Field evaluation of the gut microbiome composition of pre-school and school-aged children in Tha Song Yang, Thailand, following oral MDA for STH infections

Author summary Soil-transmitted helminth infections exhibit a significant negative impact on population health worldwide. In particular in endemic regions sub-groups such as children suffer disproportionally from infection due to impoverished living conditions. Yet many of these regions have no or limited availability of infection prevalence data to inform intervention strategies. Application of low sensitivity diagnostic tools such as microscopy exacerbate this issue. Moving towards molecular tools is key in order to establish a more accurate and complete epidemiological profile that can serve as a reference standard for future studies. Recently, a number of studies investigated the microbiota as an important factor determining overall patient health. The gut microbiota can be altered through medication, lifestyle factors and co-inhabitation of the same environmental niche with STHs. However, these microbiota studies often lack a characterised baseline. The current study provides baseline epidemiology data for a cohort of pre-school and school-age Thai children using a molecular diagnostic technique. We estimate the STH infection prevalence and intensity and characterise the host gut microbiota profile at a single cross-sectional timepoint comparing infected with uninfected children. This data can serve as a starting point for future studies investigating the impact of environmental factors and parasitic infections on patient health. Soil-transmitted helminths, such as roundworms (Ascaris lumbricoides), whipworms (Trichuris trichiura) and hookworms (Necator americanus and Ancylostoma spp.), are gastrointestinal parasites that occur predominantly in low- to middle-income countries worldwide and disproportionally impact children. Depending on the STH species, health status of the host and infection intensity, direct impacts of these parasites include malnutrition, anaemia, diarrhoea and physical and cognitive stunting. The indirect consequences of these infections are less well understood. Specifically, gastrointestinal infections may exert acute or chronic impacts on the natural gut microfauna, leading to increased risk of post-infectious gastrointestinal disorders, and reduced gut and overall health through immunomodulating mechanisms. To date a small number of preliminary studies have assessed the impact of helminths on the gut microbiome, but these studies are conflicting. Here, we assessed STH burden in 273 pre-school and school-aged children in Tha Song Yang district, Tak province, Thailand receiving annual oral mebendazole treatment. Ascaris lumbricoides (107/273) and Trichuris trichiura (100/273) were the most prevalent species and often occurred as co-infections (66/273). Ancylostoma ceylanicum was detected in a small number of children as well (n = 3). All of these infections were of low intensity (<4,999 or 999 eggs per gram for Ascaris and Trichuris respectively). Using this information, we characterised the baseline gut microbiome profile and investigated acute STH-induced alterations, comparing infected with uninfected children at the time of sampling. We found no difference between these groups in bacterial alpha-diversity, but did observe differences in beta-diversity and specific differentially abundant OTUs, including increased Akkermansia muciniphila and Bacteroides coprophilus, and reduced Bifidobacterium adolescentis, each of which have been previously implicated in STH-associated changes in the gut microfauna.

Automated summary

Soil-transmitted helminth infections have a significant negative impact on global population health, especially affecting children disproportionately. The lack of infection prevalence data in many endemic regions highlights the importance of molecular tools for establishing accurate epidemiological profiles. The gut microbiota can be influenced by medication, lifestyle factors, and co-inhabitation with parasites, but baseline studies in this area are limited.