ROCK SPRINGS -- Chronic wasting disease (CWD) has spread throughout the state of Wyoming. Wyoming Game and Fish is tracking the spread and doing new research to understand the health of wildlife herds affected.
CWD has been found everywhere east of the Continental Divide in Wyoming, and there are more reports scattered throughout the western part of the state, according to Game and Fish. Nationwide, the disease has been identified in 24 states.
“Chronic wasting disease is a chronic, fatal disease of the central nervous system in mule deer, white-tailed deer, elk, and moose,” according to the WGF website. “CWD belongs to the group of rare diseases called transmissible spongiform encephalopathies (TSEs). These disorders are caused by abnormally folded proteins called ‘prions.’”
SEARCHING FOR SIGNS AND NEW DEVELOPMENTS
Early on in the disease, animals show little signs of being ill. Later on, however, affected animals will show severe weight loss, be reluctant to move, produce excessive salivation, and experience an increase in drinking and urinating. They eventually become lethargic and die.
Animals who have CWD may not show signs for a long time but can still pass it on to other animals that they come in contact with. It can also be spread through the soil and from waste or carcasses. Soil contamination can last up to a decade.
Wyoming Game and Fish is beginning new research into CWD. In the past, it tested to see if vaccines would be effective against the virus, and sadly that was not the case.
Hank Edwards, research supervisor for the Game and Fish Department said, “The Game and Fish is just starting some research to see what CWD is doing out in the field.”
For example, research in Casper is investigating if mountain lions prey upon more animals with CWD. Other research in Casper is identifying where animals are affected.
“Are there areas where animals revisit like a mineral rock, and are there things we can do to mitigate that?” Edwards asked.
According to a new management plan, Game and Fish is looking to see if hunter harvest can be an effective way to combat CWD, and it wants input in from the public to see if the people are interested in trying.
Research that has been proposed in Laramie could bring more sensitive diagnostics to detect CWD.
“Can we do a better job detecting this in deer?” Edwards asked
TESTING FOR CWD
Testing is very important, because you typically can’t tell by looking at an animal if it has CWD, so proper management and testing is crucial.
Samples from all over the state are sent to Laramie for testing.
Edwards said, “At the Laramie Regional Office there we do have a laboratory there, and that’s where we process tissues as well as enter the data from each of the head tags from their samples.”
They then bring the tissues to the Wyoming State Veterinarian Lab, where they test for CWD in animal lymph nodes.
CWD testing is a very in-depth process. Prions are incredibly tough; they can live a long time in the environment. A prion is a changed protein that causes CWD.
“The problem is the body can’t get rid of it” Edwards said, “eventually it starts to kill cells.”
Game and Fish use a Bio-Rad ELISA test to look for positive prions. The test involves a small plate that has 96 wells drilled into a plate with an antibody attached to the bottom of each one. They then put tissue in the wells – either brain homogenates or lymph node homogenates.
“Each well is one animal, one test sample,” Edwards added.
Prions stick to the antibodies. Then they wash the surface to clear out everything but the remaining prions.
Edward said, “Then what we do is bring in protease enzyme, which is an enzyme that eats up all the prions that aren’t resistant.”
CWD prions are resistant, so they will stay. Then there is another washing cycle. Next they add a chemical that makes a CWD prion light up. They will test prions three times before they deem an animal 100% positive and notify the hunter.
According to its management plan, Wyoming Game and Fish has been monitoring CWD since 1997. The plan includes multiple tactics that hold promise, and WGF tests them in select areas to see if they will work for Wyoming.
“Think of the plan as menu,” Edwards said.
He added it took a year and a half to get the whole plan processed.
When it comes to execution, Game and Fish leaves herd decisions up to managers and the public. Together they determine what they find acceptable and what they want to do.
Edwards said Wyoming has not done a lot on the management side of CWD. However, Game and Fish has more than 20 years of surveillance data on the disease where other states don’t. It is going to take some time to get good effective management actions, and public patience is key.
“This is a problem that has been going on since the ‘50s. We documented it in 1985 in our free ranging mule deer,” Edwards said. “We have seen this expand over almost the entire state and it’s time to do something.”