Transport of the Pathogenic Prion Protein through Landfill Materials

Transmissible spongiform encephalopathies (TSEs, prion diseases) are a class of fatal neurodegenerative diseases affecting a variety of mammalian species including humans. A misfolded form of the prion protein (PrP^TSE) is the major, if not sole, component of the infectious agent. Recent TSE outbreaks in domesticated and wild animal populations have created the need for safe and effective disposal of large quantities of potentially infected materials. Here, we report results of a study to evaluate the potential for transport of PrP^TSE derived from carcasses and associated wastes in municipal solid waste (MSW) landfills. Column experiments were conducted to evaluate PrP^TSE transport in quartz sand, two fine-textured burial soils currently used in landfill practice, a green waste residual material (a potential burial material), and fresh and aged MSW. PrP^TSE was retained by quartz sand and the fine-textured burial soils, with no detectable PrP^TSE eluted over more than 40 pore volumes. In contrast, PrP^TSE was more mobile in MSW and green waste residual. Transport parameters were estimated from the experimental data and used to model PrP^TSE migration in a MSW landfill. To the extent that the PrP^TSE used mimics that released from decomposing carcasses and the column experiments adequately simulate prion transport through burial soils, burial of CWD-infected materials at MSW landfills could provide secure containment of PrP^TSE provided reasonable burial strategies (e.g., encasement in fine-grained soil) are used.