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MAD COW DISEASE AND HUMANS

When a new form of an old human disease appeared in England in1995, some medical specialists immediately suspected that itmight be a human version of "mad cow disease," but they had noproof. Mad cow disease had appeared in British dairy cattlefor the first time in 1985 and during the subsequent decade175,000 British cows had died from it. British health authoritiesspent that decade reassuring the public that there was no dangerfrom eating the meat of infected cows. They said a "speciesbarrier" prevented mad cows from infecting humans. A "speciesbarrier" does prevent many diseases from crossing from onespecies to another -- for example, measles and canine distemperare closely related diseases, but dogs don't get measles andhumans don't get distemper.

While the British government was placing its faith in the speciesbarrier, British citizens began to die of a new disease, called"new variant Creutzfeld-Jakob disease" or nvCJD. A similardisease, CJD (Creutzfeld-Jakob disease) had been recognized for along time but it almost never occurs in people younger than 30;nvCJD, on the other hand, strikes people as young as 13. Thereare several other differences between CJD and nvCJD, so nvCJDrepresents something new. To date, nvCJD has killed 48 people inEngland and one or two others elsewhere in Europe. The mainfeature of both mad cow disease and nvCJD is the progressivedestruction of brain cells, inevitably leading to totaldisability and death.

New research published late in 1999 showed that nvCJD is, infact, a human form of mad cow disease, dashing all hope that aspecies barrier can protect humans from this deadly bovineaffliction.

Mad cow disease is formally known as "bovine spongiformencephalopathy" or BSE. BSE is the cow version of a larger classof diseases called "transmissible spongiform encephalopathies,"or TSEs. TSEs can afflict sheep, deer, elk, cows, mink, cats,squirrels, monkeys, humans and other species. In all species thesymptoms of TSEs are the same -- progressive destruction of braincells leading to dementia and death.

Traditional Creutzfeld-Jakob disease (CJD) is a rare humanaffliction. The visible symptoms are similar to Alzheimer'sdisease; in fact, CJD is sometimes diagnosed as Alzheimer's andtherefore may go unrecognized. CJD strikes one in a millionpeople almost all of whom are older than 55. In people youngerthan age 30, CJD is extremely rare, striking an average of 5people per billion each year, worldwide (not counting the recentoutbreak in England).

In cows, the latency (or incubation) period for mad cow diseaseis about 5 years, meaning that cows have the disease for fiveyears before symptoms begin to appear. No one knows the latencyperiod for nvCJD in humans, but it is thought to be around 10years. Because of this uncertainty, no one is sure how manypeople in England already have the disease but are not yetshowing symptoms. The British government's chief medical officer,Professor Liam Donaldson, said December 21, 1999, "We're notgoing to know for several years whether the size of the epidemicwill be a small one, in other words in the hundreds, or a verylarge one, in the hundreds of thousands."

The epidemic of mad cow disease was caused by an agriculturalinnovation -- feeding dead cows to live cows. Cows are, bynature, vegetarians. But modern agricultural techniques changedthat. Cows that died mysteriously were sent to rendering plantswhere they were boiled down and ground up into the consistency ofbrown sugar, and eventually added to cattle feed. It was laterdetermined that mad cow disease was being transmitted throughsuch feed, and especially through certain specific tissues --brain, spinal cord, eyes, spleen and perhaps other nerve tissues.

Ten new cases of nvCJD were reported in England in 1999, bringingthe total to 48. It has been more than 10 years since governmentauthorities banned the use of the particular parts of cowsthought to transmit mad cow disease. The appearance of new casesof nvCJD in 1999 implies either that the latency period for thedisease is longer than 10 years, or that infected meat was noteffectively eliminated from the food chain when governmentauthorities said it was, or both.

The SUNDAY TIMES of London reported in late December that somemeat banned for human consumption is still being marketed inEngland. After the mad cow scandal erupted, the Britishgovernment attempted to eradicate the disease by requiring thatall cows older than 30 months be slaughtered. As a result, bylast September more than 2.5 million British cows had beenkilled. But the TIMES reported that British investigators havedocumented at least 50 cases of farmers and cattle dealers usingbogus identity documents to falsify the ages of cows in order tosell them for human consumption. Furthermore, the AgricultureMinistry acknowledged that as many as 90,000 cattle could not beaccounted for. About 1600 new cases of mad cow disease are stillbeing reported each year in England.

In December, French health authorities announced finding a secondcase of nvCJD, a 36-year-old woman in Paris. France has continuedto refuse to import British beef, even though the European Unionon August 1, 1999, formally declared British beef as safe as anyin the European Union. The European Union said in December itwill take France to the European Court of Justice to force it toimport British beef. Germany is also refusing to import Britishbeef.

The U.S. government says mad cow disease has never been observedin any U.S. cows. However, a closely-related TSE disease, calledchronic wasting disease (CWD), has been increasing for almost 20years among wild deer and elk in northern Colorado and southernWyoming. Since 1981, CWD has been spreading slowly among wilddeer and elk herds in the Rocky Mountains and now afflictsbetween 4% and 8% of 62,000 deer in the region between FortCollins, Colorado and Cheyenne, Wyoming.

During 1999, CWD erupted among a herd of elk on the David KeslerGame Farm near Philipsburg, Montana, which raised elkcommercially. A few of Mr. Kesler's elk had been shipped toOklahoma and Idaho, and perhaps elsewhere, and CWD was discoveredin some of those animals, too. In early December, Montana healthauthorities slaughtered 81 elk on Mr. Kesler's farm. Theyinitially announced plans to incinerate the carcasses, but laterdecided that incineration would be too expensive. The animalswere finally buried at the High Plains Sanitary Landfill north ofGreat Falls. Equipment used to feed, water and care for theanimals was also buried in the landfill. Montana authoritiesannounced that the fenceline at the elk farm would bedecontaminated, but they did not say what procedure they woulduse. Nor did they announce what would become of Mr. Kesler'scontaminated land. The disease agent that causes CWD -- a prionprotein -- is very hardy and resists destruction by traditionalsterilization techniques like alcohol and heat.

The diseased elk carcasses in the High Plains landfill have beenburied under a mound of garbage but will still be accessible torainwater and perhaps to scavenging animals.

In northeastern Colorado and southeastern Wyoming, stateofficials are urging hunters to protect themselves when dressingwild deer and elk they have shot. Hunters should wear rubbergloves, minimize contact with brain and spinal cord tissues,discard the brain, spinal cord, eyes, spleen and lymph nodes anddefinitely not eat them. There is no evidence that CWD can crossover from deer and elk to humans, but there was no firm evidencethat mad cow disease could afflict humans until 1999, so wildlifeofficials in the Rocky Mountain states say caution is warranted.

Writing in the BOSTON GLOBE, Terry J. Allen reported in late 1999that, since 1996, Creutzfeld-Jakob disease has been identified in3 Americans younger than age 30. All three are known to havehunted extensively or eaten venison. There is no evidence thatCWD disease has jumped from deer or elk to humans, but theappearance of this extremely-rare disease in young people was thefirst evidence of a problem in England, so health authorities inthe U.S. say they are aggressively investigating all thepossibilities.

A statistician at the federal Centers for Disease Control (CDC)in Atlanta told Terry Allen that, if one more case of CJD hadsurfaced in a person younger than 30 in the U.S., it "might tipthe balance," meaning it might convince authorities thatsomething truly unusual was occurring. Dr. Michael Hansen ofConsumer's Union says, "Given how rare the disease is in youngpeople and how difficult it is to make a diagnosis, thepossibility that some cases go undetected cannot be ruledout."

Indeed, of the 3 cases detected in the U.S. since 1996, onenearly went undetected. Last year in Utah, Doug McEwan, 28, beganto show an array of mysterious symptoms: loss of memory, loss ofmotor control, mood swings, and disorientation. His wife, Tracey,says his doctors conducted hundreds of tests but could notdiagnose his disease. She happened to see a TV program on mad cowdisease and she insisted that Doug's doctors must test for CJD. Abrain biopsy confirmed the diagnosis.

One of the three young CJD victims had eaten deer shot nearRangely, Maine, so last November federal officials took samplesof brains from 299 deer shot in western Maine. Authorities saidat the time they were quite sure Maine deer are not harboringCWD. So far, test results have not been released.

Federal authorities have quarantined two herds of sheep inVermont because they say the sheep may have been given feed thatcontained parts of animals afflicted by mad cow disease. Thesheep had been imported into Vermont from Belgium and theNetherlands, where they may have been fed improperly. A similarherd of sheep in New York state was recently purchased by thefederal government and slaughtered.

Meanwhile, a 68-year-old Indiana man with a fondness forbeef-brain sandwiches died of CJD last summer. Beef-brainsandwiches are a local delicacy in Indiana, introduced years agoby German immigrants. The EVANSVILLE (INDIANA) COURIER reportedthat John Hiedingsfelder, a forensic pathologist in Evansville,said he had seen three cases of CJD in the past year. Noconnection to mad cow disease has been established in the Indianacases. Roberta Heiman, a staff writer for the EVANSVILLE(INDIANA) COURIER reportedly received a warning from acattleman's association not to publish any further articles aboutthis subject.

Written by: Rachel's Environment


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