title: 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.
abstract: 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.
authors.affiliation: School of Applied Sciences, RMIT University, Plenty Road, Bundoora 3083, Victoria, Australia. s3174725@student.rmit.edu.au
authors.forename: Alaa
authors.initials: A
authors.lastname: Karkashan
authors.forename: Basma
authors.initials: B
authors.lastname: Khallaf
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Morris
authors.forename: Nerida
authors.initials: N
authors.lastname: Thurbon
authors.forename: Duncan
authors.initials: D
authors.lastname: Rouch
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Smith
authors.forename: Margaret
authors.initials: M
authors.lastname: Deighton
mesh_terms: D000818:Animals; D017164:Ascaris lumbricoides / Q000166:cytology*; D017165:Ascaris suum / Q000166:cytology*; D002470:Cell Survival; D005243:Feces / Q000469:parasitology; D005260:Female; D008853:Microscopy / Q000379:methods*; D018613:Microscopy, Confocal; D010063:Ovum / Q000166:cytology*; D010270:Parasite Egg Count / Q000379:methods; D012722:Sewage / Q000469:parasitology*; D013194:Staining and Labeling / Q000379:methods; D013552:Swine
chemical_list: D012722:Sewage