Infectious Prions in Wastewater Treatment Plants Studied

MADISON, Wisconsin, May 20, 2004 (ENS) - Infectious prion proteins - the cause of mad cow disease and chronic wasting disease - can be considered an environmental contaminant if they enter wastewater treatment plants, but the consequences of prions in wastewater is presently not known.

To find out, the U.S. Environmental Protection Agency (EPA) is funding a study of what occurs in treatment plants receiving water from slaughterhouses or rendering facilities, as well as in septic tanks used by householders who dress deer and potentially wash infected tissue down the drain.

University of Wisconsin-Madison researchers announced on Wednesday that they have been awarded nearly $100,000 in EPA funding to investigate what happens to infectious prion proteins in wastewater treatment plants.

UW-Madison scientists Judd Aiken and Joel Pedersen, who are currently investigating the fate of prion proteins in soil and landfills, will be joined on the research project by Katherine McMahon and Craig Benson, both faculty members in civil and environmental engineering. The team will examine the ability of the 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, she points out, prion proteins generally are very resistant to degradation.

"Prion proteins can be viewed as an environmental contaminant," says McMahon, but 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, the team will try to find out 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.

"The EPA 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," said McMahon.