CWD FAQs

Chronic Wasting Disease (CWD) and Wisconsin Deer

CWD Basics

What is chronic wasting disease?
Chronic wasting disease (CWD) is a fatal disease of the central nervous system in cervids, a group of animals that includes whitetail deer, black tail deer, mule deer, and elk. It affects the brain and spinal cord. There is no treatment, vaccine, or live test for CWD.

How is it related to mad cow disease?
Both are in a family of diseases called transmissible spongiform encephalopathies (TSE). Mad cow disease is the common name for bovine spongiform encephalopathy or BSE, which affects cattle. Other TSEs in animals are scrapie in sheep, transmissible mink encephalopathy, and feline spongiform encephalopathy in cats.

There are several human TSEs: classic Creutzfeldt-Jakob disease, new variant Creutzfeldt-Jakob disease, fatal familial insomnia, Gertstmass-Straussler-Scheinker disease, and kuru.

TSEs are separate diseases with similar symptoms, which arise from different sources and are transmitted differently. BSE may be the exception - scientists believe it may have infected cattle when they ate feed containing parts from scrapie-infected sheep. New variant Creutzfeldt-Jakob disease in humans has been linked to eating BSE-infected meat.

Is CWD a human health threat?
According to the World Health Organization, there is no scientific evidence that CWD affects humans. It has not been associated with eating infected animals. In 16 years of surveillance in infected areas of the western United States, there has been no evidence of the disease affecting any species other than deer and elk.

What causes CWD?
Like other TSEs, chronic wasting disease is apparently caused by an abnormal prion, a type of protein, that replicates itself in the animal’s brain and spinal cord. It causes sponge-like lesions in the animal’s brain.

How is CWD transmitted?
Scientists are not certain, but believe CWD passes from animal to animal in close contact, and perhaps from mother to offspring. CWD has not been associated with any particular feeding practice, as BSE has.

What are the symptoms of CWD?
The disease progresses slowly, so animals may be infected and not show any signs for several years. Symptoms include lack of coordination, separation from other animals in the herd, excessive salivation, depression, unusual behavior, paralysis, weight loss, difficulty swallowing, increased thirst and urination, and pneumonia. Signs usually last weeks to months before the animal dies. Most animals are 15 to 35 months old when signs appear, but they may be as old as 13 years.

How is CWD diagnosed?
The only sure way to diagnose CWD is to examine the animal’s brain for the characteristic lesions that make the brain look like a sponge. There is no approved test for live animals, although one is in development.

Where has CWD been found?
CWD was first seen in Colorado deer belonging to several research facilities in 1967. Since then, it has been found in wild deer and elk herds in the area where Wyoming, Nebraska and Colorado meet. It has been found in captive elk herds in Colorado, Nebraska, Montana, Oklahoma, South Dakota, and Saskatchewan, Canada. In June 2002, it was discovered in a free-ranging mule deer in New Mexico.

Is CWD an animal health threat?
The greatest threat in Wisconsin is probably to Wisconsin’s wild whitetail deer population, because testing and tracing are difficult in wild animals. Wisconsin also has 575 farms with captive whitetail deer, and 272 with captive elk. We have about 100 farms raising red deer, reindeer, fallow deer and sika deer. We don’t know if these species are susceptible to CWD.

There is no evidence that species other than deer and elk are susceptible to CWD.

What are we doing to prevent the spread of CWD in Wisconsin?
We have a monitoring program for deer and elk farms. Farmers who want to move live deer or elk from their farms must be enrolled in the program, which also includes mandatory testing for all animals that die or are killed on surveillance farms, as well as for some animals from other farms. We have also set import controls that are so strict that they have the effect of a temporary moratorium on imports.

The Department of Natural Resources has collected samples for testing at deer registration stations during the gun deer season since 1999.

In 2000, Wisconsin ranked fourth in the nation in the number of samples submitted for CWD testing to the National Veterinary Services Laboratory in Ames, Iowa, and in 2001, we ranked sixth. Four of the 5 states ranked higher have mandatory testing.

The DNR registers whitetail farms and the Department of Agriculture, Trade and Consumer Protection registers elk farms and those raising non-native deer species. This makes tracking animals for disease purposes easier and enforcing rules easier. Among those rules is a requirement that deer and elk farms must have fencing that is high enough to keep wild and captive populations from mingling.

The U.S. Department of Agriculture is developing a program to eradicate the disease.

What can elk and deer farmers do?
Captive deer and elk herds are required to be fenced according to standards set in our rules. In addition, we recommend that these herds be surrounded by a second fence. The outer fence should be at least 10 feet away from the inner one. We also strongly urge deer and elk farmers to enroll in the surveillance program.