CWD expert vouches for safety of venison Dennis Anderson Star Tribune Published Sep 13, 2002
Dr. Elizabeth Williams of the Wyoming Veterinary Laboratory in Laramie, Wyo., has studied chronic wasting disease in deer and elk since 1977. A recognized authority on the disease, Williams, in the interview below, discusses, among other aspects of the disease, theories on how CWD is transmitted. She also advises Minnesota deer hunters afield this fall to “enjoy their hunt” and, as she does herself, to eat venison.
Q: Chronic wasting disease was first found in 1967 in Colorado at a government testing facility. Was there panic at that time among hunters and the public?
A: No, it was just another oddball disease. There was no reason to be that concerned, except to the degree that it had an impact on the animals that were being studied for other purposes. Certainly there was no sense of alarm. Frankly, until the cases were found in Wisconsin recently, and news of CWD there hit the media, most people were taking the disease in stride. People have gotten much more concerned about it since then, and interest has heightened.
Q: How do you think CWD found its way to Wisconsin?
A: I don’t know. It will take more work to get a better idea about that. How wide the distribution is in wild deer in Wisconsin will be important to know. What’s happening in the captive cervid industry in the state will also be important to know. Even then, I’m not sure we’ll ever know.
There are multiple ways the disease could have traveled. One is the captive cervid industry. Another, theoretically, at least, involves the transportation of carcasses by hunters from outside the state. One of the origins also could be scrapie, which is a disease in goats and sheep. That hasn’t been proven, but it’s possible. One other idea is that the disease simply occurs spontaneously.
Q: What is the possibility that CWD has always been around?
A: We’ll have a much better idea after Wisconsin and other states, including Minnesota, test a lot of deer, as they plan to this fall. Don’t forget, if it is present at a very, very low level in wild herds, predators, including coyotes, usually are pretty good at cleaning up sick animals. So without testing of a lot of animals, it might otherwise be difficult to detect.
Q: How sure are you that CWD can’t infect humans?
A: The term “species barrier” describes the level of resistance that exists to transmitting a disease from one species to another. I’m a veterinarian, and I rely on the information about these barriers that is given to me by the Center for Disease Control. I also refer to laboratories that develop models using species that have certain things in common with human genetics.
So far, the models indicate that there is quite a barrier blocking this type of transmission. At this point in time, no human link has been found to CWD.
Obviously, there are some unknowns, so you take precautions to minimize risk. You don’t eat sick animals, for instance.
Q: CWD tests are performed, or will be performed, for hunters this fall in Colorado and Wyoming.
A: Yes. Here at our lab, we use a test that has long been recognized as reliable and verifiable. In Colorado this fall, they will be using a new test. It’s a good test, developed in France. The problem is that this test hasn’t yet been validated for CWD, and as a diagnostic person, I like to use tests that are validated. At our lab, we test about 1,000 animals a year, including those from the public. We’ve been testing for about five years, but obviously at only 1,000 animals there hasn’t been a huge demand for it. We charge $25.
Q: Do you typically find many positive CWD cases in wild deer and elk submitted to you?
A: Yes. It runs around 6 to 7 percent. These are animals that are positive for CWD but are not clinically ill.
Q: By “clinical” you mean the animal is showing symptoms of behavior changes.
A: Yes. And if an animal is symptomatic, it means the disease has been there a while. A minimum incubation period is 17 to 18 months. In fact, for an elk, that would be quick. More likely would be three to five years. Once they show symptoms, they can be sick for a few weeks or up to a year before they die.
Q: Are moose and caribou susceptible?
A: As far as we know they’re not naturally susceptible.
Q: Are mule deer and whitetails equally vulnerable to CWD?
A: They’re very similar. My guess is we won’t see a lot of difference in them. It might be that whitetails are more susceptible. But that’s only a gut feeling of mine.
Q: What role, if any, has the domestic elk industry had in the spreading of CWD?
A: We know that domestic elk are, or have been, moved in commerce, from place to place, on trucks. So they make larger geographic jumps than would otherwise be the case. We also know the disease was transferred from a domestic elk herd in South Dakota to a domestic herd in Saskatchewan.
Q: Minnesota and Wisconsin hunters and their families seem to be quite concerned about CWD and its potential ill effects on their health, this despite what officials have said about CWD being a deer and elk disease, not a human disease. What’s your advice to people in the Midwest as the fall hunting seasons begin?
A: Enjoy your hunt. If you see a skinny animal, contact authorities. Otherwise, enjoy your hunt and enjoy your venison. I say that as a hunter myself. I enjoy venison a lot. I’m not about to stop hunting deer or eating venison.
Q: But some people worry that CWD will prove to be similar to mad cow disease, in which it was found in livestock quite a while before it was diagnosed in people.
A: Mad cow was diagnosed in livestock in 1986, and they first recognized cases in humans in 1996. So a 10-year span separated the two. But the situation with CWD is quite different. Obviously, the number of people exposed to CWD would, even theoretically, be a lot less than the people in England who ate beef. So they aren’t directly comparable.
Additionally, public health people in Colorado and Wyoming have studied health records in the two states for any unusual numbers of neurological diseases over the years, but there haven’t been any, either in the public at large or among hunters.
— Dennis Anderson is at [email protected]
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