DETERMINANTS OF MALARIA IN THE CHITTAGONG HILL DISTRICTS OF BANGLADESH
Shannon, Kerry Lee
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Objective: This dissertation focuses on understanding the epidemiology of malaria in the Chittagong Hill Districts of Bangladesh, with particular focus on the genetic, seasonal, geographic, demographic and behavioral factors that influence symptomatic and asymptomatic malaria. Methods: The data for this analysis comes from a longitudinal cohort study of approximately 24,000 people that began in October 2009 in an area of Bandarban District of Bangladesh covering an area of 179 km2. A series of detailed surveys were conducted encompassing symptomatic, uncomplicated or asymptomatic malaria; demographics of the population; knowledge and practices related to malaria, hemoglobin E, geographic locations and environmental factors. Results: This dissertation demonstrates a number of risk factors for malaria. Homozygous, but not heterozygous, Hemoglobin E was shown to be associated with an increase in mild clinical malaria infection. A detailed exploration of the epidemiology of sub-clinical P. falciparum infections demonstrated that they occur year-round, and account for the overwhelming majority of infections at any given time. An adjusted prevalence of sub-clinical infection based on active case finding and diagnosis by RDT and or microscopy was found to be 1.0% in the overall population and 3.2% in pregnant woman. The adjusted incidence was 32.9 (19.7-54.9) per 1,000 person-years. When examining incidence during pregnancy we found 19.4 (4.9-76.6) and 19.5 (8.8-43.11) per 1,000 person-years incidence among 15- to 39-year-old pregnant and recently pregnant women respectively compared to zero cases among non-pregnant 15- to 39-year-old women. Risk factors for asymptomatic malaria include pregnant women, males, jhum cultivators, those living closer to forests and at higher elevations, and marginally among 5- to 14-year-olds and day laborers. When comparing sub-clinical and symptomatic clinical P. falciparum infections we found that hotspots overlapped, but there were substantial differences. Conclusions: This study demonstrates a number of risk factors for both clinical and sub-clinical P. falciparum infections and describes when and where these infections are most likely to occur. This information can help to inform prevention and control programs, and to focus resources in areas and populations that are of high risk.