases of Lyme disease reported to the Centers for Disease Control during 1992-2006 using descriptive and inferential statistics. In the United States, Lyme disease is caused by Borrelia burgdorferi sensu stricto, a spirochete transmitted to humans by infected Ixodes scapularis and I. pacificus ticks. During the 15-year study period, the number of cases reported annually increased 101% and the majority of cases occurred in northeastern and north-central states. An increasing trend in the number of counties reporting at least one case annually was observed in Minnesota, Rhode Island, and Wisconsin. A disproportionate increasing trend in reported cases was observed in children and young males compared with other demographic groups. The third study is a pilot ecologic analysis of human social or economic factors affecting, or resulting from, Lyme disease emergence. The objectives were to identify space-time clusters of increased Lyme disease risk and determine if risk could be partially explained using existing data on environment, socioeconomics, and healthcare. As expected, Ixodes tick distribution was a significant predictor of counties with increased risk. Measures of socioeconomic status surfaced as predictors of ecologic risk, and it appeared that persons of high SES lived where ticks were reported in northeastern states and persons of low SES lived where ticks were reported in the north-central states.
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    Potential environmental factors associated with the newly emerging bat white-nose syndrome in the northeastern United States: an exlporatory modeling approach and case-control study
    (Colorado State University. Libraries, 2010) Flory, Abigail R., author; Bachand, Annette M., advisor; Duncan, Colleen G., committee member; Reif, John S., committee member; Stohlgren, Thomas J., committee member
    The emergence of mortality-causing bat White-Nose Syndrome (WNS) in the Northeastern United States during 2006 prompted an immediate need for research surrounding possible causation factors influencing its spread. Due to the mysterious nature of fungal pathogens, it has been very difficult to determine how the WNS-related Geomyces destructans fungus is causing bat mortality. Several different hypotheses have been formulated by bat and ecological experts in the field, but major influencing factors remain undetermined. To initiate WNS environmental research, this study utilizes a new machine-learning modeling technique, Maxent modeling, along with a case-control study to assess the hypothesis that certain environmental variables may be associated with the occurrence and distribution of bat WNS. Maxent data uses presence-only data and bases its algorithms on the principal of maximum entropy. Maxent results using 58 environmental predictor variables revealed Slope, Growing-Degree Days, Annual Temperature Range, and Land-Cover as the top four predicting variables for WNS infected bat hibernacula locations. Similarly, the case-control study showed that two of these top four predictor variables (Growing-Degree Days and Annual Temperature Range) were statistically significantly associated with a hibernacula's WNS infection status. Cases had a slightly higher mean Average Temperature Range than controls (Cases=38.0, Controls=36.0) and lower mean Growing-Degree Days than controls (Cases=3419.1, Controls=3838.1). Both of these variables, along with their correlated terms, are largely temperature-dependent, suggesting a need for further research on the role of temperature in predicting the occurrence and distribution of Geomyces destructans. As a starting point for future research, this study has identified the most likely environmental variables related to the potential devastating ecological consequences of WNS-related bat mortality.