Tests show chronic wasting disease is more widespread than once thought
HOT SULPHUR SPRINGS, Colo. - High on a bluff above the Colorado River, the last cottonwood leaves twirl to the ground with a papery rustle, as two hunters from Austin, Texas, unload several bull elk heads from the back of their truck. With the help of Rob Firth, a Colorado Division of Wildlife area manager, they cut off the top of a skull with a bow saw, exposing the wobbly, wrinkled, pink brain.
Part of the brain slips out of the skull and lands in the gravel parking lot, spattering blood. The three men work bare-handed, and Firth acknowledges that he's not being as cautious as his agency recommends. The hunters, 29-year-old Mike Ashby and 59-year-old Terry Leifeste, take the antlers, and fill out the requisite forms. Firth stuffs each of the heads into a garbage bag and hauls them to a walk-in refrigerator, where they await delivery to the chronic wasting disease testing laboratory in Fort Collins (HCN, 6/10/02: No magic bullet for wasting disease).
At the lab, researchers will examine the brain tissue for the presence of the abnormal protein, called a prion, that causes chronic wasting disease, a fatal brain disease in deer and elk. The disease is related to mad-cow disease and its human counterpart, new variant Creutzfeldt-Jakob disease. And while hunters who consumed game meat from infected areas have died from Creutzfeldt-Jakob, researchers have not found proof that chronic wasting disease is transmissible to humans.
So far, predictions that hunters would be deterred by recent discoveries of chronic wasting disease west of the Continental Divide have not come true: In fact, the Colorado DOW forecasts a record-breaking 300,000 licenses this season.
"I don't think the probability is very high that it's transmissible to humans," says Leifeste, who is also a cattle rancher and has familiarized himself with mad-cow disease.
The sentiment is shared by Casey Weimer, a hunter from Hot Sulphur Springs, who says that while he's participating in his county's voluntary testing policy, his family has started eating the meat of an elk that his father shot a few days ago, before they received its test results.
But while some hunters are complacent, the state's wildlife agencies are grappling with a malady that's little understood and spreading rapidly across eight other states, including Wyoming, New Mexico and Montana.
Chasing the spread
To track the disease, the state of Colorado has set up an ambitious testing program. In northeastern counties, such as Routt County, where chronic wasting disease has existed for decades, hunters are required to deposit heads at collection sites. Elsewhere in the state, testing is voluntary. Right now, wildlife officials say they're prepared to handle as many as 50,000 heads, and can deliver test results within one to two weeks.
The results will help DOW officials determine whether they should continue killing deer and elk in infected areas - a controversial eradication strategy that may not work if the disease is already widespread across the state.
"We want to see the distribution before taking any action," says John Ellenberger, the state's big-game manager. "Is it going to be clustered in the southwestern corner of Routt County, or is it random? We're really trying to get hunters to help us so we can figure out the distribution and prevalence."
Local business owners worry that positive results could repeat the trend that's emerged in Wisconsin, where the number of deer licenses has dropped 22 percent from last year. The Colorado Division of Wildlife, which depends on big-game licenses for more than 50 percent of its budget, would be severely strained with any substantial drop in hunting. To guard against a low turnout, the DOW has offered cheaper out-of-state hunting licenses and higher allotments for elk.
Long live the prion
Scientists have assumed that the prion responsible for chronic wasting disease is passed between animals through bodily fluids, and have pointed to a high number of cases found in game farms as evidence that close quarters increase its spread. But some scientists contend that the prions persist in soil and air, and that chronic wasting disease can appear spontaneously in animals who may be genetically susceptible to it.
For this reason, epidemiologists recommend handling potentially infected tissue with extreme caution. In September, the U.S. Environmental Protection Agency cracked down on the chronic wasting disease testing facility in Fort Collins, requiring technicians to destroy all tissues and fluids in incinerators heated to 1,200 degrees - the only way to destroy the prion - and not wash them down drains, which could contaminate water supplies.
At the end of the first weekend of hunting season in mid-October, wildlife managers at voluntary sample-collection points said they were experiencing a steady flow of submissions. But, as most managers at these sites can attest, their operations are anything but sterile.
In between cutting heads, Firth washes his saw blade with bleach to "prevent contaminating" other samples, even though the prion can survive bleach and other chemical agents. For the time being, the DOW has neither the funds nor the staff to adhere to stringent bio-lab protocol. A positive result is simply a marker for further study. But for hunters directly affected, it can be frightening.
"It really takes the wind out of your sails," says Bobby Galloway, whose elk was one of the recent animals that tested positive. "It's a setback for everyone, the hunters, the economy. I talked to my wife and we got rid of the elk we still had in the freezer from last year."
The author writes from Summit County, Colorado.
- You can
- The Colorado Division of Wildlife, 303/297-1192, www.wildlife.state.co.us/cwd;
- The Chronic Wasting Disease Alliance, firstname.lastname@example.org, www.cwd-info.org.