OP5 -Parasitic helminth stages isolated from soil samples of selected public areas in Gampaha and Colombo, Sri Lanka.

Abstract

Introduction

Sri Lanka has successfully controlled soil-transmitted helminthiases affecting humans through mass deworming and improved sanitation. However, soil contamination with animal excreta is widespread, allowing the ova of gut-dwelling geohelminths in canines and felines to develop into infective ova or larvae in the soil. Such contaminated soil poses a public health hazard for toxocariasis and cutaneous larva migrans. 

Objective

This study aimed to determine the prevalence of soil contamination with parasitic helminth ova and larvae in selected public areas of the Gampaha and Colombo districts.

Design, setting and methods

Study locations were selected randomly from Gampaha and Colombo districts. Sampling was conducted at four sites in each location from May 2024 to January 2025. A 15x15cm square wooden template was placed, and approximately 200g of soil was collected into labeled zip-lock bags after scraping off the topsoil using a clean spade. The samples were processed using the Magnesium sulfate floatation and Baermann funnel technique for the detection of helminth ova and larvae, respectively. Identification of parasitic helminth stages was based on morphology on light microscopy at 40x10 magnification.

Results

A total of 140 soil samples were analyzed from Colombo (n=56) and Gampaha (n=84). Study sites included parks (n = 12), temples (n = 20), university grounds (n = 12), side roads (n = 12), beaches (n = 4), school grounds (n = 28), hospital grounds (n = 4), and home gardens (n = 48). The overall prevalence of parasitic helminth stages in soil, determined by Magnesium sulfate flotation, was 32.1% (45/140), with rates of 39.3% (22/56) and 27.4% (23/84) in Colombo and Gampaha districts, respectively. Ova of Toxocara spp. were detected in 31.1% (14/45), Ascaris lumbricoides in 8.9% (4/45), and hookworm in 4.4% (2/45) of positive samples through the floatation method. Hookworm larvae, probable Ancylostoma spp., were detected in 24.3% (34/140) by the Baermann technique. The highest contamination rates were observed in parks at 41.7% (5/12) and temple grounds at 40.0% (8/20).

Conclusions

Soil contamination with parasitic helminth stages was widespread in Colombo and Gampaha districts. The high prevalence in children's parks and temples indicates risks to children while they are playing or walking barefoot. Health education, regular deworming of pets, and controlling stray animal populations are recommended.

Acknowledgments

Financial assistance by the University of Kelaniya Research grant RP/03/04/06/01/2023.