Understanding sources and determinants of fecal contamination of water, hands, food, and household floors in low-income countries
- Diarrheal disease is one of the leading causes of death in children under 5 years, causing approximately 0.8 million annual deaths globally. Almost 50% of these deaths come from Africa and 30% from Southeast Asia, where diarrheal diseases account for 11% of all child-deaths. Diarrheal pathogens are transmitted primarily through a fecal-oral route, with illness being predominately caused by ingestion of the pathogens from water, food, or hands, which have been contaminated by inadequate sanitation and hygiene. Additionally, contaminated surfaces can serve as a reservoir for fecal pathogens within the household. Fecal pathogens can come from both human and non-human, animal sources. In order to develop effective strategies to protect human health, understanding the levels of contamination on different surfaces or media in household environments is important. Furthermore, it is important to understand how the different vehicles of transmission (i.e., water, hands, food, floors) become contaminated; that is, identifying the sources of the fecal contamination and the behaviors and practices associated with contamination. In Tanzania, a structured observation study was conducted coupled with intensive sampling to measure levels of fecal contamination in drinking water to determine mechanisms for post-supply contamination of drinking water. The storage container and extraction methods were found to introduce fecal indicator bacteria in the stored water. Also, stored water quality and female caregiver hand contamination data from 1200 households in Tanzania was collected. Three different data-driven statistical methods, ordinary least squares regression, logistic regression, and classification tree, were used to explain variation of levels of contamination in stored water and female caregiver hands. Our study results highlight the complexity of predicting stored water quality and hand contamination. Despite using three different analytical techniques for modeling stored water quality and hand contamination, contamination was incorrectly predicted for a large fraction of samples. In rural Kenya and rural and urban Bangladesh, a validation of molecular microbial source tracking assays was conducted to determine if these techniques could be used on environmental samples to identify the human and animal sources of contamination. The human-specific assays performed well in the rural sites but the assays were not sensitive or specific in Dhaka, Bangladesh. The ruminant assay, BacR, performed well across all study sites, exhibiting high sensitivity and specificity. The Avian GFD assay was sensitive and specific in the rural sites, but was not specific in Dhaka, Bangladesh. Evidence of ruminant fecal contamination was found on household floors and child hand rinse samples in Dhaka, Bangladesh. Therefore, even in dense urban slums, the transmission pathway of ruminant feces should be considered in order to reduce contamination in household environments. Researchers should consider that non-host specific fecal indicator bacteria detected in environmental samples in these settings could be of animal origin. Finally, levels of fecal contamination on produce from neighborhood distribution markets and wholesale markets in Dhaka, Bangladesh were assessed. Fecal contamination, as measured by E. coli and enterococci, was found on carrots, eggplants, lal shak leaves, and tomatoes. Items from the neighborhood markets had higher levels of general fecal indicators than items from wholesale markets. The results of the study suggest that market-level mechanisms, such a vendor handling practices, could be influencing produce contamination. Evidence of fecal contamination from ruminants was also found on produce items, both from the wholesale and neighborhood distribution markets. Therefore, not only the pathway of human fecal contamination, but also that of animals, should be considered when developing interventions to reduce contamination on produce. This dissertation assesses the levels of fecal contamination in stored drinking water and on female caregiver hands in Tanzania, and of household floors, child hands, and vegetable produce in Bangladesh. The use of different models to explain variation of fecal contamination in water and on hands was explored. In addition, the dissertation evaluates the use of molecular techniques to identify the fecal source of contamination found in environmental samples in Kenya and Bangladesh. Data-driven understanding of the environmental conditions that are associated with fecal contamination will help inform studies to develop interventions and policies to protect human health. This dissertation work provides insight to the sources and correlates of fecal contamination of stored drinking water, female caregiver and child hands, household floors, and vegetable produce in low income countries. It also critically assesses methods for measuring and explaining fecal contamination in these setting.
|Type of resource
|electronic; electronic resource; remote
|1 online resource.
|Harris, Angela R
|Stanford University, Department of Civil and Environmental Engineering.
|Davis, J. A. (Jennifer Ann)
|Mitch, William A
|Davis, J. A. (Jennifer Ann)
|Mitch, William A
|Statement of responsibility
|Angela R. Harris.
|Submitted to the Department of Civil and Environmental Engineering.
|Thesis (Ph.D.)--Stanford University, 2015.
- © 2015 by Angela Rose Harris
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
Also listed in
Loading usage metrics...