Composting Inactivates Dangerous Prions

Canadian researchers report that composting animal waste could be a simple, low-cost method for ranchers to dispose of and inactivate infectious prion proteins. The disease-causing proteins are misfolded versions of natural prions that can cause neurodegenerative illnesses when consumed by people and animals. Government regulations in North America and Europe mandate or recommend methods such as incineration for diseased animal remains contaminated with misfolded prions. Tim A. McAllister of Agriculture & Agri-Food Canada and his colleagues tested the ability of composting to break down the recalcitrant prions by building a 100-ton compost pile containing straw and cattle manure and carcasses. They added stainless steel pellets coated with prions responsible for the sheep disease scrapie. After seven months, the team injected proteins from the pellets into the brains of hamsters. Given the number of infected hamsters, the composting reduced prion infectivity by 99.999% compared with a control treatment (Environ. Sci. Technol. 2014, DOI: 10.1021/es500916v). McAllister points out that the normal exposure route—an animal eating contaminated material—transmits the disease much less effectively than introducing prions directly into the brain.