Continued spread of Chronic Wasting Disease prompts state response
Chronic Wasting Disease has been a point of concern for state wildlife managers for the last five decades, but ongoing concern about the continued spread of the neurological disease prompted the recent development of a state response plan with potential ramifications for Grand County.
Chronic Wasting Disease, or CWD, is a brain disease that affects deer, elk, moose and caribou. University researchers near Fort Collins initially discovered the fatal disease in the 1960s. Since then wildlife managers in Colorado, and in numerous other regions of North America, have watched as the number of infected animals has trended upwards.
According to the Colorado Chronic Wasting Disease Response Plan, at least 31 of Colorado’s 54 deer herds, 16 of its 43 elk herds and two of nine moose herds had infected individuals within them in 2018.
“Not only are the number of infected herds increasing, the past 15 years of disease trends generally show an increase in the proportion of infected animals within herds as well,” reads the response plan.
Luckily, the issue is less pronounced in Grand County.
According to Bryan Lamont, terrestrial biologist for Colorado Parks and Wildlife’s Hot Sulphur Springs Office, there were 30 recorded cases of CWD in Grand County in 2018. Twenty-nine of the cases were found in Grand County’s one and only deer herd.
Lamont noted that CPW required mandatory testing of all bucks harvested in Grand County in 2018, part of a broader monitoring effort CPW is undertaking to hopefully stymie the disease’s spread.
Overall, Grand County’s deer population is believed to have a CWD infection rate, also called a prevalence rate, of 3.5 percent. Lamont said 833 bucks harvested in 2018 in Grand County were tested for CWD. Of those, 29 came back positive.
According to the state’s CWD Response Plan, an infection rate of 5 percent or greater will prompt “compulsory intervention” by the state, prompting additional wildlife management activities such as herd reductions, reducing the male-female ratio within an infected herd, changing the herd’s age structure. The plan lists six different strategies with numerous management action recommendations within each strategy category.
Comparing the infection rate of deer in Grand County to other herds around the state offers a mix of both good and bad news.
While Grand County’s infection rate is not zero, which is the case for just 23 of Colorado’s 54 deer herds, the local infection rate is significantly lower.
According to Lamont, recent mandatory testing of harvested deer near Fort Collins and Craig revealed strikingly higher infection rates. Officials tested bucks from two herds near Fort Collins that showed infection rates of 33.9 and 25 percent. And tests of two herds near Craig revealed infection rates of 15.3 and 18.6 percent.
Mike Miller, senior wildlife veterinarian for CPW, said that CWD was first found in Grand County during the early 2000s. He praised the management practices of the local CPW team as being a major factor in the county’s comparatively low infection rate.
“When we first found it in Middle Park it was just a little bit lower than that (our current rate),” Miller said. “It hasn’t really increased very much over the years. We had similar low infection rates in some of the herds further west. In those cases, under what appears to be a different harvest approach, infection rates have gone up dramatically.”
Miller called the county a good example of the way proper population management can drive infection rates down.
Looking at the other species in Grand County’s impacted by CWD, namely elk and moose, the situation is even better.
There are three separate elk herds that technically reside in the county. One herd, named the Troublesome Herd, can be found primarily in and around the Troublesome Creek area. A second, the Williams Fork Herd, can be found around the Williams Fork River. The third, called the Gore Pass Herd, lives primarily in the Gore Pass area between the Colorado River and Rabbit Ears Pass.
In 2018, state officials conducted CWD tests on elk from both the Troublesome and Williams Fork Herds. A total of 39 animals from the Troublesome Herd were tested with one single elk coming back positive for CWD.
“Between our two (elk) herds of around 11,000 animals we had one positive,” Lamont said, while also acknowledging that the sample size CPW relied upon was not large.
Colorado Parks and Wildlife can test for CWD in various ways, though according to Lamont, testing of specific lymph nodes, located within the necks of deer, elk and moose, is the most effective way to check for the disease’s presence.
There have been no recorded cases of the transfer of CWD from deer, elk or moose into humans though he said the potential for transfer remains a concern for public officials. Likewise there have been no recorded cases of the transfer of CWD from elk, deer or moose into livestock, pets or predators.
“All of the work to date suggest not,” Miller said of the possibility of transmission to other animals. “We have done experimental studies. Under natural conditions it seems to be limited to species in the deer family.”
While CPW does not require that any harvested animals that have tested positive for CWD be disposed, state wildlife managers strongly suggest destroying any meat derived from an infected animal.
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