Investigating Environmental Determinants of Soil-Transmitted Helminths Transmission using GPS Tracking and Metagenomics Technologies
Authors: Sumboh Jeffrey Gabriel , Agyenkwa-Mawuli Kwasi , Schwinger Eyram , Donkor Irene Owusu , Akorli Jewelna E. B. , Dwomoh Duah , Ashong Yvonne , Osabutey Dickson , Ababio Felix Owusu , Koram Kwadwo Ansah , Humphries Debbie , Cappello Michael , Kwofie Samuel K. , Wilson Michael D. 
Published: July 2023

Background

The Global Health community aims to eliminate soil-transmitted helminth (STH) infections by 2030. Current preventive methods such as Mass Drug Administration, WASH practices, and health education needs to be complimented to halt transmission. We tracked the movement of hookworm-infected and non-infected persons and investigated soil factors in the places they frequented within an endemic community to further understand the role of human movement and sources of infections.

Methods

59 positive and negative participants wore GPS tracking devices for 10 consecutive days and their movement data captured in real time. The data was overlaid on the community map to determine where each group differentially spent most of their time. Soil samples were collected from these identified sites and other communal places. Physical and chemical properties were determined for each sample using standard methods and helminth eggs cultured into larvae using the Baermann technique. Bivariate and multivariate analyses were used to determine associations between larvae counts and soil factors. Helminth species were identified with metagenomic sequencing and their distributions mapped to sampling sites in the community.

Results

The study found that there was no significant difference in the average larvae counts in soil between sites assessed by infected and non-infected participants (P=0.59). However, soil factors, such as pH, carbon and sandy-loamy texture were associated with high larvae counts (P<0.001) while nitrogen and clay content were associated with low counts(P<0.001). The dominant helminth species identified werePanagrolaimus superbus(an anhydrobiotic helminth),Parastrongyloides trichosuri(a parasite of small mammals),Trichuris trichuria(whipworm), andAncylostoma caninum(dog hookworm). Notably, noNecator americanuswas identified in any soil sample.

Conclusion

This study provides important insights into the association between soil factors and soil-transmitted helminths. These findings contribute to our understanding of STH epidemiology and support evidence-based decision-making for elimination strategies.

Author Summary

Soil-transmitted helminth (STH) infections has been set to be eliminated 2030. To better understand how infections spread to achieve this, we tracked the movement of people positive and negative for infections. We enrolled 59 participants and equipped them with GPS tracking devices for 10 days continuously monitoring their movements in real time. We identified areas where each group spent the most time. Soil samples were collected from these locations and other communal areas. The physical and chemical properties of the soils were analysed using standard methods and helminth eggs cultured into larvae. Bivariate and multivariate analyses were used to study the relationship between larvae counts and soil factors. Metagenomic sequencing identified the types of helminths present in the soil samples. The study revealed that soil factors such as pH, carbon content, and sandy-loamy texture were associated with high larvae counts, while nitrogen and clay content were associated with lower counts. The dominant helminth species identifiedwere Panagrolaimus superbus, Parastrongyloides trichosuri, Trichuris trichiura(whipworm), andAncylostoma caninum(dog hookworm). Interestingly, no samples containedNecator americanus. This study provides important insights into the connection between soil factors and STHs infections enhancing our understanding of STH epidemiology to inform evidence-based strategies for eliminating.