Assessing the contribution of water, sanitation, and hygiene to schistosome transmission in sub-Saharan Africa
Professor Deirdre Hollingsworth, Nuffield Department of Medicine
An estimated 250 million people worldwide have schistosomiasis, of which 80% are in sub-Saharan Africa. In 2019, schistosomiasis caused at least 1.64 million disability-adjusted life years lost. Blood flukes (parasitic worms) cause schistosomiasis. Transmission to humans is via contact with freshwater sources that are contaminated through open defecation/urination and that harbour competent intermediate snail hosts. Water, sanitation, and hygiene (WASH) interventions are promoted to reduce pathogen transmission.
Consistently identifying effective WASH interventions that reduce infection risks is challenging. One issue entails the heterogeneity in human activities that puts individuals at risk of infection. Exposure to parasites varies based on the water-related activity, time of day, duration in the water, location, and individual characteristics. Another issue is the lack of a systematic framework for identifying water-related exposures. There is a need to effectively combine diverse types of data to construct robust infection risk indicators that can be utilized across study settings and data collection methods. Even more challenging is distinguishing among activities related to exposure (water contact without open defecation/urination) versus activities specific to contamination.
Survey-based approaches or direct observations are common methods for recording schistosomiasis-related exposures. Yet, triangulation of these methods is rarely done and little is known about how best to construct exposure/contamination indices from these measurement tools.
RESEARCH EXPERIENCE, RESEARCH METHODS AND TRAINING
This project will use data from an ongoing study in rural villages in Uganda where Schistosoma mansoni is endemic. Ethical approvals have been obtained. It is expected that this data will be collected prior to the start of this DPhil project. This DPhil analysis will focus on a random sample of approximately 1600 households from 39 villages. To measure infection status/intensity, one child (aged 5+ years) and one adult (aged 18+ years) will be sampled from each study household (3120 individuals). Household surveys will be used to collect information on socioeconomic status, and water, sanitation, and hygiene access/behaviours.
To directly observe water contact patterns at the village level, an observational study will be conducted, whereby trained water site observers will record information on every person entering pre-identified lake sites (including the time of day, duration, and activity). Contact sites will be observed for 1-2 weeks.
- Establish a systematic framework for identifying exposures
- Construct and validate exposure and contamination indices
- Build transmission models to understand the association of WASH exposures with infection prevalence and intensity at the individual, household, and community levels
The student will gain skills in literature review, study design, primary data collection, transmission modelling, statistical programming, data cleaning, and research presentation. Training in schistosomiasis epidemiology and infection modelling will be provided.
FIELD WORK, SECONDMENTS, INDUSTRY PLACEMENTS AND TRAINING
The DPhil candidate will have the opportunity to contribute to the cohort through follow-up studies. This project requires approximately 1-2 months of fieldwork in rural Uganda over the course of the DPhil project. The study is in close collaboration with the Uganda Ministry of Health. Experienced field teams from Uganda will co-lead the primary data collection with the primary supervisor.
Candidates ideally will have postgraduate training in global health, epidemiology, or a related discipline as well as experience in statistical/quantitative analyses of health data.