MADISON -- The rogue proteins that cause chronic wasting disease (CWD) exhibit a dramatic increase in their infectious nature when bound to common soil particles, according to a new study.

Writing in the journal Public Library of Science (PLoS) Pathogens, a group led by University of Wisconsin-Madison prion expert Judd Aiken reports that prions, the protein agents of a family of fatal brain disorders, bind tightly to a common soil mineral and significantly increase the oral transmissibility of the agent.

The finding is important because it may help explain how chronic wasting disease and scrapie persist in the environment and spread efficiently in animal populations.

"We found a huge difference between infectious agent alone and infectious agent bound to these soil particles," says Aiken, the senior author of the new study and a professor of comparative biosciences in the UW-Madison School of Veterinary Medicine. "We observed an almost 700-fold difference" in the rate of infection.

Prions are an abnormal form of a protein produced normally by the body. Tough as nails, they can persist in the environment for long periods of time and retain their infectious capabilities. It is believed that prions may persist in the soil around the carcasses of dead animals and other locations where infected animals shed the protein in body fluids.

"These disease agents can stay out there for years and stay infectious," Aiken explains.

And herbivores such as deer and sheep, which are susceptible to prion infection, tend to consume a fair amount of dirt daily as they graze and forage. They are also known to consume soil as a source of minerals. Mineral licks are frequented by many animals, raising the prospect that the agents may become concentrated in the soil.

Relatively little is known about the routes of prion transmission in animals, but the new Wisconsin study may help to resolve one puzzle: Oral transmissio
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Contact: Judd Aiken
jma@svm.vetmed.wisc.edu
608-262-7362
University of Wisconsin-Madison
5-Jul-2007