Researchers at UW-Madison have discovered chronic wasting disease may have to be fought not only in the animals that carry it, but also in soil.
Their research has shown that abnormal prion proteins believed to cause CWD in deer and elk stick to certain soil types. After draining water through mixtures of clay and sand laced with prions, they saw that most of the prions washed out of the sand, but stuck to the clay. If the same thing happened in the wild, the prions responsible for CWD could remain in clay-rich soil and infect animals.
Joel Pedersen, a UW-Madison assistant professor of soil science and lead author of the study, presented the findings Wednesday at the 226th annual meeting of the American Chemical Society in New York City.
Scientists believe abnormal prions are also responsible for scrapie in sheep, mad cow disease in bovines and Creutzfeldt-Jakob disease in humans. They attack the nervous system, causing paralysis, shaking and death.
\All mammals have prion proteins,"" said Judd Aiken, co-author and UW-Madison professor of animal health and biomedical sciences. ""The specific sequence varies from species to species.""
When abnormal prions enter an animal's nerve cells, they convert normal prions into abnormal ones. This kills the cells, releasing the abnormal prions into nearby cells and carving out holes in the animal's brain. Prions are highly resistant to treatment and can even survive sterilization, Aiken said.
Deer can ingest dirt for several reasons.
""Bucks lick soil that [female deer] have urinated on to determine whether they are in heat,"" said Pedersen.
This could help explain why CWD is usually passed from does to bucks, according to Nancy Mathews, an associate professor of wildlife ecology who studies deer behavior.
Deer also visit mineral licks looking for salt, she added. If the soil contains infectious prions, there are opportunities for deer to be affected.
The next question Pedersen wants to answer is whether prions trapped in clay are still dangerous.
""We need to determine whether such particle-bound prions retain their infectivity,"" he said.
Further studies, funded by a recent $2.4 million grant from the Department of Defense National Prion Research Program, will involve more varied types of soil, which better simulate the natural environment. Researchers will also attempt to determine how long prions remain in soil.
""The results we presented in New York are initial findings only,"" Pedersen said. ""We have much work to do in order to understand how prions behave in the environment.\
