Theses and Dissertations from UMD
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Item Effects of the 2014-2016 Ebola Epidemic on Infectious Disease Prevention in Guinea(2021) Callaway, Julia; Dyer, Typhanye V; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)From 2014-2016, Ebola ravaged the three West African countries of Guinea, Sierra Leone, and Liberia. There were more than 28,000 cases and 11,000 deaths, with more than 10,600 additional deaths due to other medical conditions. We aimed to examine how utilization of infectious disease prevention services changed in Guinea over the course of the Ebola epidemic, using Andersen’s model of healthcare utilization as a theoretical framework. The specific aims of this study were: 1) to examine differences in measles vaccination rates among children ages 12-35 months before and after the Ebola epidemic by wealth quintile; 2) to estimate mosquito net possession at two time points post-epidemic compared to pre-epidemic among households with at least one child under five, nationally and regionally; and 3) to quantify how much of the association between exposure to the Ebola epidemic and HIV testing prevalence can be explained by changes in urban/rural residence rates among adults in Guinea. The studies use data from the 2012 and 2018 Guinea DHS, and the 2016 MICS. Studies 1 and 2 use quasi-Poisson regression models to estimate prevalence ratios, and study 3 uses log-binomial regression models in a mediation analysis. In study 1 (n = 2,573 children ages 12-35 months), the poorest children were 54% (95% CI = 58%-67%) as likely to be vaccinated for measles in 2018 compared to 2012, and the wealthiest children were 78% (95% CI = 69%-90%) as likely. In study 2 (n = 14,756 households with at least one child under five), mosquito net possession in 2016 was 72% (95% CI = 56%-90%) higher and in 2018 was 12% (95% CI = 8%-15%) higher than in 2012. In study 3 (n = 27,809 adults), of the 4.59% (95% CI = 4%-6%) increase in the log-likelihood of ever having been tested for HIV due to being in the 2018 cohort, an estimated 0.269% of the effect (95% CI = 0.04%-1%) could be attributed to differences in urban/rural residence. Understanding these changes gives a more complete picture of the effects of epidemics on infectious disease prevention and can help public health officials plan for future epidemics.Item Interdisciplinary Geospatial Assessment of Malaria Exposure in Ann Township, Myanmar(2020) Hall, Amanda Hoffman; Loboda, Tatiana V; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Despite considerable progress toward malaria elimination in Myanmar, challenges remain owing to the persistence of complex focal transmission reservoirs. Nearly all remaining infections are clinically silent, rendering them invisible to routine monitoring. Moreover, limited knowledge of population distributions and human activity on the landscape in remote regions of Myanmar hinders the development of targeted malaria elimination approaches, as advocated by the World Health Organization (WHO). This is especially true for Ann Township, a remote region of Myanmar with a high malaria burden, where a comprehensive understanding of local exposure, which includes the characterization of environmental settings and land use activities, is crucial to developing successful malaria elimination strategies. In this dissertation, I present an interdisciplinary approach that combines satellite earth observations with two separate on-the-ground surveys to assess human exposure to malaria at multiple scales. First, I mapped rural settlements using a fusion of Landsat imagery and multi-temporal auxiliary data sensitive to human activity patterns with a classification accuracy of 93.1%. A satellite data-based map of land cover and land use was then used to assess landscape-scale malaria exposure as a function of environmental settings for a subset of ten villages where a malaria prevalence survey was carried out. While multiple significant associations were discovered, the relationship found between malaria exposure and satellite-measured village forest cover was the most significant. Finally, a separate detailed survey that explored a variety of land use activities, including their frequency and duration along with testing for clinical or subclinical malaria, was used to identify and quantify factors promoting an individual’s likelihood of malaria infection regardless of the environmental settings. This analysis established strong associations between malaria and individual land use activities that bring respondents into direct contact with forested areas. These results highlight that the current Myanmar malaria elimination strategies, which focus on prevention from within the home (i.e., bednets and indoor spraying), are no longer sufficient to remove remaining malaria reservoirs in the country. A paradigm shift in malaria elimination strategies towards targeted interventions that can disrupt malaria transmission in the settings where the exposure occurs are critical to achieving country-wide malaria elimination.Item Fitness of the transgenic malaria-refractory mosquito Anopheles gambiae(2004-11-11) Ladner, Deborah Tillman; Hawthorne, David J; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The African mosquito Anopheles gambiae is the insect vector responsible for half of worldwide malaria infections. One option for reducing malaria is genetic manipulation of the vector. By creating transgenic mosquitoes incapable of spreading the malaria pathogen, the human-mosquito-human cycle of infection may be interrupted. In order for the engineered Plasmodium-refractory mosquitoes to be effective they need to be able to thrive in nature and to compete successfully with nontransformed conspecifics. Two lines of transgenic An. gambiae were used in this study to evaluate the fitness consequences of transgenesis in this insect. Life table characteristics of two transformed An. gambiae lines were compared to a control line to determine if fitness costs were present. Specific traits measures between transgenic and control mosquitoes were not significantly different, and the transgenic lines had no evidence of position effects.