Pathways of diarrheal illness and risk mitigation in wastewater-irrigated urban vegetable farming

Urban agriculture in low- and middle-income countries often relies on untreated wastewater, creating multiple pathways for diarrheal disease transmission. To investigate exposure, hygiene, and risk perception, a comparative cross-sectional study was conducted among 315 urban farming households along the Akaki Rivers in Ethiopia. Data were collected via structured questionnaires, and multivariable logistic regression, multilevel mixed-effects models, and bootstrapped mediation analysis were applied. The two-week prevalence of diarrhea was 11.4% (36/315) among children and 8.7% among adults. In this cross-sectional study (which cannot establish causality), wastewater irrigation was associated with more than twofold increased odds of diarrhea (AOR = 2.10; 95% CI 1.30–3.40). Frequent contact with irrigation water was associated with 80% higher odds (AOR = 1.80; 95% CI 1.10–2.90), and regular consumption of raw vegetables was associated with 60% higher odds (AOR = 1.60; 95% CI 1.00–2.50). Protective factors included consistent handwashing with soap (57% risk reduction), bathing after farm work (41% reduction), and household water treatment (45% reduction; AOR = 0.55; 95% CI 0.34–0.88). Clustering by irrigation site was modest (ICC ≈ 6%), while hygiene practices mediated 28% of the exposure–outcome relationship. Findings underscore that diarrheal illness in wastewater-irrigated farming systems is shaped by both environmental exposures and modifiable behaviors. Integrated, multi-barrier interventions are essential to reduce disease burden.