The Impact of Targeted Treatment and Mass Drug Administration Delivery Strategies on the Prevalence and Intensity of Schistosomiasis in School Aged Children in Africa: A Systematic Review

Schistosomiasis is a neglected tropical disease causing significant morbidity across 78 countries. Urogenital schistosomiasis is caused primarily by Schistosoma haematobium, while intestinal disease can be caused by S. mansoni, S. guineensis, S. intercalatum, S. japonicum, or S. mekongi. Approximately 700 million people are at risk and over 240 million are infected globally, with 90% of cases in sub-Saharan Africa. Since the mid-1980s, WHO has recommended praziquantel as the cornerstone of schistosomiasis morbidity control, and WHA resolution 54.4 (2001) emphasized reducing schistosomiasis morbidity via treatment of schoolchildren. MDA involves diagnosis-free periodic preventive chemotherapy to at-risk populations; targeted treatment focuses on specific groups (e.g., school-aged children) based on risk. WHO recommends annual treatment for high-endemic areas (prevalence ≥50%), biennial or less frequent treatment for moderate/low-endemic areas. This review focused on Africa due to its high disease burden and aimed to summarize the effects of targeted and mass praziquantel delivery strategies—considering frequency, duration, delivery mode, and adjunct measures—on schistosomiasis prevalence and intensity in school-aged children.

Design: Scoping systematic review following PRISMA guidance. Data sources: Google Scholar, Medline, PubMed, and EBSCO Host. Search period: studies published 2010–2022. Search terms included combinations of: Schistosomiasis OR Bilharzia AND Targeted treatment OR Mass Drug Administration AND Prevalence, Intensity AND African Children OR Primary School. Eligibility criteria: primary research in peer‑reviewed journals; African school-aged children (5–19 years); interventions with praziquantel delivered as targeted treatment or MDA; explicit reporting of baseline and post-intervention prevalence and/or intensity; infections restricted to S. haematobium and S. mansoni; English language. Exclusions: studies without baseline prevalence/intensity, studies outside Africa, non‑English, or not addressing impact on prevalence/intensity. Study selection: 846 records identified; 65 duplicates removed; 682 excluded at title/abstract screening; 99 full text assessed; 72 excluded; 27 included. Data extraction: standardized charting of study identification, methodology (population, design, sample size, species, intervention, duration), outcomes (changes in prevalence/intensity, coverage), and conclusions by two independent reviewers; discrepancies resolved by discussion. Risk of bias/quality appraisal: Mixed Methods Appraisal Tool (MMAT, 2018) used to assess methodological quality; risk of bias summarized descriptively. Delivery strategies assessed: school-based treatment (SBT), community-based/community-wide treatment (CBT/CWT), treatment frequency (annual, biennial, biannual), intervention duration (single round up to six years), and adjuncts (health education, snail control, safe water).

- Included studies: 27 peer‑reviewed articles. - Prevalence outcomes: All studies reported decreases after intervention. Five studies (18.5%) showed <40% reduction; 18 (66.7%) showed 40–80% reduction; four (14.8%) showed >80% reduction. - Intensity outcomes: Majority reported reductions after MDA; 24 studies showed decreased intensity; two reported increased intensity (typically where only a single round was delivered and reinfection was high); one study reported no significant change in intensity in narrative sections. - Treatment coverage: In 14 studies, coverage exceeded the WHA recommended ≥75% threshold; six studies did not meet 75%; several studies did not report coverage. Higher coverage correlated with larger reductions in prevalence/intensity; e.g., >90% coverage associated with ~80% declines. - Frequency and duration: Multiple rounds (annual/biannual over several years) produced sustained declines in prevalence and intensity. Single rounds or programs with gaps often showed modest reductions, persistent hotspots, or recrudescence. - Delivery mode: SBT and CWT/CBT achieved similar prevalence reductions; SBT tended to achieve slightly higher coverage and greater intensity reduction among children due to easier access to the target population; combining SBT and CWT can be complementary. - Complementary interventions: Adding snail control, health education, and safe water/sanitation improved outcomes beyond MDA alone, with greater reductions in prevalence and intensity observed in arms receiving combined measures. - Reinfection and hotspots: High reinfection rates were common where uptake was low, environmental transmission persisted, or MDA frequency was insufficient, leading to persistent hotspots despite repeated treatment. - Illustrative data points: Mean egg counts reduced markedly in several settings (e.g., from 134.53 to 18.98 epg after multi-year MDA); microhematuria and anemia indicators decreased following MDA in some studies.

The review demonstrates that the impact of praziquantel targeted treatment and MDA on schistosomiasis among school-aged children in Africa is shaped by implementation strategy. Frequency and continuity of MDA are critical; single rounds or interrupted schedules yield modest and often transient prevalence reductions and can permit reinfection and persistence of hotspots. Multiple rounds—especially annual or biannual schedules sustained for several years—produce larger and more durable declines in both prevalence and intensity. Delivery mode influences program reach: SBT typically attains higher coverage in children and slightly greater reductions in intensity, while CWT/CBT better reaches broader at‑risk populations; combining approaches can enhance overall impact. Complementary interventions (snail control, health education, safe water/sanitation) consistently augment MDA effects and help reduce reinfection pressure. Despite reductions, targeted treatment alone rarely achieves elimination; persistent transmission dynamics and environmental reservoirs sustain reinfection risk. High coverage (≥75%) is associated with significantly greater reductions, underscoring the importance of community engagement and accessibility. The findings support integrated, sustained control strategies tailored to endemicity levels, with attention to hotspot identification, timing interventions to local transmission seasonality, and addressing social and environmental determinants.

Targeted praziquantel treatment and MDA substantially reduce schistosomiasis prevalence and intensity in African school-aged children but are insufficient alone for elimination. Sustained, high‑coverage MDA programs, ideally biannual or annual depending on endemicity, should be paired with complementary measures such as snail control, health education, and provision of safe water and sanitation to mitigate reinfection. Policies should emphasize prevention as well as treatment, strengthen community engagement to achieve ≥75% coverage, and address socioeconomic and environmental drivers. Future research should advance alternative or adjunctive control tools (e.g., vaccines, prophylactic supplements) and optimize timing of interventions to local transmission cycles. Additional high‑quality implementation studies are warranted to refine delivery strategies at national and subnational levels.

Access limitations to some full texts (paywalls, limited institutional access during the COVID-19 pandemic) constrained inclusion of potentially relevant studies.