Environmental transmission of cholera in Tanzania: Building resilience in rural communities

This interdisciplinary project uses different aspects of physical science to make significant advances in understanding and predicting environmental cholera transmission. The project outcomes will be used to improve prediction of location and exposure risk of populations to Vibrio cholerae, the bacterium that hosts cholera. The project builds on previous developments in the coupling of sediment movement and ambient light exposure via luminescence signals within mineral grains (McGuire and Rhodes 2015a, b; Gray et al., 2015), and is based within three core EPSRC themes: Physical Science, Healthcare Technologies, and Living with Environmental Change. This project will devise solutions to improve human health and understanding of water-borne disease transmission, and represents a contribution to the grand challenges of water security.
Despite significant scientific advances, cholera continues to destroy lives and livelihoods in the global south as we live through the seventh cholera pandemic (Mpazi & Mnyika, 2005), with global reports of ~2.9 million cases and ~95,000 deaths annually (WHO, 2018). In Africa alone, 40 million people live in cholera-prone areas (Anderson, 2020). Since 1974, Tanzania has remained one of the top cholera-reporting counties on the continent, with over 250,000 cases and 13,078 deaths, up to 2018 (Lessler et al. 2018). In Tanzania, cholera outbreaks occur against a backdrop of a health system suffering in the wake of volatile prices and debt-servicing policies imposed by the World Bank, the adverse effects of which are disproportionately felt by the rural poor. (Baker et al., 2013; Mamdani & Bangser, 2004). Furthermore, in times of COVID-19 health systems are overwhelmed and the country is under increasing financial burden (Saleh, 2020).
Recent climate modelling efforts suggest East Africa will experience shorter, more intense wet seasons, followed by severe drought, which is projected to cause a significant shift in the african cholera burden towards the east of the continent (Colwell, 1996; Traeup et al. 2011). Water scarcity forces people to use unsafe water sources, whereas flooding causes fecal contamination of drinking water (Moore et al. 2017). This highlights the need for accurate prediction of cholera outbreaks in rural areas, to enable the timely allocation of resources (Akanda et al. 2011; Azman et al. 2019; Emch et al. 2008), and maximise the value of investment that underpins the Tanzanian healthcare system.
Bacteria can attach to mineral surfaces as biofilms. Vibrio cholerae are able to develop protective mechanisms and enter a state of dormancy in conditions unfavourable for its survival and growth, and 2
can return to virulence when conditions improve (Lutz et al., 2013). Vibrio cholerae have been recorded in this non-virulent state in fluvial and lacustrine fine-grained sediment stores, where it persists until the onset of a disturbance event, such as heavy rainfall, and then causes an outbreak (Abia et al., 2017; Perkins et al., 2014). Thus, stores of Vibrio cholerae in fluvial and lacustrine sediment, which is muddy material within active river channels and lake systems, pose a major public health risk. Understanding where these stores are, and how sediment is transported during periods of high flow, holds great potential for predicting cholera outbreaks.
Novel application of luminescence techniques will be used to construct optimised approaches and equipment to monitor and measure hydrological processes within fluvial and lacustrine systems, and apply these to tackle the public health threat described above. Luminescence exploits the charge trapped within the crystal lattice of quartz and feldspar grains. Charge is built up when grains are buried and subject to natural ionising radiation, and reduces when grains are exposed to heat or light. This can be measured as a luminescence signal, stimulated by heating or exposing the grains to light