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.

Comparison of methodologies for enumerating and detecting the viability of Ascaris eggs in sewage sludge by standard incubation-microscopy, the BacLight Live/Dead viability assay and other vital dyes.

The aim of this study was to evaluate the Live/Dead BacLight viability kit as a method for enumerating viable eggs of Ascaris suum in sewage sludge as a surrogate for the human roundworm. The number and viability status of eggs of A. suum were accurately measured directly in sewage sludge samples by the BacLight method, compared to the conventional incubation-microscopy procedure. BacLight stains were not toxic to A. suum eggs, in contrast to some conventional vital dyes which disrupted viable eggs. The method was effective for the direct examination of eggs in heavily contaminated samples or seeded sludge containing ∼200 eggs/g DS in sludge with 5% DS content. However, a recovery method would be necessary to examine samples with small numbers of eggs, for instance in sludge from regions where the prevalence of infection with Ascaris lumbricoides is low. The BacLight technique may therefore be an effective alternative to conventional incubation-microscopy for enumerating Ascaris eggs in contaminated field samples or to validate sludge treatment processes by examining decay rates of inoculated A. suum eggs in laboratory simulations. Most field samples would require recovery from an appropriate number of composite samples prior to vital staining.