Biodegradation of prions in compost

Area of Science:

• Veterinary Science
• Environmental Science
• Biotechnology

Background:

• Specified risk materials (SRM) and animal mortalities can harbor prion diseases (transmissible spongiform encephalopathies, TSE).
• Disposal of TSE-infected materials requires effective and economical methods to prevent disease spread.
• Composting is explored as a potential sustainable disposal strategy.

Purpose of the Study:

• To investigate the efficacy of composting in degrading various prion strains (PrP(263K), PrP(CWD), PrP(BSE)).
• To quantify prion reduction in both laboratory and field-scale composting conditions.
• To assess the safety of compost for land application after prion inactivation.

Main Methods:

• Lab-scale composting experiments with defined prion types (PrP(263K), PrP(CWD), PrP(BSE)).
• Western blotting (WB) and protein misfolding cyclic amplification (PMCA) to measure prion reduction.
• Field-scale composting of PrP(263K) followed by bioassays in Syrian hamsters.

Main Results:

• Lab-scale composting reduced PrP(263K), PrP(CWD), and PrP(BSE) by 2, 1-2, and 1 log10, respectively.
• PMCA confirmed significant reductions, particularly for PrP(CWD) (3 log10).
• Field-scale composting demonstrated at least a 4.8 log10 reduction in PrP(263K) infectivity after 230 days.

Conclusions:

• Composting significantly reduces prion loads in animal waste materials.
• Enriching compost with feather keratin enhances prion degradation.
• Composting is a viable method for disposing of SRM, with minimal residual infectivity in the final product.