Last May I reported on an outbreak of chronic wasting disease (CWD) in wild whitetail deer in Wisconsin. CWD attacks the nervous tissues in cervids — or deer and elk. It is one of a family of diseases of the nervous system known as “transmissible spongiform encephalopathies” (TSE), which include scrapie in sheep, Creutzfeldt-Jakob disease in humans, and bovine spongiform encephalopathy (BSE) or “mad cow” disease. TSE’s are always fatal and are believed to be caused by extremely tiny particles of protein called “prions” that become malignant and infectious. TSE’s are also not well-understood by modern science.
Aside from the impact on deer and elk, there is cause for concern about CWD. Like mad cow disease, CWD might be able to jump the species barrier to humans who eat venison, or to livestock who come into contact with infected cervids. To date, mad cow disease has not been found in the U.S. But in the U.K. it has killed over 200,000 cattle and 133 people who have contracted new-variant Creutzfeldt-Jakob disease, which is thought to occur in humans who are infected by BSE.
CWD was first identified in l967 in a herd of penned mule deer at the Foothills Wildlife Research Center in Ft. Collins, Colorado. Initially it was found only in game farms, but then zoos began to report it, quite possibly because of gifts of deer and elk to zoos from game farms and the Foothills Center. In l981 CWD made the jump to a herd of about 62,000 wild deer and elk that live between southeastern Wyoming, northeastern Colorado, and southwestern Nebraska. Between 4 and 8 percent of that herd have it for certain, but some biologists believe that 15 percent may be infected.
It is not certain how CWD is transmitted, but many believe some kind of contact or exchange of body fluids, or consumption of diseased tissues, is required. Just how CWD could suddenly appear 1,000 miles east of its original identification point is unknown. This development is very worrisome as deer herds to the east are much more densely populated — reaching 150 or more per square mile — thus making the expected spread of CWD much quicker in the eastern whitetail range.
There have been many developments in this story since I covered it last May. Here’s a digest:
1. When it was decided that some Europeans who ate BSE-infected beef had contracted a new form of Creutzfeldt-Jakob, five million head of livestock were killed and burned. The same eradication-control strategy is being used in Wisconsin to attempt to control the spread of CWD in free-ranging deer. Wisconsin wants to kill all deer inside the 411 square-mile zone around Mt. Horeb — that’s about 30,000 animals.
In the 10-county area surrounding the eradication zone, 50 to 75 percent of the deer will be killed (up to another 70,000). In each of the remaining 59 counties in the state, 500 will be tested. If none of the 500 deer test positive in any county, hunters will know “with a 99 percent degree of certainty” there is no CWD there, officials say. Hunters worried about eating infected venison can submit the heads of deer they kill for testing, and can freeze their meat until the results come back.
Last Spring the Wisconsin Department of Natural Resources asked hunters to help shoot deer, and they also hired sharpshooters. This plan did not sit well with many in the state who have grown up on an ethic of shooting only what will be eaten. Some groups filed lawsuits and some farmers refused to cooperate. Nonetheless, since May, more than half of the deer in the eradication zone have been killed.
2. The eradication program is costly for several reasons: the use of sharpshooters, testing of killed animals (which requires that samples are sent to a government lab), and the disposal of the carcasses. Just where this money will be coming from is not clear. Numerous state and federal bills are in the works.
3. May surveys showed that almost 40 percent of the deer hunters in Wisconsin were considering not hunting last fall. Since Wisconsin’s deer hunting is a $1.5 billion a year industry, this would have been an economic disaster. However, license sales in the nine-day general rifle season in November were down only 10 percent for a loss of $2.5 million in license revenues. But that’s hardly as bad as expected.
4. Fewer deer were killed in Wisconsin last fall (261,093) than in the previous year (291,563). State biologists would like the state’s herd to be about 1.1 million. Presently it is about 1.6 million. With such a light kill, there could be 2 million deer in Wisconsin this coming summer. That translates to more deer-car collisions, more crop damage, more Lyme disease, a possibility of deer carrying bovine TB (found in Michigan), and chances for a more rapid spread of CWD. In 2001, the state reimbursed farmers $1.5 million for crop damage, using money collected from a $1 hunting-license surcharge.
5. Hunters donated 4,823 deer to Wisconsin food banks last fall. That’s 1,000 more than the year before. The state uses a surcharge on hunting licenses to pay butcher shops to process venison donated to charity. In 2001, the state of Wisconsin paid $350,000 for butchering donated venison. Food banks are not accepting venison from deer killed in the eradication zone.
6. A total of 48 CWD-positive deer have been found in Wisconsin. Beyond Wisconsin, four wild deer in Illinois, and one in White Sands, New Mexico, have recently tested positive for CWD. The disease has now been found in wild deer and elk in Colorado, Kansas, Minnesota, Illinois, Nebraska, New Mexico, Oklahoma, South Dakota, Wisconsin, and Wyoming, as well as in the Canadian provinces of Saskatchewan and Alberta. Whether the disease is spreading or simply being better detected by more widespread testing is uncertain.
7. Seven states and several Canadian provinces have found CWD in captive herds. Canada has destroyed more than 7,800 elk in trying to stop the disease. Korea, which started elk farming with U.S. animals, has now banned the practice. Over 30 states have tightened laws on transporting cervids. The 931 Wisconsin deer and elk farms now manage approximately 35,000 animals, making this one of the leading states in the multibillion-dollar U.S. deer-and-elk trade.
8. Two Wisconsin hunters who were thought to have died of Creutzfeldt-Jakob were found not to have had the disease. Still, if CWD can jump the species barrier to humans or livestock, the economic and biological implications are monumental and staggering.
9. Until very recently there was no way to test for CWD except by cutting off the head of a dead animal. But there is a new live test for CWD. It’s like a tonsillectomy. It takes about 20 minutes to collect the tissue and the deer needs an hour to recover. This means you don’t have to kill a deer to test for CWD. But the costs of sedating and testing wild deer on any large scale are not cheap.
Testing itself is fraught with controversy. Government labs do not accept the results of private labs, which report some additional CWD-positive animals in Wisconsin. At least one private company is marketing do-it-yourself test kits for hunters, but government agencies question the accuracy of these tests.
10. There is a serious problem of disposing the carcasses of dead animals generated by the eradication programs. Only incineration, bleach, and chemical tissue digesters destroy the infectious prions. Many landfills will not accept dead deer for fear of contaminating the ground water. In Wisconsin, when a dead deer from the eradication zone is delivered to a Department of Natural Resources checkpoint, the deer’s head is removed for testing. The rest of the body is then sealed in plastic, awaiting incineration.
DEER AND DIRE CIRCUMSTANCES? There are 33 million whitetail deer in the U.S., most east of the Rockies. Wildlife biologists in Wyoming say CWD is spreading at a rate of about 50 miles per year. Considering the density of deer in many areas, the potential for an epidemic that could devastate deer and elk populations is clearly there.
In attempt to calm panic among hunters, Safari Club International is distributing one million copies of a brochure on chronic wasting disease. It assures hunters that CWD-infected animals have never infected humans. Let’s hope this finding stays. Should it be found that CWD can jump the species barrier, the Centers for Disease Control and Prevention and the Agriculture Department will step in and a war will be declared on the millions of deer and elk in America.
This will turn what has been a conservation story into an unprecedented tale of disaster.