CWD and the prion connection – 11/02/2005

  • November 22, 2013 at 3:39 am #1075

    from bridget
    In the search for answers about chronic wasting disease, hunters can

    Keeping tabs on a mysterious disease.
    By Cara Eastwood
    Published in the Wyoming Tribune-Eagle

    LARAMIE – With a razor-sharp scalpel clasped between her blue-gloved
    fingers, lab technician Linda Cope carefully slices tiny pieces off
    a lump of flesh that sits on a plastic cutting board.
    Cope adds the sections to a small pile on a digital scale and
    watches the weight creep up to 25 milligrams.

    Once at the correct weight, she chops the small tissue pieces into
    even smaller 2 millimeter cubes and then scoops the bits of flesh
    into a vial containing water and tiny white porcelain beads.
    When placed into a machine and spun at high speeds, the beads break
    the flesh apart and help it dissolve into the water.

    Then the technician removes the liquefied tissue from the vial and
    puts it through several more steps to determine one question: Was
    the animal infected with chronic wasting disease?
    The fatal central nervous system disease found in mule deer, white-
    tailed deer and Rocky Mountain elk causes the animals to lose body
    control, exhibit odd behavior, increase drinking and urinating and,
    eventually, to die.

    The disease is not believed to be a danger to humans and has not yet
    shown up in the meat of infected animals.

    But the World Health Organization recommends not eating animals
    infected with the illness, said Michelle Zitek, Wyoming Game and
    Fish public information specialist.

    In 1997 the Game and Fish Laboratory in Laramie began testing hunter-
    harvested animals to gauge the extent of the disease in the state
    and to let hunters know if their animals were infected. Since then,
    the studies have continued annually.

    With this year’s hunting season now in full swing, Cope and her
    colleague Jessica Jennings are swamped with samples from hunter-
    harvested animals from throughout the state.

    Hank Edwards, wildlife disease specialist responsible for the
    testing and mapping of chronic wasting disease data, says that by
    the end of the season he and his staff will have tested more than
    4,000 lymph nodes from mule deer, elk and whitetails.

    The data will take months to analyze, he said, and any conclusions
    about the status of the disease won’t be drawn almost until next
    hunting season.

    But with such a baffling disease, collecting any data at all helps
    wildlife officials begin to understand it.
    With their quick, reliable and sensitive Elisa test, lab staff gives
    answers to hunters within only a few weeks – much faster than the
    previous testing method.

    But the disease’s mysterious origin makes it difficult to draw
    conclusions about how fast it is spreading, Edwards said.
    “It’s hard to say if we started seeing (chronic wasting disease)
    because we started looking or because it was spreading,” he
    said. “It’s probably a combination of both.”

    Finding evidence

    Game and Fish officials craft a strategy each year on how to conduct
    the chronic wasting disease survey, Edwards said.
    “This year we tried to cover the whole state and also concentrate on
    areas where we think the disease already exists in high
    concentrations,” he said.

    The southwestern corner near the Utah border will get special
    attention. So will places where new cases have cropped up – like
    Kaycee and Worland.

    Hunter-harvested animals represent a random selection of deer and
    elk, Edwards said, but the lab also tests road kills and animals
    that Game and Fish staff kills as part of the “targeted
    surveillance” operation.

    If a warden or a wildlife biologist sees an animal that is sick and
    exhibiting symptoms of chronic wasting disease, the animal will be
    killed and tested.

    Hunters who see an animal that might be exhibiting signs of the
    disease should contact the Game and Fish, Edwards said. There are
    many diseases that look similar but are not chronic wasting disease,
    he added.

    Before the start of hunting season, lab staff assembled about 6,000
    chronic wasting disease test kits containing head tags and small
    sample containers. These went out to Game and Fish staff and meat
    processors throughout Wyoming.

    On the tag, hunters are asked to give specific information about
    where the animal was killed. This is critical once the statewide
    results come in and Edwards and his staff plot location points.
    “Mostly we get ranches,” Edwards said, but that’s not specific

    At check stations around the state, Game and Fish biologists give
    hunters the option to take part in the free testing program. They
    remove the lymph nodes of hunter-killed animals and label them with
    sample and hunter numbers

    Edwards said the goal is to get between 4,000 and 5,000 samples,
    giving a good cross-section of the statewide deer and elk

    Chronic wasting disease is a member of a group of diseases called
    transmissible spongiform encephalopathies that are caused by
    abnormal proteins, or “prions,” that attack the animals’ brains.
    Even though scientists have yet to determine how the disease is
    transmitted, they know that prions will appear in an animal’s lymph
    nodes long before it starts to show the symptoms of chronic wasting

    To increase the likelihood of finding prions, lab staff dissects the
    lymph nodes into three sections after separating the tissue from any
    skin or hair.

    “In an early positive, the prions are randomly distributed in the
    lymph node,” Edwards said. “As it gets to be a stronger positive, it
    doesn’t make a hoot of difference where the sample comes from: The
    prions are everywhere.”

    On average, Edwards said, it takes about five hours to process one
    sample and to determine a positive or negative result. With the
    volume of samples coming through the lab, results take about four to
    six weeks to appear on the Game and Fish Web site, he added.
    “It’s all we can do to keep up with everything else we do here,” he

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