Researchers to study fate of prions in wastewater

May 19, 2004

With funding from the U.S. Environmental Protection Agency, a group of UW-Madison researchers will investigate what happens if infectious prion proteins - considered the cause of chronic wasting disease and mad cow disease - enter wastewater treatment plants.

Joining UW-Madison scientists Judd Aiken and Joel Pedersen currently investigating the fate of prion proteins in soil and landfills, Katherine (Trina) McMahon and Craig Benson, both faculty members in civil and environmental engineering, will examine the ability of these infectious proteins to withstand the processes used to treat wastewater.

At most treatment plants, microorganisms decompose biodegradable material in the sewage and, in theory, should also disintegrate infectious proteins, says McMahon. But as she points out, prion proteins generally are very resistant to degradation.

"Prion proteins can be viewed as an environmental contaminant," says McMahon, adding that it currently is not known how long these proteins can remain intact and infectious in the environment.

"Prions have not been detected in wastewater entering treatment plants, but we can imagine several scenarios in which we may need to be concerned about the presence of prions in wastewater," she says.

During this one-year project, which is supported with a grant of nearly $100,000, McMahon and her co-investigators will focus on several questions, including what percentage of these proteins would be degraded during treatment and what percentage would be released back into the environment in treated water. If prions are released, the researchers will determine if the proteins remain infectious.

McMahon says answers to these questions will be of particular interest to the engineers of treatment plants receiving water from slaughterhouses or rendering facilities, as well as septic tank owners who dress deer and potentially wash infected tissue down the drain.

"The EPA," adds McMahon, "would like to know what the fate of prions would be in wastewater treatment plants to determine if they need to ensure that prions are excluded from waste streams entering these facilities."