image

Photograph by Joe Mac Hudspeth, Jr. · www.southernfocus.com

Magazine


Chronic Wasting Disease - Mississippi Prepares For The Future

From the Winter 2002 issue

image

The following information is based on the best available science of today. Chronic wasting disease has so far not been found in Mississippi, but North American hunters and the wildlife resource they value most are about to face their greatest challenge since white-tailed deer were nearly eliminated almost 100 years ago. The technical nature of this disease demands that hunters become better informed if they are to understand and support science-based measures to control the disease.

Over the last 35 years chronic wasting disease (CWD) has grown from a novel captive deer syndrome, of only local interest to scientists in Colorado and Wyoming, into the most notorious wildlife disease of our time. Hunters, and the general public, throughout Mississippi and across the nation, will continue to hear from three clearly distinct sources of information.

  • Sensationalized media accounts predicting the end of deer and deer hunting.
  • Individuals and entities who have something to lose from the perception that CWD is, indeed, a serious problem.
  • Scientists and wildlife managers whose primary consideration is the wildlife resource.

Our objective for this article is to provide Mississippi hunters and the general public with factual information relative to CWD on which to base their support for management of this disease.

The danger of CWD to Mississippi is very real. CWD is invariably fatal. There is no treatment for the disease, no vaccination for prevention, and no practical live animal test to determine if an animal is infected. Laboratory analysis of the brain of a dead animal is the only method currently accepted by the USDA as conclusive. Once this disease occurs in an area, evidence from the past 30 years demonstrates that it will not go away on its own - aggressive intervention is required to manage the impacts.

Debate continues as to how CWD began in North America. Typically, wildlife managers blame captive deer facilities while deer farmers blame free-ranging deer. Realistically, it matters little, today, where the blame lies. What is critical now, for Mississippi and the rest of the Southeast, is how we respond to the threat of CWD.

Effective response must be based on an understanding of how the disease is spread. We know that healthy deer can be infected with CWD through direct contact with a diseased animal. We also know that animals can become infected simply by exposure to an area where the disease occurred years earlier. Since direct contact has been shown to spread the disease, and nose to nose contact between animals through fences has also been documented, it is common sense that the possibility of transmission between captive animals and wild deer is real.

Because live animal testing is not currently available to insure disease-free status for deer, the first line of defense is prevention of CWD introduction through restrictions on the importation and translocation of any members of the deer family. These restrictions are equally important for high-fenced enclosures, where deer are brought in from other areas for perceived “genetic enhancements,” and for commercial deer farming operations.

The second line of defense is to prevent the spread of CWD if it does occur. One scientifically supported method is to eliminate unnecessary direct or indirect contact caused by artificially concentrating animals at feeders, mineral licks, and bait sites. The best current science supports another, more drastic, method of preventing further spread and theoretically eradicating the disease over time. This approach is to reduce deer population numbers in and around an area where CWD is confirmed. The reasoning behind this approach is two-fold. One reason is to prevent the further spread of the disease by lowering deer density and subsequent direct contact. The other is to remove potentially infected deer that may contaminate the environment.

CWD is a progressively degenerative fatal disease that attacks the central nervous system of members of the deer family. To date it has been diagnosed in elk, mule deer, black-tailed deer, and white-tailed deer. CWD is one of a group of diseases known as transmissible spongiform encephalopathies (TSEs). These diseases are characterized as transmissible because they can be transmitted from one infected animal to another. They are further classified as spongiform due to the “spongy-like” areas that form in the brain of the infected animal, hence the encephalopathy portion of the name.

Animals suffering from CWD typically behave abnormally by separating themselves from their usual social group. They often stand alone, with a drooped posture, and may not respond to human presence. As the disease progresses they will appear very skinny on close examination and will salivate, drink, and urinate excessively.

The scientific community generally accepts that the infectious agents of CWD are prions. Prions are abnormal proteins that seem to have the ability to alter the structure of normal proteins found in the body of the animal they enter. Logical natural methods of prion transmission include, but may not be limited to, secretions and excretions from infected animals. Also, human activity contributes to environmental prion contamination. Prions are hideously durable and impervious to most disinfectants and natural conditions, remaining in the environment for years.

In 1967 CWD was first recognized at a captive mule deer research facility in Colorado. A Wyoming research facility documented the disease in deer and elk in 1978. CWD was then documented in free-ranging deer in Colorado and Wyoming in the 1980s. Further testing from 1996 through the end of 2001 found additional positive animals (either captive or wild elk or deer) in Kansas, Nebraska, Montana, Oklahoma, South Dakota, and the Canadian provinces of Saskatchewan and Alberta. Then in February 2002 the first case was confirmed east of the Mississippi River in Wisconsin, in wild white-tailed deer. In the summer of 2002, two more positive states were added to the growing list - New Mexico and Minnesota.

As the documented distribution of the disease has grown, so has concern among hunters that CWD could have human health implications. Their major fear is that CWD might make the same jump from deer to humans that bovine spongiform encephalopathy (BSE) recently did from cattle in the United Kingdom. Currently, the TSE Advisory Committee of the Food and Drug Administration (FDA) and public health officials have reviewed all the scientific information available. They have concluded that there is no evidence that CWD in infected animals can be transmitted to humans. Further concern did arise in 1997-98 when Creutzfeld-Jacob Disease (CJD), a naturally occurring human TSE, was diagnosed in three young U.S. adults who had regularly eaten venison. This led to speculation, and some hysteria, that CWD could be spread from elk or deer to humans. However, the Centers for Disease Control and Prevention, the World Health Organization, and the FDA reviewed the clinical and pathological studies of all of these cases and found no link to CWD.

Recently, additional human cases of brain diseases have been diagnosed in Wisconsin with alleged ties to consumption of venison from a CWD positive area. To date one conclusive diagnosis has been issued and the other cases remain under investigation. The confirmed cause of death in the first case was Pick’s Disease, a more common, and likely hereditary, brain disorder somewhat resembling Alzheimer’s Disease. The victim’s brain tissue showed no evidence of the prions that are associated with CWD. So, there has still never been a documented case of a person contracting a brain disease from eating wild animals with CWD.

All public health officials have continued to indicate that venison is safe for human consumption. However, hunters who wish to take additional steps to avoid potential unnecessary contact with prions or environmental contamination can:

  • Avoid shooting, handling, or consuming any animal that appears sick. Contact the Mississippi Department of Wildlife, Fisheries, and Parks (MDWFP) at 601-432-2400 if you see or harvest an animal that appears sick.
  • Wear latex gloves when field dressing or processing deer.
  • Avoid eating, or contact with, brain, spinal cord, spleen, lymph nodes, or eyes.
  • Cut through the spinal cord only when removing the head. Use a knife designated solely for this purpose.
  • Bone out meat to avoid cutting into or through bones. Remove all fat and connective tissue to avoid lymph nodes.
  • Dispose of all carcass material, including the head, in a landfill or pit dug for carcass disposal purposes.
  • Either process your animal individually, or request that it be processed individually, without meat from other animals being added to meat from your animal.
  • Disinfect knives and other processing equipment in a 50% bleach solution for a minimum of one hour.

The MDWFP, in cooperation with the Mississippi Board of Animal Health (MBAH) and the USDA, has implemented plans for target animal surveillance. A target animal is one that exhibits the clinical symptoms of CWD previously discussed. These target animals should be reported to the local county conservation officer who has been trained to properly handle them and coordinate their transport to the appropriate laboratory to determine if they are infected with CWD. Most deer exhibiting symptoms of CWD are actually suffering from other diseases common to white-tailed deer in Mississippi. Malnutrition disease, bluetongue, brain abscesses, and other conditions may cause some of the same symptoms. However, due to the seriousness of CWD and the importance of early detection and control, it is necessary to test target animals for infection. Hunters who encounter potential target animals should contact the local county conservation officer before any further action is taken. The ability to diagnose disease is dependent on quick reporting because deer carcasses deteriorate rapidly in Mississippi’s climate.

In addition to target animal surveillance, MDWFP is also cooperating with MBAH and USDA to implement routine CWD testing of deer during the fall and winter of 2002-03 on a statewide basis. The goal for this upcoming monitoring period is to test 1,000 deer. Routine testing will involve Mississippi hunters in this critical disease monitoring effort. Hunters throughout the state may be asked to voluntarily submit the heads of harvested deer for CWD testing. It is expected that most of these samples will come from wildlife management areas and Deer Management Assistance Program cooperators.

The issues associated with CWD are rapidly changing. When the disease was first identified over 30 years ago, words like control and eradication were never mentioned. Today, aggressive measures are being employed to combat its further spread. Wisconsin, Colorado, and Wyoming are currently trying to reduce, if not eliminate, local deer populations in infected areas. Furthermore, Wisconsin has imposed a statewide ban on all artificial supplemental feeding and baiting in an attempt to keep CWD from spreading throughout the state’s deer herd. Other states have implemented rules prescribing legal methods for transporting hunter trophies within or through their states.

One way that Mississippi hunters can support the fight against the spread of CWD is by properly disposing of deer carcasses by burying. Another is to voluntarily discontinue baiting and feeding which unnaturally concentrate deer.

Anyone interested in finding additional accurate information and following the latest developments related to CWD can access the website of the CWD Alliance at http://www.cwd-info.org.