광우병, 한국인 더 위험


● 앵커： 광우병과 관련해 얘기가 너무나 엇갈려 누구 말이 맞는지 과학적， 의학적으로 접근하겠습니다.

광우병에 대한 한국인의 특징, 증상과 치료, 알아보겠습니다.

신재원 의학기자는 우울한 진단을 내리고 있습니다.

들어보겠습니다.


● 민동석 (한미쇠고기협상 수석대표) : '미국산 쇠고기는 안전합니다. 국내에서 광우병이 지나치게 과장이 됐다고 생각이 드는데요'

농림수산식품부 장관은 한발 더 나아갔습니다

'광우병은 구제역과 달리 전염병이 아니다' 라고 못박았습니다

그러나 정부 말은 사실과 다릅니다. 인간 광우병은 분명한 전염병입니다.

광우병의 원인 물질은 '변형 프리온'.

미국의 소 사육 방식처럼 소에 동물성 사료를 먹이면, 정상 프리온이 뇌 조직을 파괴하는 변형 프리온으로 변해 소가 광우병에 걸립니다.

이 쇠고기를 먹은 사람은 인간광우병에 전염됩니다.

변형 프리온은 설렁탕처럼 끓여도 안 죽고, 곱창구이처럼 익혀도 안 죽습니다.


● 우희종 교수 (서울대학교 수의과대학) : '아주 진한 양잿물로 처리하거나 아니면 태우거나 이런 극단적인 방법 외에는 프리온의 병원성을 없앨 수 있는 방법은 없습니다.'

변형 프리온은 전염성도 무척 강해, 인간 광우병 환자의 혈액이 상처에 닿기만 해도 광우병에 걸릴 가능성이 높습니다.

그리고 일단 걸리면 100% 죽습니다.


● 정해관 교수 (성균관대학교 의과대학) : '아주 빠른 속도로 진행하는 치매와 비슷한 양상을 보입니다. 움직일 수도 없고 식물인간 상태로 갔다가 사망하시게 되는 거죠.'

특히 이번에 미국에서 수입하기로 한 뇌와 척수,척추,내장은 30개월 미만의 광우병에 걸리지 않은 소라도 얼마든지 변형 프리온이 존재할 가능성이 있습니다.

더 큰 문제는 한국인이 전세계에서 가장 광우병에 걸리기 쉬운 유전자를 갖고 있다는 점입니다.


● 정병훈 박사 (한림대 일송생명과학 연구소) : '한국인이 광우병에 걸린 쇠고기를 섭취했을 때 광우병에 걸릴 위험이 상당히 높다는 것을 의미하고 있습니다.'

인간에게 존재하는 정상 프리온 유전자는 3가지 종류인데, 지금까지 확인된 180여명의 인간 광우병 환자는 모두 MM 유전자형을 가진 사람들입니다.

그런데 한국인의 94% 가 바로 MM 형 유전자를 갖고 있습니다.

38% 인 영국사람, 50% 인 미국사람 보다 두배 세배 광우병에 걸릴 가능성이 높다는 겁니다.


● 정병훈 박사 (한림대 일송생명과학 연구소): '한국인은 MM형이 높기 때문에 한국인끼리 결혼했을때 자식들은 광우병에 취약한 유전자를 갖고 태어날 수 밖에 없습니다.'

미국산 쇠고기를 먹고 인간 광우병에 걸린 사람이 거의 없다며 위험을 과소 평가하는 사람들이 있습니다.

과학적 무지에서 비롯된 잘못된 생각입니다

현재의 의학기술로는 죽어서 뇌를 부검해봐야 광우병에 걸렸는지 알 수 있기 때문입니다.

특히 인간에게 없던 병이 생긴 것 자체가 대재앙의 시작일 수 있습니다.


● 우희종 교수 (서울대학교 수의과대학) : '에이즈만 해도 1980년대 시작된 병이 지금까지 4천만명 이상을 사망시켰거든요.처음에는 서너명으로 시작했습니다. 이것이 생물학적 질병의 위험성인데요.'

● 정해관 교수 (성균관대학교 의과대학) : '일정 시점에 이르렀을 때 환자수가 폭발적으로 늘어날 수 있고 천문학적인 피해를 볼 수 있는 것이죠.'


MBC 뉴스 신재원입니다.
(MBC뉴스데스크 2008-04-30일자 보도)


*한 자료(확인된 것)

ㅇ 선진국 포함한 세계 96개국이 미국産 쇠고기를 먹고 있으나, 광
우병은 1명도 걸리지 않아
ㅇ 3억명 미국 국민들이 쇠고기를 먹고 있으나, 광우병에는 1명도
걸리지 않아
ㅇ 1997년까지 동물성 사료를 먹인 미국 쇠고기를 5000만 한국인
이 먹었으나, 광우병에 1명도 걸리지 않아
ㅇ 미국소의 내장과 뼈를 먹은 재미동포들 중 단1명도 광우병에
걸리지 않았다고 한다.

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광우병은 사라지고 있는 질병

1. 97년 8월 이후 소, 양 등 동물성 사료를 먹은 미국 소는 없다

□ 광우병은 원인체인 변형프리온이 포함된 동물성 사료를 먹은 소에게 발생하는 것으로 동물성 사료 급여를 중단할 경우 발생하지 않음

□ 미국은 1997년 8월 소, 양 등 되새김질하는 동물로 만든 사료를 다시 소, 양 등에게 주는 것은 금지하였고, 이 조치는 광우병 위험을 통제하는데 충분한 조치로 인정되어 국제수역사무국이 미국을 광우병 위험통제국으로 인정함

□ 이번 미국이 발표한 강화된 사료조치는 닭이나 돼지 등에도 광우병 감염소, 도축검사 불합격 소 등을 사료로 주지 않도록 하여 만에 하나 발생할 위험을 최소화하는 조치임
※ 따라서, 시행시점이 아닌 고시시점에 수입을 재개함에 따라 안전성을 담보할 수 없다는 주장은 잘못된 것임

2. 동물성 사료를 먹이지 않고, 특정위험물질(SRM) 부위마저 제거하므로 광우병 확률은 매우 낮다

□ 광우병은 변형프리온에 오염된 동물성 사료를 먹은 소가 걸리는 병이며, 광우병에 걸리면 생성되는 변형프리온은 SRM에 축적됨

□ 따라서, 원천적으로 동물성 사료를 먹이지 않고, SRM을 제거한 쇠고기를 섭취한 경우 인간광우병이 발생한 사례는 없음
※ 미국에서 사료 금지 조치가 시행된 ‘97년 8월 이후 출생한 소에서 광우병이 발견된 사례는 없음

3. SRM부위는 30개월 미만이든 이상이든 원천적으로 수입을 금지했다

4. 미국 쇠고기를 제한 없이 수입하는 나라는 유럽을 포함한 96개국이다

□ 미국에서 연간 도축되는 소는 3,500만 마리에서 4,000만 마리 정도로, 이 중 90% 이상은 미국에서 소비되며 미국소를 수입하는 나라는 117개국임(특히, 96개국은 제한 없이 전면 수입)

5. 한국인 95%가 광우병에 취약한 유전자를 갖고 있지만, 광우병 원인체를 통제하면 발병하지 않는다.

□ 현재까지 대다수 인간광우병 환자의 유전자에서 MM 동일형이 나온 것은 사실이나, 단일 유전자 하나가 질환의 발병을 좌우하지 않음
- 즉 외부관련요인(SRM 등 프리온이 많은 부분)이 통제되면 발병하지 않는다는 뜻임

6. 미국 도축소의 97%는 마블링이 적고, 사료값이 경제적인 20개월 미만의 소들이다.

□ 통상 한국인이 좋아하는 마블링은 20개월 이후 생성되는 관계로 한국은 24개월에서 30개월 정도 되는 국내산을 식용으로 사용하나 미국은 마블링에 대한 선호가 낮기 때문에 몸집이 충분히 커지는 20개월 이내에서 도축하는 것이 일반적임

7. 젤라틴, 콜라겐 등 화장품 원료를 비롯, 108가지의 제품은 광우병 위험이 없는 소가죽 등으로 만든 것으로 광우병과 아무 상관이 없다고 국제수역사무국이 규정했다.

□ 인간광우병은 광우병에 걸린 소에게 생성된 변형단백질을 인간이 섭취할 때에만 감염되는 것으로, 광우병 감염 소에게 생성된 변형단백질은 주로 SRM에만 축적됨

□ SRM은 모두 수입금지되며, 젤라틴이나 콜라겐은 광우병과 무관

8. 1997년을 기점으로 전 세계적으로 광우병은 급속도로 사라져가고 있다.

□ 1990년대 초 수만건에 달하던 광우병 발생건수는 1990년대 말 이후 급속히 낮아지고 있는 추세임

9. 카우보이의 나라 미국인들은 쇠고기를 주식으로 하며 가정이나 레스토랑에서 자국산 쇠고기를 먹는다.

□ 미국의 3억 명의 인구는 주식으로 쇠고기를 먹으며, 자국민 외에 연간 5,000만 명의 관광객, 특히 연간 100만 명에 육박하는 한국인이 미국을 방문, 쇠고기를 소비하고 있음

10. 도축된 지 1년이 지난 미 쇠고기도 통관된다

□ ‘도축기간 그리고/또는 가공기간’을 명시하도록 하는 등의 규정은 현행 미국산 수입위생조건과 같은 조건임

(출처: 농림수산식품부 홈페이지)


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인간광우병(vCJD)과 치매는 분명히 구분이 가능

주간 시민사회신문 제50호(2008년 5월 5일 발간) 1면에 김성훈 상지대 총장(전 농림부장관)이 기고한 “10년 뒤 인간광우병을 주목하라'라는 제하의 내용은 사실과 달라 다음과 같이 반박합니다.

[기고내용]

□ 전세계적으로 인간광우병 사망자 180여명 외에 최소 25～65만명의 비공식적인 인간광우병 환자가 치매환자로 은폐되어 사망하였음
○ 예일대와 피츠버그대 의학팀의 실험결과 치매로 죽은 환자의 사후 부검결과 5～13%가 인간광우병으로 드러남

[반박내용]

기고문에서 인용한 예일대와 피츠버그대 의학팀의 연구결과는 인간광우병(vCJD)과는 완전히 다른 크로이펠트-야콥병(CJD)에 대한 연구결과로,
예일대는 알츠하이머병으로 사망한 46명의 환자중 13%, 피츠버그대는 알츠하이머병으로 사망한 54명의 환자중 5%가 크로이펠트-야콥병으로 밝혀진 연구사례입니다.

치매는 발생연령이 평균 63세 정도로 신경학적 증상이 주증상이지만 인간 광우병은 젊은 연령층에 나타나며 정신과적 증상이 주증상으로 치매와 인간광우병(vCJD)은 분명히 구분이 가능합니다.

또한, 지난 4월초 미국에서 사망한 미국처녀(아레사 빈슨)의 경우 지난 5.5일 미 농무부의 예비조사 결과 인간광우병(vCJD)이 아니라고 발표하였습니다.

(출처: 농림수산식품부 홈페이지)

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한국인은 인간 광우병에 취약하다는데요?


국내 김용선 교수의 연구결과 유전자 분석결과 우리나라 사람이 인간광우병에 걸릴 확률이 높다고 하지만 안전성이 확보된 미국산 쇠고기를 통해 인간 광우병이 걸릴 가능성은 매우 희박합니다.

또한 사람과 소 사이에는 종간장벽(種間 障壁)이 존재하므로 소에게 감염되는 광우병이 사람에게 감염되려면 소에게 감염되는 양보다 훨씬 많은 양의 특정위험물질(SRM)을 섭취해야 한다는 사실은 과학계에 널리 알려진 사실입니다.

인간광우병 환자가 가장 많이 발견된 영국은 이미 전세계 광우병 감염소의 96% 정도가 발생하였으나, 미국의 경우 당시 8세 이상된 3마리의 소에서만 광우병이 발생하였기 때문에 영국과 미국의 광우병 발생 상황은 근본적으로 차이가 있습니다.

미국산 쇠고기를 수입하는 한국 상황에 대비하는 것은 적절한 비교가 아니라고 생각합니다.

(출처: 농림수산식품부 홈페이지)

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FDA Home Page

January 14, 2004; Updated July 9, 2004, June 30, 2005 and September 14, 2005



Commonly Asked Questions About BSE in Products Regulated by FDA's Center for Food Safety and Applied Nutrition (CFSAN)
In light of the June 24, 2005 announcement of the second case of BSE in a cow in the United States, CFSAN has reviewed the products it regulates to ensure their safety.
What is 'Mad Cow Disease' (Bovine Spongiform Encephalopathy/BSE)?
Mad Cow Disease is the commonly used name for Bovine Spongiform Encephalopathy (BSE), a slowly progressive, degenerative, fatal disease affecting the central nervous system of adult cattle. Since 1990, the U.S. Department of Agriculture (USDA) has conducted aggressive surveillance of the highest risk cattle going to slaughter in the United States.

What causes BSE?
The exact cause of BSE is not known but it is generally accepted by the scientific community that the likely cause is infectious forms of a type of protein, prions, normally found in animals cause BSE. In cattle with BSE, these abnormal prions initially occur in the small intestines and tonsils, and are found in central nervous tissues, such as the brain and spinal cord, and other tissues of infected animals experiencing later stages of the disease.

Was a second case of BSE identified in the U.S. in June 2005?
Yes, the USDA surveillance program identified the second BSE case in the U.S. This cow was originally identified in November 2004. Results from this animal were inconclusive in screening tests, but negative in confirmatory immunohistochemical tests. USDA recently conducted an additional confirmatory test, Western Blot, and the results were positive for BSE. USDA sent the samples to the Weybridge, UK lab where BSE was confirmed. An epidemiological investigation to trace the origins of the cow is underway. USDA confirms that the cow was born before the U.S. instituted its ban on the use of most mammalian protein in feed for ruminant animals-believed to be the most critical protective measure in preventing the spread of BSE among cattle.

Did meat and meat products from the June 2005 cow enter the food supply?
No, the cow was presented at slaughter as non-ambulatory (a downer). Therefore, in accordance with BSE regulations established by USDA and FDA the material from the animal did not enter the human food supply.

Was a case of BSE identified in the U.S. in December 2003?
Yes, the USDA surveillance program identified the first BSE case in the U.S. in a dairy cow in Washington State. The cow was bought from a farm in Canada.

Did meat and meat products from the 2003 BSE cow enter the food supply?
As soon as the BSE case was identified, both USDA and FDA activated their BSE Emergency Response Plans, and USDA immediately recalled the meat. Meat that did enter the food supply was quickly traced and was removed from the marketplace. Moreover, all the organs in which infectious prions occur were removed at slaughter and did not enter the food supply. Consumers should feel very confident that the system of multiple firewalls maintained by Federal agencies protects them from possible exposure to BSE. In addition, we believe it is important for consumers to also understand that scientific research indicates that muscle meat is not a source of infectious prions.

Will there be additional cases?
In 1998, USDA commissioned the Harvard Center for Risk Analysis to conduct an analysis and evaluation of the U.S. regulatory measures to prevent the spread of BSE in the U.S. and to reduce the potential exposure of U.S. consumers to BSE. The Harvard study concluded that, if introduced, due to the preventive measures currently in place in the U.S., BSE is extremely unlikely to become established in the United States.

FDA and other Federal agencies have been vigilant in strengthening protective measures to reduce the U.S. consumer's risk of exposure to BSE-contaminated food and cosmetic products. Since 1989, USDA has banned imports of live ruminants, such as cattle, sheep and goats, and most products from these animals from countries known to have BSE. Subsequently, USDA expanded this ban to include both countries with BSE and countries at risk for BSE. In 1997, FDA prohibited, with some exceptions, the use of protein derived from mammalian tissues in animal feed intended for cows and other ruminants. See the FDA/CVM website at www.fda.gov/cvm for information on the 'ruminant feed ban.'

On Jan. 8, 2004, the USDA's Food Safety and Inspection Service issued new rules to enhance safeguards against BSE. Details on these rules may be found at USDA's website, www.usda.gov. Also in 2004, FDA issued a rule that prohibits the use of certain cattle material, because of the risk of BSE, in human food and cosmetics.

Does BSE affect people?
There is a disease similar to BSE called Creutzfeldt-Jacob Disease (CJD) that is found in people. A variant form of CJD (vCJD) is believed to be caused by eating contaminated beef products from BSE-affected cattle. To date, there have been 155 confirmed and probable cases of vCJD worldwide among the hundreds of thousands of people that may have consumed BSE-contaminated beef products. The one reported case of vCJD in the United States was in a young woman who contracted the disease while residing in the UK and developed symptoms after moving to the U.S.

What measures are being taken to ensure food safety in the U.S. from BSE?
Since 1989, the FDA and other federal agencies have had ongoing regulatory measures in place to prevent BSE contamination of U.S. food and food products. Following the identification in a Washington state dairy herd of a BSE-positive cow imported from Canada, USDA issued new regulations containing additional safeguards to further minimize risk for introduction of the BSE agent into the U.S. food supply. See USDA's website www.usda.gov for further information.

Similarly, FDA has prohibited the use of the cattle materials that carry the highest risk of BSE in human food, including dietary supplements, and in cosmetics. FDA's rule (and September 2005 amendments) prohibit use of the following cattle material in human food and cosmetics:

cattle material from non-ambulatory, disabled cattle,
cattle material from organs from cattle 30 months of age or older in which infectious prions are most likely to occur, and the tonsils and the distal ileum of the small intestine of cattle of all ages,
cattle material from mechanically separated (MS) (beef), and
cattle material from cattle that are not inspected and passed for human consumption
FDA's rule also requires that food and cosmetics manufacturers and processors make available to FDA any existing records relevant to their compliance with these prohibitions. FDA has also published a proposal requiring manufacturers and processors of food and cosmetics made with cattle material to establish and maintain records demonstrating that their products do not contain prohibited cattle material.

In September 2005, FDA amended the interim final rule to allow use of the small intestine in human food and cosmetics, provided the distal ileum has been removed. FDA also clarified that milk and milk products, hide and hide-derived products and tallow derivatives are not considered prohibited cattle materials. Finally, in response to comments the agency has reconsidered the method cited in the interim final rule for determining insoluble impurities in tallow and is citing a method that is less costly and requires less specialized equipment.

Are the protective measures in place sufficient to ensure the safety of the human food supply in light of the June 2005 BSE positive cow?
Yes, the protective measures put into place in July 2004 by FDA ensure that cattle materials that carry the highest risk of transmitting the agent that causes BSE are excluded from human food, including dietary supplements, and cosmetics. These measures, along with similar measures established by USDA, provide a uniform national BSE policy and ensure the safety of human food.

Is the food in the U.S. likely to be a BSE risk to consumers?
FDA and other federal agencies have had preventive measures in place to reduce the U.S. consumer's risk of exposure to any BSE-contaminated meat and food products. Since 1989, USDA has prohibited the importation of live animals and animal products from BSE-positive countries. Subsequently, USDA expanded the ban to include both countries with BSE and countries at risk for BSE. Since 1997, FDA has prohibited the use of most mammalian protein in the manufacture of ruminant feed. In 2004, FDA issued a rule prohibiting the use of certain cattle materials in human food and cosmetics, and USDA issued a rule prohibiting certain cattle materials from use as human food.

Is cow's milk a source of BSE?
Scientific research indicates that BSE is not transmitted in cow's milk, even if the milk comes from a cow with BSE. Milk and milk products, even in countries with a high incidence of BSE are, therefore, considered safe.

Can milk be infected with BSE from a BSE-positive cow?
No detectable infectivity in cow's milk has been reported from any BSE-infected cows. Infectious prions have not been detected by bioassay of milk from cattle with BSE.

Does the use of bovine-derived ingredients in dietary supplements mean that they are not safe?
No. The requirements that FDA has in place should give consumers confidence that their food, including dietary supplements, is safe. Most recently, FDA published a rule that prohibits the use in human food, including dietary supplements, of the cattle materials that have the highest risk of harboring BSE infectivity. The rule applies to both imported and domestic dietary supplements and their ingredients. Furthermore, most ingredients used to produce dietary supplements and most other food ingredients come from cattle that are slaughtered when they are less than 30-months of age and, because of their age, present little risk of being BSE-positive. It is not a common occurrence for animals younger than 30 months to develop BSE.

Since the BSE-positive cows were discovered in the U.S., does that mean that dietary supplements made with domestic ingredients might be unsafe?
No. The requirements that FDA has in place should give consumers confidence that their food, including dietary supplements, is safe. Most recently, FDA published a rule that prohibits the use in human food, including dietary supplements, of the cattle materials that have the highest risk of harboring BSE infectivity. Furthermore, most ingredients used to produce dietary supplements and most other food ingredients come from cattle that are slaughtered when they are less than 30-months of age and, because of their age, present little risk of being BSE-positive.

Even though BSE-positive cows have been identified in the U.S., one of which was imported, the risk to human health from dietary supplements and other foods containing cattle-derived ingredients is extremely low.

What steps is FDA currently taking to ensure the safety of dietary supplements that contain bovine ingredients?
Most recently, FDA published a rule that prohibits the use in human food, including dietary supplements, of the cattle materials that have the highest risk of harboring BSE infectivity. The rule applies to both domestic and imported dietary supplements and their ingredients. In addition, most ingredients used to produce dietary supplements and most other food ingredients come from cattle that are slaughtered when they are less than 30-months of age and, because of their age, present little risk of being BSE-positive. Further, the restrictions by USDA on the use of certain cattle and cattle tissues in human food also reduce the risks that potentially infective tissue would be used in dietary supplements. FDA also has proposed a requirement that manufacturers and processors that use cattle material in their products would be required to keep records demonstrating that these materials do not contain prohibited cattle material and that these records be made available to FDA for ! inspection.

Given the BSE case in Washington State and the case in Texas, should consumers be concerned about cosmetics made using tallow from the rendering process?
No. The World Health Organization considers tallow to be a low risk for transmission of BSE. Specifically, the rendering process separates fats from proteins. Because the disease is transmitted by prions, which are a type of protein, they would be separated by the rendering process from the tallow or fat, which is the portion that goes into cosmetics. Additionally, the tallow is processed with excessive heat and pressure which may further minimize any risk of infectivity prior to use in cosmetics.

What about the use of gelatin, another bovine-related material, in cosmetics and dietary supplements and other foods?
FDA's rule prohibiting the use of the cattle materials that have the highest risk of harboring BSE infectivity in human food applies to gelatin. Therefore, gelatin used in human food may not be made from these cattle materials.

When and how did BSE in cattle occur?
BSE in cattle was first reported in 1986 in the United Kingdom (UK). The exact origins of BSE remain uncertain, but it is thought that cattle initially may have become infected when fed feed contaminated with scrapie-infected sheep meat-and-bone meal (MBM). Scrapie is a prion disease in sheep similar to BSE in cattle. The scientific evidence suggests that the U.K. BSE outbreak in cattle then was expanded by feeding BSE-contaminated cattle protein (MBM) to calves. The definitive nature of the BSE agent is not completely known. The agent is thought to be a modified form of a protein, called a prion, which becomes infectious and accumulates in neural tissues causing a fatal, degenerative, neurological disease. These abnormal prions are resistant to common food disinfection treatments, such as heat, to reduce or eliminate their infectivity or presence. Research is ongoing to better understand TSE diseases and the nature of prion transmission.

Is BSE in cattle the same disease as CWD in deer and elk in the U.S.?
BSE is a Transmissible Spongiform Encephalopathy (TSE), a family of similar diseases that may infect certain species of animals and people such as scrapie in sheep and goats, BSE in cattle, chronic wasting disease (CWD) in deer and elk, and variant Creutzfeldt-Jakob disease (vCJD) in people.

To date, there is no scientific evidence that BSE in cattle is related to CWD in deer and elk. FDA is working closely with other government agencies and the public health community to address CWD in wild and domesticated deer and elk herds. Wildlife and public health officials advise people not to harvest, handle, or consume any wild deer or elk that appear to be sick, regardless of the cause, especially in those states where CWD has been detected.

What countries have reported cases of BSE or are considered to have a substantial risk associated with BSE?
These countries are: Albania, Austria, Belgium, Bosnia-Herzegovina, Bulgaria, Croatia, Czech Republic, Denmark, Federal Republic of Yugoslavia, Finland, France, Germany, Greece, Hungary, Ireland, Israel, Italy, Liechtenstein, Luxembourg, former Yugoslavia Republic of Macedonia, The Netherlands, Norway, Oman, Poland, Portugal, Romania, Slovak Republic, Slovenia, Spain, Sweden, Switzerland, Japan, and United Kingdom (Great Britain including Northern Ireland and the Falkland Islands).


This document was issued in January 2004 and updated in July 2004 and June 2005.
For more recent information on Bovine Spongiform Encephalopathy (BSE)
see http://www.fda.gov/oc/opacom/hottopics/bse.html

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KidsHealth > Teens > Q & A > Illnesses & Infections > Mad Cow Disease

Mad cow disease seems to pop up in the news now and then. But what is it, and how likely is it that people will get it?

What Is Mad Cow Disease and How Do People Get It?
Mad cow disease is an incurable, fatal brain disease that affects cattle and possibly some other animals, such as goats and sheep. The medical name for mad cow disease is bovine spongiform encephalopathy (pronounced: bo-vine spun-jih-form en-seh-fah-la-puh-thee), or BSE for short. It's called mad cow disease because it affects a cow's nervous system, causing a cow to act strangely and lose control of its ability to do normal things, such as walk.

Only certain animals can get BSE — people don't actually get mad cow disease. However, experts have found a link between BSE and a rare brain condition that affects people, called variant Creutzfeldt-Jakob disease (CJD). Researchers believe that people who eat beef from cows that have BSE are at risk of developing a form of CJD.

CJD is caused by an abnormal type of protein in the brain called a prion. When people have CJD, cells in the brain die until the brain eventually has a 'sponge-like' appearance. During this time, people with the disease gradually lose control of their mental and physical capabilities.

To date, very few people have been diagnosed with the form of CJD that's been linked to mad cow disease. By November 2006, only 200 cases of this rare condition had been reported worldwide. Of these, most were identified in Britain. Several of the people diagnosed with the disease outside Britain — including two cases in the United States — had a history of exposure in Britain or in a country where government officials reported BSE. Experts believe that the people got CJD after eating beef products from cows that had BSE.

Because the form of CJD that's been linked to mad cow disease is relatively new and extremely rare, experts are still learning about it. However, researchers believe that the disease is not contagious among people. In other words, you cannot get CJD from someone else who has it. At present, it appears that the main way people get the disease is from eating contaminated meat.

Experts don't yet know exactly how long the incubation period is for CJD (in other words, how long it takes from the time a person contracts it to the time that symptoms first appear). However, they do believe that it takes years, if not decades, from the time someone is exposed to the disease until the first signs appear. After the first signs appear, the brain can deteriorate within a year.

What's Being Done?
If you're worried about mad cow disease, tell whoever buys the food in your household about how you feel. The type of protein that causes mad cow disease cannot be removed or destroyed when beef is processed or cooked. For this reason, the U.S. government has established several meat processing procedures to protect the public. One of these steps involves removing the parts of the cow that are at highest risk of containing BSE-causing proteins — the brain and spinal cord — to reduce the chances of them contaminating the meat people eat.

In October 2005, the U.S. Food and Drug Administration (FDA) proposed additional safeguards to help protect consumers from BSE. These prohibit the use of any high-risk cattle materials in the feed of any animal. In this way, the FDA continues to decrease the already tiny possibility of infection with BSE.

There is also a system in place to test samples of meat regularly. The testing system helped officials identify some contaminated meat in Washington state in December 2003 — one of only three cases of mad cow disease found in the United States so far.

The government has a recall policy for meat that's suspected of being contaminated. This helps prevent contaminated meat from reaching the shelves.

If you're wondering if you can get sick from drinking cow's milk, rest assured that you can't. The United States Department of Agriculture (USDA) says there is no evidence that the disease is transmitted through cow's milk and milk products.

The good news is that it's highly unlikely that a person will contract CJD from eating beef. CJD itself is pretty rare. And because only three cows in the United States have been found to be infected with mad cow disease, which can't be spread from cow to cow, the chance that you will eat meat infected with the disease is extremely low.

Reviewed by: Larissa Hirsch, MD
Date reviewed: January 2007
Originally reviewed by: Steven Dowshen, MD


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Bovine spongiform encephalopathy
From Wikipedia, the free encyclopedia
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Classic image of a cow with BSE. A notable feature of such disease is the inability of the infected animal to stand.
Source: APHIS
Bovine spongiform encephalopathy (BSE), commonly known as mad-cow disease, is a fatal, neurodegenerative disease in cattle, that causes a spongy degeneration in the brain and spinal cord and red eyes. BSE has a long incubation period, about 4 years, usually affecting adult cattle at a peak age onset of four to five years, all breeds being equally susceptible.[1] In the United Kingdom, the country worst affected, more than 179,000 cattle have been infected and 4.4 million slaughtered during the eradication programme.[2]

It is believed, but not proven, that the disease may be transmitted to human beings who eat the brain or spinal cord of infected carcasses.[3] In humans, it is known as new variant Creutzfeldt-Jakob disease (vCJD or nvCJD), and by April 2008, it had killed 163 people in Britain, and 37 elsewhere[4] with the number expected to rise because of the disease's long incubation period.[5] Between 460,000 and 482,000 BSE-infected animals had entered the human food chain before controls on high-risk offal were introduced in 1989.[6]

A British inquiry into BSE concluded that the epidemic was caused by cattle, who are normally herbivores, being fed the remains of other cattle in the form of meat and bone meal (MBM), which caused the infectious agent to spread.[7][8] The origin of the disease itself remains unknown. The infectious agent is distinctive for the high temperatures at which it remains viable; this contributed to the spread of the disease in Britain, which had reduced the temperatures used during its rendering process.[7] Another contributory factor was the feeding of infected protein supplements to very young calves.[7][9]

Contents [hide]
1 Infectious agent
2 The BSE epidemic in British cattle
2.1 UK epizootic and UK licensed medicines
3 Husbandry practices in the United States relating to BSE
4 BSE statistics by country
5 References
6 External links



[edit] Infectious agent

Microscopic 'holes' of tissue sections are examined in the lab. Source: APHISThe infectious agent in BSE is believed to be a specific type of misfolded protein called a prion. Those prion proteins carry the disease between individuals and cause deterioration of the brain. BSE is a type of transmissible spongiform encephalopathy (TSE).[10] TSEs can arise in animals that carry an allele which causes previously normal protein molecules to contort by themselves from an alpha helical arrangement to a beta pleated sheet, which is the disease-causing shape for the particular protein. Transmission can occur when healthy animals come in contact with tainted tissues from others with the disease. In the brain these proteins cause native cellular prion protein to deform into the infectious state, which then goes on to deform further prion protein in an exponential cascade. This results in protein aggregates, which then form dense plaque fibers, leading to the microscopic appearance of '! holes' in the brain, degeneration of physical and mental abilities, and ultimately death.

Different theories exist for the origin of prion proteins in cattle. Two leading theories suggest that it may have jumped species from the disease scrapie in sheep, or that it evolved from a spontaneous form of 'mad-cow disease' that has been seen occasionally in cattle for many centuries.[11] Publius Flavius Vegetius Renatus records cases of a disease with similar characteristics in the 4th and 5th Century AD.[12] The British Government enquiry took the view the cause was not scrapie as had originally been postulated, and was some event in the 1970s that was not possible to identify.[13]


[edit] The BSE epidemic in British cattle
Cattle, like other food animals, are normally herbivores. In nature, cattle eat grass. In modern industrial cattle-farming, various commercial feeds are used, which may contain ingredients including antibiotics, hormones, pesticides, fertilizers, and protein supplements. The use of meat and bone meal, produced from the ground and cooked left-overs of the slaughtering process as well as from the cadavers of sick and injured animals such as cattle, sheep, or chickens, as a protein supplement in cattle feed was widespread in Europe prior to about 1987.[citation needed] Worldwide, soya bean meal is the primary plant-based protein supplement fed to cattle. However, soya beans do not grow well in Europe, so cattle raisers throughout Europe turned to the less expensive animal by-product feeds as an alternative. A change to the rendering process in the early 1980s may have resulted in a large increase of the infectious agents in the cattle feed. A contributing factor was suggested t! o have been a change in British laws that allowed a lower temperature sterilization of the protein meal. While other European countries like Germany required said animal byproducts to undergo a high temperature steam boiling process, this requirement had been eased in Britain as a measure to keep prices competitive. Later the British Inquiry dismissed this theory saying 'changes in process could not have been solely responsible for the emergence of BSE, and changes in regulation were not a factor at all.'[14]

Following an epizootic of BSE in Britain, 165 people (up until 2007) acquired and died of a disease with similar neurological symptoms subsequently called vCJD, or (new) variant Creutzfeldt-Jakob disease. This is a separate disease from 'classical' Creutzfeldt-Jakob disease, which is not related to BSE and has been known about since the early 1900s. Three cases of vCJD occurred in people who had lived in or visited Britain — one each in Ireland, Canada and the United States. There is also some concern about those who work with (and therefore inhale) cattle meat and bone meal, such as horticulturists, who use it as fertilizer. Up to date statistics on all types of CJD are published by the UK CJD Surveillance Centre in Edinburgh.

For many of the vCJD patients, direct evidence exists that they had consumed tainted beef, and this is assumed to be the mechanism by which all affected individuals contracted it. Disease incidence also appears to correlate with slaughtering practices that led to the mixture of nervous system tissue with hamburger and other beef. It is estimated that 400,000 cattle infected with BSE entered the human food chain in the 1980s. Although the BSE epizootic was eventually brought under control by culling all suspect cattle populations, people are still being diagnosed with vCJD each year (though the number of new cases currently has dropped to less than 5 per year). This is attributed to the long incubation period for prion diseases, which are typically measured in years or decades. As a result the full extent of the human vCJD outbreak is still not fully known.

The scientific consensus is that infectious BSE prion material is not destroyed through normal cooking procedures, meaning that contaminated beef foodstuffs prepared 'well done' may remain infectious.[15][16]

In 2004 researchers reported evidence of a second contorted shape of prions in a rare minority of diseased cattle. In other words, this implies a second strain of BSE prion. Very little is known about the shape of disease-causing prions, because their insolubility and tendency to clump thwarts application of the detailed measurement techniques of structural biology. But cruder measures yield a 'biochemical signature' by which the newly discovered cattle strain appears different from the familiar one, but similar to the clumped prions in humans with traditional CJD Creutzfeldt-Jakob Disease .The finding of a second strain of BSE prion raises the possibility that transmission of BSE to humans has been underestimated, because some of the individuals diagnosed with spontaneous or 'sporadic' CJD may have actually contracted the disease from tainted beef. So far nothing is known about the relative transmissibility of the two disease strains of BSE prion.

Alan Colchester, a professor of neurology at the University of Kent, writing in the September 3, 2005 issue of the controversial medical journal, The Lancet, proposed a theory that the most likely initial origin of BSE in Britain was the importation from the Indian subcontinent of bone meal which contained CJD infected human remains.[17] The government of India vehemently responded to the research calling it 'Misleading, highly mischievous, a figment of imagination, absurd,' further adding that India maintained constant surveillance and had not had a single case of either BSE or vCJD.[18][19] The authors responded in the January 22, 2006 issue of The Lancet that their theory is unprovable only in the same sense as all other BSE origin theories are and that the theory warrants further investigation.[20]


[edit] UK epizootic and UK licensed medicines
During the course of the investigation into the BSE epizootic, an enquiry was also made into the activities of the Department of Health and its Medicines Control Agency. On May 7, 1999, in his written statement number 476 to the BSE Inquiry, David Osborne Hagger reported on behalf of the Medicines Control Agency that in a previous enquiry the Agency had been asked to:

'... identify relevant manufacturers and obtain information about the bovine material contained in children’s vaccines, the stocks of these vaccines and how long it would take to switch to other products.' It was further reported that the: '... use of bovine insulin in a small group of mainly elderly patients was noted and it was recognised that alternative products for this group were not considered satisfactory.' A medicines licensing committee report that same year recommended that: '... no licensing action is required at present in regard to products produced from bovine material or using prepared bovine brain in nutrient media and sourced from outside the United Kingdom, the Channel Isles and the Republic of Ireland provided that the country of origin is known to be free of BSE, has competent veterinary advisers and is known to practise good animal husbandry.' In 1990 the British Diabetic Association became concerned regarding the safety of bovine insulin and the go! vernment licensing agency assured them that: '... there was no insulin sourced from cattle in the UK or Ireland and that the situation in other countries was being monitored.' In 1991 a European Community Commission: '... expressed concerns about the possible transmission of the BSE/scrapie agent to man through use of certain cosmetic treatments.' Sources in France reported to the British Medicines Control Agency: '... that there were some licensed surgical sutures derived from French bovine material.' Concerns were also raised: '... regarding a possible risk of transmission of the BSE agent in gelatin products.'


[edit] Husbandry practices in the United States relating to BSE
Soybean meal is cheap and plentiful in the United States. As a result, the use of animal byproduct feeds was never common, as it was in Europe. However, U.S. regulations only partially prohibit the use of animal byproducts in feed. In 1997, regulations prohibited the feeding of mammalian byproducts to ruminants such as cows and goats. However, the byproducts of ruminants can still be legally fed to pets or other livestock such as pigs and poultry such as chickens. In addition, it is legal for ruminants to be fed byproducts from some of these animals. [2] A proposal to end the use of cow blood, restaurant scraps, and poultry litter (fecal matter, feathers)[21] in January 2004 has yet to be implemented [3], despite the efforts of some advocates of such a policy, who cite the fact that cows are herbivores, and that blood and fecal matter could potentially carry BSE.

In February 2001, the USGAO reported that the FDA, which is responsible for regulating feed, had not adequately policed the various bans. [4] Compliance with the regulations was shown to be extremely poor before the discovery of the Washington cow, but industry representatives report that compliance is now 100%. Even so, critics call the partial prohibitions insufficient. Indeed, US meat producer Creekstone Farms alleges that the USDA is preventing BSE testing from being conducted [5].

Japan was the top importer of U.S. beef, buying 240,000 tons valued at $1.4 billion in 2003. After the discovery of the first case of BSE in the U.S. on December 23, 2003, Japan stopped U.S. beef imports in December 2003. In December 2005, Japan once again allowed imports of U.S. beef, but reinstated its ban in mid-January 2006 after a technical violation of the U.S.-Japan beef import agreement: a vertebral column, which should have been removed prior to shipment, was included in a shipment of veal.

Tokyo yielded to U.S. pressure to resume imports, ignoring consumer worries about the safety of U.S. beef, said Japanese consumer groups. Michiko Kamiyama from Food Safety Citizen Watch said about this: 'The government has put priority on the political schedule between the two countries, not on food safety or human health.'

Possibly due to pressure from large agribusiness, the United States has drastically cut back on the number of cows inspected for BSE.[22]

65 nations have full or partial restrictions on importing U.S. beef products because of concerns that U.S. testing lacks sufficient rigor. As a result, exports of U.S. beef declined from $3.8 billion in 2003, before the first mad cow was detected in the US, to $1.4 billion in 2005. [22]

On December 31, 2006, Hematech, a biotechnology company based in Sioux Falls, South Dakota, announced that it had used genetic engineering and cloning technology to produce cattle that lacked a necessary gene for prion production - thus theoretically making them immune to BSE.[23]


[edit] BSE statistics by country
Country BSE cases vCJD cases Country BSE cases vCJD cases
Austria 5 0 Belgium 125 0
Canada 10 1 Czech Republic 9 0
Denmark 15 0 Falkland Islands 1 0
Finland 1 0 France 900+ 11
Germany 312 0 Greece 1 0
Hong Kong 2 0 Israel 1 0
Italy 117 1 Japan 26 1
Liechtenstein 2 0 Luxembourg 2 1
Netherlands 75 2 Oman 2 0
Poland 21 0 Portugal 875 2
Republic of Ireland 1,353 4 Slovakia 15 0
Slovenia 7 0 Spain 412 2
Sweden 1 0 Switzerland 453 0
Thailand n/a 2 United Kingdom 183,823 163
United States 3 3 Total 188,535 193 (+ 60 results pending)

Dark green areas are countries with confirmed human cases of vCJD. Light green shows countries which have reported cases of BSE only.The table to the right summarizes reported cases of BSE and of vCJD by country. BSE is the disease in cattle, while vCJD is the disease in people.

The tests used for detecting BSE vary considerably as do the regulations in various jurisdictions for when, and which cattle, must be tested. For instance, in the EU the cattle tested are older (30 months+), while many cattle are slaughtered earlier than that. At the opposite end of the scale, Japan tests all cattle at the time of slaughter. Tests are also difficult as the altered prion protein has very small levels in blood or urine, and no other signal has been found. Newer tests are faster, more sensitive, and cheaper, so it is possible that future figures may be more comprehensive. Even so, currently the only reliable test is examination of tissues during an autopsy.

It is notable that there are no cases reported in Australia, New Zealand and Vanuatu where cattle are mainly fed outside on grass pasture and, mainly in Australia, non-grass feeding is done only as a final finishing process before the animals are processed for meat.

As for vCJD in humans, autopsy tests are not always done and so those figures too are likely to be too low, but probably by a lesser fraction. In the UK anyone with possible vCJD symptoms must be reported to the UK Creutzfeldt-Jakob Disease Surveillance Unit and so it is unlikely that any cases would be missed. In the U.S., the CDC has refused to impose a national requirement that physicians and hospitals report cases of the disease. Instead, the agency relies on other methods, including death certificates and urging physicians to send suspicious cases to the National Prion Disease Pathology Surveillance Center (NPDPSC) at Case Western Reserve University in Cleveland, which is funded by the CDC.