Proof Mad Cow Prions Stick To, Remain In Certain Soils
University of Wisconsin-Madison
Dirt may help scientists answer a question that has baffled them for decades: How does chronic wasting disease (CWD) in deer and elk spread from animal to animal?
By turning to the land, University of Wisconsin-Madison researchers show that prions - infectious proteins considered to be at the root of the disease - literally stick to some soil types, suggesting that the landscape may serve as an environmental reservoir for the disease.
The findings will be discussed during a poster presentation on Wednesday, Sept. 10, in New York City at the 226th national meeting of the American Chemical Society.
Extraordinarily resistant to a range of environmental conditions and decontamination measures, prions are abnormally folded proteins that can make an animal,s brain as holey as a sponge. They,ve been implicated as the cause of diseases such as mad cow and scrapie in sheep.
Once infected, deer and elk, for example, experience a number of neurological and behavioral problems - staggering, shaking and excessive salivation, thirst and urination - until they waste away, many times dying in fields or woods. The disease is always fatal, and, to date, there is no cure.
Even though chronic wasting disease was first detected in free-ranging deer and elk in Colorado and Wyoming during the mid-1980s, it received a charge in scientific and public interest in February 2002, when the first evidence of the disease in Wisconsin appeared.
"The route by which CWD is transmitted from animal to animal is not understood," says Joel Pedersen, an environmental chemist and lead investigator on the soil study. "Strong circumstantial evidence suggests an environmental reservoir exists." Reports show, for instance, that healthy elk placed in pens where animals infected with CWD had once lived developed the fatal disease.
With funding from a recently awarded five-year, $2.4 million grant from the Department of Defense,s National Prion Research Program, Pedersen and his colleagues are examining the ability of the infectious agent to associate with or be absorbed by certain soil particles.
"Soil is a candidate [as an environmental reservoir] because grazing animals ingest it both inadvertently, as part of feeding, and on purpose, as part of certain deer behaviors," explains Pedersen.
To begin to understand how the disease stays in the environment, Pedersen and his colleagues turned to sand and clay - common components found in soils. Because of differences in surface area and mineral composition, Pedersen says sand and clay represent different ends of the spectrum in the ability to absorb proteins.
From the study,s results, the capacity of sand and clay to take up abnormally folded proteins, says the lead researcher, "differs dramatically."
Pedersen and his colleagues determined this by taking samples of sand and clay and adding infectious prions taken from hamsters, as well as a water-based solution representing one found naturally in soils. After removing the water and doing further analysis, they noticed that many of the prions in the sand mixture remained in the water solution, whereas those in the clay mixture stuck to the particles, surface.
"Almost all the prions in the clay mixture associated with the clay, not the water," says Pedersen, adding that this finding suggests that the movement of prions through the landscape depends on the soil environment.
Understanding how the infectious agent moves - or, in the case of soils with high clay concentrations, stays put - could lead to new information on disease transmission or techniques for managing CWD. For instance, Pedersen says, "If we decide to bury infected carcasses, a clay liner underneath the landfill may be a good idea."
But while clay soils may work to contain infection, they may also help spread it. Whereas prions in sandy soils either may wash away or travel deeper into the ground, says Pedersen, those in clay soils may remain near the surface. "Because the material may be more available for ingestion by animals," he explains, "the rate of infection may be greater."
Analyzing the absorption capacity of sand and clay is just the first step, says Pedersen. In addition to quantifying the ability of prions to bind to these two soil components, they,ll consider other soil materials, additional soil minerals and organic matter. Also under way are studies to determine the degree to which prions in different soil types remain infectious.
"What we,ll be getting at is if prions are more likely to persist in some environments," says Pedersen, adding that results from all these studies will help natural resource managers and other experts perform risk assessments for the spread of CWD and similar diseases across the landscape. "Understanding the role of soil in the spread of CWD is critical in designing and implementing effective disease strategies."
Can Mad Cow/CWD Prions Get Into The Water? - Yes
From Patricia Doyle, PhD
Note - As we know, the Brits killed and buried millions of cattle... and some of them had mad cow. As these bodies decompose, prions will enter the groundwater. But, even more amazing, is the use of cow bones in some UK municipal water filters! -ed
Researchers To Study Fate Of Prions In Wastewater
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."
More Madness Over Cow bones In English Water Filters
By Dirk Beveridge
The Associated Press
After stirring up a ruckus with vegetarians by filtering water through charcoaled cattle bones, an English utility said Tuesday it's looking for less controversial ways to keep the supply clean. Yorkshire Water PLC said it would "continue to consult closely" with the vegetarians, while assuring the handful of affected rural customers that their water is safe.
"There is a whole vast array of treatment processes that are available," Yorkshire Water spokesman Richard Sears said. "All are not suitable for every water treatment plant."
Before the Vegetarian Society started complaining, the charcoal cow filters seemed perfect for remote areas of the Yorkshire moors, where water is frequently discolored by peaty minerals after a heavy rainfall. Yorkshire Water's filters are made from the brittle bones of sacred Indian cattle that live to an old age because of religious custom. Yorkshire Water has always said none of the infamous British "mad cows" were ever carbonized into the charcoal.
The utility said Tuesday that no good alternatives had immediately been found for the 11 small filtration plants that use the cow bones, but that it's still investigating -- without making any promises.
"We've got through the first hurdle," enthused Chris Dessent, a spokesman at the Vegetarian Society. "Yorkshire Water is admitting there is a problem."
The dispute gained new momentum in December when Yorkshire Water complained to advertising regulators about a one-time newspaper advertisement taken out by the vegetarian group showing a dead cow by a water well.
"In some parts of the world, dead cows can end up in the drinking water," the headline read. "In some parts of Yorkshire, they're put there."The message continued: "If you're a vegetarian, or wish to avoid meat, you'd think you'd be safe with a glass of ordinary tap water. Not in North Yorkshire."
Just 2,868 of Yorkshire Water's 4.5 million customers are affected. But it was an emotive appeal in a land where 6 percent of the 58 million residents are believed to be vegetarian and animal rights are a significant political issue.
The Advertising Standards Authority planned to issue a ruling Wednesday siding with Yorkshire Water on two out of three counts.The ruling, which carries no sanctions, finds the ad "offensive and distressing because of the gratuitous use of the headline and the photograph," and also "unfairly denigratory to Yorkshire Water.
"Despite that, the ad was not "misleading and irresponsible," as Yorkshire Water had contended, the ruling says. After the charcoaled cows made news last summer, Yorkshire Water had said it could not cater to the "individual dietary needs or individual religious, ethical or medical needs" of all customers.
(First published 4-8-98)
EPA Concern Over CJD Prions Entering The Water Supply
By Todd Hartman
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The EPA is scrutinizing laboratory practices at the Colorado Division of Wildlife, worried that the infectious agents believed to cause chronic wasting disease could wash into public sewers and underground septic tanks.
Water regulators with the Environmental Protection Agency could require wildlife officials to alter plumbing at division laboratories in Fort Collins, Craig and elsewhere to ensure that the persistent protein - called a prion - doesn't accumulate in water supplies.
"The concern is that there's so little known about the prions, that we think we ought to be taking a relatively protective, conservative approach to things," said Steve Tuber, director of water programs for EPA's regional office in Denver. "We're just being careful." For the moment, the agencies are exchanging proposals on how to handle the matter. At the root of the problem: How to ensure tiny bits of tissue, or other possibly contaminated fluids or animal hair, don't make it through floor drains when laboratory areas are washed down.
The EPA hasn't been a visible player in the CWD problem - a fatal brain malady in deer and elk - until now.
The federal agency's timing could make things tough for the Division of Wildlife, as it gears up for a fall hunting season in which state workers are prepared to conduct up to 50,000 analyses on deer and elk heads to test for the presence of the disease.
"At this point, we're still in operation (for testing). We intend to be - we hope to be - all the way through hunting season," said John Smeltzer, a division supervisor. "If we need to modify our processes, we will do so."
With archery season under way for nearly a week and some rifle hunting allowed on private lands, about 100 heads - most of them elk - have been submitted to the state for CWD testing, said Division of Wildlife spokesman Todd Malmsbury.
Neither agency could say what the ultimate solution will be. The EPA has recommended a number of possibilities, including the use of absorbent paper on lab benches to soak up blood or other fluids. The division has pledged to come back with some ideas of its own, Tuber said.
Prions pose the same problem as some toxic and radioactive contaminants: They appear to have a long life and survive in the environment for at least a few years. Researchers have found that animals placed in long-empty pens once home to infected animals can acquire the disease, presumably because the prions remain viable in the soil.
In addition, prions are hard to destroy, resistant to extreme heat - up to 1,100 degrees - sunlight and many disinfectants. Agencies responsible for containing the spread of CWD have often incinerated deer and elk carcasses at very high temperature to ensure destruction of the prion.
There are no known cases of a human developing CWD. Nevertheless, scientists urge people to avoid eating meat from infected animals. A related ailment, mad cow disease, which strikes cattle, has made the leap into humans, killing more than 120 people overseas.
Tuber emphasized that the Division of Wildlife isn't disposing contaminated animal tissue "in any intentional way," but that the EPA is concerned with residue left behind. "They are taking precautions; we've asked them to take additional ones," Tuber said.
Of most immediate concern is a special EPA permit needed for a Fort Collins laboratory where parts of the brain, tonsils and lymph nodes are removed from deer and elk heads. When the lab is washed down, the rinse water flows to an underground septic tank. Under the law, the lab is considered an industrial discharger and is operating under temporary permission. But the EPA wants more steps taken before issuing a permit.
It will be several more weeks, after more detailed talks between EPA and Division of Wildlife scientists, before the agency will decide whether to grant a permit, Tuber said.
He said the EPA wanted to avoid interfering in the division's testing program.
"We want to give them an opportunity to keep that protection in place, and at the same time be protective of groundwater," Tuber said.
Also of concern is the division's laboratory in Craig, where rinse water is sent to a public wastewater treatment plant. The solution there could involve pre-treatment of some kind before the discharge can be released into the sewers, Tuber said.
Smeltzer said the division will work with the EPA, but believes it takes significant precautions already. He notes that very small amounts of tissue are handled in the labs - the brain samples extracted are about the size of two grains of rice, he said - and that workers frequently spray down work areas with a disinfectant known to be effective in neutralizing prions.
Tuber said the EPA also needs to look at processing plants, where deer and elk are carcasses are prepared. "It's something that we're just starting to get to," he said. (First published 9-6-2)
Patricia A. Doyle, PhD
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