Assessment of Environmental Contamination With Soil-Transmitted Helminth Eggs From Human and Animal Faeces in...

Soil-transmitted helminth (STH) infections remain a major public health problem in low- and middle-income regions, including the humid and lagoon areas in Côte d'Ivoire, where sanitation facilities are limited at the community level. Few studies have investigated the relationship between environmental (soil and water) contamination by STH eggs and their infection prevalence in humans and animals in endemic areas. We assume that assessing soil contamination with STH eggs could provide a rapid and cost-effective indicator for identifying high-risk communities. A cross-sectional study was conducted in October 2024 in three villages (Attehou, Bekpou and Tiagba) selected based on previous epidemiological data. A total of 215 and 58 stool samples, respectively, from school-aged children and animals (pigs, goats and sheep), in addition to 86 soil samples and 41 stagnant water samples, were collected. Human stool samples were examined using the Kato-Katz method, and animal stool samples using the McMaster flotation technique. Soil samples were analysed using an optimised flotation method with different solutions, and water samples using a sedimentation-concentration technique. Proportions were compared using Fisher's exact test. STH eggs were detected in all matrices investigated, with an overall prevalence of 44.6%, 24.1%, 25.5% and 2.43%, respectively, in children, animals, soil and water. Only Ascaris, Trichuris and hookworm eggs were identified. The highest prevalence was observed in Tiagba among children (83.67%) and soil samples (33.33%). NaCl solution provided better egg recovery from soil samples (> 50%, p = 0.02). Higher soil egg counts were observed in the same villages where higher egg counts were found in children, particularly in Attehou and Tiagba. The abundance of STH eggs in the environment was associated with that observed in school-aged children. Our findings suggest that egg density in contaminated soil could serve as a reliable and cost-effective alternative to human stool examination for identifying high-risk communities, particularly in resource-limited settings. Furthermore, assessing soil contamination could help guide integrated control strategies and epidemiological surveillance approaches aiming to reach eliminating STH infections.