Spatial Distribution and Associated Risk Factors of Soil-Transmitted Helminth Infection in a Semi-urban Community in Southwest Nigeria

Nwuba Roseangela Ifeyinwa,Oluwatoba Olufunke Abiodun,Taiwo Olalekan John

doi:10.11648/j.jher.20210704.13

Abstract

Parasite distribution exhibit heterogeneity within households and communities. The aim of this study is to identify the spatial distribution, clustering and associated risk factors of Soil-transmitted Helminths infection in a semi-urban area in Southwest Nigeria. Geographical information System (GIS) was used to map the town into three density areas; low, medium and high density areas. Two hundred and thirty six soil samples were obtained from the surroundings of 137 households and stool samples were collected from the inhabitant of the households. Moran index was used to analyze the spatial distribution of STH within the community. A total of 137 households were sampled for human STH and environmental soil samples from the household were analyzed. The prevalence of human STH infection was 41.7% while that of soil parasite was 27.7% within the selected household. Ascaris lumbricoides was the predominant STH infection in the community sampled with 24.1% prevalence followed by Hookworm. Spatial analysis showed that A. lumbricoides infection was significantly clustered only in the GIS mapped medium density area of Igbo-Ora (z-score 2.302, p=0.021), while hookworm infection was randomly distributed in all the GIS mapped areas of Igbo-Ora. There was a statistically significant association between human STH infection and presence of parasite in the household soil (x2 5.74, p-value 0.017). None of the risk factors evaluated was found to have significant association for the clustering pattern of infection found in the medium density area of the community. Meanwhile, factors such as; the physical presence of a popularly patronized local market in the area, lack of any visible public toilet and the use of bushes around the area by the people for defecation contribute to the reasons for the clustering of the Ascaris infection. Also, the ability of Ascaris to withstand environmental conditions than other STH parasite may contribute to the pattern observed. The differences in the pattern of distribution and associated risk factors revealed that environmental conditions and exposure factors are major determinant of STH infection.

Highlights

The soil-transmitted helminths are a group of parasitic nematode worms causing human infection through contact with parasite eggs or larvae that thrive in the warm and moist soil of the world's tropical and subtropical countries [1].In order to effectively control STH infection, there is a need for accurate description and understanding of the geographical distribution of infection
Many epidemiological studies have been done by examining the stool sample of the inhabitant, these results do not indicate the extent to which the residents are at the risk of parasitic infection but demonstrate the point prevalence of infection within the community sampled [4]
Ascaris lumbricoides was the major parasite found in the soil followed by hookworm and only one S. stercoralis was found, other parasite found include Taenia and S. haematobium ova

Summary

Introduction

The soil-transmitted helminths are a group of parasitic nematode worms causing human infection through contact with parasite eggs or larvae that thrive in the warm and moist soil of the world's tropical and subtropical countries [1].In order to effectively control STH infection, there is a need for accurate description and understanding of the geographical distribution of infection. The initial difficulty presented by the traditional cartography was one of the reasons for lack of information about the spatial patterns of infection. These difficulties have been dramatically resolved by the advent of Oluwatoba Olufunke Abiodun et al.: Spatial Distribution and Associated Risk Factors of Soil-Transmitted Helminth. The use of geographical information systems has provided a novel understanding of ecology of infection. This has led to the development of low cost ways to identify target populations for treatment [2, 5, 6]. There is paucity of information on the spatial distribution of STH infection in Nigerian community

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