Primary prevention
Prevention focuses on integrated interruption of transmission (i.e., mass drug administration, modification of human behaviour, improved sanitation, and use of chemicals or habitat modification to remove snails) in endemic communities.[30] People should be advised to avoid all non-chlorinated freshwater exposure, whether flowing (rivers and streams) or static (ponds and ditches), in countries endemic for schistosomiasis.[28] Health-education programmes have been successfully implemented in some endemic areas.[31]
Water, sanitation, and hygiene (WASH) interventions, environmental interventions (e.g., water engineering, focal snail control with molluscicides), and behavioural change interventions are essential to help reduce transmission of Schistosoma spp. in endemic areas.[6]
A Cochrane review found that WASH interventions may slightly protect against soil-transmitted helminth infections, as well as serve as a broad preventive measure for many other diseases that have a faecal-oral route of transmission.[32] [
]
[Evidence B]
Preventative chemotherapy
Large-scale, targeted, regular treatment with praziquantel in at-risk populations in endemic areas is one of the main strategies for disease control. Repeated mass treatment substantially reduces the prevalence and morbidity of schistosomiasis.[2][33]
The World Health Organization recommends the following in endemic communities:[6]
Prevalence of Schistosoma spp. infection ≥10%: annual preventive chemotherapy with a single dose of praziquantel at ≥75% treatment coverage in all age groups from 2 years old, including adults, pregnant women after the first trimester, and lactating women. In communities that demonstrate a lack of response to annual preventive chemotherapy despite adequate treatment coverage, biannual (twice yearly) preventive chemotherapy should be considered.
Prevalence of Schistosoma spp. infection <10%: (a) where there has been a programme of regular preventive chemotherapy, to continue the intervention at the same or reduced frequency towards interruption of transmission; or (b) where there has not been a programme of regular preventive chemotherapy, to use a clinical approach of test-and-treat.
There is data to suggest that two important at-risk patient groups, preschool-aged children and pregnant women, are being neglected in mass drug administration programmes. There is sufficient evidence to suggest praziquantel is safe in these two groups, and that it should be considered in these patients to promote healthy birth, growth, and development.[34]
In some instances, long-term travellers who have spent extended time with high-risk water exposure in schistosomiasis-endemic countries should take a presumptive course of praziquantel on return. The benefits of such treatment probably outweigh the minimal risk of adverse effects from a single course of therapy.
Vaccines
No vaccines are currently available for Schistosoma infection; however, vaccine candidates are being evaluated in clinical trials.[35]
Secondary prevention
People residing in or travelling to areas where schistosomiasis is transmitted should avoid any contact with freshwater or nearby damp or marshy areas harbouring the intermediate-host snails (Biomphalaria, Bulinus, or Onchomelania species).[3] Personal protection includes boots and gloves to prevent skin contact with infested water or vegetation. This is not always possible, and for those with significant risk of re-exposure to infection an annual or once-every-2-years treatment with praziquantel may be appropriate to attempt to remove or suppress a potential schistosomiasis infection, despite conflicting evidence on the efficacy of such techniques.[101]
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