Environmental Contamination and Transmission Pathways of Microbial and Parasitic Pathogens in Wastewater-Irrigated Food Systems

Abstract

The reuse of wastewater in agriculture is increasingly practiced but poses significant risks to food safety due to microbial and parasitic contamination. This study investigated environmental contamination and transmission pathways of pathogens in wastewater-irrigated food systems using wastewater, soil, and vegetable samples. Wastewater recorded the highest microbial load, with total coliform counts of (3.45 ± 0.12) × 10⁵ CFU/mL, compared to (2.15 ± 0.09) × 10⁴ CFU/g in soil and (4.85 ± 0.13) × 10⁴ CFU/g in vegetables. Escherichia coli prevalence was 93.3% in wastewater and 83.3% in vegetables, while Salmonella spp. occurred in 70.0% and 63.3%, respectively. Parasitic contamination showed Ascaris lumbricoides as the most prevalent (66.7% in wastewater; 60.0% in vegetables). Physicochemical analysis revealed high biochemical oxygen demand (185.4 ± 12.6 mg/L) and turbidity (132.7 ± 15.3 NTU), indicating favorable conditions for pathogen survival. Strong correlations were observed between wastewater and vegetable contamination (r = 0.891), while regression analysis identified wastewater as the strongest predictor of vegetable contamination (β = 0.58, R² = 0.843), indicating a strong model fit. Pathway analysis confirmed both direct (β = 0.51) and indirect (β = 0.47) contamination routes. These findings indicate that wastewater is a major driver of microbial and parasitic contamination in food systems, posing significant public health risks. Improved wastewater treatment, safer irrigation practices, and strengthened hygiene and monitoring systems are recommended to reduce contamination and enhance food safety.