CWD in Wyoming – 12/21/2005

  • November 23, 2013 at 12:05 am #1099

    How big is the threat?
    Star-Tribune environmental reporter

    Casper, Wyoming – Monday, December 19, 2005

    JACKSON — People interested in the future of elk herds in northwest Wyoming understandably have an interest in the movement of chronic wasting disease. But just how threatening is the disease to those elk herds?

    The answer is unclear.

    Will chronic wasting move to northwest Wyoming? Probably, and it’s possible it is already in the environment here. But its impact on elk populations is the subject of ongoing research, and figuring out how to protect elk is difficult without concrete answers.

    Terry Kreeger, wildlife veterinarian with the Wyoming Game and Fish Department, said the agency has several ongoing studies on chronic wasting and its effects on elk that spend time on feedgrounds. But more years of research are needed to make any conclusions about the disease.
    “The question is, ‘Are we premature to apply that (existing) information to a feedground situation?'” Kreeger said. “It’s fair to say (we’re) concerned about it.”

    But Tom Roffe, an infectious disease expert with the U.S. Fish and Wildlife Service, said enough is known about chronic wasting to realize the disease will indeed spread to northwest Wyoming, and will have a “significant impact” on elk herds. How significant the threat is unclear.

    Roffe said the question is not necessarily whether to dismantle feedgrounds, which are known to increase disease transmission. “A better question is, should we manage in a way that balances ungulate populations with the available habitat with the ecosystem, and have whatever consequences we have there for CWD, or, should we continue with the paradigm of feeding and (accept) whatever consequences that has with CWD?”

    In November, two deer west of Thermopolis tested positive for chronic wasting, raising concerns about the spread of the disease. It has been found in northern Colorado and southeastern Wyoming.

    Chronic wasting is a fatal brain disease that can affect all members of Wyoming’s deer family.

    Many who advocate closing state-run feedgrounds in the northwest cite chronic wasting threats as a main reason to pursue an end to the elk feeding program. The disease is transmitted more readily among concentrated animals.

    Others argue elk are herd animals, and chronic wasting will spread to wild animals with or without feedgrounds, and the feeding is necessary to support robust elk herds.

    Mike Miller, senior wildlife veterinarian for the Colorado Division of Wildlife, said in an e-mail that based on “current management practices and epidemic patterns, it seems likely that CWD will eventually spread into northwestern Wyoming and the (greater Yellowstone area).”

    He said northwest Wyoming is different than other ecosystems, so it’s difficult to know what will happen with the disease in that part of the state.

    “From what we’ve seen to date, there are few diseases that can completely ‘wipe out’ a wildlife population,” Miller said. “However, if CWD were to become sufficiently prevalent in the (greater Yellowstone area), it could conceivably lower elk abundance and lead to other effects on that system.”

    State research

    There are numerous ongoing studies being conducted in Wyoming that may help researchers better understand the effects of chronic wasting disease.

    One study that may shed light on chronic wasting disease infection is being conducted in Sybille Canyon in southeast Wyoming, studying captive elk exposed to the disease.

    In that study, elk are exposed to chronic wasting that is in the environment. Researchers watch if they contract the disease, how long it takes to get it, what happens when they get it, and how many die.

    The study has been going on three years.

    Another eight-year-long study in wild populations has researchers watching elk herds in the central part of the state where there is chronic wasting surveillance data. But Kreeger said studies on wild populations have other factors like drought that may cast shadows on the research, as it is unclear how much those outside factors may affect animal numbers and the prevalence of disease.

    Yet another study examines elk that have been intentionally infected with the disease.

    The study in Sybille, Kreeger said, would give the department a basis to model what chronic wasting might do in a feedground environment. For example, if elk don’t get the disease until age 6, they could still produce several offspring before dying. If chronic wasting has a 50 percent infection rate, that does not necessarily mean that 50 percent of the herd will die.

    “From a population perspective, you need to look at all those things to see what effect disease has on population parameters,” Kreeger said.

    The real question, Roffe said, is what effect chronic wasting will have on feedground elk herds. Available research suggests a wide probability of chronic wasting disease. While there aren’t models that duplicate feedground conditions, the likely result of the disease on the herds would be somewhere between what happens in the wild — where infection rates have reached up to 9 percent — and on game farms, where infection rates have topped 80 percent. The exact upper threshold on game farm animals is not known because herds are destroyed when the infection rates become so high.

    Elk in northwest Wyoming do not spend the bulk of the year on feedgrounds, so comparing effects of game farms to these herds is not an precise comparison.

    Because the Wyoming study is in the early stages, Kreeger said it may be too soon to draw any conclusions.

    “Should we take the data that’s now only three years old and start suggesting things when we know we’ve got a long way to go?” he said, adding the end of the study — as long as the animals live (about 10 to 12 years) — is the safest time to discuss possible models.

    Effects known?

    Even as Game and Fish wrestles with conclusions, scientists including Roffe say society can’t “stick our heads in the sand and pretend not to know anything about transmissible diseases.”

    “We can predict there is likely to be a significant effect,” he said. Still, he said, it is “hard to sell preventative medicine,” such as eliminating feedgrounds. If the disease does not have dramatic effects after implementing preventive measures, some might say the preventive measure was not needed.

    And without any sound answers to the question of how chronic wasting will affect elk herds, selling any remedy is all the more difficult.

    “There is no research that is going to tell us that,” Roffe said. “The answer is going to come when it hits.”

    Vicky Davis

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