Widespread Soil-Transmitted Parasitic Contamination in Raw Vegetables at Fresh Markets in the Inner Zone of Bangkok: Findings from a Cross-Sectional Study

Abstract

Bangkok, a globally popular travel destination, hosts numerous fresh markets and street food vendors catering to locals and visitors. Although raw vegetables are integral to Thai cuisine, their consumption may pose risks of soil-transmitted parasitic infections. This cross-sectional study assessed the prevalence of parasitic contamination in raw vegetables from Bangkok’s inner zones, focusing on five districts: Huai Khwang, Khlong Toei, Pathum Wan, Chatuchak, and Phra Nakhon. A total of 200 samples across eight vegetable types were randomly collected from these areas and prepared for analysis using sedimentation techniques followed by microscopic examination. Observers conducting the microscopy were blinded and operated independently to minimize bias. The overall prevalence of parasitic contamination was 77% (n 5 154/200). The highest contamination levels were in Huai Khwang and Chatuchak (90%, P ,0.05). Identified contaminants included Strongyloides stercoralis larvae (57%), hookworm eggs (20%), Ascaris lumbricoides eggs (16%), Trichuris trichiura eggs (12%), Toxocara spp. eggs (10%), and others. Chinese cabbage was significantly more contaminated with hookworm eggs (P ,0.0001) and T. trichiura eggs (P ,0.001) than other vegetables, although less so with S. stercoralis (P ,0.0001). These findings highlight raw vegetables as potential sources of parasitic infections. Consumers are advised to thoroughly wash vegetables before consumption, whereas vendors should wear gloves to minimize exposure to skin-penetrating parasites. Prophylactic antiparasitic treatment, particularly for children and immunocompromised individuals, is recommended annually.