The roles of water, sanitation and hygiene in reducing schistosomiasis: a review

Abstract

Schistosomiasis is a disease caused by infection with blood flukes of the genus Schistosoma. Transmission of, and exposure to, the parasite result from faecal or urinary contamination of freshwater containing intermediate host snails, and dermal contact with the same water. The World Health Assembly resolution 65.21 from May 2012 urges member states to eliminate schistosomiasis through preventive chemotherapy (i.e. periodic large-scale administration of the antischistosomal drug praziquantel to school-aged children and other high-risk groups), provision of water, sanitation and hygiene (WASH) and snail control. However, control measures focus almost exclusively on preventive chemotherapy, while only few studies made an attempt to determine the impact of upgraded access to safe water, adequate sanitation and good hygiene on schistosome transmission. We recently completed a systematic review and meta-analysis pertaining to WASH and schistosomiasis and found that people with safe water and adequate sanitation have significantly lower odds of a Schistosoma infection. Importantly though, the transmission of schistosomiasis is deeply entrenched in social-ecological systems, and hence is governed by setting-specific cultural and environmental factors that determine human behaviour and snail populations. Here, we provide a comprehensive review of the literature, which explores the transmission routes of schistosomes, particularly focussing on how these might be disrupted with WASH-related technologies and human behaviour. Additionally, future research directions in this area are highlighted.

Knowledge, Attitudes, and Practices Related to Schistosomiasis Among Children in Northern Senegal

“…19,28 Wearing shoes was associated with less schistosomiasis in this study. Alemu et al reported similar results.…”

Low Prevalence of Intestinal Schistosomiasis Among Fisherfolk Living Along the River Nile in North-Western Uganda: A Biosocial Investigation

“…Are there behavioural or environmental reasons that can help explain the low prevalence of infection? While access to safe water and sanitation reduces the probability of schistosomiasis infection (Grimes et al, 2014), associations between water, sanitation and hygiene on transmission are complex and depend on many contextual factors (Grimes et al, 2015). Even with improved access to safe water sources, preventing water contact completely is highly unlikely.…”

“…Therefore, at times, during women's contact with the river water, soap is used. This may have significance for the control of schistosomiasis as soap use during water contact is thought to provide some protection due to its toxic effect on the S. mansoni cercariae (reviewed in Grimes et al, 2015). It is thus possible that through this mechanism, risk of schistosomiasis is reduced, despite people's ongoing contact with the river water.…”

“…There are undoubtedly limitations with relying on the distribution of free drugs for sustained schistosomiasis control. It is acknowledged that a combination of strategies is needed beyond mass drug administration, particularly in areas of low transmission (Rollinson et al, 2013;Grimes et al, 2015). In this regard, previous programmes have taken an integrated approach, most notably the Blue Nile Health Project in Sudan (for schistosomiasis and malaria) and a World Bank Loan Project in China (for S. japonicum).…”

“…They then release microscopic cercariae into the water which enter the human body through the skin when a person comes in contact with infested water (see Gryseels et al, 2006). Transmission is, therefore, influenced by broader social determinants beyond the biological life cycle, and disease patterns show microgeographical variations, with interactions between biological, social, behavioural and environmental factors determining vulnerability to schistosomiasis (Grimes et al, 2015).…”