Incidence and Risk Factors of Soil-Transmitted Helminths Among Vegetable Farmers of Addis Ababa, Ethiopia

Soil-transmitted helminth (STH) infections are common neglected tropical diseases in areas with poor sanitation. In Ethiopia, urban farmers using contaminated river water for irrigation are exposed to parasite infection. This study examined the incidence and associated risk factors of STH infections among vegetable farmers in Addis Ababa, comparing those using wastewater with those using clean water.

A mixed-methods design was applied, incorporating a community-based cross-sectional survey and a longitudinal laboratory investigation from December 2021 to December 2023. The study involved 290 farmers (136 wastewater-exposed and 129 unexposed) across 10 sites along the Big and Little Akaki Rivers. Data were collected via questionnaires, observation, health diaries, and stool samples, with diagnosis performed using the Kato-Katz method. STATA 14 was used for data analysis, including logistic regression to identify significant risk factors (p < 0.05).

STH incidence was significantly higher among wastewater-irrigating farmers (19.8%) compared to nonusers (8.5%), with incidence rates of 7.1 and 3.04 per 1000 person-months, respectively. The relative risk was 2.32, indicating wastewater irrigation increases STH infection. Risk factors among wastewater-exposed farmers, poor fingernail hygiene (AOR = 2.25; 95% CI: 1.65-42.7), and not wearing boots (AOR = 3.4; 95% CI: 1.66-11.5) increased STH infection risk. Defecating on farms raised infection odds in both exposed (AOR = 2.89; 95% CI: 1.55-3.05) and unexposed (AOR = 1.92; 95% CI: 1.55-2.10) groups. Hand contamination (AOR = 6.9; 95% CI: 2.92-55.7), washing vegetables with wastewater (AOR = 11.6; 95% CI: 3.64-23.9), and not wearing protective clothing (exposed: AOR = 1.97; 95% CI: 1.11-87.9; unexposed: AOR = 1.89; 95% CI: 1.31-22.8) also significantly contributed to STH infection.

Wastewater irrigation significantly elevates the risk of STH infections, promoting affordable safe wastewater irrigation practices (sand or gravel filters, drip irrigation) along with hygiene, sanitation, and health education for farmers, to protect farming communities.