CWD may never be eradicated from farms or wild

[Oak]

Deer disease lingers in environment, study says
Chronic wasting spread from pen, carcass after 2 years
By JOHN FAUBER
Posted: May 6, 2004

New research showing that chronic wasting disease can be transmitted through soil and from decomposed carcasses of infected deer suggests that the effort to eradicate the disease in Wisconsin may be much more difficult than once thought.

Previously, research showed that the disease could be transmitted by animal-to-animal contact.

Ever since the deadly brain disorder first appeared in Wisconsin in 2002, wildlife officials had feared that the infectious agent that causes the disease could linger in the environment.

Now there is evidence showing that the disease can persist for at least two years.

"This is an important piece, this study," said Julie Langenberg, a wildlife veterinarian with the Wisconsin Department of Natural Resources. "It verifies a concern that we have had since we started working with chronic wasting disease."

The study, which appears in the online edition of the journal Emerging Infectious Diseases, involved three types of experimental enclosures that were designed to simulate at least some of the conditions found in the wild.

One set of paddocks housed mule deer that once had been infected with chronic wasting disease, but the areas had been kept empty for about two years. Residual excrement from the sick deer remained in the enclosures.

In other types of paddocks, carcasses of infected deer had been allowed to decompose in place for nearly two years.

The researchers then brought in mule deer that were believed to be disease-free and confined them to the enclosures.

In both types of enclosures, one or more of the reintroduced healthy deer became infected within a year.

In a third type of enclosure, infected deer were kept with uninfected deer. That too resulted in the spread of the disease.

The authors of the study acknowledge that confining the deer to an area may have exaggerated the likelihood of transmission.

However, "This kind of thing could happen in the wild," said co-author Beth Williams, the researcher who in 1977 first identified chronic wasting disease as an infectious brain illness in deer.

The research reinforces the idea of prohibiting baiting and feeding in areas where the disease exists, Williams said.

In addition, she said, the research also raises concerns about efforts to eradicate chronic wasting disease.

"If all the deer are removed, there may be residual infectivity," she said. "It may be difficult to get rid of CWD."

Still, Williams said she believes the effort by the Wisconsin DNR to eradicate the disease is worthwhile.

Using hunters and sharpshooters, the DNR wants to kill as many deer in areas where animals have tested positive for the disease as possible, as well as create buffer zones around those areas.

In the eradication zones surrounding hot spots where numerous chronic wasting disease cases have been found, the DNR hopes to reduce the deer population to fewer than five animals per square mile. In the larger intensive harvest zones, the goal is 10 to 15 deer per square mile.

Judd Aiken, a professor of animal health and biomedical sciences at the University of Wisconsin-Madison, said he believes that by reducing the number of infected animals in the wild, the state stands a better chance of someday eliminating the disease.

The study is the best research to date showing how the disease can be spread in the environment, he said. What it does not show, he said, is what type of excrement carries the disease and how long the infectivity lasts in the environment.

"I don't think I would conclude that it will be permanently in the environment," he said.

Langenberg, of the DNR, said she believes the study reinforces the idea of quickly culling diseased animals from the herd.

"I still think what the state is doing makes sense," she said. "We still have a chance to control and possibly eliminate the disease. We are making the choice to act and not wait."

 

[Oak]

Study links environment with CWD transmission
By Rob Gebhart

Friday, May 7, 2004

New research on chronic wasting disease has proven the disease can be transmitted through environments contaminated by carcasses or excrement of animals infected with the illness.

The report, released by a team of Colorado and Wyoming researchers, proves what the Colorado Division of Wildlife has long suspected, said, DOW spokesman Todd Malmsbury.

"We had long assumed it could be spread through environmental contamination," Malmsbury said.

The discovery shouldn't significantly impact the DOW's chronic wasting disease management strategy, he said.

Chronic wasting disease is a fatal neurological ailment of elk, white-tailed deer and mule deer.

Because the research was conducted through a controlled study, Malmsbury said there is some question as to how the results would play out in the natural habitat of elk and mule deer.

In the wild, elk and deer won't remain in close contact with dead members of their species. Nor would they likely live in one another's excrement.

But in a captive setting, animals could find themselves living in both settings. Many chronic wasting disease outbreaks have occurred where animals live in confined quarters, Malmsbury said.

"This underscores why we don't want people to artificially feed elk or deer," he said.

Artificial feeding encourages animals to continually congregate in the same location, increasing the chances of contracting the disease through contamination of the environment

Previous disease models have been based on animal-to-animal contact as the sole source of infection, said Tom Hobbs, a researcher with Colorado State University's Natural Resource Ecology Laboratory.

That model indicated that the prevalence of chronic wasting disease would decline as infected animals died and their population was reduced. The new findings mean infection rates could decline much slower than expected, Hobbs said.

Researchers confined healthy deer in three sets of separate paddocks. In the first set, healthy deer were exposed to another deer already infected with chronic wasting disease. In the second set, deer were exposed to carcasses of deer that had died of chronic wasting disease. In the third set, deer were confined to paddocks where infected deer previously had been kept.

"Although confinement likely exaggerated transmission probabilities, the conditions we simulated in this experiment do arise in the wild," said Michael Miller, a veterinarian researching the disease.

 

[Tom]

Oak, why don't you do a study where you have a paddock where the carcasses are burned?

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The study, which appears in the online edition of the journal Emerging Infectious Diseases, involved three types of experimental enclosures that were designed to simulate at least some of the conditions found in the wild.

One set of paddocks housed mule deer that once had been infected with chronic wasting disease, but the areas had been kept empty for about two years. Residual excrement from the sick deer remained in the enclosures.

In other types of paddocks, carcasses of infected deer had been allowed to decompose in place for nearly two years.
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We have anthrax in the ground down here, and under certain conditions it comes back up and people and animals can get anthrax poisoning.

They quarantine the ranch, animals and people, go in and burn up all the carcases and treat the people. That apparantly controls it, whenever it comes up. People were burning carcases of elk a few years ago, I wonder if they showed that that works ever for CWD? Is it spreading more slowly as a function of the number burnt in an area, or something like that?

This study, you found and posted, showed letting them naturally decay, doesn't work, basically, as well as, the other two paddock ways of spreading. Thanks for the info.