What is Chronic Wasting Disease?
CWD is a neurologic disease of deer and elk, belonging to the family of diseases known as transmissible spongiform encephalopathies (TSE’s) or prion diseases.  Though it shares certain features with other TSE’s like bovine spongiform encephalopathy (“Mad Cow Disease”) or scrapie in sheep, it is a distinct disease apparently affecting only deer and elk.  CWD occurs in wild deer and elk primarily in Colorado and adjacent parts of Wyoming, Nebraska, and Utah; it has been diagnosed in wild deer in Saskatchewan, South Dakota, Wisconsin, Illinois, New Mexico and most recently in wild deer in New York, West Virginia, Kansas and Alberta.  CWD has also been found on elk farms in Colorado, Kansas, Montana, Nebraska, Oklahoma, South Dakota, Minnesota, Saskatchewan, and Alberta.

What are the Signs of CWD in Deer and Elk?
CWD attacks the brains of infected deer and elk causing the animals to become emaciated, display abnormal behavior, lose bodily functions and die.  Signs identified in captive cervids include excessive salivation, loss of appetite, progressive weight loss, excessive thirst and urination, listlessness, teeth grinding, holding the head in a lowered position, and drooping ears.  CWD is a slowly progressive disease; signs are usually not seen until the animal is 18 months of age or older.

How is CWD Transmitted?
The mode of transmission between deer or elk is not completely understood.  However, it is thought that the disease is transmitted laterally (i.e., from direct contact between animals in a herd).  Environmental factors, heat or disaffection does not easily kill the disease causing prion, so transmission from a contaminated environment may also be possible.

How is CWD Diagnosed?
Brain samples are collected from hunter-harvested or dead deer and are examined microscopically using special stains to identify the CWD prion.  A research team in Colorado has recently developed the first live animal test for CWD, based on the collection of tonsil samples for microscopic examination.  This test seems to work well in deer, but not in elk.

Is CWD Transmissible to Humans?
A World Health Organization panel of experts reviewed all available information on CWD and concluded that there is no scientific evidence that CWD can infect humans.  CWD is similar to the human TSE disease, Creutzfeldt-Jakob Disease, but the two diseases have not been linked the way new-variant Creutzfeldt-Jakob Disease in people has been linked to consumption of products from cattle with bovine spongiform encephalopathy.

Is CWD a Risk for Iowa’s Livestock?
There is no evidence that CWD can be transmitted under natural conditions to cattle.  Scientists have attempted to transmit CWD to cattle by injecting CWD infected material directly into the brain, but the cattle did not develop signs of disease.  CWD has been a problem in farmed elk in several western states, but has not been documented to date on elk or deer farms in Iowa.

Is it Safe to Eat Venison from Iowa Deer?
To date, CWD has not been diagnosed in captive or wild deer in Iowa.  There is no scientific evidence that CWD is transmissible through consumption of meat from an infected animal.  The prion that causes CWD accumulates only in certain parts of infected animals – the brain, eyes, spinal cord, lymph nodes, tonsils and spleen.  Health officials, however, advise that no part of any animal known to be infected with CWD should be consumed by humans or other animals.   In addition, they suggest that hunters take simple precautions when field dressing deer in areas where CWD is found:

· Wear rubber gloves when field dressing carcasses.
· Bone out the meat from your animal.
· Minimize the handling of brain and spinal tissues.
· Wash hands and instruments thoroughly after field dressing is completed.
· Avoid consuming brain, spinal cord, eyes, spleen, tonsils and lymph nodes of harvested animals.  (Normal field dressing coupled with boning out of a carcass will remove essentially all of these parts.)
· Request that your animal be processed individually, without meat from other animals being added to meat from your animal.

Links regarding food safety risk: University of Wisconsin Extension (PDF)