Schistosomiasis in Yemen: Focal Persistence, Possible Resurgence, and Challenges to Elimination.

Schistosomiasis in Yemen, caused by Schistosoma mansoni and S. haematobium, persists as a focal public health problem despite decades of control based largely on repeated praziquantel (PZQ)-based mass drug administration (MDA). This review synthesizes epidemiological, malacological, clinical, and programmatic evidence to examine why substantial national prevalence reductions have not culminated in sustained progress toward elimination. The evidence indicates a shift from broad endemicity toward geographically uneven persistence and possible resurgence, particularly where unsafe freshwater exposure, inadequate water, sanitation, and hygiene (WASH), receptive snail habitats, population movement, and surveillance gaps coincide. By 2017, MDA impact evaluation showed that overall prevalence had fallen below the 10% treatment threshold, but recent school-based surveys show persistent or resurgent district-level transmission. PZQ-based MDA has achieved important gains in morbidity control, but elimination will require geographically targeted preventive chemotherapy, supported by updated micro-mapping, species-specific sentinel surveillance, improved diagnostics, WASH strengthening, health education, focal snail surveillance and control, and rapid response to residual or re-emerging hotspots. Integrating these measures within primary healthcare, school health, and humanitarian platforms will be essential for preserving previous gains and preventing localized transmission from expanding.