Risk-based tools to prevent excreta-bornedisease transmission in semi-arid ruralcommunities

According to the United Nations (2015), more than 40% of the world’s population already face water scarcity. Although past reports estimate that 91% of the global population have access to some form of improved drinking water source, this does not necessarily guarantee the consumption of ‘safe’ drinking water. Furthermore, huge disparities still exist in sanitation and water supply services between urban and rural areas, and rural populations demonstrate higher levels of human excreta-borne diseases. The research described in this thesis aimed to develop an evidence-based tiered approach to risk assessment that can be used to support the development of water safety plan to protect the health of rural communities in semi-arid regions. Information on current provision of sanitation and water supplies, as well as local perceptions with regard to drinking water supply issues and hygiene practice were recorded through the use of community surveys, sanitary inspections and field observations. Furthermore, a microbial monitoring programme was undertaken to measure levels of faecal contamination through the water supply chain. Finally, quantitative microbial risk assessment (QMRA) was developed and used to predict the risk of infection posed by locally relevant pathogens through the hand-to-mouth and drinking water routes, considering all alternative water sources identified and hypothetical interventions in water, sanitation and hygiene (WASH). Relatively high levels of E. coli and intestinal enterococci were observed in most water storage reservoirs (22 CFU/100 mL and 103 CFU/100 mL, respectively) and in-house storage containers (3 CFU/100 mL and 54 CFU/100 mL, respectively), which appears to be strongly related to a significant lack of awareness and knowledge regarding the relationship between domestic water-related activities and domestic and personal hygiene among local householders. Moreover, stakeholders involved in the water supply, as well as health adviser professionals working at the communities, demonstrated a limited understanding of water-related hygiene issues. The QMRA outcomes indicated that the rural communities in the ‘Sertao’ of Brazil are likely to be at a high risk of infection from waterborne pathogens, including Salmonella spp. (3.97 x 10-2 ), Giardia lamblia (6.24 x 10-2 ) and norovirus (one) via both the drinking water in relation to the maximum level of risk (10-4 ) suggested by the US-EPA guidelines. The hand-to-mouth route also resulted in high levels of risk for Salmonella spp. (1.12 x 10-2 ), Giardia lamblia (3.65 x 10-2 ) and norovirus (8.00 x 10-1 ). The tiered approach to risk assessment developed in this research helped to identify and elucidate microbial transmission pathways and supported the development of locally-appropriate safety plans to reduce the incidence of excreta-borne diseases. It was concluded that a significant reduction in the burden of human infectious diseases could be achieved through a combination of simple interventions (e.g., chlorination and filtration of water, training on water handling and storage and hand hygiene). Furthermore, domestic ‘WASH safety plans’ appear to offer greater potential than water safety plans as a way to minimise the transmission of infectious diseases within the household environment of these communities. Finally, practical recommendations to support the reduction of excreta-borne disease in the rural ‘Sertao’ of Brazil, such as raising awareness and understanding on potential crosscontamination routes within the domestic environment, are provided.