Guidelines for implementation of control and elimination of schistosomiasis and verification of interruption of transmission

Background and context

Schistosomiasis is an acute and chronic parasitic disease caused by blood flukes (trematode worms) of the genus Schistosoma. Transmission occurs when people suffering from schistosomiasis contaminate freshwater sources with their excreta (faeces and/or urine) containing parasite eggs, which hatch in water. People become infected when larval forms of the parasite – released after multiplication by freshwater snails – penetrate the skin during contact with infested water. In the human body, the larvae develop into adult schistosomes. Adult worms live in the blood vessels where the females release eggs after coupled. Some of the eggs are passed out of the body in the faeces or urine to continue the parasite’s lifecycle. Others become trapped in body tissues, causing immune reactions and progressive damage to organs.

Schistosomiasis transmission has been reported from 78 countries. However, preventive chemotherapy for control of morbidity due to schistosomiasis, where people and communities are targeted for large-scale treatment, is only required in 52 endemic countries with moderate-to-high transmission.

The WHO-recommended strategy to control schistosomiasis involves large-scale treatment of affected populations through periodic treatment with praziquantel. Implementation is supported by WHO technical guidelines and tools and in collaboration with partners, research institutions, the private sector, nongovernmental organizations, international development agencies and other United Nations organizations.

Praziquantel is the recommended treatment against all forms of schistosomiasis. It is effective, safe, and low-cost. Even though re-infection may occur after treatment, the risk of developing severe disease is diminished and even reversed when treatment is initiated and repeated in childhood.

In 2001, the 54th World Health Assembly resolved to introduce measures to reduce mortality and morbidity and improve the health and development of affected communities as well as promote primary health care services, complemented by the simultaneous implementation of plans for basic sanitation and adequate safe water supplies.

In 2012, the World Health Assembly adopted resolution WHA65.21 on the elimination of schistosomiasis, calling on all countries endemic for schistosomiasis to analyse and develop applicable plans with progressive targets, to intensify control interventions towards elimination, to ensure the provision of essential medicines and WHO to elaborate a procedure to evaluate the interruption of transmission of schistosomiasis.

Due to expansion of control interventions, almost 90 million individuals were treated in 2016, including 70.9 million children and 18.3 million adults. This represents a global coverage target of 54% in school-aged children (and an impressive 57% coverage in the African Region¹). The global target set in WHO’s Roadmap on NTDs is to reach at least 75% of all school-children in endemic areas by 2020.

Schistosomiasis control has been successfully implemented over the past 40 years in several countries, including Brazil, Cambodia, China, Egypt, Mauritius, Morocco, Islamic Republic of Iran, Oman, Jordan and Saudi Arabia. In Burkina Faso, Ghana, Niger, Rwanda, Sierra Leone, the United Republic of Tanzania, and Yemen, it has been possible to scale-up schistosomiasis treatment to the national level and have an impact on the disease in a few years. An assessment of the status of transmission is being made in several countries.

As a consequence, WHO is holding a Schistosomiasis Guideline Development Group meeting to steer work towards the drafting of a schistosomiasis implementation guideline and the methods to be used to verify its interruption of transmission in countries that claim to have successfully stopped transmission.

^{1 The highest burden of schistosomiasis is found in the WHO African Region, where almost 9 out of 10 people requiring treatment for the disease live. Of the 41 countries where treatment is needed, 30 reported data to WHO in 2016; 12 countries achieved 75% treatment coverage.}

General scope and objectives

Currently, there is no guidance available to evaluate the interruption of schistosomiasis transmission. The existing implementation guidelines are based mainly on expert opinion and need to be revised according to the available scientific evidence.

The goal of this GDG meeting will be to provide evidence-based recommendations to countries in their efforts to control morbidity from schistosomiasis and eventually interrupt transmission. They will help countries to implement national schistosomiasis control programmes and to verify whether transmission of the disease has been interrupted in the country.

In keeping with the requirements of the WHO Guidelines Review Committee and the WHO Compliance, Risk Management and Ethics Office, WHO is proceeding with the online publication for two weeks of the names and biosketches of the proposed GDG members.

The listed experts have also submitted a Declaration of Interest form stating any conflict of interests. WHO has applied its internal processes to ensure the absence of any conflicts of interest (academic, financial, or other) that could undermine the credibility of the guideline.

As a measure of added transparency, WHO invites the public to review the list of experts and stakeholders and provide feedback on any member deemed to have any conflict of interest with respect to the terms of reference for this group.

Comments and feedbacks should be cordial and constructive, and sent to schistosomiasis@who.int

No anonymous letters will be considered.

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Guideline Development Groups provide technical and/or normative advice and recommendations to WHO. Participation in a Guideline Development Group convened by WHO does not necessarily mean that the views expressed by the expert concerned are shared by WHO and/or represent the decisions or stated policy of WHO.

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