Contribution of Wastewater Irrigation to Soil Transmitted Helminths Infection among Vegetable Farmers in Kumasi, Ghana

Abstract

Wastewater irrigation is associated with several benefits but can also lead to significant health risks. The health risk for contracting infections from Soil Transmitted Helminths (STHs) among farmers has mainly been assessed indirectly through measured quantities in the wastewater or on the crops alone and only on a limited scale through epidemiological assessments. In this study we broadened the concept of infection risks in the exposure assessments by measurements of the concentration of STHs both in wastewater used for irrigation and the soil, as well as the actual load of STHs ova in the stool of farmers and their family members (165 and 127 in the wet and dry seasons respectively) and a control group of non-farmers (100 and 52 in the wet and dry seasons, respectively). Odds ratios were calculated for exposure and non-exposure to wastewater irrigation. The results obtained indicate positive correlation between STH concentrations in irrigation water/soil and STHs ova as measured in the stool of the exposed farmer population. The correlations are based on reinfection during a 3 months period after prior confirmed deworming. Farmers and family members exposed to irrigation water were three times more likely as compared to the control group of non-farmers to be infected with Ascaris (OR = 3.9, 95% CI, 1.15–13.86) and hookworm (OR = 3.07, 95% CI, 0.87–10.82). This study therefore contributes to the evidence-based conclusion that wastewater irrigation contributes to a higher incidence of STHs infection for farmers exposed annually, with higher odds of infection in the wet season.

Soil‐transmitted helminth infections associated with wastewater and sludge reuse: a review of current evidence

“…As this accumulation persists over time, the risk of infection is not diminished due to the latency period. Coupled with the persistence of these eggs in the environment of 10–12 months , STH egg concentrations on farm soil could be higher than concentrations in the wastewater or sludge resulting in higher infection risks . For instance, Amoah et al .…”

“…For instance, Amoah et al . reported an average concentration of 3.70 (±0.23) eggs/g for Ascaris spp and 2.01 (±0.23) eggs/g for hookworm on farms in Ghana. Fixed time periods for survival may be difficult to give as conditions may vary greatly.…”

“…As this accumulation persists over time, the risk of infection is not diminished due to the latency period. Coupled with the persistence of these eggs in the environment of 10-12 months [55], STH egg concentrations on farm soil could be higher than concentrations in the wastewater or sludge resulting in higher infection risks [54,56]. For instance, Amoah et al [54] reported an average concentration of 3.70 (AE0.23) eggs/g for Ascaris spp and 2.01 (AE0.23) eggs/g Farming households Wastewater No significant association was found between wastewater exposure and helminth infections Trang et al [122] Adults and children Wastewater and human excreta…”

“…Higher prevalence of Ascaris infection among exposed compared to unexposed for children. Children under 5 years had higher odds of infection (OR = 18.0) than children above 5 years (13.5) Cifuentes et al [125] Agricultural workers and their family members Wastewater Higher prevalence of diarrheal disease (30% vs. 23%) and Ascaris infection (15% vs. 3%) for exposed children Amoah et al [54] Agricultural workers and their family members Wastewater Increased odds of infection for farmers for both Ascaris spp and hookworm for farmers and family members as compared to unexposed populations, especially in the raining season Pham-Duc et al [18] Farming households Wastewater People having close contact with wastewater polluted surface water had a higher risk of helminth infections compared with those without contact Fuhrimann et al [72] Community members Wastewater High prevalence of intestinal parasite infections for peri-urban farmers, using wastewater for irrigation, as compared to other groups for hookworm on farms in Ghana. Fixed time periods for survival may be difficult to give as conditions may vary greatly.…”

Biological HRPs in wastewater

“…The soil-transmitted helminth eggs relate to infection risk through different exposure routes. For instance, wastewater irrigation to the soil, which transmitted helminth infections were found among vegetable farmers in Ghana (Amoah et al, 2016). The raw and treated wastewater samples collected from 8 WWTPs in Tehran and 2 WWTPs in Isfahan were explored for the presence of helminth eggs during 2002e03, revealing that level of eggs was Table 3.5 Major helminths in the environment (Garcia, 1997;Cohen et al, 2017 high in influent and it significantly reduced after treatment (Mahvi and Kia, 2006).…”