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
Implementation considerations
Prevalence of infection is defined as the percentage of individuals of all ages in a population targeted for treatment who are infected with any species of
Schistosoma. The strategy of
preventive chemotherapy does not differ by
Schistosoma species.
The prevalence threshold of 10% is based on estimation by parasitological microscopy, using duplicate Kato–Katz smears from one stool sample for intestinal schistosomiasis, predominantly S. mansoni and S. japonicum, and single 10 mL urine filtration for urogenital schistosomiasis due to S. haematobium.
The point-of-care circulating cathodic antigen test can be used to determine prevalence of S. mansoni; 30% prevalence by this test is to be considered equivalent to 10% prevalence by the Kato–Katz technique.
Routine monitoring for effective coverage and evaluation of the impact of the intervention (using repeat population-based surveys conducted after five rounds of
preventive chemotherapy, or more frequently with a mid-term evaluation after three rounds) should be integral parts of preventive chemotherapy programmes, to help inform the decision on changing the strategy and continuing or stopping the programme.
Expanded
preventive chemotherapy programmes pose a greater theoretical risk to the development of drug resistance. Evidence of the potential emergence of reduced praziquantel efficacy in response to increased drug use is rarely reported; thus, continued vigilance to monitor drug efficacy over time through efficacy surveys is imperative to detect any emergence of drug resistance.
Routine monitoring for safety of the intervention should also be an integral part of
preventive chemotherapy programmes.
Preventive chemotherapy in
preschool-aged children (pre-SAC) is appropriate for those aged ≥ 2 years. Younger children, aged < 2 years, may be considered for treatment on an individual clinical basis. The medication for children aged < 2 years should be an oral disintegrating tablet formulation (under development) that is easily administered, disintegrates in the mouth and, ideally, has a sweet taste and smell; if paediatric formulations are not available, praziquantel crushed in soft food may be used for individual case treatment only.
Available evidence does not differentiate approaches to infection with the different species of Schistosoma.
The 10% prevalence threshold for intervention will expand eligibility for
preventive chemotherapy programmes and necessitate a larger global supply of praziquantel than that currently available via donation schemes (estimated at 300 million tablets annually at the time of publication of this guideline).
Community mapping of the epidemiology of schistosomiasis can reduce the need for praziquantel, as treatment can be better targeted to communities and at-risk regions.
Ensuring high coverage is essential for
preventive chemotherapy and may require incentivization of local community drug distributors.
Public health awareness campaigns are necessary to ensure high coverage in
preventive chemotherapy programmes and to address concerns about adverse events from medication.
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 test-and-treat, instead of preventive chemotherapy targeting a population.
Conditional recommendation
Certainty of evidence: very low
Implementation considerations
Close epidemiological monitoring (sentinel sites surveys or mid-term evaluation every 3 years) should be established to monitor
Schistosoma spp. prevalence, especially in settings in which the prevalence was previously ≥ 10% or with a history of
preventive chemotherapy with praziquantel if reducing the frequency of preventive chemotherapy with praziquantel.
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
Implementation considerations
Lack of an appropriate response should be defined as a less than one-third relative reduction in prevalence comparing the baseline prevalence survey and a repeat prevalence survey completed after 2 years of annual
preventive chemotherapy. The intervening period should include a minimum of two rounds of preventive chemotherapy to all at-risk groups at adequate
treatment coverage (≥ 75%). The relative reduction in prevalence can be estimated as follows: [(prevalence at baseline − prevalence at year 3)/(prevalence at baseline)]. Alternative definitions could consider absolute changes in
prevalence of infection, or changes in average
intensity of infection (defined as egg concentrations in stool or urine).
The timing of prevalence surveys should consider the seasonality of transmission to ensure that prevalence is measured at the same point in each seasonal transmission cycle.
Communities suspected to be “persistent hot spots” or of high endemicity (defined as areas with baseline prevalence ≥ 50% in
school-aged children (SAC) are encouraged to conduct early prevalence surveys (after two annual rounds of
preventive chemotherapy) to inform any decision on the use of biannual treatment.
Biannual
preventive chemotherapy should be prioritized in areas of higher prevalence (defined as areas with baseline prevalence ≥ 50% in SAC and
persistent hot spot settings already achieving high levels of coverage of annual preventive chemotherapy without appropriate response. In settings of moderate prevalence (defined as areas with prevalence 10
–49% in SAC), annual treatment may be sufficient.
Routine monitoring for effective
treatment coverage should be an integral part of
preventive chemotherapy programmes, with attention to ensuring that annual treatment achieves high coverage (≥ 75%) before any decision to move to biannual treatment.
There is currently a lack of evidence to inform recommendations on the duration of biannual treatment. As an interim measure, 3 consecutive years of biannual
preventive chemotherapy is suggested, followed by implementation of an impact survey to assess if it should be continued or reduced in frequency.
Biannual treatment programmes will require a larger global supply of praziquantel than that currently available via donation schemes (estimated at 300 million tablets annually at the time of publication of this guideline).
Biannual treatment programmes should have administrations spaced out equally throughout the year (approximately 6 months between treatments).
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
Implementation considerations
Pregnancy status should be assessed by discretely questioning the individual herself. If she is uncertain, a negative urine-based pregnancy test can be requested before the treatment is administered.
The medicine for children aged < 2 years should be an oral formulation (currently under development) that is easily administered, disintegrates in the mouth and, ideally, has a sweet taste and smell; if paediatric formulations are not available, praziquantel crushed in soft food may be used for individual case treatment only.
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
Implementation considerations
WASH interventions are expected to provide modest benefits in limiting Schistosoma transmission, but these benefits extend also to reducing risk for multiple infectious diseases.
Coordination and joint planning between programmes for
control of schistosomiasis and WASH are essential. Inclusion of WASH in the schistosomiasis strategy will require mapping and sharing of epidemiological information alongside WASH coverage to ensure prioritization of water and sanitation services to areas that are endemic for schistosomiasis.
Similarly, schistosomiasis education and health programme delivery should include inputs to WASH programme design, collaboration on behavioural change interventions and integration of behavioural change promotion.
Where persistent hot spots of transmission emerge during the course of
preventive chemotherapy campaigns,
control of intermediate host snail populations should be prioritized especially if the programme is already achieving high levels of
treatment coverage.
Snail
control will be essential to ultimately eliminate local transmission, in combination with WASH interventions.
Sensitization and public health awareness campaigns will be necessary to ensure high acceptance of snail
control interventions.
Development of snail
control programmes will require a larger and less expensive global supply of molluscicides.
Skilled and dedicated snail
control workers will be essential to the success of snail control initiatives.
Deworming should be delivered together with promotion of health and hygiene to reduce transmission by encouraging healthy behaviours such as proper disposal of faeces.
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:
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.
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.
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
Implementation considerations
The eventual predictive performance of the sampling of humans, snails and non-human mammalian hosts to identify settings that have eliminated transmission will depend upon the sampling strategy, with decisions on sample size, geographical zone and timespan for sampling.
Future work could consider a two-step verification of Schistosoma infection status in humans with a first highly sensitive test (for example, serology) and a second confirmatory highly specific test (for example, miracidia hatching test).
Sampling and diagnostic tools in snail populations and in non-human mammalian hosts should be considered when interruption of transmission is the public health goal and is suspected based on recent epidemiological surveys in human populations.
The magnitude of the contribution of non-human mammalian hosts to transmission of schistosomiasis remains understudied, especially for species other than S. japonicum.
