Soil-transmitted helminths and childhood development: Nutrition, anemia, cognitive outcomes, and school-based deworming

Infections with soil-transmitted helminths (STHs) are one of the most common neglected tropical diseases globally and drive poor childhood development, which is a cycle within low and middle-income countries (LMICs). The infection is caused by Ascaris lumbricoides , Trichuris trichiura , and the hookworms ( Necator americanus, Ancylostoma duodenale ) and disproportionately affects school-age children and adolescents in the impoverished areas where water, sanitation, and hygiene are inadequate. This review is an integration to understand the association between STH infection and 4 key domains of childhood development: nutrition status, anemia, cognitive function and effect of school-based deworming, a public health intervention. At the global level, 37.16% of school-age children in LMICs are infected with STH, and the highest prevalence can be found in the Western Pacific (50.41%) and in Africa (37.10%). Chronic STH infection causes damage to nutritional status by inducing intestinal blood loss, malabsorption of nutrients and anorexia, directly contributing to stunting and underweight. In addition, hookworm infection worsens iron deficiency anemia, which is closely associated with cognitive development problems and lower academic attainment. Preventive chemotherapy, which is deworming for STH at school, is the main method for controlling STH at the global level and the World Health Organization recommends that children be dewormed annually or biannually depending on endemicity. Recent programmatic evaluations indicate that school-based deworming can decrease STH prevalence, improve nutritional markers, and can have long-term cognitive and economic impacts. Despite this, there are still barriers to be addressed: suboptimal deworming coverage in many areas, high risk of reinfection following deworming, low efficacy against Trichuris and Strongyloides , and a limited number of large-scale RCTs that provide evidence of benefit with regards to hemoglobin concentrations and cognitive function. The current review summarizes epidemiological data from the different regions, explains how STH is related to poor developmental outcomes, and summarizes the effectiveness of school-based deworming. It also identifies key areas of uncertainty that require research such as long-term cohort studies, identifiable and standardized integrated deworming protocols, and scalable protocols to help ensure the sustainability of deworming benefits.