역학조사 결과 인구 1백만명 당 1명씩의 비율로 산발적으로 발생하는 것으로 보고된 산발성 크로이츠펠트-야콥병(sCJD)처럼 광우병(BSE)의 경우도 몇몇 사례에서는 아주 드물게 유전자 돌연변이( genetic mutation )에 의해 발생할 수 있다는 연구결과가 발표되었습니다.
미국의 연구자들은 지난 2006년 Alabama주에서 발생한 광우병(BSE) 사례가 바로 이러한 사례에 해당된다고 밝히고 있습니다.
이러한 주장은 광우병이 자연발생적으로 발생할 수 있으며…결국 광우병을 완전히 박멸시키는 것은 불가능하다는 논리적 귀결에 도달하게 됩니다.(지난 해 국내에서는 5년내에 광우병이 지구상에서 영원히 사라질 것이라는 용감무쌍(?)한 주장도 나왔었는데… 유전자 돌연변이에 의한 자연발생적 광우병 발병 이론과 정면으로 충돌하네요.)
물론 산발성 크로이츠펠트-야콥병(sCJD)과 마찬가지로 산발성 광우병의 경우에도 변형 프리온에 의한 인체 전염은 가능하기 때문에… 사전예방적 원칙에 따라 광우병 위험물질의 철저한 제거 및 소각, 육골분 사료의 금지, 광우병 검사정책 등을 고려해야 할 것이라고 생각합니다.
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BSE Case Associated with Prion Protein Gene Mutation
1 National Animal Disease Center, United States Department of Agriculture, Agriculture Research Service, Ames, Iowa, United States of America, 2 National Veterinary Services Laboratories, Pathobiology Laboratory, Animal and Plant Health Inspection Service, United States Department of Agriculture, Ames, Iowa, United States of America
출처 : http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1000156
(전문 PDF 파일 첨부)
Abstract
Bovine spongiform encephalopathy (BSE) is a transmissible spongiform encephalopathy (TSE) of cattle and was first detected in 1986 in the United Kingdom. It is the most likely cause of variant Creutzfeldt-Jakob disease (CJD) in humans. The origin of BSE remains an enigma. Here we report an H-type BSE case associated with the novel mutation E211K within the prion protein gene (Prnp). Sequence analysis revealed that the animal with H-type BSE was heterozygous at Prnp nucleotides 631 through 633. An identical pathogenic mutation at the homologous codon position (E200K) in the human Prnp has been described as the most common cause of genetic CJD. This finding represents the first report of a confirmed case of BSE with a potential pathogenic mutation within the bovine Prnp gene. A recent epidemiological study revealed that the K211 allele was not detected in 6062 cattle from commercial beef processing plants and 42 cattle breeds, indicating an extremely low prevalence of the E211K variant (less than 1 in 2000) in cattle.
Author Summary
Bovine spongiform encephalopathy (BSE or Mad Cow Disease), a transmissible spongiform encephalopathy (TSE) or prion disease of cattle, was first discovered in the United Kingdom in 1986. BSE is most likely the cause of a human prion disease known as variant Creutzfeldt Jakob Disease (vCJD). In this study, we identified a novel mutation in the bovine prion protein gene (Prnp), called E211K, of a confirmed BSE positive cow from Alabama, United States of America. This mutation is identical to the E200K pathogenic mutation found in humans with a genetic form of CJD. This finding represents the first report of a confirmed case of BSE with a potential pathogenic mutation within the bovine Prnp gene. We hypothesize that the bovine Prnp E211K mutation most likely has caused BSE in “the approximately 10-year-old cow” carrying the E221K mutation.
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Gene mutation seen underlying some mad cow disease
출처 : 로이터통신 13/09/2008 11:12
By Maggie Fox, Health and Science Editor
WASHINGTON (Reuters) – A rare genetic mutation may underlie some cases of mad cow disease in cattle and its discovery may help shed light on where the epidemic started, U.S. researchers reported on Friday.
The mutation, in an Alabama cow that tested positive in 2006 for bovine spongiform encephalopathy, or BSE, is identical to one that causes a related brain-wasting disease in humans. This suggests BSE may sometimes arise spontaneously in cattle.
Jurgen Richt of Kansas State University said cattle producers must never let down their guard against BSE because cattle anywhere, at any time, can develop the disease.
The finding may support a 2005 theory that the BSE epidemic in cattle could be traced to feed contaminated with cattle remains from India, the researchers report in the Public Library of Science journal PLoS Pathogens.
BSE or mad cow disease swept through British dairy herds in the 1980s, forcing the destruction of millions of animals. No one ever found where it came from but most experts thought at the time it came from cattle feed that contained the remains of sheep infected with a similar disease called scrapie.
Cattle were never known to develop BSE before the epidemic, but some experts have argued they may have. This report lends credence to that idea.
and a human version called Creutzfeldt-Jakob disease, or CJD, are brain-destroying illnesses called transmissible spongiform encephalopathies. In some cases, animals or people that eat brain and nervous system material from victims of these diseases can develop them, too.
They are passed along by misfolded infectious protein fragments called prions.
’ANOTHER EPIDEMIC SOMEWHERE’
A very rare disease called variant CJD has been found in people who ate infected beef products. Fatal and incurable, it has affected just 167 people so far.
Most countries now ban the use of meat and other parts from mammals in food for cattle. They also ban the use of potentially infectious tissues such as brain and spinal cord in human food.
“There are tendencies around the world, now that the feed-borne epidemic has gone down, to relax these rules and regulations,” Richt said in a telephone interview.
“So if we have these genetic cases popping up here and there and we don’t have our mitigations in place, we will have another epidemic somewhere.”
He suggested breeding the gene out of cattle. “We can clean the world cattle herd of that mutation,” Richt said.
CJD is also known to pop up spontaneously in the human population. A genetic mutation causes the disease in one in a million people globally.
Richt and colleagues tested the brain of the Alabama cow and found a mutation identical to the prion gene mutation that causes some cases of CJD.
It is probably rare in cattle, found in fewer than one in 2,000, they said in the report, published at http://dx.plos.org/10.1371/journal.ppat.1000156.
But the animal passed along its mutation to its heifer, which suggests it is inherited.
(Editing by Xavier Briand)
