WISER-Water Infrastructure for Schistosomiasis-Endemic Regions

Schistosomiasis, also known as bilharzia or 'snail fever', is a parasitic disease carried by fresh water snails that are infected by one of five varieties of the pararasite Schistosoma. Schistosomiasis is transmitted by human contact with contaminated fresh water that are inhabited by snails carrying the parasite. Larvae, known as cercariae, emerge from the infected snails and swim in the water until they come into contact with an individual and penetrate the skin. The transmission to humans can occur through a range of normal water contact activities such as collection of drinking water, bathing, washing clothes, swimming or fishing. Once inside the body the larvae develop into worms which live in the blood vessels for years. Female worms shed eggs which end up in urine and faeces; if infected individuals urinate or defecate into freshwater bodies, the eggs migrate to snails where they hatch and begin the cycle again. The symptoms of schistosomiasis can include frequent painful and bloody urine, abdominal pain and bloody diarrhoea, inflammation and scarring of the bladder, enlargement of the liver or spleen, and where infection persists, bladder cancer may develop. In children it leads to anemia, malnutrition and learning difficulties, thus dramatically impairing their future quality of life and productivity. It is estimated that 258 million people are infected in 78 countries worldwide, though 90% of the infections occur in Africa. Schistosomiasis kills an estimated 280,000 people annually and ranks second only to malaria as the most common parasitic disease. Praziquantel is the primary form of treatment, with a single dose of the drug having been shown to reduce the burden of infection and severity of symptoms. However, re-infection will quickly occur when people are re-exposed to contaminated water. Education campaigns about the risks of exposure to contaminated water and improved water supply and sanitation should in theory break the life cycle of the disease. Universal sanitation coverage should prevent the passage of urine and faeces into contaminated water bodies, however there is always a danger of transmission by infected people visiting from elsewhere and urinating or defecating into the water body, or occasional lapses in the usage of sanitation facilities. Mollusciciding has also been suggested as a solution, however there are concerns regarding potential unintended consequences of dosing molluscicides into water bodies and the long-term effectiveness and sustainability of this strategy is questionable, since the snails could return at some point in the future. In some cases there may be alternative water sources (e.g. boreholes) which can be accessed, however often there are no alternative safe water sources available to meet the full water needs of communities in endemic regions. In such cases, therefore, the immediate focus for cutting schistosomiasis transmission must be treating the contaminated freshwater body to provide a safe alternative supply. Unfortunately however, there is very limited and incomplete information available regarding the effectiveness of water treatment processes at removing or inactivating cercariae of different Schistosoma. Also, there are no rapid means for detecting cercariae in water samples and determining their viability, which makes assessing the risk and degree of contamination of a water body and testing the effectiveness of water treatment processes as barriers against cercariae very difficult. This three-year research programme aims to address these gaps in critical knowledge through a collaboration between water engineers, synthetic biologists, parasitologists, and social scientists in the UK, Ethiopia and Tanzania, in the hope of developing invaluable new knowledge to guide the design of sustainable water infrastructure for schistosomiasis-endemic regions.