Table 1 Summary of the key points regarding water, sanitation and hygiene for schistosomiasis control, and suggested directions for future research

Water

• Water from safe supplies is usually schistosome-free, and hence it may play an important role in reducing exposure

• Do communities provided with safe water supplies experience slower reinfection (lower intensities of infection at set points in time following preventive chemotherapy)?

• People’s motivations for water contact are highly context-dependent, and water supplies that do not account for local attitudes and practices cannot be expected to consistently reduce water contact

• How do different types of water supply infrastructure (e.g. household and community supplies, with and without sinks and showers) affect the amount of exposure to cercaria-infested water in different groups of people (preschool-aged children, school-aged children, adults, males, females and people in communities of different religions and engaged in different forms of water contact)?

• Where possible, water supplies should incorporate additional infrastructure such as sinks and showers, to prevent as much water contact as possible

• How do reductions in water contact affect the intensity of schistosome infection in different groups of people (preschool-aged children, school-aged children, adults, males, females, those from or not from endemic communities)?

• The relationships between people’s access to safe water supplies and their degree of water contact, and between their degree of water contact and their intensity of infection, are not well understood

Sanitation

• Eggs in latrine pits cannot sustain schistosome transmission, but eggs may still enter the water despite the use of adequate sanitation

• Do communities provided with adequate sanitation experience slower reinfection (lower intensities of infection at set points in time following preventive chemotherapy)?

• High levels of organic pollution, and infection with schistosome sporocysts, are detrimental to intermediate host snails, and therefore the impact on cercaria populations, of a reduction in miracidial contamination, is very difficult to predict

• Is sanitation in fields and near transmission sites effective at reducing the number of miracidia at those transmission sites?

• By contaminating freshwater bodies with schistosome eggs in their faeces and urine, reservoir hosts play an important role in S. japonicum transmission, and may also play a role in S. mansoni and S. haematobium transmission

• How does the number of snails affect the relationship between the numbers of miracidia and cercariae at transmission sites?

• What role do reservoir hosts play in the transmission of S. mansoni and S. haematobium?

Hygiene

• Soap and endod are toxic to miracidia, cercariae and intermediate host snails – they may therefore reduce risk of infection in the short term, by killing and reducing the infectivity of cercariae, and in the long term, by killing snails and miracidia, and thus reducing cercaria populations

• Does sustained soap use during water contact slow reinfection (lower intensities of infection at set points in time following preventive chemotherapy)?

• Very few studies have compared human use of soap or endod during water contact, with subsequent schistosome infections

• What impact does sustained soap use have on snail, miracidium and cercaria populations?

• Does protection from infection arising from soap use extend to people not using the soap, by virtue of the impacts on snail populations and miracidial infections?

• How might soap use during human water contact be best promoted?