Low risk for helminth infection in wastewater-fed rice cultivation in Vietnam

Abstract

This study was done to assess the risk of helminth infection in association with wastewater-fed rice cultivation in an agricultural setting of Nam Dinh city, Vietnam. In a cross sectional survey data were collected for 202 households in a commune where wastewater was used for irrigation and for 201 households in a commune that used river water. Parasitological examination was conducted on single stool samples obtained from 1,088 individuals aged ≥15 years from the households. The irrigation water used in both communes was enumerated for helminth eggs and thermotolerant coliforms. The prevalence of infection with Ascaris spp., Trichuris spp., and hookworm was 42.2%, 19.9% and 10.5% respectively, with an overall prevalence of infection with any helminth of 53.4%. Surprisingly, the prevalence of infection with Ascaris and Trichuris was lower among people exposed to wastewater (containing 40–200 helminth eggs/l and 104 thermotolerant coliforms/100 ml) compared to people exposed to river water that contained lower worm egg and bacterial numbers. Poor sanitation and hygiene practices and not using protective measures were important independent risk factors for helminth infection. For hookworm infection, no significant difference was observed between the wastewater exposed and unexposed groups. Children living in the wastewater use area had a significantly better nutritional status than those in the area using river water. This suggests a generally higher welfare level of the wastewater use area. In conclusion, this study showed no evidence that rice cultivation with wastewater poses a risk for helminth infection. More detailed studies are needed on the reduction of fecal indicators and helminth eggs in peri-urban wastewater-irrigated rice culture systems and on the relative importance of wastewater irrigation compared to other risk factors for human helminth infection such as poor sanitation and poverty.

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

“…For instance, Trang et al . found no increase in STH infections from exposure to wastewater in Vietnam. The interlinkages between different contamination sources and transmission routes are essential in these types of studies.…”

“…Independently of that, a review of the scarce literature shows an overwhelming evidence of increased risks of STH infections due to wastewater/sludge reuse [1,18,54,72,73] even if some studies were unable to establish links. For instance, Trang et al [74] found no increase in STH infections from exposure to wastewater in Vietnam. The interlinkages between different contamination sources and transmission routes are essential in these types of studies.…”

The challenges of wastewater irrigation in developing countries

“…Many farmers cannot afford treatment for some of the health problems caused by the exposure. Generally, farmers irrigating with wastewater have higher rates of helminth infections than farmers using freshwater, but there are exceptions (Trang et al, 2006). In addition, skin and nail problems may occur among farmers using wastewater (Van der Hoek et al, 2002;Trang et al, 2007).…”

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

“…However, in Vietnam, Trang et al . [17] found no evidence that rice cultivation with wastewater posed any significant helminth infection risk to farmers, even though they were exposed to wastewater containing 40–200 helminth eggs/L. Prevalence of and risk factors for helminth infections have been studied in Ghana [18].…”