Colorado 2022 2024 CWD TSE Prion prevalence increased in 14 herds, remained about the same in 16 herds, and decreased in 4 herds
Colorado 2022 2024 CWD TSE Prion prevalence increased in 14 herds, remained about the same in 16 herds, and decreased in 4 herds
Colorado CWD has gotten so bad, they can’t even give a Total To Date count. Best they can do is is give you Total Herds With CWD…sad…terry
Jeff Davis, Director, Colorado Parks and Wildlife Parks and Wildlife Commission: Dallas May, Chair ∙ Richard Reading, Vice-Chair ∙ Karen Bailey, Secretary ∙ Jessica Beaulieu Marie Haskett ∙ Tai Jacober ∙ Jack Murphy ∙ Gabriel Otero ∙ Murphy Robinson ∙ James Jay Tutchton ∙ Eden Vardy
MEMORANDUM
April 25, 2025
TO: Colorado Parks and Wildlife Commissioners
FROM: Brian Dreher, Assistant Director, Terrestrial Branch
Subject: Chronic Wasting Disease Update for Parks and Wildlife Commission
Dear Commissioners,
This briefing summarizes CPW’s mandatory chronic wasting disease (CWD) findings from the 2022- 2024 hunting seasons. Results provide the first indication of whether CWD management actions taken for deer over the past 5-7 years have had an effect on CWD prevalence (estimated percent infected) in each herd. In summary, CWD prevalence decreased in 4 herds, increased in 14 herds, and remained about the same in 16 herds.
Background
Chronic wasting disease, a fatal neurological disease found in deer, elk, and moose, is well established in herds throughout much of Colorado. We have detected CWD in 42 of our 51 deer herds, 17 of 42 elk herds, and 2 of 13 moose herds. CWD prevalence is highest in deer and lowest in moose. This disease is always fatal and animals die from the disease within about 2-2.5 years of infection. CWD infection shortens the lifespan of infected animals. If infection rates become too high, CWD can affect a herd’s ability to sustain itself.
In response to increasing CWD prevalence, the Parks and Wildlife Commission approved a statewide CWD Response Plan in 2019. One element was a 15-year mandatory testing plan, which will include three 5-year rotations for deer. Pilot work in 2017 and 2018 had shown that the number of deer submitted for testing is much higher through mandatory testing than for voluntary submissions, which allows CPW to generate reliable estimates of CWD prevalence at the herd level.
In addition, the CWD Response Plan establishes a compulsory management threshold, which means when prevalence exceeds 5% in adult (>2 years) male deer then some form of management action will be taken to reduce prevalence until it falls below the 5% threshold. CPW identifies various management actions in the plan that are available to local managers to prescribe in herd management efforts, all of which have the potential to help reduce prevalence in deer herds.
CWD prevalence was assessed via mandatory testing in all deer herds from 2017-2020; mandatory testing focused on elk in 2021. In 2022, CPW restarted the 5-year testing rotation for deer. Thirty-four deer herds have been included in a second round of mandatory testing. Three herds, White River (D- 07, 2024) Middle Park (D-09, 2024), and Bears Ears (D-02, 2025) were already scheduled for a third round of mandatory testing to learn more about how prevalence is changing in these herds related to the 2022-2023 severe winter and exponential growth in CWD prevalence. CPW will conclude the second round of mandatory testing for deer in 2025 and for elk in 2026.
Mandatory Testing Results CWD prevalence estimates have decreased in 4 deer herds, increased in 14 deer herds, and remained about the same in 16 deer herds (Figure 1, Table 1).
Prevalence was expected to increase in many high-prevalence herds. However, prevalence stayed about the same between the two rounds of mandatory testing in many high- prevalence herds. This is an indication that prescribed management actions are preventing or slowing increases in CWD prevalence, even if we are not seeing a reduction in prevalence. Additional data and robust analyses are needed over the next 7 years of mandatory testing to guide CPW's interpretation of these results before we are in a position to show an association between prescribed management actions and CWD prevalence.
CPW prescribed various management actions in each of these 34 herds and the response in prevalence varies. Therefore, CPW will evaluate why prevalence increased in some herds and decreased in others. Overall, these preliminary data are encouraging for some herds and suggest harvest-based management actions could be a promising CWD control strategy.
Further Analyses
CPW will continue analyses of these CWD prevalence changes by comparing various factors between herds and the respective management actions prescribed. Comparing changes to license quotas by season, dates of harvest and prevalence estimates by season, post-hunt buck/doe ratios, abundance of bucks and does, and the percent change in buck licenses and buck harvest, etc., all in relation to changes in CWD prevalence, should improve our ability to evaluate relationships between various management actions and disease prevalence. CPW plans to complete these analyses as the 15-year mandatory testing period concludes, if not sooner.
In our more than 40-year history working with CWD, one of the most important lessons we have learned is that we rarely see immediate changes in CWD dynamics. This is a slow-moving disease and changes in prevalence (both increases and decreases) may not be readily apparent. Multiple repeated prevalence estimates over the long-term along with consistent management application will be necessary to evaluate patterns of change in relationship to management actions.
Lastly, severe winter conditions seen in Northwestern Colorado during the 2022-2023 winter generated many questions on potential implications for CWD dynamics in the region. Harsh winter conditions may cause more rapid mortality of infected deer in the clinical phase of disease and could reduce the number of infected animals on the landscape. Overall population reductions associated with harsh winter conditions may also affect deer/elk density on the landscape and reduce direct animal-to-animal transmission. On the other hand, prolonged concentrations of deer and elk on very limited winter ranges could facilitate increased contact as well as environmental accumulation of CWD prions (infectious agent) that could increase both direct and indirect transmission pathways. Preliminary, based on 2024 results, it does not appear that the severe winter of 2022-2023 resulted in reduced CWD prevalence. Ultimately, the interplay of weather conditions, changing population dynamics, and changes in habitat use associated with a severe winter limit our capacity to predict how CWD prevalence might change. As we proceed with analyses to evaluate factors influencing CWD prevalence in Colorado wildlife populations, incorporating changes associated with periodic severe winters will be an important consideration.
CC: J. Davis R. DeWalt Regional Managers M. Eckert Senior Biologists J. Runge A. Holland
2022 Colorado detected CWD in 40 of our 54 deer herds, 17 of 42 elk herds, and 2 of 9 moose herds
MEMORANDUM
To: Members of the Colorado Parks and Wildlife Commission
From: Dan Prenzlow, Director
Date: April 22, 2022
Subject: Chronic Wasting Disease Update for Parks and Wildlife Commission
Dear Commissioners,
This briefing summarizes CPW’s mandatory chronic wasting disease (CWD) findings from the 2021-2022 hunting seasons and, more broadly, things we have learned over the first 5-year rotation of mandatory testing (2017-2021 hunting seasons). Overall, the decision to commit to annual mandatory testing has been resoundingly important to understanding the status of this disease in Colorado, acquiring and communicating reliable prevalence estimates, and laying a foundation to assess herd-specific management actions to combat CWD. It is my pleasure to present this current information to keep you apprised on the status of CWD in our big game herds.
Background
Chronic wasting disease, a fatal neurological disease found in deer, elk, and moose, is well established in herds throughout much of Colorado. We have detected CWD in 40 of our 54 deer herds, 17 of 42 elk herds, and 2 of 9 moose herds. Disease prevalence (percent infected) is highest in deer and lowest in moose. This disease is always fatal and animals die from the disease within about 2-2.5 years of infection. CWD infection shortens the lifespan of infected animals. If infection rates become too high, CWD can affect a herd’s ability to sustain itself.
Snip…
MONDAY, MAY 09, 2022
Colorado CWD TSE Prion Detected in 40 of 54 deer herds, 17 of 42 elk herds, and 2 of 9 moose herds
Colorado As of July 2018, at least 31 of Colorado's 54 deer herds (57%), 16 of 43 elk herds (37%), and 2 of 9 moose herds (22%) are known to be infected with CWD. Four of Colorado's 5 largest deer herds and 2 of the state’s 5 largest elk herds are infected.
As of July 2018, at least 31 of Colorado's 54 deer herds (57%), 16 of 43 elk herds (37%), and 2 of 9 moose herds (22%) are known to be infected with CWD. Four of Colorado's 5 largest deer herds and 2 of the state’s 5 largest elk herds are infected. Deer herds tend to be more heavily infected than elk and moose herds living in the same geographic area. 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. Of most concern, greater than a 10-fold increase in CWD prevalence has been estimated in some mule deer herds since the early 2000s; CWD is now adversely affecting the performance of these herds…
terry
posted by Terry S. Singeltary Sr. at
12:42 PM
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