Steve Quayle News Alerts

August 14, 2003

Mike Miller accelerates to keep up with a cantering elk in an upmarket suburb of Estes Park, a town nestling beneath the Rocky Mountains in Colorado.

"Some of the non-native plants are like ice cream to them," says the state wildlife vet as the animal veers away from the road and Miller gives up the chase.

Although elk are unpopular because they nibble the flowers, many are attracted by the food that local residents leave out for them. That is what sparks Miller's watchfulness. For the deer and elk here harbour chronic wasting disease (CWD), once regarded as an interesting local phenomenon, now a potential threat to human health and the US and state economies.

Miller is keen to ensure this does not become his nation's BSE. Already around here as many as one in 10 deer, and half that proportion of elk, probably have CWD. The big fear is, of course, that this disease may spread directly to humans, either through venison or some other route. Or perhaps more seriously still, given the amount of beef eaten in the US, that it will spread to cattle, and then to humans. And the big problem is that deer and elk are hard to avoid in this country.

Even at the height of summer, elk and mule deer (so named because of their prodigious equine-like ears) are regular sights in Estes Park. In winter they are commonplace, a tourist attraction even for those who have not yet wandered out of their B&B. Fines for feeding the wildlife are a "slap on the wrist" $65 (£40).

"Deer become more crowded and come back to the same places day in, day out," Miller says. "We don't understand how [CWD] is transmitted but the standard rule of thumb is the more crowded animals become and the more often they go to places infected animals have been, the more likely they are to be infected themselves." His team are using a new tonsil test on wild deer they capture to establish whether they have early signs of the disease, killing them only if results suggest they have.

CWD first emerged more than 35 years ago. A decade later it was identified as part of the fatal family BSE. Yet it was still largely ignored even when BSE hit Britain in 1986. After 1996, when the grim news that BSE had, in all probability, jumped to humans, US researchers found it difficult to get funds to investigate CWD, which in wild deer was gradually spreading beyond north-east Colorado and southern Wyoming.

It began to appear in farmed elk too, and early last year the disease breached the Rockies, and became established on their western slopes, and appeared unexpectedly in Wisconsin, the "dairy state", hundreds of miles to the east. Finally Congress began to take notice. In all, 12 states now have CWD either in wildlife, farmed animals or both. In some areas, hunters can have their kills tested before taking them home to the freezer, and now national rules are being thrashed out for uniform testing on wildlife and farmed animals and for controls over captive herds.

Nerves have also been jangled by the discovery of BSE in Alberta, one of two Canadian provinces where CWD has been found (the other is Saskatchewan). A BSE-induced collapse in the US beef industry would dwarf, in economic terms at least, previous crises in Britain and Europe.

And as the US gets more worried about CWD, attention in Britain is finally turning to deer, 17 years after BSE arrived. Plans will soon be drawn up for organised testing of deer, particularly of farmed animals. Discussions are in the early stages, although the government insists that checks on animals killed by hunters or in road accidents so far have given no cause for alarm. This autumn experi ments will also begin to see whether BSE can be induced in red deer, which are genetically similar to elk, through feeding or by injecting infectious material into various parts of the body.

No one has any idea what they're going to find in the deer; the wonder is that no one has tested them before.

CWD is always fatal. There is a long incubation period before symptoms become obvious in adults aged three to four years or older. Victims suffer weight loss, socialise less, grow listless, or walk in set patterns repetitively. Many drink or urinate more. Of course no one has any idea whether the disease could be passed from deer to humans, but the feeling is that this is not a risk we should take lightly.

As to the cause of CWD, most scientists favour the same prion theory that dominates BSE research. Prion proteins are found in the brain, the central nervous system and other parts of many animals although their function remains unclear. Sometimes they fold wrongly, become killers and attack others. They have the ability to refold normal prions in their own image, thereby increasing their own numbers. Other theories blame an unconventional virus, a virino (an incomplete virus with nucleic acid protected by host proteins), or bacteria. The infectious agent, whatever it may be, resists enzymes and chemicals that might break down proteins. As with BSE in cattle, there are those who think the original culprit for CWD in deer was scrapie in sheep, a disease that has been dated back to the 1940s in the US but the 1730s in Britain. And as with BSE, others think it was a naturally occurring sporadic disease that suddenly "took off".

The first recorded incidence of CWD, in 1967, was in deer used for nutrition studies in a research facility in Fort Collins, Colorado, less than 90 minutes' drive from Estes Park. The unit was at the time run by Colorado State University, later taken over by the state wildlife department. Research pens in Wyoming were contaminated too after exchanges of deer.

In the mid-1980s, deer and elk at Fort Collins were slaughtered, their pens decontaminated and left unused for a year. Within three years, however, the disease was back.

"It is entirely possible our research facilities in the 1970s and 80s may well have exacerbated the local occurrence of CWD but whether it is the true origin or not is pretty hard to sort out," says Miller. "It is possible it started in the wild and was brought into one or both of our facilities."

An elk was the first known wild CWD victim in 1981, but there must have been others before. "Deer you see showing clinical signs are easily confused with those associated with old age or injury. A thin, poor-doing, wild deer is not that unusual." By the early 90s checks to establish whether TB was prevalent in wild deer locally found 1 to 1.5% of those killed had CWD.

E lizabeth Williams, who has conducted CWD research for 25 years, says: "There is a difference between where something starts and where it is recognised." She was a graduate student at Fort Collins when, in 1978, she identified CWD as a transmissible spongiform encephalopathy, similar to one in mink, sheep and humans, among whom Creutzfeldt-Jakob disease (CJD) is thankfully rare but kills one in a million.

She and others are striving to determine how the disease travels. It is not obviously through food - the main route in BSE (in infected meat and bone meal rations), and the manner in which BSE is assumed to have leapt to humans. Grazing on infected pasture may be a factor, as it may well be in sheep scrapie. Disease may be spread through urine, saliva or faeces. Meeting and greeting, fighting between males and sexual activity may all be involved - and more males than female seem to succumb. All genotypes of mule deer are susceptible, although one genotype of elk seems more resistant.

Williams, long established at the department of veterinary science at the University of Wyoming, Laramie, has fed faeces from CWD-infected animals to others, since this is a common route for parasites to travel, "but it is going on for two years and so far we have not got anything figured out yet".

Deer around Estes Park are now fitted with tags or satellite collars to establish how far they are travelling. The evidence points to some suddenly moving more than 50 miles within a few days. The transport of farmed elk may have also helped carry the disease. Farmed elk, which provide not only meat but antlers (used in vitamin supplements and, in Asia, as an aphrodisiac), crossed state boundaries between breeding units for years before the alarm bells rang.

Miller has long campaigned for more fencing. "Wild animals, particularly deer, are very good at getting through fences if they want to. The farm animals are not many years domestic either. If they want to leave, they will. There aren't any biological or behavioural differences between them."

Such thoughts anger elk breeders who have already seen herds slaughtered and incinerated to contain the spread of CWD.

"BSE is a problem, yes. But what in the world does a BSE cow have to do with a CWD elk? It is ludicrous," says Lisa Villella, executive director of the National Association of Elk Breeders, and defender of 3,000 farms with 175,000 animals across the US.

"People just don't believe we should be eating animals at all. That agenda driving this is making it such a big deal. When people go to a grocery store, they see ground beef, they don't see an animal, They are removed from it, non-rural, non agricultural."

Farmers have a tetchy relationship with wildlife vets too. As elk became farmed, state wildlife agencies feared loss of control and lost hunting revenues, she argues. "It is basically an old story. It is dollars," says Villella.

There is now compensation - ranging from $500 to $3,000 (£300 to £1,800) per slaughtered animal - but early in the crisis there was none. So far, Villella says , CWD has been found in 0.04% of farm animals tested. She argues that many people in the US have eaten venison and there has been no evidence of any link to a similar disease in humans. But then of course the disease might take decades to show up in humans.

John Pape, of the Colorado department of public health and the environment, has been looking for such evidence by monitoring incidence of CJD in humans since 1996, and he hasn't seen it yet. The state incidence of 1.1 per million is about the norm.

"In a state like this, a fairly large proportion of the population hunts or consumes game meat or has done at some stage in their life. With a lot of guys it is 300lb of meat in the freezer and they hunt it very locally. The wife, the kids, the in-laws eventually eat some of that.

"I have had people tell me hunters eat scrambled egg and brain, but I have never talked to a hunter who has told me they eat that _ They take the prime cuts and the rest becomes landfill."

The low consumption of venison, compared to beef, makes assessing the threat difficult. It also is an advantage. In Britain, hundreds of thousands of BSE-infected cattle entered the food chain before any controls to remove the most infective parts of the animal were introduced. Venison is not included in the same bewildering range of processed foods as beef, nor has tissue been mechanically recovered from the bones as it was with cattle.

So far, the lack of evidence of infection of humans is reassuring, says Pape. "But it is not proof it could not happen. It is either not occurring or it is occurring so rarely we can't pick it up at this point. But we are continuing to look."

A test-tube study in 2000 suggested that while CWD prions could quickly play havoc with other healthy deer and elk prions, it was far more difficult, while not impossible, to convert human prions. Beth Williams, in Laramie, a venison eater, thinks if CWD were readily transmissible to humans, "we probably would have seen that by now. CWD has probably been here (undiagnosed) since the 1950s."

"I am not saying it is impossible," she adds.

She and other spongiform encephalopathy specialists tried, often on shoestring budgets in the early years, to establish whether CWD could jump species. Infected material was injected into the brains of minks, ferrets and squirrel monkeys, and they developed signs of CWD. The material only infected hamsters after travelling through ferrets. CWD would not transfer with any great efficiency to mice.

More recently scientists at Ames, Iowa, injected CWD-infected material into the brains of 13 cattle. Five have so far succumbed over a two- to five-year incubation period. Their brains revealed toxic prions but not the signature left by conventional BSE.

Williams has fed young cattle infected material, and six years into one of these experiments, there is no sign of transmission. Nor is there in units where deer, elk and cattle are kept in constant contact. The fact that deer have roamed naturally for years alongside farmed cattle reassures those who think CWD's threat to human health is exaggerated.

Other deers' propensity for the disease is being tested as is that of other wildlife. Cats can get a BSE-like disease but mountain lions have so far displayed no evidence of it, nor have big-horn sheep, another wildlife tourist attraction in the Estes Park area. But as Miller puts it, "no one is placing any bets on the host ranges of this disease any more".

In Wisconsin, the discovery of CWD among white-tail deer, more sociable than mule deer or elk and more common in much of the US, prompted special hunting periods.

Hunters and sharp-shooters were called in to wipe out thousands of deer in a relatively small area. They probably bagged about a quarter of the adults. In an area within that zone, where CWD was most prevalent, there was evidence of the disease even in yearlings, running at more than 3% of animals killed in both sexes. Among three-year-olds however the prevalence in males was running at 16%, twice that in females.

Officials in Wisconsin, where CWD has also been found on farms, have to decide whether to try another blitz to wipe out the disease. Other states that have yet to find the disease, but fear it is slumbering unnoticed hope such a strategy works. Miller has his doubts.

For years Colorado has tried to manage, rather than obliterate, the disease and the new live test will enable them to catch many with disease early. But wildlife is by definition wild.

"We need people to continue hunting," says Miller. "It is the only cost-effective way to manage the population. We must just reduce infection levels so it does not spread and we can minimise the long-term effects on population stability.

"To get rid of the disease we would have to eliminate deer and elk from the entire northern half of Colorado. That is something we could not do, nor would we be willing to advocate."

Guardian Unlimited © Guardian Newspapers Limited 2003

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