Parasitic Contamination of Fresh Green Leafy Vegetables Sold in Open Markets in Sri Lanka during the Second Inter-Monsoon Season: A Cross-Sectional Study

Introduction

Intestinal parasitic infections remain a public health concern in Sri Lanka, where contaminated green leafy vegetables are an important transmission route. This study assessed intestinal parasite prevalence in fresh green leafy vegetables across all nine provinces of Sri Lanka and examined variations in parasitic contamination according to the site of collection in different geographical locations.

Methods

A cross-sectional study was conducted from October 1 to November 30, 2025, during the Second Inter-Monsoon (SIM) season across all nine provinces of Sri Lanka. Ninety open markets were included, with ten per province. Five fresh green leafy vegetable types consumed either raw, steamed, or half-cooked namely; Centella asiatica (Gotukola, [n=84]), Alternanthera sessilis (Mukunuwenna, [n=86]), Ipomoea aquatica (Kankun, [n=83]), Trianthema portulacastrum (Sarana, [n=52]), and Amaranthus viridis (Thampala, [n=44]) were selected. Approximately 50g of each sample was processed with a Tween 20 (5%) wash followed by overnight sedimentation, and centrifugation (2000×g, 15 min). Microscopic examination of parasites was performed on both the supernatant and sediment of each sample.

Results

The overall parasitic contamination was 22.6% (n=79). A. sessilis recorded the highest prevalence (24/86; 27.9%), while I. aquatica exhibited the lowest (10/83; 12.1%). Medically important parasites, including protozoans (Balantidium coli, Cystoisospora belli, coccidian oocysts morphologically consistent with Toxoplasma gondii) and helminths (Ascaris spp., Hymenolepis spp., Strongyloides spp., Capillaria spp., Toxocara spp., hookworm and taeniid eggs) were detected. Strongyloides spp. was the most prevalent parasite (31/349; 8.9%). No statistically significant differences were observed in the distribution of parasitic species across vegetable types or in prevalence across provinces (P > 0.05).

Conclusions

This study confirms uniform parasitic contamination of fresh green leafy vegetables across all nine provinces of Sri Lanka, regardless of vegetable type or geographical location during the Second Inter-Monsoon season.