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WHO guideline on control and elimination of human schistosomiasis
On 15 February 2022, WHO organized an virtual conference to officially issue Guidelines guideline on control and elimination of human schistosomiasis. This is the first WHO guidance on the evaluation of interruption of schistosomiasis transmission. This guideline provides evidence-based recommendations to support countries in morbidity control and elimination of the disease as a public health problem, and to move towards interruption of transmission. Human schistosomiasis is a chronic parasitic disease caused by infection with blood flukes (trematode worms) of the genus Schistosoma. The disease is a public health problem in tropical and subtropical regions of Africa, Asia, the Caribbean and South America. Approximately 779 million people are at risk of acquiring the infection (1). Some 236.6 million people required preventive chemotherapy in 2019 (2). Schistosomiasis is a neglected tropical disease (NTD), a diverse group of diseases and conditions that affect predominantly low-income populations worldwide.
In response to resolutions adopted by the World Health Assembly and in line with the Organization's 13th General Programme of Work 2019-2023, WHO supports Member States to expand access to prevention, diagnosis, treatment and care interventions for NTDs as a contribution towards the achievement of universal health coverage by 2030.
In 2020, WHO published a new road map to guide action against NTDs during the decade 2021-2030. The road map targets the elimination of schistosomiasis as a public health problem by 2030 and the interruption of schistosome transmission in humans in selected countries by 2030. Attainment of these targets will contribute to progress towards Sustainable Development Goal 3: "ensure healthy lives and promote well-being for all at all ages". The WHO strategy to control and eliminate human schistosomiasis includes preventive chemotherapy of at-risk groups, access to improved drinking-water, and improved sanitation, hygiene education, environmental management and snail control.
This WHO guideline1 was developed in accordance with the WHO handbook for guideline development (2014). A guideline steering group was established to formulate the key questions to be addressed in the guideline using the population, intervention, comparator and outcome (PICO) format and to prioritize outcomes. The PICO questions were reviewed by a guideline development group (GDG) and then used to systematically retrieve, appraise and synthesize the evidence, formulate the recommendations, and plan for dissemination and implementation of the guideline. All policy recommendations were formulated through consensus based on the judgements of the GDG, informed by the evidence and by the expertise and experience of its members; on the one occasion when consensus was not reached, members adopted a voting process. The external review group commented on the final draft of the guideline but could not alter the recommendations made by the GDG. Table. Status of mass drug administration in countries and territories endemic for schistosomiasis in 2020 MDA not started | MDA started but not at scale or irregular | MDA expanded to all endemic IU | Evaluation needed to verify interruption of transmission | Mapping needed to determine the current situation | Equatorial Guinea South Africa | Botswana Brazil Central African Republic Chad Congo Gabon Guinea-Bissau Namibia Nigeria Sao Tome and Principe Somalia South Sudan Venezuela (Bolivarian Republic of) Zambia | Benin Burkina Faso Burundi Cambodia Cameroon Côte d'Ivoire Democratic Republic of the Congo Eritrea Eswatini Ethiopia Egypt Gambia Ghana Guinea Indonesia Kenya Liberia Lao People's Democratic Republic Madagascar Malawi Mali Mauritania Mozambique Niger Philippines Rwanda Senegal Sierra Leone Sudan Togo United Republic of Tanzania Uganda Yemen Zimbabwe. | Antigua and Barbuda Dominican Republic China Guadeloupe Iraq Islamic Republic of Iran Japan Jordan Mauritius Martinique Montserrat Morocco Oman Puerto Rico Saudi Arabia Syrian Arab Republic Saint Lucia Suriname Tunisia. | Algeria Djibouti India Lebanon Libya Malaysia Myanmar Thailand Turkey. | 2 | 15 | 34 | 19 | 9 | 51 countries requiring preventive chemotherapy | | |
IU: implementation unit; MDA: mass drug administration.
Goal and objectives of the guideline The goal of this guideline is to provide evidence-based recommendations to countries in their efforts to accomplish schistosomiasis morbidity control and elimination as a public health problem, and to move towards interruption of transmission. The recommendations contained herein will help countries to implement national schistosomiasis control and elimination programmes and support efforts to verify the interruption of transmission. The specific objectives are to provide guidance on: § prevalence thresholds, target age groups and frequency of preventive chemotherapy for schistosomiasis; § establishment of water, sanitation and hygiene (WASH) and snail control activities to support control and elimination of schistosomiasis; § use of diagnostic tests in humans in low transmission areas and for moving to, and evaluating the interruption of transmission of schistosomiasis; § tools for the assessment of Schistosoma spp. infection in snail hosts; and § diagnostic tests for the assessment of schistosomiasis infection in animal reservoirs of infection The current guideline updates and supersedes previous schistosomiasis-related recommendations contained in the following WHO publications: § Schistosomiasis: progress report 2001-2011 and strategic plan 2012-2020. Geneva: World Health Organization; 2013 § Preventive chemotherapy in human helminthiasis: coordinated use of anthelminthic drugs in control interventions: a manual for health professionals and programme managers. Geneva: World Health Organization; 2006 § Prevention and control of schistosomiasis and soil-transmitted helminthiasis: report of a WHO Expert Committee. Geneva: World Health Organization; 2002 (WHO Technical Report Series, No. 912) § The control of schistosomiasis: second report of the WHO expert committee. Geneva: World Health Organization, 1993 (WHO Technical Report Series, No. 830) § Elimination of schistosomiasis from low-transmission areas: report of a WHO informal consultation, Brazil. Geneva: World Health Organization; 2008 § Helminth control in school-age children: a guide for managers of control programmes, second edition. Geneva: World Health Organization; 2011 Rationale for developing the guideline This guideline is warranted for the following reasons. 1. Previous implementation guidelines for schistosomiasis were based mainly on expert opinion. 2. There was no previously published guidance on the evaluation of the interruption of schistosomiasis transmission. 3. Resolution WHA65.21 on elimination of schistosomiasis, adopted by the Sixty-fifth World Health Assembly in 2012, called on WHO to prepare guidance for Member States in order to determine when to embark on elimination programmes where appropriate and to provide tools to document progress. 4. Schistosomiasis remains a significant public health problem in many countries. Preventive chemotherapy has been demonstrated to deliver benefits to affected communities but is still not readily accessible by all. By providing a revised guideline, the intention is to empower and support health ministries and local communities to extend the use of preventive chemotherapy in order to support wider target populations in their efforts to control and eliminate this disease. 5. From a patient and a public health perspective, there is no acceptable level of schistosomiasis morbidity. The approaches recommended in this revised guideline are designed to eliminate morbidity from schistosomiasis, but this will require sustained effort. 6. Recent impact assessment surveys (3-8) have shown that the prevalence of schistosomiasis infection determined using parasitological techniques has dropped to low levels in some countries. New guidance is therefore required for countries that need to move from morbidity control towards elimination as a public health problem (9-13). 7. Sensitive diagnostic tools have been developed for use in humans, animals and snail intermediate hosts (14-18). Guidance is needed for their use, in particular the thresholds for their utilization in low transmission areas. Target audience The key audiences for this guideline are policy-makers, national NTD control programmes and national NTD task forces in health ministries, regional programme review groups and implementation partners. This guideline is intended as a reference document for all stakeholders, including WHO, pharmaceutical manufacturers of preventive chemotherapy medicines, donor organizations, nongovernmental organizations and academic institutions. The following groups will be empowered and impacted by the guideline: § residents of communities in which schistosomiasis is endemic; § visitors and tourists to schistosomiasis-endemic areas; § distributors of medicines during preventive chemotherapy; xv § district or other administrative level focal points for preventive chemotherapy in the health ministry; § national NTD programme managers and NTD coordinators in endemic countries; § national pharmacovigilance agencies in endemic countries; § national medicine regulatory authorities; § ministries of education and the environment; § manufacturers of preventive chemotherapy medicines; and § donor organizations that support schistosomiasis control and elimination programmes. Limitations This guideline is based on the best evidence available to the GDG in 2021. For many questions that the guideline set out to answer, the evidence base was limited. Evidence is in any event subject to change. The guideline will therefore be updated accordingly as new evidence emerges. Summary of recommendations Recommendation 1 In endemic communities with prevalence of Schistosoma spp. infection >=10%, WHO recommends 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, to control schistosomiasis morbidity and advance towards eliminating the disease as a public health problem. Strong recommendation Certainty of evidence: moderate Recommendation 2 In endemic communities with prevalence of Schistosoma spp. infection <10%, WHO suggests one of two approaches based on programmatic objectives and resources: (i) 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 (ii) where there has not been a programme of regular preventive chemotherapy, to use a clinical approach of testand-treat, instead of preventive chemotherapy targeting a population. Conditional recommendation Certainty of evidence: very low Recommendation 3 In endemic communities with prevalence of Schistosoma spp. infection >=10% that demonstrate lack of an appropriate response to annual preventive chemotherapy, despite adequate treatment coverage (>=75%), WHO suggests consideration of biannual (twice yearly) instead of annual preventive chemotherapy. Conditional recommendation Certainty of evidence: very low Recommendation 4 WHO recommends that health facilities provide access to treatment with praziquantel to control morbidity due to schistosomiasis in all infected individuals regardless of age, including infected pregnant excluding the first trimester, lactating women and pre-SAC aged <2 years. The decision to administer treatment in children under 2 years of age should be based on testing and clinical judgement. Strong recommendation Certainty of evidence: moderate Recommendation 5 WHO recommends WASH interventions, environmental interventions (water engineering and focal snail control with molluscicides) and behavioural change interventions as essential measures to help reduce transmission of Schistosoma spp. in endemic areas. Strong recommendation Certainty of evidence: low Recommendation 6 In communities approaching the interruption of transmission (defined as having no autochthonous human cases reported for 5 consecutive years), WHO suggests a verification framework that consists of: 1. Testing for Schistosoma infection in humans with a diagnostic that has high sensitivity and specificity. This may require the use of a two-step diagnostic process starting with a high sensitivity test confirmed with a second, high specificity test. 2. Testing for Schistosoma infection in snails with a diagnostic that has high sensitivity and specificity. This may require the use of a two-step diagnostic process starting with a high sensitivity test confirmed with a second, high specificity test. 3. Testing for Schistosoma infection in non-human mammalian hosts, as applicable, with a diagnostic that has high sensitivity and specificity. This may require the use of a two-step diagnostic process starting with a high sensitivity test confirmed with a second, high specificity test. Conditional recommendation Certainty of evidence: low
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