Chronic Wasting Disease
Date posted: 07/16/2008
Quick Data Links
Estimated CWD Prevalence in Larimer County
Chronic wasting disease (CWD) is a fatal neurological disease found in North American cervids (the deer family including elk, deer, and moose). CWD belongs to a family of diseases known as transmissible spongiform encephalopathies. Abnormally shaped prions (a type of protein) become stored in the lymphatic and neural system of the animal. After an incubation period of 18-24 months, infected animals become emaciated, display abnormal behavior, lose bodily functions, and eventually die. CWD was first observed in captive mule deer from Colorado during the late 1960's by biologists with the Colorado Division of Wildlife (CDOW). Until 2000, CWD was confined to Northeastern Colorado and Southeastern Wyoming. Since then, the disease has increased in prevalence locally and spread geographically including documented cases in 14 states and 2 Canadian providences. (See USGS Fact Sheet for more detailed information on symptoms and prevalence). Surveillance and precautions are pertinent in Larimer County, as the herds with the current greatest estimates of CWD in Colorado for each of the reported animal species are found in Larimer County (See the CDOW summary for details of all Colorado herds).
Current research has not displayed a link between CWD and any disease in domestic animals and humans, but monitoring continues until scientists can be certain. There are two related diseases: scrapie and Creutzfeldt-Jakob Disease. Scrapie, found in sheep and goats, has been studied for over 200 years without showing any link to human diseases. On the other hand, a bovine version of spongiform encephalopathy ('mad cow disease') has been linked to variant Creutzfeldt-Jakob Disease (CJD) and cited for 154 deaths in England. After a series of suspicious cases of CJD in Wisconsin, Minnesota, and Michigan, food safety advocates are pressing for tighter regulations on venison products. However, scientists have yet to make a concrete connection between CWD and CJD. As a precaution, CDOW regulates the processing and transport of deer and elk carcasses from areas where the disease has been detected, and advises certain precautions for handling animals in CWD areas.
CDOW researchers and biologists use a data analysis unit (DAU) to estimate CWD prevalence in Colorado's big game herds. The unit encompasses a herd's entire range throughout the year. It is expensive and often inconclusive to test live animals for the disease, so CDOW tests elk, deer, and moose heads that are submitted by hunters in affected units. CDOW has also begun other methods of sampling including testing of noticeably sick and vehicle-killed animals. (See USGS Wildlife Health Center for information on the development of live animal testing procedures at CSU). While it is mandatory to test any harvested moose, the prevalence of the disease is extremely low among moose herds. The first diagnosis of CWD in a harvest moose occurred in September 2005, providing evidence that CWD can naturally occur in moose herds. Deer and elk testing is voluntary. CDOW estimates the prevalence of CWD in herds dependent on the number of heads that test positive for CWD.
CDOW has set a goal of 300 tested animals in one unit over a 2-3 year period (all units shown on this page met this goal). A sample of this size allows researchers to calculate a 95% confidence interval for the prevalence of CWD with greater accuracy. A confidence interval of 95% indicates that the researchers are 95% certain that the given interval encompasses the actual prevalence of CWD within the DAU. The confidence intervals are shown in the data tables.
What this chart shows: Estimated Chronic Wasting Disease (CWD) Prevalence in Larimer County Elk Herds
* 2004-2006 represents three biological years: June 2004 - June 2007. Pooling the years' estimates increases sample size and thus the accuracy of the confidence intervals. Pooling the years does not affect accuracy of the estimate.
Data Source: Colorado Division of Wildlife
What these data tell us:
The pooled estimate for 2004-2006 shows a distinct Chronic Wasting Disease (CWD) prevalence increase in the E-4 elk herd located in Larimer County. Based on the Colorado Division of Wildlife (CDOW) sample, researchers estimate that between 0.8% and 3.1% of the herd has CWD. Future estimates will indicate if there is a true trend of increasing CWD. Even with the increase, prevalence of CWD is still lower in the E-4 herd than in the E-9 herd which is located in south Larimer County and north Boulder County.What this chart shows: Estimated Chronic Wasting Disease (CWD) Prevalence in Larimer County Mule Deer Herds
* 2004-2006 represents three biological years: June 2004 - June 2007.
Data Source: Colorado Division of Wildlife
What these data tell us:
This chart shows estimated prevalence of Chronic Wasting Disease (CWD) among the four mule deer herds with ranges within Larimer County. While herds D-4 and D-5 show fluctuation over the samples, both D-44 and D-10 estimates have consistently increased since the 2002-2003 year. The latest estimate shows the highest potential percentage of mule deer infected in each herd.Additional Information:
Colorado Division of Wildlife (CDOW) Carcass Regulations
The following is from the CDOW website:
As a precaution against the possible spread of chronic wasting disease, only
the following carcass parts may be transported out of infected units in northeastern Colorado or brought into any part of Colorado from infected areas in other states:
1. Meat that is cut and wrapped (either commercially or privately).
2. Quarters or other portions of meat with no part of the spinal column or head attached.
3. Meat that has been boned out.
4. Hides with no heads attached.
5. Clean (no meat or tissue attached) skull plates with antlers attached.
6. Antlers with no meat or tissue attached.
7. Upper canine teeth, also known as "buglers," "whistler," or 'ivories'.
8. Finished taxidermied heads.
Public health officials advise hunters to take the following precautions when pursuing or handling deer and elk in infected units:
• Do not shoot, handle or consume any animal that appears sick; contact the Division of Wildlife in Fort Collins at (970) 472-4300 if you see or harvest an animal that appears sick.
• Wear rubber gloves when field dressing and processing animals;
• Bone out the meat from your animal;
• Minimize the handling of brain and spinal tissues, and wash hands and instruments thoroughly after field-dressing;
• Wash hands and instruments thoroughly after field dressing is completed.
• Avoid consuming brain, spinal cord, eyes, spleen, tonsils, pancreas, and lymph nodes of harvested animals. Normal field dressing, coupled with boning out a carcass, will remove most, if not all, of these body parts. Cutting away all fatty tissue will remove remaining lymph nodes.
• Do not consume meat from animals known to be infected with CWD.
• Knives, saws and cutting table surfaces can be disinfected by soaking in a solution of 50% unscented household bleach and 50% water for an hour. Afterward, allow them to air dry.
Prion diseases (including CWD) are characterized by certain misshapen protein molecules that appear in brain tissue. Normal forms of these prion protein molecules reside on the surface of many types of cells, including brain cells, but scientists do not understand what normal prion protein does. On the other hand, scientists believe that abnormal prion proteins, which clump together and accumulate in brain tissue, is the likely cause of the brain damage that occurs with prion diseases. Scientists do not have a good understanding of what causes the normal prion protein to take on the misshapen abnormal form. CWD, originally believed to be transmitted only through direct contact between animals, can also be transmitted indirectly through contact with objects in the environment touched by infected animals' saliva.
- Ambient Air Quality
- Electricity Consumption
- Natural Gas Consumption
- Public Drinking Water Quality
- Recycling
- Solid Waste
- Surface Water Quality
- Visibility
- Water Consumption
- Wildlife
- Wind Energy Consumption
Outside Compass-
- Chronic Wasting Disease Alliance: A collaboration of wildlife management agencies. This site provides information on all aspects of the disease, including history, legislation, and research.
- Colorado Division of Wildlife - Chronic Wasting Disease: Information on CWD management efforts in Colorado, as well as testing results.
- National Wildlife Health Center - Chronic Wasting Disease: Information on CWD from the United States Geological Survey.
- U.S. Department of Agriculture - Veterinary Services: Branch of the USDA concerned with animal health. Site includes information on CWD as well as other diseases of domestic and wild animals.
Estimated Chronic Wasting Disease (CWD) Prevalence in Larimer County Elk Herds
|
Elk DAUs |
Biological Year |
Estimate |
95% Confidence Interval |
Animals Tested |
|
Larimer (E-4) |
2002-2003 |
0.6% |
0.0-1.2% |
643 |
|
2003-2004 |
0.6% |
0.0-1.2% |
663 |
|
|
2004-2006 |
2.0% |
0.8-3.1% |
556 |
|
|
S Larimer/N Boulder (E-9) |
2002-2003 |
3.0% |
1.6-4.5% |
526 |
|
2003-2004 |
1.3% |
0.4-2.3% |
526 |
|
|
2004-2006 |
2.8% |
1.4-4.2% |
571 |
Estimated Chronic Wasting Disease (CWD) Prevalence in Larimer County Mule Deer Herds
|
Mule Deer DAUs |
Biological Year |
Estimate |
95% Confidence Interval |
Animals Tested |
|
Larimer (D-4) |
2002-2003 |
6.5% |
5.2-7.7% |
1,535 |
|
2003-2004 |
3.9% |
2.7-5.2% |
990 |
|
|
2004-2006 |
8.8% |
6.8-10.7% |
822 |
|
|
NE Larimer/NW Weld (D-5) |
2002-2003 |
6.3% |
3.9-8.7% |
396 |
|
2003-2004 |
3.2% |
1.0-5.4% |
248 |
|
|
2004-2006 |
8.2% |
4.2-12.1% |
184 |
|
|
SE Larimer/SW Weld (D-44) |
2002-2003 |
1.8% |
0.0-4.2% |
114 |
|
2003-2004 |
3.8% |
1.0-7.5% |
106 |
|
|
2004-2006 |
8.6% |
3.5-13.8% |
116 |
|
|
S Larimer/N Boulder (D-10) |
2002-2003 |
6.9% |
4.9-8.9% |
636 |
|
2003-2004 |
7.2% |
5.1-9.4% |
566 |
|
|
2004-2006 |
10.0% |
7.9-12.1% |
760 |