Abstract
Almost one-quarter of the world’s population is infected with soil-transmitted helminths (STH). We conducted a study to determine the prevalence and location of STH—Ascaris, Trichuris, and hookworm spp.—egg contamination in soil within rural household plots in Kenya. Field staff collected soil samples from July to September 2014 from the house entrance and the latrine entrance of households in Kakamega County; additional spatial sampling was conducted at a subset of households (N = 22 samples from 3 households). We analyzed soil samples using a modified version of the US Environmental Protection Agency (EPA) method for enumerating Ascaris in biosolids. We found 26.8% of households had one or more species of STH eggs present in the soil in at least one household location (n = 18 out of 67 households), and Ascaris was the most commonly detected STH (19.4%, n = 13 out of 67 households). Prevalence of STH eggs in soil was equally likely at the house entrance (19.4%, N = 67) as at the latrine entrance (11.3%, N = 62) (p = 0.41). We also detected STH eggs at bathing and food preparation areas in the three houses revisited for additional spatial sampling, indicating STH exposure can occur at multiple sites within a household plot, not just near the latrine. The highest concentration of eggs in one house occurred in the child’s play area. Our findings suggest interventions to limit child exposure to household soil could complement other STH control strategies.
Highlights
About 1.5 billion people are infected with at least one species of soil-transmitted helminth (STH) [1]
Our findings suggest STH soil contamination is present within households in rural Kenya, a setting with high coverage of on-site sanitation facilities and an ongoing national school-based deworming campaign [14]. 26.8% of households had soil contaminated with at least one species of STH at either the house entrance, the latrine entrance, or both soil sampling locations
Our results agree with a study that looked at STH in soil in Brazilian households that found that the median concentration inside the house was 0.8 eggs/g and 0.6 eggs/g near the defecation site [13]
Summary
About 1.5 billion people are infected with at least one species of soil-transmitted helminth (STH) [1]. STH are parasitic worms that live in the intestines of humans and other animals. The three predominant STH that can infect humans are Ascaris lumbricoides, Trichuris trichiura, and hookworm species (Ancylostoma duodenale and Necator americanus). Ascaris is the most prevalent, with an estimated global burden of 820 million infections [1]. PLOS ONE | DOI:10.1371/journal.pone.0157780 June 24, 2016
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