A systematic review of mathematical models for soil-transmitted helminthiasis control strategies

Soil-transmitted helminthiasis (STH) remains an important public health challenge in endemic settings, and mathematical transmission models are widely used to evaluate STH transmission and control strategies. However, no systematic review has comprehensively classified STH transmission models according to their biological and structural characteristics and intervention designs while examining the operational incorporation of World Health Organization (WHO) roadmap targets and projected timelines. This review therefore aimed to classify STH transmission models and interventions and examine the operational incorporation of WHO roadmap targets and projected timelines.

We searched Web of Science, Scopus, and Embase for English-language studies published between January 2015 and December 2024. Five reviewers participated in screening and data extraction. Models were classified by transmission unit, mathematical framework, and population structure, and interventions by strategy, delivery platform, target population, and treatment regimen. WHO alignment was classified as explicit or implicit against the 2011-2020 and 2021-2030 roadmaps using pre-defined criteria. Projected timelines were extracted, and methodological quality was assessed using the Assessment of Modelling Studies tool.

Forty-two studies satisfied the inclusion criteria. Parasite-based (69%), age-structured (67%), and deterministic (62%) formulations were frequently represented than host-based (31%), homogeneous (33%), and stochastic (38%) formulations, respectively. Preventive chemotherapy was the most frequently modelled intervention strategy (81%), whereas integrated strategies represented 19%. Thirty-three studies (79%) aligned with at least one WHO roadmap objective, including 12 (29%) explicitly and 21 (50%) implicitly aligned studies. Fourteen studies (33%) reported projected timelines for WHO-relevant outcomes. External validation was reported in 14% of studies.

The literature was predominantly characterised by parasite-based, age-structured, and deterministic formulations, with preventive chemotherapy forming the principal intervention focus. Integrated strategies were less represented. Projected timelines and external validation were also infrequently reported. Models addressing programme planning or policy evaluation could benefit from relevant integrated interventions, projected timelines, and external validation.