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History and Background

CWD overview, symptoms, transmission and history in the United States

The biology of CWD is not yet fully understood. It is a disease of white-tailed deer, mule deer and 

elk that attacks the central nervous system. It is a member of the TSE (Transmissible Spongiform

Encephalopathy) group, which is the same disease family as BSE or "mad cow disease" in cattle and

scrapie in sheep. There is no evidence to date that CWD affects humans or other animals.

CWD is caused by prions (pronounced ĎPREE ONí Ė mutant versions of normal proteins), which 

are not sensitive to normal sterilization, disinfectants, or cooking. The multiplying prions eventually 

destroy nerve cells and account for symptoms.  At this point there is no live-animal test, no

treatment and no vaccine for CWD. The disease is  found by a screening process looking for 

vacuoles (sponge-like bubbles) in brain tissue and special stains for the prions in brain and lymph 

tissues.  Symptoms of CWD do not develop until deer and elk are least 16 months of age and the 

disease is always fatal. Clinical signs include chronic weight loss, behavioral changes (loss of fear of  

humans, listlessness, lowering of head, repetitive walking,  blank facial expression, hyperexcitability),

excessive salivation and grinding of teeth.  Symptoms can sometimes be confused with other

diseases such as brain worm, parasites, rabies or simply malnutrition/starvation.  The transmission 

route in unknown but is suspected to occur from cervid to cervid through saliva, feces, and possibly 

urine. It has a long incubation period of 18 months or longer. Again, there is no evidence of 

transmission to humans or other species of animals.  Again, CWD has not been found in Michigan 

to date.  Michigan is home to about 1.8 million free ranging deer and elk as well as 900 to 

1000 privately owned deer and elk facilities.

Michigan Surveillance and Response Plan

It was first observed in 1967 and diagnosed in 1977 at a Colorado cervid research facility and, in 1

1981, in free ranging cervids in northeastern Colorado.  Since then, CWD has been found in both 

privately owned and wild, free-ranging cervids in other states  and other countries. Specifically, it 

has been discovered in wild deer herds in Wyoming, Nebraska, South Dakota, the Canadian 

province of Saskatchewan, Wisconsin, and most recently, New Mexico. In addition to Colorado, 

CWD has been diagnosed in privately owned deer and elk herds in Kansas, Nebraska, Montana, 

Oklahoma, South Dakota, the Canadian provinces of Saskatchewan and Alberta, and South 


Michiganís efforts to-date to prevent CWD Free ranging cervids

In past years, MDNR scientists and the National Veterinary Services Laboratory have tested

approximately 450 deer for CWD, all of which have been negative. In addition, MDNR has tested 

deer having symptoms similar to those of CWD on an ongoing basis. All of these animals have 

tested negative as well.  In 2002, the Michigan Natural Resources Commission, which serves as 

MDNRís policymaking body, moved in the first of a series of steps to prevent CWD from entering 

Michigan.  The Commission ordered an end to supplemental deer feeding in the Upper Peninsula, 

starting with the four U.P. counties bordering Wisconsin and including the remaining 11 counties by 

May, 2003.  Supplemental feeding is presently banned in the Lower Peninsula. The move is aimed 

at lowering deer numbers that are kept artificially high through unnatural feeding and reducing the 

nose-to-nose contact inherent with congregated feeding.  Further, the NRC implemented a 50-mile 

buffer zone around the state. If CWD is discovered within 50 miles of any state border, all baiting 

and feeding activities in the adjacent peninsula will be immediately banned.

Privately owned cervids

MDA enacted a one-year ban or moratorium effective April 26, 2002, on any imports of deer and

elk destined for privately owned cervid farm operations. Before the temporary ban, MDA had 

prohibited the importation of any deer or elk from a county or adjoining county in any state where 

CWD has been diagnosed. Cervids brought into Michigan were also required to obtain a pre-entry 

permit, accompanied by a health certificate and statement from an accredited veterinarian attesting 

that the animals had not been exposed to CWD or any other communicable disease.  In addition, 

after the CWD discovery in Wisconsin, the Department enacted a ban on all cervid imports

from Wisconsin effective March 6, 2002.  The stateís act governing privately owned cervid

operations also provides important tools, including mandatory herd inventory reporting, mandatory

fence inspection, standards for fence construction and mandatory record keeping of all animal

movement, that help MDA and the state prevent, monitor for and potentially respond to CWD.

"MDNR and MDA are committed to doing whatever is necessary to ensure

the future health of Michiganís deer and elk. Our long-term success with

protecting free ranging cervids will be underpinned by the close partnership

we have with the hunting community." K.L. Cool, DNR Director

White-tailed deer closely gathered at an unnatural feeding site.  Michigan is working to end this practice.


Michiganís success in preventing and responding to the threat of Chronic Wasting Disease is 

underpinned by rigorous surveillance, strong public education efforts, and responsive scientific 

laboratory support. Also key to dealing with this disease are strong partnerships between state, 

federal, local and university entities, as well as Michiganís sportsmen and deer and elk farmers. 

Continued nationwide research efforts to better understand CWD could someday offer cures and 

vaccines for this disease. Until then, the State of Michigan remains committed to a two-prong 

approach focused primarily on strong prevention and surveillance activities, and timely response in 

the event that CWD is ever detected here.  For more information or questions, contact:

Wildlife inquiries:

Rose Lake Wildlife Disease Laboratory

MDNR Wildlife Division


Producer or veterinarian inquiries:

Dr. Joan Arnoldi, State Veterinarian and MDA Animal Industry Division Director

517/373-1077 or

Dr. Doug Hoort, MDA Cervidae, Aquaculture, Exotic Species Program Manager

517/373-1077 or

Media inquiries:

Brad Wurfel, MDNR Press Secretary

517/335-3014 or

Sara Linsmeier-Wurfel, MDA Public Information Officer

517/241-4282 or

On the web:

Visit;; or

To report a potential animal disease:

State Veterinarianís Office

Phone: 517/373-1077

Fax: 517/373-6015

After hours/weekends: 517/373-0440

U.S. Department of Agriculture

Animal and Plant Health Inspection Services

Veterinary Services

Phone: 517/324-5290

Fax: 517/324-5289


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