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Mad Deer Disease (video)
July 19, 2002

Interviewee: Scott Wright, United States Geological Survey.

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Produced by Sanjanthi Velu


Copyright ScienCentral, Inc., with additional footage from Wisconsin Department of Natural Resources and ABC

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Elsewhere on the web

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USDA CWD page


Hunters are again taking to the woods in Wisconsin this weekend. Their goal is to kill 25,000 deer by the end of January.

Experts say mass-killing may be the only way to stop a deadly brain disease affecting deer and elk. It has struck nine states and as we speak could be moving to others.

This ScienCentral News video gives us the latest on this and whether it could affect humans.


Mad Deer FAQ

What’s the cause?

Although the exact cause of Chronic Wasting Disease (CWD) is not known, it has certain similarities to Mad Cow Disease in cattle, also known as Bovine Spongiform Encephalopathy (BSE). It is also similar to Scrapie Disease in sheep, and new-variant Creutzfeldt-Jakob Disease in humans. Scott Wright, Branch Chief for Disease Investigations at the US Geological Survey National Wildlife Health Center in Madison, Wisconsin, explains that these diseases are similar for at least two reasons. The first is that "they are called Transmissible Spongiform Encyphalopathy, which is a real fancy way of saying that these diseases cause lesions in the brain that are very characteristic." Second is that they all have "a normal protein that has become abnormal." This protein, called a prion, mutates and makes adjacent proteins do the same thing. However, they do not know what causes this to happen in the first place. The diseases are characterized by loss of motor control, dementia, paralysis, wasting, and eventually death.

How does it spread?

There are several theories on the transmission or spread of CWD in wild herds and captive animals. The most common theory, according to Wright, is that "it is spread by animal contact primarily through contact with animal excreta." He pointed to other possibilities as well. As the prion proteins are hardy and they are very difficult to get rid of, "there is a possibility that the prions may persist in the soil." But again, even the experts don’t have all the answers. Researchers want to know how these animals come in contact with the prion if it is in the soil.

Is mass-killing the best solution?

Since there are more questions than answers on the cause and spread, there is a lot of debate and disagreement about how to stop the disease. Opponents of the mass eradication method say more time and research is needed to understand the issues. Even Wright admits that mass eradication is not a proven strategy in stopping the disease from moving. "But in the face of doing nothing or doing something less, it seems to be the most logical thing to do," he says. He warned that something must be done quickly because "the population doesn’t sit still; the population expands, it grows." And the more animals we have the harder it will be to deal with.

According to Wright, any kind of research will take years since it takes several years for the animal to present any kind of evidence of the disease. Meanwhile they could be spreading it to others. So the eradication method seems to be the most practical at this time. "We are using the broad brush approach because we really don’t have any alternatives," Wright explains. "However, as we learn more we may be able to focus on individuals in the population and therefore eradicate the disease without having to remove larger numbers."

How do they test for the disease?

In the case of white-tailed deer and mule deer, the lymphoid tissue including the tonsil tissue can be tested for the disease. However in the case of elk, lymphoid tissue does not seem to contain the prions. The only reliable tissue to test in the case of elk is brain tissue. The current tests employed are accurate and fast. But since there is a huge backlog of samples to be tested there are considerable delays in getting the results. Other tests are under development.

How do they safely dispose of the dead deer?

There is additional concern for how to dispose of the dead deer carcasses. The prion proteins are hardy and difficult to get rid of, and it takes extremely high temperatures to destroy them. Initially the dead deer were incinerated, but this is an expensive process and the state wants a less costly solution. The Department of Natural Resources has requested proposals and bids on how to dispose of the deer. One option is to bury them in specially lined landfills. But there is a possibility that the prions may persist in the soil and there is public concern that prions could escape when liquid leaches from buried waste.

Is CWD dangerous to humans?

At the present time there is no documentation of humans getting the disease from the consumption of contaminated venison. However scientists are still concerned. Part of the problem with understanding CWD and its related diseases is that these are long-term diseases. It takes years for the animal to present any symptoms. It may also take years for human patients to exhibit any symptoms of the disease. "Because we haven’t seen something right now does not necessarily mean that there isn’t a problem," cautions Wright. "It means that we’re not aware of it yet."

What precautions should we take?

  • Do not consume any kind of organs.
  • Do not consume any kind of lymphoid tissue.
  • Remove the bone from the meat, but do not cut into the bone, because you would be accessing lymphoid tissue in the form of bone marrow.
  • If you know that the deer has tested positive for CWD, do not consume the carcass at all.

Is there a federal plan?

The detection of the disease in new portions of the country has alarmed the government. The Department of the Interior and the Department of Agriculture, at the direction of the President, have formed a CWD Task Force. The task force has met over the last several weeks and has identified a number of working groups. Delegates from around the country have participated in identifying and developing a task force plan. This plan is being put before Congress in order to develop a way to help states deal with CWD in the future.



by Sanjanthi Velu


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