Kansas Officials Discuss Chronic Wasting Disease 1/24/02

Q&A on chronic wasting disease

Answers by Dr. George Kennedy, Kansas State University veterinarian

1) What is chronic wasting disease?
2) What is the cause of CWD?
3) What are the clinical signs?
4) How is the disease transmitted?
5) Is it prevalent only in deer and elk?
6) Why is this a concern in Kansas now?
7) Is there a relationship between CWD and mad cow disease?
8) Is there a threat to farm livestock or humans?
9) Is there a threat to the food supply?
10) How is CWD diagnosed?
11) Are there regulations to protect deer and elk?

MANHATTAN, Kan. – Wildlife officials in Kansas are paying close attention to the potential spread of chronic wasting disease (CWD), which causes the degeneration of brain tissue in deer and elk.

The disease is not a threat to the health of common farm livestock or humans, nor to the U.S. food supply, said George Kennedy, a veterinarian at Kansas State University.

Since the late 1960s, the disease has been limited to low numbers of free-ranging deer and elk in northeastern Colorado, southeastern Wyoming and Nebraska. An infected elk – apparently brought from Colorado – was found in a herd of 16 deer and elk in Kingman County, Kan. That herd has since been destroyed.

To help understand the potential threat of CWD, Kennedy answers these important questions:

Chronic wasting disease is a specific infectious, neurological disease of deer and elk in the United States. The disease is one of a group of diseases called transmissible spongiform encephalopathies (TSEs).

It is similar to, but not the same as, such diseases as scrapie in sheep, bovine spongiform encephalopathy (BSE or mad cow disease), and a disease in humans called Creutzfeldt-Jakob disease. A variant of Creutzfeld-Jakob disease called new variant (or, vCJD) has been linked with bovine spongiform encephalopathy in people in Great Britain and Europe.

Scientific evidence to date indicates CWD is a distinct disease from these other diseases.

The cause of CWD and the other TSEs is not known for sure, but is thought to involve a novel protein called a prion in the brain, that when present can transform other proteins and result in the degeneration of brain tissue.

The clinical signs of CWD include excessive salivation, emaciation or wasting, behavioral changes and weakness. It generally affects older animals and appears to always be ultimately fatal.

Current evidence suggests oral exposure, or ingestion, is the primary natural route of transmission. Close contact seems to be necessary, or at least increases the chances for transmission.

Captive and free-ranging mule deer, white-tailed deer, and elk are all susceptible. Limited experimental work has suggested other ruminants, such as wild and domestic sheep and goats, cattle, pronghorn antelope, bison, and moose are either resistant or less susceptible. It is thought that mule deer may be the primary host.

Affected animals have been found in commercial or farmed elk and deer in Colorado, South Dakota, Nebraska, Oklahoma, Montana, Saskatchewan, Canada, and most recently in Kansas.

Diseased animals have been found in low numbers of free-ranging deer and elk only in a relatively limited area of northeastern Colorado, southeastern Wyoming, and recently in a small area of southwestern Nebraska. Surveillance of numerous animals in many states, including Kansas, has failed to find diseased animals anywhere else.

This disease is of concern in Kansas because of our proximity to states affected with free-ranging animals (Colorado, Wyoming, and Nebraska) and because it was recently identified in an elk in a captive herd in south central Kansas.

Both CWD and mad cow disease (bovine spongiform encephalopathy or BSE) belong to the same group of diseases, the transmissible spongiform encephalopathies (TSEs), but appear to be specific to each species. In different species, the disease may be caused by different strains of the same or a similar agent.

As far as is currently known, neither people nor common farm livestock (cattle, sheep and pigs) are susceptible to CWD.

This disease has been known since the late 1960s and no cases have been discovered linking any disease in humans or livestock to CWD. Even where wild, free-ranging deer and elk share common pastures with domestic livestock, there has been no evidence of natural transmission to livestock.

There is no known threat to the food supply from CWD. However, because of Great Britain’s experience with vCJD in people, which has been linked to BSE, and the fact that there is still a lot to learn about CWD, experts are suggesting a few common sense precautions to hunters:

* If you see a deer or elk that fits that description, immediately contact the nearest Kansas Department of Wildlife and Parks Conservation Officer or District Wildlife Biologist.

* In areas where CWD has been reported, minimize contact with a dead deer or elk’s brain and spinal cord and wash your hands after contact.

* When boning deer or elk meat, do not include the brain or spinal cord and discard the brain, spinal cord, eyes, spleen, and lymph nodes.

Research into the exact cause and transmission of CWD and the other TSEs has been slow, in part because diagnosis has depended on microscopic examination of brain tissue from dead animals. Several promising new tests are currently being evaluated that should facilitate diagnosis and further the knowledge of CWD and the other TSEs and, hopefully, enable eventual eradication.

Because of the threat of CWD, the Kansas Animal Health Department has recently promulgated new regulations to help protect the health of Kansas deer and elk. These regulations require certain stringent qualifications for all animals of the cervidae family (deer and elk) being imported into Kansas.

For farmed deer and elk in Kansas, a monitoring program is being developed for producers to follow to determine the status of their herds and to work toward certification of being free of CWD.

K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.