Systematic review to evaluate a potential association between helminth infection and physical stunting in children

Abstract

Background Despite considerable public health efforts over the past 20 years, childhood stunting (physical and/or cognitive) levels globally remain unacceptably high—at 22% amongst children under 5 years old in 2020. The aetiology of stunting is complex and still largely unknown. Helminths can cause significant mortality and morbidity and have often been cited as major causative agents for stunting, although their actual role in childhood stunting remains unclear. Our aim was to systematically review the current evidence to help support or refute the hypothesis that helminths cause physical stunting in children. Methods Inclusion criteria were as follows: infected with (and/or exposed to) helminths (soil-transmitted helminths, schistosomes or food-borne trematodes), children, pregnant or breastfeeding women as study participants (children included infants 0–1 year old, preschool-age children 1–5 years and school-age children > 5 years old), anthelmintic treatment intervention, stunting-related variables reported (e.g. height, height-for-age z-score, birth weight), helminth infection reported in relation to stunting, any geographic location, any date, peer-reviewed literature only. Exclusion criteria were: non-primary research, study protocols, studies with no new data, non-English language papers and animal (non-human) helminth studies. Seven databases were searched on 28 May 2021. Risk of bias was assessed for included studies and GRADE was used for studies included in RCT subgroup meta-analyses (in preschool-age children and pregnant women). This systematic review was registered with PROSPERO (CRD42021256201). Results Eighty studies were included in the analyses. No significant overall evidence was found in support of the hypothesis that helminths cause physical stunting in children, although there was some association with wasting. Conclusions Whilst analyses of the available literature to date failed to support a direct association between helminth infection and childhood stunting, there was significant heterogeneity between studies, and many had follow-up periods which may have been too short to detect impacts on growth. Most apparent was a lack of available data from key demographic groups wherein one may predict the greatest association of helminth infection with stunting—notably that of infants, preschool-age children, and pregnant or nursing women. Thus this review highlights the urgent need for further targeted empirical research amongst these potentially most vulnerable demographic groups. Graphical Abstract

The eukaryome of African children is influenced by geographic location, gut biogeography, and nutritional status

“…Earlier reports showing a direct role of helminths in undernutrition led to the recommendation of WHO for systematic antihelminthic treatments. However, our observation is consistent with a recent meta-analysis on 80 studies showing that helminths are not directly involved in undernutrition (Raj et al 2022 ). In line with this observation, a recent meta-analysis found very little impact of antihelminthic treatments on stunting or development (Taylor-Robinson et al 2019 ).…”

Cross-Sectional Study of Soil-Transmitted Helminthiases in Black Belt Region of Alabama, USA

“…In endemic populations, the prevalence of hookworm and S. stercoralis threadworm increases with age ( 39 , 40 ) because adult worms can live in the gut for several years ( 41 ); thus, although residual infections were reported by McKenna et al, transmission may have since ceased. We only enrolled children because they are most at risk for adverse outcomes associated with STH infection, including anemia ( 42 ), cognitive deficits, potential growth faltering ( 43 ), and other outcomes ( 44 ). In addition, our studies used different methods for sample preservation before analysis; the McKenna et al study processing stool stored initially on dry ice for up to 5 days, followed by storage until analysis at –20°C (time from collection until analysis not reported).…”

Assessment of the role of gut health in childhood stunting in a multisite, longitudinal study in India, Indonesia and Senegal: a UKRI GCRF Action Against Stunting Hub protocol

“…Kato-Katz thick smear microscopy (duplicate slides per single stool) will be performed on fresh (untreated) stool to obtain individual egg counts of key helminth parasites reported and/or predicted to be associated with physical and/or cognitive childhood stunting (eg, Ascaris spp., hookworm, Trichuris trichiura, Hymenolepis nana ). 22 Slides will be read within 60 min post Kato-Katz preparation to obtain hookworm data. The slides will then be maintained at room temperature prior to microscopic examination of the remaining parasites present.…”