Consider the lowly cow: docile, moon-eyed, and when cooked properly, so very tasty. But could this humble, pastoral beast, so prevalent on the western landscape and so central to the American diet, be a silent killer?
The families of more than 80 people in England, where mad cow disease has taken a terrible toll on people and agriculture, might say yes. But from this side of the pond, mad cow disease appears to be strictly a European problem, and a rather exotic one at that—the First World’s Ebola, one might say.
The scientific name for mad cow disease is bovine spongiform encephalopathy, or BSE. Despite the difficult-sounding title, BSE is precisely what its name suggests: a disease that eats away the brains of its bovine victims, leaving sponge-like holes.
Dr. Byron Caughey, a biochemist with the Rocky Mountain Laboratories in Hamilton, has researched BSE, one of many similar diseases that fall under the larger category of transmissible spongiform encephalopathy, or TSE, a brain-eating disease that affects a large variety of mammals, including humans, sheep, cows, deer, elk, mink, goats, domestic and wild cats and hamsters. It is, he says, a mystery.
The disease, which goes by different names from one species to the next, is always fatal to its victims, and there is no diagnostic test. Confirmation of the disease comes only after the brain is studied post-mortem.
In humans, mad cow disease is called variant Creutzfeld-Jacob disease, or vCJD, to differentiate it from sporadic CJD, a brain-eating disease of humans scientists have known since the 19th century.
Sporadic CJD, which causes dementia, occurs spontaneously in one in 2 million people worldwide each year, usually in older people, according to Caughey. “And we have no idea where it’s coming from.” Whether it’s a spontaneous corruption of a rogue protein, or whether there’s a widespread source of infection that one in 2 million people are susceptible to is unknown.
Its newly discovered relative, vCJD, occurs from eating BSE-contaminated beef. The cows get it from eating feed made partly of ground-up sheep that have been contaminated with their own variety of TSE, called scrapie. It is, says Caughey, a case of “agricultural-related cannibalism.”
But how do sheep get it? That’s a matter of speculation at this point. The newly discovered variant of CJD showed up in the late 1990s in healthy young people who ate BSE-contaminated beef in England sometime before rendering practices were changed to eliminate animal protein from cattle feed. (Caughey and his wife, as “poor grad students” living in London in the mid-1980s, ate low-grade beef then to survive the lean years. “We worry about it ourselves,” he says now about contracting vCJD.)
Unlike sporadic CJD, the variant manifested itself not in dementia but in loss of motor control. Though the deaths of more than 80 people seems alarming, that number is, so far, about what would be expected, Caughey says, given England’s population and the number of sporadic CJD cases that occur there spontaneously every year.
Had it not been for the fact that people in their late teens and early 20s were dying of the disease, Caughey says, it might have gone unnoticed.
Because sporadic CJD has a lengthy incubation period—as long as 20 years in some cases—dire predictions have been made that the number of vCJD deaths will jump dramatically in England over the years, especially considering that 1 million BSE-infected cattle found their way into the British food supply before rendering practices changed.
Far from England, in the wilds of the Rocky Mountain west, TSE also is endemic in resident elk and deer populations, in which it is called Chronic Wasting Disease. So concerned were Montanans about CWD and the possibility it could spread from private land to the wild that in the November 2000 election, canned hunts on private ranches were made illegal. The threat of CWD may now be confined to the wild. But the likelihood that humans could contract vCJD through eating infected game is remote, says Caughey. Scientists don’t know how CWD is spread in the wild, but the fact remains that there are few infected elk and deer and few hunters, generally speaking, making the likelihood of game-to-human infection slight.
The cause of TSE is, like the disease itself, a bit of a medical mystery. In 1997, San Francisco scientist Dr. Stanley Prusiner was awarded the Nobel Prize in Physiology or Medicine after he fingered the TSE culprit. Neither a virus, a bacterium, fungus nor parasite, TSE appears to be caused by a rogue protein he called a prion, a completely new biological principle of infection. Though not as solidly confirmed as, say, bacteria, the scientific community generally leans towards acceptance of prions as the cause of TSEs. There is still debate over whether prions exist, however, even among scientists at the Rocky Mountain Labs. Some scientists insist that there isn’t enough evidence to support the prion theory, and that the TSEs are caused by a slow-acting virus that just hasn’t been identified yet.
“You can criticize the virus fans by saying, ‘if there’s a virus in there, show it to us,’” Caughey says. “If it’s a virus its genes are unusually well protected from the environment and really hard to find with traditional cloning techniques.”
His own experiments in duplicating the corrupted protein have been inconclusive. Caughey has by now developed some opinions on BSE, a disease so gruesome it might have sprung from the fertile imagination of Stephen King.
Caughey’s ongoing research is focused on developing therapeutic strategies and coming up with a live test for the disease. “We’re covering the gamut here, trying to understand what’s going on at the molecular level,” he says. “Those are the kinds of things we’re looking at.”