A modified assay for the enumeration of ascaris eggs in fresh raw sewage

Soil-transmitted helminths (STHs) pose a significant public health problem, infecting approximately 2 billion people globally. Despite relatively low prevalence in developed countries, the removal of STHs from wastewater remains crucial to allow the safe use of biosolids or recycled water for agriculture. Wastewater helminth egg count data can contribute to an assessment of the need for, or success of, a parasite management program. Although the World Health Organisation (WHO) has recommended a standard method for counting helminth eggs in raw sewage based on the method of Bailenger (Ayres et al., 1996), the method generally results in low percentage egg recoveries. Given the importance of determining the presence of STHs, it is essential to develop novel techniques that optimise the recovery rate of eggs from raw sewage. In the present study: • The method described by Bowman et al. (2003) was optimized for the concentration and enumeration of helminth eggs in raw sewage from municipal sewage treatment plants. • The method is simple and reproducible and recovers a greater percentage of helminth eggs compared to the WHO method.