Water, sanitation, and hygiene in soil-transmitted helminth control: A scoping review of evidence gaps across transmission pathways

Soil-transmitted helminths (STH) are parasitic intestinal worms infecting humans through contact with, or ingestion of, soil contaminated with eggs shed by infected individuals. STHs include roundworms (Ascaris lumbricoides, Strongyloides stercoralis), whipworm (Trichuris trichiura) and hookworms (Ancylostoma duodenale, Necator americanus, Ancylostoma ceylanicum). Their transmission is influenced by water, sanitation and hygiene (WASH) services and practices. Unlike past reviews, this scoping review did not assess effect sizes or strength of associations. Instead, it aimed to: map WASH-related risk factors in relation to STH infection; assess whether these align with plausible transmission pathways and conceptual frameworks; and characterise methodological features of the evidence base, including diagnostic approaches, that affect comparability of findings.