2. Mad cow disease The 2001 biology project Made by TommyChan

3. The Contents of the project  Section1 : What is Mad Cow Disease  Section2 : The cause of Mad Cow Disease  Section3 : Mad Cow Disease with Human  Section4 : Mad Cow Disease in the world  Section5 ： Prevention

4. What is Mad Cow Disease (The definition of Mad Cow Disease)  Mad cow disease, formally known as Bovine Spongiform Encephalopathy (BSE), chronic degenerative brain disease of cattle that attacks the central nervous system of cattle, destroying brain tissue and eventually causing dementia and death.braincattle

5.  Bovine Spongiform Encephalopathy (BSE) is so named because of the spongy appearance of the brain tissue of infected cattle when sections are examined under a microscope.

6. Clinical Signs  Cattle affected by BSE experience progressive degeneration of the nervous system.  Affected animals may display changes in temperament, such as nervousness or aggression, abnormal posture, inco-ordination and difficulty in rising, decreased milk production, or loss of body weight despite continued appetite. Affected cattle die.

7. Take a change for the worse  The incubation period (the time from when an animal becomes infected until it first shows disease signs) is from 2 to 8 years.  Following the onset of clinical signs, the animals condition deteriorates until it either dies or is destroyed. This process usually takes from 2 weeks to 6 months. Most cases in Great Britain have occurred in dairy cows between 3 and 6 years of age.

8. Inspection  Currently, there is no test to detect the disease in a live animal; veterinary pathologists confirm BSE by postmortem microscopic examination of brain tissue or by the detection of the abnormal form of the prion protein.

9. The cause of Mad Cow Disease  The causative agent of the disease is not completely characterized, and there is neither any treatment nor a vaccine to prevent the disease.  However, there is strong evidence that the disease may be caused by prions.prions

10. What is Prion  Prion (pronounced "pree- on"), shortened term for proteinaceous infectious particle, a small protein linked to certain rare, fatal brain diseases in cows, sheep, humans, and other mammals.  If the prion is an infectious agent, it is the first infectious agent identified that does not contain the nucleic acids deoxyribonucleic acid (DNA) or ribonucleic acid (RNA).

11.  Discovered by American neurologist Stanley B. Prusiner, prions are a mutated form of a normal protein.Stanley B. Prusiner  The mutated protein causes disease when it contacts the normal protein and triggers part of it to switch from the coiled to the pleated form.  A chain reaction follows, resulting in a cluster of tangled, nonfunctional proteins called plaques. These plaques are found in the brains of animals that die from prion-related diseases.

14.  The plaques destroy the brain cells, resulting in one of the diseases collectively known as transmissible spongiform encephalopathies (TSEs).  TSEs cause inflammation and characteristic sponge like holes in the delicate membranes surrounding brain cells. This physical damage results in loss of coordination, dementia, and, eventually, death. Perhaps the best-known TSE is bovine spongiform encephalopathy (BSE), more popularly known as mad cow disease.bovine spongiform encephalopathy

15.  In addition,prion is not easily killed by cooking or freezing and can survive for an indefinite period outside the body.  Scientists and doctors still feel quite helpless towards prions.  Therefore, we have to use high temperature to treat the dead cattle.

16. The source of Prion  Prion in cattle are from the carcasses of scrapie-infected sheep.  After these infected sheep having died, their brains and other sheep byproducts infected with scrapie and, later, brain tissue taken from cows that had become infected with BSE.

17. Mad Cow Disease with Human  As well as the situation in scrapie-infected sheep, the cattle brains and other cattle byproducts infected with BSE are taken by human after the cattle have died.  In this case, human become infected with Variant Creutzfeldt-Jakob Disease (VCJD).

18. What is VCJD  Variant Creutzfeldt-Jakob Disease (VCJD), this type of CJD differs from the classical form in that victims are all under the age of 42 (the classical form of the disease typically develops around age 65).  However, they are both caused by prion.

20.  CJD causes fatal degradation of brain tissue and nerve system. The symptoms include loss of expressiveness, muscular tremble, spasm, loss of memory and dementia.  Apart from these effects, VCJD victims display unusual psychiatric problems, and the victims have no family history of the disease.

21. Mad Cow Disease in the world  Mad cow disease was first identified in Britian in 1985, and a widespread outbreak infected more than 100,000 cows across Europe in the mid- 1990s.  The recent resurgence of the disease comes despite widespread beef import restrictions and other measures intended to protect the food supply.

23.  Cases of BSE have now been identified in 10 of the 15 European Union (EU) countries, as well as Switzerland and Liechtenstein, which are not members. Although incidences are still relatively few in number, the discovery of the disease across the continent has had a dramatic effect on beef consumption, which has fallen by 27 percent across the EU.

24.  Along with a rise in the number of cattle infected with BSE (Bovine Spongiform Encephalopathy), the number of people who have died from its human equivalent, variant Creutzfeldt Jacobs Disease (vCJD), is also growing. By the end of last year nearly 90 people had either died or were dying from the fatal brain- wasting disease in the UK; with the yearly number rising from 15 in 1999 to 25 in 2000. A further six suspicious cases are also under investigation. Deaths from vCJD have also been reported in France and Italy.

25. Franc e  Over 160 cases of BSE were diagnosed last year, more than five times as many as the 31 cases the previous year. The government has also admitted there are some 50,000 “mysterious deaths” in cattle every year. As a result, beef sales have dropped by more than 25 percent and beef has been removed from the menu in school canteens in several French cities.

26. Britai n  The UK still remains the single largest source of BSE, with 1,277 cases confirmed last year. This brings the total number of cattle identified with the disease since 1987 to over 180,000.  In a related development, hundreds of hemophiliacs, who require blood-clotting agents produced from donated blood/plasma, have been warned they may have been infected with vCJD. Bio Products Laboratory confirmed that a person who donated blood in 1997 has been diagnosed with vCJD. Because of the potential risk, blood plasma for British hemophiliacs has been sourced in the USA since 1998.

27. Germa ny  After insisting for years that its herds were disease free, German officials have confirmed 20 cases of BSE since November. The ministers of health and agriculture were forced to resign in the ensuing public uproar. Government officials now predict as many as 500 cases may be confirmed by the end of the year.  Beef sales are down as much as 50 percent and angry farmers and ranchers protesting a strict new regulation which requires the slaughter of the entire herd whenever a single case is found.

28. Hong Kong  Hong Kong has banned to import beer from UK since 1996. However, the UK beer by-product such as milk, butter and sausage are not restrained and can be bought in Hong Kong.  However, many brain specialist in Hong Kong point out that citizens can be infected BSE from beer by-products. Hence, they suggest Hong Kong government should banned all the UK beer products.  The beer sold in Hong Kong are imported Brazil, China, Australia, New Zealand,and USA. Therefore, citizens needn’t worry to eat beer.

29.  Because of the worst situation, many European countries has banned to import beer from France, Germany and Great Britain to control the spread of Mad Cow Disease.

30. Prevention  Unfortunately, there is neither any treatment nor a vaccine to prevent the disease.  However, citizens should avoid eating beer’s brain and spinal cord as prions accumulate in the brain and the nerve system.

31. Reference Website  瘋 牛 症 飼 料 疑 經 港 輸 內 地 ( 明 報 / 18-06-2001 ) 瘋 牛 症 飼 料 疑 經 港 輸 內 地 ( 明 報 / 18-06-2001 ) 瘋 牛 症 越 洋 侵 襲 ( 明報 / 16-06-2001 ) 瘋 牛 症 越 洋 侵 襲 ( 明報 / 16-06-2001 ) 非 典 型 克 症 檔 案 ( 明報 / 16-06-2001 ) 非 典 型 克 症 檔 案 ( 明報 / 16-06-2001 ) 女 子 證 實 患 瘋 牛 症 ( 明 報 / 15-06-2001 ) 女 子 證 實 患 瘋 牛 症 ( 明 報 / 15-06-2001 ) 羊 臟 餵 草 牛 惹 不 治 之 症 ( 明 報 / 10-06-2001 ) 羊 臟 餵 草 牛 惹 不 治 之 症 ( 明 報 / 10-06-2001 )  CBC News : Mad Cow - the science and the story CBC News : Mad Cow - the science and the story PBS organization : The Brain Eater The BSE inquiry World Health Organization Related News