document: Thus began another chapter in one of medicine 's most bizarre mysteries , a tale of sick sheep and mad cows , cannibals and Pennsylvanians , ancient life forms and a cat named Max . The plot revolves around a family of brain diseases , probably variations of a single disorder , called spongiform encephalopathy . It is infectious , invariably fatal and as insidious as termites , sometimes eating away brain cells for years without detection before a critical mass is spongified . Then , over a few months , motor control buckles and cognition crumbles . Victims then die quickly , usually within a year . Now , after decades of detective work , medical sleuths appear to be closing in on the molecular culprits behind the disease . Their dogged pursuit wo n't nail a public-health enemy No. 1 -- the disease is rare -- but it may pay off in a big way because the findings could shed light on more common killers , including Alzheimer 's disease . The work also promises basic science breakthroughs . Spongiform research already has raised questions about a cornerstone of biology and spawned a Nobel Prize . The uncanny nature of the disorder sometimes grips scientists with a kind of obsessive fascination , notes NIH researcher D. Carleton Gajdusek . He should know , having chased spongiform leads around the globe for 33 years and won a Nobel Prize in the process . Recently the fascination has taken on a more anxious cast as the disease has struck humans and animals with suspicious regularity in several places , underscoring a longstanding question : Do people get the disease from animals ? The question has burned with special intensity since scrapie , the form of the disease in sheep , jumped to British cattle a few years ago after they were fed ground-up parts of infected sheep . About 20,000 British cattle have been destroyed since 1986 in hopes of eradicating the spongiform `` mad cow '' disease , which makes the animals jittery before they keel over . A few weeks ago , the first confirmed case of mad cow disease outside Britain turned up in Switzerland . U.S. meat producers have reason to be anxious about this because the incidence of scrapie has been rising in American sheep since the mid-1980s , says Richard Marsh , a University of Wisconsin scrapie expert . Scientists agree , however , that the disease in animals probably poses little danger to people . Scrapie has existed for centuries and `` the world is bathed '' in its infectious agent , says Dr. Gajdusek . Yet sheep have never been strongly implicated in cases of the human form of the disease , Creutzfeldt-Jakob disease , or CJD . At least not until the Poltar journalist and two other people died of CJD at about the same time in a rural , sheep-herding part of eastern Czechoslovakia . When Dr. Mitrova , a researcher at a Bratislava medical institute , heard of the unusual cluster of cases , she decided to investigate . From the first , one clue stood out like a bloodstain : `` Almost all of the people are involved in raising and taking care of sheep , '' she says . The local cuisine includes a soup of sheep meat stewed in sheep milk . The area 's equivalent of chicken soup for colds is sheep brain fried in onions . One CJD victim even slept with a pet sheep until age 13 . Now such coincidences seem like a serial killer 's pattern . Against all odds , CJD has struck again and again in the same region , called Slovakia -- 69 times since 1975 , mainly grouped in two areas . The outbreak has become something of an epidemic around the Orava area , where 26 cases have occurred since 1987 , a rate hundreds of times higher than normal for CJD . Residents of the affected areas `` are very afraid , '' says Dr. Mitrova . She has found evidence of scrapie in the area 's sheep . Now villagers there call CJD `` our sheep disease . '' That 's a leap of folklore , though , and the sheep link may well turn out to be false , cautions Dr. Mitrova . Indeed , CJD is a nefarious trickster ; the first reported case of the disease , which entered medical texts in the 1920s , really was n't CJD after all , scientists now believe . And it usually strikes so rarely and randomly -- killing about one in a million people world-wide each year -- that scientists did n't even begin to suspect it was infectious until 1957 . That year , the NIH 's Dr. Gajdusek , then a young scientist casting about for big questions , planned a trip to Papua New Guinea to visit a friend . He never arrived . En route , he heard that a primitive New Guinea tribe , the Fore , were dying in droves from an unknown brain disorder they called kuru , `` the shivering disease , '' because it started with tremors . Fascinated , he dropped everything , plunged into the backwoods with a local doctor and took charge of investigating the affair , to the great annoyance of Australian authorities then overseeing the area . `` Gajdusek ... has an intelligence quotient up in the 180s and the emotional immaturity of a 15-year-old , '' one of his mentors warned the Australians in a letter , and `` wo n't let danger , physical difficulty , or other people 's feelings interfere in the least with what he wants to do . '' In short , he was perfect for the job . Soon kuru victims ' brains started issuing from the heart of darkness to distant medical centers , compliments of Dr. Gajdusek . He swapped axes and salt for autopsy rights , dissecting one victim with a carving knife by lantern-light in a native hut during a howling storm , according to his letters home . He and the local doctor , Vincent Zigas , tried everything from tranquilizers to hormones on kuru patients . Nothing helped . The cause remained elusive . Two years later , William Hadlow , a U.S. veterinarian , saw a picture of one of the kuru brains in a medical journal and was struck by its spongy appearance . He had seen that look before in scrapie , the sheep disease , and put in a call to the NIH . Another link fell into place when Igor Klatzo , an NIH scientist , noticed kuru brains resembled ones from CJD victims . Based on the clues , Dr. Gajdusek , back at NIH , led studies in the 1960s showing kuru , CJD and scrapie to be essentially the same infectious disease , studies that won the 1976 Nobel Prize for medicine . The discoveries confirmed a long-suspected connection : The kuru outbreak sprang from a Fore mourning ritual , in which relatives ate their deceased kin 's lightly cooked , and often kuru-infected , brains . But the infectious agent continued to baffle scientists . It somehow could hide in the brain for decades without causing the usual signs of infection , such as fever . Brain tissue of infected animals could transmit the disease when injected into different animals ' brains , yet microscopes revealed no signs of infectious microbes . And why did the agent sporadically appear in people with no known exposure ? It seemed like `` biological spontaneous combustion , '' says NIH researcher Paul Brown . In the early 1980s , scientists discovered that CJD , like Alzheimer 's disease , often gums up the brain with a kind of junk , or `` amyloid , '' protein . Further studies showed the junk mainly contains a botched form of a naturally occurring brain protein , sometimes called a prion . Many scientists now believe it 's the culprit . But their theory entails a biologically weird premise : that the altered protein replicates itself without the aid of genetic material , the basis of all known reproduction . If they 're right , such self-replicating proteins might be representatives of an ancient twilight zone between life and nonlife-evolution 's bridge between molecules and microbes . When formed in a brain cell , a molecule of such stuff might be `` like a bad apple in a barrel converting all the other apples , '' says the NIH 's Dr. Brown . A hot question : Does the amyloid in Alzheimer 's disease form similarly ? All this , however , does n't explain what happened after Dr. Brown baked isolates of the disease agent for an hour at 680 degrees Fahrenheit , a temperature that melts proteins . He injected the ashy residue into animals ' brains , expecting nothing to happen . But a few of them got spongiform disease . He also buried isolates in his garden for three years and found they remained infectious . The results may be `` very disquieting , '' he says , to British farmers , who have been burning and burying mad cow corpses . Still , Dr. Brown and other scientists are n't much worried about mad cows because their animal studies show spongiform disease is very hard to transmit orally . Eating huge doses of the agent is required . Perhaps the mad cows got such doses `` every time they went to the feedbag , '' says Dr. Brown . Kuru victims apparently consumed similar mega-doses . And so may have Max . He was a Siamese cat in Bristol , England , that died last spring . Examining his brain , a veterinarian found a telltale sponginess , sparking another round of panic in the U.K. about spongiform disease . Now more than 10 British cats have died of it , suggesting brains from infected sheep or cows got into cat food . Meanwhile , yet another spongiform outbreak has occurred , this time among northeastern Pennsylvanians . The cluster of more than a dozen CJD cases `` is n't an epidemic '' and appears to have topped out in 1989 , says Brian Little , an Allentown neuropathologist leading a study of it . But it is worrisome because , like the Slovakian outbreak , it suggests a common underlying cause that could strike again . During the past few months , the NIH team , working with Dr. Mitrova , has found a thread that for the first time may link many such CJD cases . The discovery began when the scientists ferreted out a genetic defect in two U.S. brothers who had died of CJD . In itself , that was nothing new . Scientists have long known that CJD runs in some families and therefore suspected a genetic problem . But Dr. Brown 's excitement grew when three other , unrelated CJD victims were found to carry the same genetic defect . `` On a flyer , '' he says , `` I called relatives of the victims and struck gold . '' They were all of Eastern European descent , suggesting people of similar ancestry might carry the gene . Drs. Brown and Gajdusek knew just where to look for such people . They grabbed a plane for Czechoslovakia . Since then , the team has confirmed that many of the Slovakian CJD victims , and a cluster of Libyan-born Jews whose tissues were preserved , carried the defect . The findings suggest one of two things : Either the defect alone produces the deadly agent or it predisposes its carriers to get CJD when they are exposed to the agent . The findings have opened the door for early diagnosis and possible prevention of CJD . But they also have introduced a new riddle , says Dr. Gajdusek : Why has the genetic defect , which has apparently existed for decades in some Eastern Europeans , turned deadly only in the past 15 years or so ? `` Essentially , we 're stuck with another paradox , '' he adds . `` But there 's nothing else worth working on in science . ''
extractive_keyphrases: mad cow disease british cattle infected sheep sheep disease altered protein cjd victims cjd cases infection