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The Chinese Liver Fluke Clonorchis Sinensis: an Environmental Investigation Into A

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The Chinese Liver Fluke Clonorchis Sinensis: an Environmental Investigation Into A The Chinese liver fluke Clonorchis sinensis: an environmental investigation into a foodborne parasite THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Gary Lee Klase Graduate Program in Public Health The Ohio State University 2013 Master's Examination Committee: Dr. Jiyoung Lee, Advisor Dr. Song Liang Dr. J. Mac Crawford Copyright by Gary Lee Klase 2013 Abstract The Chinese liver fluke Clonorchis sinensis is a foodborne parasitic trematode transmitted through the consumption of raw or undercooked fish, and is responsible for a substantial burden of morbidity and mortality in China and other Asian countries. The present study includes two investigations into environmental factors related to clonorchiasis transmission in China. In the first study, a field investigation was carried out in Guangdong province, China to investigate the relationship between water quality factors and the abundance and infection status of the snail intermediate of C. sinensis in rural Chinese fishponds. No host snails were found during the study. From the microbial source tracking analysis it was found that a large proportion of the water samples from fishponds showed evidence of human fecal contamination (84%), pig fecal contamination (40%), and antibiotic resistant bacteria (80%), raising concerns about potential public health risks related to these fishponds. In the second study, the results of a clonorchiasis prevalence study conducted by the Jiangmen City Center for Disease Control in Guangdong province were combined with satellite imagery and geographic information systems (GIS) techniques to investigate the relationship between the proportion of water in the nearby landscape and the risk of clonorchiasis infection. It was found that proximity to water in the landscape, as measured by the proportion of water in a 4 km radius around each village, was a strong risk factor for human infection of liver flukes. Using logistic regression, it was found that doubling the proportion of water around a ii village was associated with an odds ratio of 4.6 of increasing the liver fluke infection (p < 0.001). iii Dedication This thesis is dedicated to the ideals of wise use and ecological engineering: Abundance through harmony iv Acknowledgments Many people were instrumental in supporting the work of this thesis. I would like to thank Dr. Song Liang for initiating and supporting my research in China, and Dr. Nancai Zheng and Bonian Liang at the Jiangmen City CDC for their substantial support of this research. I would like to thank Dr. Jiyoung Lee and her lab members, Seungjun Lee, Feng Zhang, and Dr. Kuo Tseng, for their support in the laboratory. I would like to thank Dr. John Mac Crawford for the much-needed reminders that nothing is ever perfect, and as such, I should not worry so much when things aren’t perfect. I would like to thank the Department of Chemistry and Biochemistry at Ohio State for entrusting me with the education of 150 students in the laboratory over the course of two years, which has been one of the most rewarding aspects of my academic career. And most of all, I would like to thank my family. I have achieved what I have achieved because of their support. v Vita 1999................................................................Hoover High School, North Canton, Ohio 2007................................................................B.A. English, Otterbein College 2009................................................................A.S. Environment and Natural Resources, The Ohio State University 2011................................................................B.S. Environmental Science, The Ohio State University 2012 to present ..............................................Graduate Teaching Associate, Department of Chemistry, The Ohio State University Fields of Study Major Field: Public Health vi Table of Contents Abstract ............................................................................................................................... ii Dedication .......................................................................................................................... iv Acknowledgments............................................................................................................... v Vita ..................................................................................................................................... vi Table of Contents .............................................................................................................. vii List of Tables ..................................................................................................................... xi List of Figures ................................................................................................................... xii Chapter 1: Introduction ....................................................................................................... 1 1.1 Clonorchis sinensis ................................................................................................... 2 1.2 Epidemiology and global burden .............................................................................. 3 1.3 Ecology...................................................................................................................... 5 1.4 Control Strategies ...................................................................................................... 7 1.4.1 Treating human and reservoir hosts .................................................................... 7 1.4.2 Health education ................................................................................................. 8 1.4.3 Snail control ........................................................................................................ 9 vii 1.4.4 Treating feces ................................................................................................... 10 1.4.5 Hazard Analysis and Critical Control Points .................................................... 11 1.4.6 Control Summary ............................................................................................. 12 1.5 Ecological approach to parasite control .................................................................. 14 Chapter 2: Environmental investigation of water quality and health risks in an endemic region of Clonorchis sinensis in Guandgong province, China ......................................... 17 2.1 Introduction ............................................................................................................. 17 2.2 Methods ................................................................................................................... 19 2.2.1 Study sites ......................................................................................................... 19 2.2.2 Snail sampling .................................................................................................. 21 2.2.3 Water sampling ................................................................................................. 22 2.2.4 Physiochemical water quality parameters ........................................................ 22 2.2.5 Fecal indicators ................................................................................................. 22 2.2.6 Water filtration ................................................................................................. 23 2.2.7 DNA extraction................................................................................................. 24 2.2.8 Microbial source tracking and antibiotic resistance ......................................... 25 2.2.9 Quantitative polymerase chain reaction (qPCR) .............................................. 25 2.2.10 Chlorophyll-a measurement ........................................................................... 26 2.2.11 Nutrient measurement ..................................................................................... 26 viii 2.2.12 Statistical analysis........................................................................................... 27 2.3 Results ..................................................................................................................... 28 2.3.1 Snail sampling .................................................................................................. 28 2.3.2 Physiochemical parameters .............................................................................. 28 2.3.3 Fecal indicators ................................................................................................. 30 2.3.4 Microbial source tracking (human, pig), and antibiotic resistance ................... 32 2.3.5 Eutrophic status ................................................................................................ 34 2.3.6 Statistical analyses ............................................................................................ 34 2.4 Discussion ............................................................................................................... 37 2.4.1 Fecal contamination .......................................................................................... 37 2.4.2 Microbial source tracking and antibiotic resistance ......................................... 38 2.4.3 Eutrophic status ................................................................................................ 39 2.4.4 Physiochemical parameters .............................................................................
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