Article by Martha Quillen
Wildlife – November 2002 – Colorado Central Magazine
As Chronic Wasting Disease spreads across our state the question arises: Is our government doing too much or too little to halt this deadly epidemic?
A fatal brain disease found in both deer and elk, Chronic Wasting Disease (CWD) was first identified in 1967 at a government research facility near Fort Collins. In the ensuing years, researchers have tried to figure out how to cure, prevent, or at least stop the spread of CWD, but the condition is still poorly understood.
The disease seems to be spread by contact between animals, but it may also linger for long periods of time in contaminated environments. In 1977, Chronic Wasting Disease was classified as a spongiform encephalopathy.
Exactly what causes transmissible spongiform encephalopathies, or TSEs, is unknown. But there are several suspects. Currently most researchers think that the disease is caused by abnormal proteins called prions which mutate and eventually leave holes in the victim’s brain.
Such proteins are definitely a factor in the disorder, but how or why they morph into infectious agents isn’t known. So some scientists still believe that the cause may be an atypical virus or virino, and many suspect that toxins, environmental factors, genetics, and secondary infections may also play a role.
Whatever it is that causes the disorder, however, is notoriously difficult to kill. Transmissible agents tend to survive heat, cold, radiation, ultraviolet light, and common disinfectants.
According to the Wall Street Journal: By 1985, “it became clear that the Fort Collins pens and Sybille Canyon [Wyoming] had become deadly reservoirs of sickness. Whatever was causing CWD was somehow loose in the dirt enclosures. That led to what Dr. Hobbs calls a ‘grisly’ clean-up effort at the Foothills facility. The deer, big horn sheep and other animals being studied on site were all destroyed, and six inches of topsoil hauled away. The outbuildings were washed with bleach, then left vacant for over a year. But when new deer were brought to the Foothills pens, the disease came back, too.”
The good news is that unlike some TSEs, CWD doesn’t appear to be spread through ingestion of contaminated foodstuffs. But nobody is taking that for granted.
Concern over the deer disease heightened considerably after bovine spongiform encephalopathy (or BSE) — which is more commonly known as Mad Cow Disease — wreaked havoc in Great Britain.
This family of diseases is hardly new, however. Scrapies, a variety found in sheep, has been around since the 1730s, and has never been associated with human illness — until Mad Cow Disease arrived. (Some researchers believe that British cattle developed spongiform encephalopathy after being fed meal made with infected sheep heads.)
Similar disorders also occur in rodents, wild animals, and humans. Some human encephalopathies seem to occur spontaneously, and others are genetic, but one notable variety, Kuru, was caused by ritual cannibalism among the Fore People of Papua New Guinea.
Another encephalopathy, the rare Creutzfeldt-Jakob Disease (CJD), was first recognized in 1920. Literally a one-person-in-a-million malady, it typically strikes older patients with certain genetic predispositions. But CJD can also be transmitted through corneal transplants, instruments used in brain surgery, injections of human growth hormone, and other medical procedures.
And sometimes CJD occurs in people who have no family history of the disorder or any known source of exposure. But even so, when numerous cases of CJD were diagnosed in British young people in the 1990s, doctors became seriously alarmed.
Typically TSEs show up anywhere from two to twenty years after transmission, so it’s hard to go back and figure out how a patient got exposed to the illness in the first place. But in the 1980s, tens of thousands of cattle in the British isles sickened and died from what appeared to be a new form of spongiform encephalopathy. So when numerous young people displayed similar symptoms a decade later, it wasn’t long before researchers noted a marked resemblance between the human and bovine disorders.
Before Mad Cow Disease terrorized Britain, however, it was thought that encephalopathies couldn’t skip from one species of animal to another — at least not naturally.
Although such neurological disorders were sometimes transmitted in the laboratory by injecting or feeding contaminated tissue to rodents, the long, uneventful history of Scrapies had lulled people into thinking that cross-species infection was impossible.
But today, no one is pretending to be entirely sure about what’s safe to eat and what isn’t.
Therefore, even though Chronic Wasting Disease doesn’t appear to be spread by the ingestion of contaminated food products, the Colorado Division of Wildlife warns hunters not to eat meat from any diseased animals, and to avoid contact with any obviously ill animals.
In addition, this year, the Colorado DOW made provisions to test 50,000 animals for CWD for a mere $17 each (veterinarians usually charge about $45). CWD tests serve a two-fold purpose. Hunters can refrain from eating the meat until test results are available, and the DOW can learn more about the spread of the disease.
To have an animal tested, a hunter merely has to refrigerate — but not freeze — the head until he can submit it to a nearby DOW office. But hunter response to the program has been meager (thus far). In early October, an estimated 45,000 hunters had turned in a mere 1,066 heads.
In the meantime, wildlife biologists are trying to determine just how CWD is spread. They’ve launched experiments to determine how deer are getting CWD from other deer; and to see whether mice can be infected with the disease through contaminated meat products; and to find out whether prions can linger in the wild as scientists suspect.
In the face of an ongoing epidemic, sharpshooters have reduced herds in infected areas, and there’s even talk of more extreme culling if the disease’s distribution expands.
Whether that’s the best solution, however, is unknown. Selective breeding has proven to be one of the best methods to reduce the incidence of Scrapies in sheep. When it comes to TSEs, genetic resistance tends to be fairly high. (For example, all of the victims of Mad Cow Disease had a mutant gene found in only 40% of Caucasians.)
Thus culling herds may not be the most desirable preventive — since the process will reduce the number of genetically resistant animals, too. In a true wilderness situation, the DOW might do well to let nature run its course. In which case, the susceptible would die and the resistant would reproduce.
In this case, however, there’s the specter of mad cows, Englishmen, and an incurable fatal disease — all prompting action. And there’s also money at stake.
After congressional hearings last spring, the May 24th Wall Street Journal implied, perhaps inadvertently, that the government may not be the best defender against CWD — because game animals are big business. As always, the Journal reported on the potential financial consequences of the situation:
“Fears that CWD could devastate regional hunting and tourist economies have sent states scurrying to Washington for financial aid.”
The Journal went on to reveal Wisconsin’s woes after tests revealed that approximately 3% of the state’s white-tail deer were infected. “Those findings have generated shock waves in a state where hunters killed 446,000 deer last year, generating more than $1 billion in economic activity and countless venison dinners.”
With so much money at stake, it’s difficult to predict whether government agencies will err on the side of cash or caution. But if CWD continues to spread, Theo Stein of The Denver Post predicts that it “might force the agency [DOW] to risk a sharp public backlash by killing hundreds of animals in parts of the state thought to be disease-free.”
It’s uncertain whether such tactics will work, though. Even with the infected animals dead, the disease (be it caused by prions, a virus, virinos, or environmental contaminants) may still be out there, hiding beneath the trees and waiting in the grass.
When it comes to CWD, the DOW is caught between the proverbial rock and hard place. There’s no cure and no easy answers. Experts don’t think CWD can be transmitted to humans through food products, but no one knows for certain.
Nobody can even be sure how much we should invest in research. First off, CWD is not currently considered a threat to humans, but even if it were…
Spongiform encephalopathies are invariably fatal, but not particularly common in humans. Salmonella, listeria and e-coli take more lives. Heart disease, cancer, and AIDS strike thousands.
Colorado citizens will probably be very angry if humans, or even barnyard animals, get CWD, though. And they’ll probably be upset if the epidemic starts to shrink hunting dollars. And they’ll no doubt get mad if thousands of deer and elk are culled unnecessarily, too.
Although CWD may be more baffling than cancer, we nevertheless expect our government to cure it.
