Survival of Prions in Class B Biosolids

The transmissible spongiform encephalopathies (TSE) are a group of neurological prion diseases of mammals caused by infectious prion proteins. Prions may be present in raw wastewater through the discharge, animal rendering and meat processing operations that may process BSE-contaminated cattle or scrapie infected sheep. Recently, a cell culture method was developed to detect the infectivity of prions in animal tissues. This study developed a method for extracting prion proteins from Class B biosolids and evaluated the survival of mouse scrapie prion proteins in Class B biosolids at 37°C and 60°C using an enzyme linked immunospot assay. A method was developed using 4 M urea (held at 80 o C for 10 minutes)to extract the prions from the biosolids followed by reduction of the urea concentration using membrane centrifugation. The efficiency of recovery of infectious prions from the biosolids was 17.2%. A 2.43-log10 reduction in prion infectivity was observed under mesophilic (37°C) temperatures after 15 days and a 3.41-log10 reduction after 10 days under thermophilic conditions (60°C). Reduction was greater in the biosolids than controls in phosphate buffered saline, suggesting factors other than temperature were also playing a role in the loss of infectivity of the prions in the biosolids.