White-tailed deer

Chronic Wasting Disease (CWD) has appeared widely in 

the media lately, but has actually been around for a while. 

It was first recognized in Colorado in 1967, in a captive 

research herd of mule deer. Its rapid expansion, to include 

eight states and two provinces by the year 2002, has 

created a crisis.

• In 1977, scientists suspected that CWD was caused 

by a transmissible spongiform encephalopathy (TSE). 

TSEs consititute a small group of fatal neurological 

disorders affecting humans and animals, including: 

Scapie in sheep, Bovine Spongiform Encephalopathy, 

or “Mad Cow Disease,” in cattle, and CreutzfeldtJakob Disease in humans. TSEs are diseases of the 

nervous system that have distinctive 

lesions in the brain. The causative 

agent may be a modified protein 

(prion) that is resistant to degradation. 

All mammals have normal cellular 

prion protein (PrP), but we do not 

know what is the transmissable agent 

that causes the transformation from 

cellular PrP to the resistant PrP.

• By the year 2000, surveillance of wild 

deer and elk by the Colorado Division 

of Wildlife showed up to 15% 

prevalence of CWD in deer and 1% in 

elk in some hunting districts.

• Prior to 1997, CWD was infrequently 

found in white-tailed deer in Wyoming 

and Colorado. Since that time the 

disease in white-tailed deer has been 

identified in South Dakota, Nebraska, 

and Wisconsin. In the white-tailed 

deer game farm where a Nebraska 

outbreak occurred, CWD prevalence 

was over 50% in the ranch and almost 7% outside the 

ranch fenceline within a five-mile radius.

• The high prevalence in Nebraska, and the discovery 

of CWD in white-tailed deer fawns, suggests a shorter 

incubation period in white-tailed deer and perhaps a 

particular sensitivity of this species to CWD. CWD 

has also been documented in elk yearlings. 

• In 2001, the U.S. Department of Agriculture (USDA) 

declared a CWD national emergency and began testing 

captive deer and elk on ranches and farms in several 

western states. The declaration of a national emergency 

allowed USDA to authorize indemnity payments for 

Chronic Wasting Disease (CWD): Just the Facts

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet Number FS-074-02

July 2002

herds slaughtered as a consequence of CWD. 

• In 2002, CWD spread over the Continental Divide in 

Colorado, and has been identified in four mule deer 

inside an elk game farm and six mule deer outside the 

game farm. The game farm had no known animals 

introduced from the endemic area. CWD has also 

been found in wild mule deer in Wyoming, Nebraska 

and Saskatchewan. In June, 2002, a mule deer in New 

Mexico tested positive for CWD.

• Due to the rapid spread of the disease, stop-gap 

radical control experiments are being conducted in 

three states. In Colorado, control consisted of killing 

as many deer and elk as could be found within five 

miles of the epicenter of the Westslope outbreak in late April (Colorado 

estimates it will need to kill 5000 deer in 

the infected area of the Western Slope). 

In Wisconsin, starting May 6, 2002, state 

agencies are attempting to kill 15,000 

to 18,000 deer within the CWD affected 

area, and as many as 100,000 deer in 

adjacent deer management units over the 

next few years. And in Nebraska, control 

efforts are underway to kill from 2500 to 

3500 deer within ten miles of the disease 

outbreak.

Who does this Disease Affect?

• Elk, mule deer and white-tailed 

deer are affected. An ante mortem test 

for CWD in deer has been recently 

developed, but no studies have been 

conducted yet to determine whether 

every infected animal dies. There is 

no treatment for CWD at present, and 

affected animals may take years before they show 

signs of the disease. Once signs of the disease are 

present, CWD is fatal.

• The recent discovery of CWD east of the Mississippi 

River is significant because of the dense population 

of white-tailed deer in the eastern United States. The 

perception by hunters that venison may be tainted with 

CWD could reduce the hunting effort for white-tailed 

deer, with negative impact on management strategies 

for this species. In a poll of Wisconsin hunters (June 

2002), over one-third of hunters indicated they may 

not participate in deer hunting in the fall.
• Conservation efforts conducted by State agencies 

that rely on hunting as a source of revenue may be 

negatively impacted. 

• The potential exists for profound ecological 

consequences related to changes in ungulate 

populations. These could occur as hunting and 

management flexibility decrease, or occur directly to 

affected populations through CWD-induced mortality 

and productivity changes; one model predicts adverse 

population effects at CWD prevalences above 5%. 

• Eradication of the disease through massive killing of 

deer and elk has the potential for significant ecological 

consequences.

• The negative economic effect of reduced hunting could 

be staggering. Many businesses depend heavily on 

hunting activity. 

• Variant Creutzfeldt-Jakob Disease (vCJD) very likely 

represents a cross-species transmission of Bovine 

Spongiform Encephalalopathy (BSE), and a recent 

review of human mortality using UK data confirmed 

its emergence coincident with BSE. If CWD is ever 

found transmissible to humans, then there will be 

significant human health implications.

What is the currently being done?

• Many Federal and State agencies and universities have 

been involved for years with CWD, with considerable 

research and diagnostic capabilities.

• A National Task Force of state and federal agencies 

has developed a National CWD Response Plan, which 

includes funding for Communication, Scientific 

and Technical Information, Diagnostics, Disease 

Management, Research and Surveillance.

• CWD is a complex disease requiring integration of 

state, federal, and academic wildlife health resources. 

Geographically, the disease is distributed primarily on 

state and private lands in resident game species and 

alternative livestock.

What is USGS doing?

• The USGS supports and augments state and USDA 

efforts in research, technical assistance and wildlife 

management with its wildlife health resources. Thus far, 

CWD has affected DOI stewardship resources on only 

one National Park and has been found in ranched elk on 

private property adjacent to another park.

• USGS is the DOI lead for information, contingency 

planning, coordination, technical assistance and 

research. The primary focus is to prevent CWD spread 

to DOI sites.

• The USGS expertise includes on-the-ground assistance 

to Montana in CWD sites with depopulation, pathology, 

epidemiology and control; providing regional and 

national briefings; assistance with setting up a statewide monitoring program; and assisting FWS with 

developing guidelines. USGS is also represented on the 

National CWD Task Force.

Want more information?

Thomas J. Roffe, Program Manager

406-994-5789

Thomas_Roffe@usgs.gov

Or 

Dick Jachowski, Center Director

406-994-5304

www.nrmsc.usgs.gov

A target population of 7,500 elk is maintained with natural forage and supplemental feed on the National Elk Refuge from October to May