Wastewater reuse in agriculture and the risk of intestinal nematode infection

The increasing use of wastewater for crop irrigation in arid and semi-arid zones means that wastewater parasitology is becoming on important research area. The World Health Organization's (WHO) current guideline states that only treated wastewater containing no more than one human intestinal nematode egg per litre should be used for irrigation. This guideline was based on very limited epidemiological evidence. In this article Rachel Ayres, Rebecca Stott, Duncan Mara and Donald Lee describe their recent work in Yorkshire and northeast Brazil and suggest that their results may be the first evidence for relaxing the WHO guideline for restricted irrigation to no more than ten intestinal nematode eggs per litre.