MAD ABOUT COWS:
THE BSE SYNDROME
Bovine Spongiform Encephalopathy (BSE) or mad cow disease is a chronic, degenerative disorder affecting the central nervous system of cattle…
vCJD is the human equivalent of BSE, and stands for ‘variant Creutzfeldt-Jakob Disease’…
- Transmissible Spongiform Encephalopathies (TSEsv) are diseases characterised by spongy degeneration of the brain with severe and fatal neurological signs and symptoms. BSE is one of several different forms of transmissible brain disease affecting a number of animal species. Scrapie is a common disease in sheep and goats. Mink and North American mule deer and elk can contract TSEs. A neurological disease in household cats and in ruminant and feline species in zoos has been linked to BSE; most cases in such animals appear to have occurred in the UK;
- BSE (Bovine Spongiform Encephalopathy) - a disease of cattle, and CJD (Creutzfeldt-Jakob Disease) - a similar disease in humans - are both incurable;
- BSE first came to the attention of the scientific community in November 1986 with the appearance in cattle of a newly recognised form of neurological disease in the United Kingdom. Epidemiological studies conducted in the UK suggest that the source of BSE was cattle feed prepared from bovine tissues, such as brain and spinal cord, that was contaminated by the BSE agent;
- between November 1986 and November 2002, 181,376 cases of BSE were confirmed in the UK;
- since 1989, when the first BSE case was reported outside the UK, relatively small numbers of BSE cases (in total 3,286) have also been reported in native cattle in other European countries (Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Ireland, Italy, Liechtenstein, Luxembourg, Netherlands, Poland, Portugal, Slovakia, Spain, Switzerland), in Israel, and in Japan. However, all but 206 cases have been reported in 6 countries - France, Germany, Ireland, Portugal, Spain and Switzerland;
- in July 1988, the UK banned the use of ruminant proteins in the preparation of animal feed. The use in the food chain of bovine offals considered to pose a potential risk to humans was also banned in the UK in 1989;
- in 2001, because of the continued risk from cross contamination, the EU introduced a total feed ban - e.g. ban on feeding meat and bone meal (MBM) to all farm animals. Starting in 1996, bans prevented the sale of food and food products containing beef from the UK to other countries. Other products (e.g. tallow, gelatin) derived from bovine tissues were also prohibited from sale from the UK to other countries;
- however, in 1999 the European Union (EU) lifted the ban for meat fulfilling specific requirements; for example, de-boned beef from animals from farms where there have been no cases of BSE and where the animals are less than 30 months of age at slaughter;
- the number of reports of BSE in the UK began to decline in 1992 and has continuously declined year by year since then. New monitoring programmes using newly developed tests for the diagnosis of BSE in dead and slaughtered cattle have been introduced throughout the EU;
- in 2002 a total of about 11 million animals were tested in Europe: 2,126 bovine, 1,576 ovine and 41 caprine animals turned out positive; (1)
- in 2003 1,389 mad cow’s cases were detected worldwide: 1,351 within the EU (612 in UK);
- a recent study reports that nearly 2 million cattle have been infected with BSE since the late 1980s. The previous estimate of animals affected during the epidemic was just over a million. Scientists involved in the research do not believe that the higher total is likely to increase the number of cases of vCJD, because the chance of infection from an individual animal is lower than had been originally thought. (2)
Summary of vCJD cases in UK (3)
- the first person to develop symptoms of what turned out to be variant Creutzfeldt-Jakob disease (vCJD) became ill in January 1994. Most people who have developed vCJD have lived in the UK. Some of the patients had been long-standing residents in Wales, Scotland or Northern Ireland;
- in contrast to the classical forms of CJD, vCJD has affected younger patients (average age 29 years, as opposed to 65 years), has a relatively longer duration of illness (median of 14 months as opposed to 4.5 months) and is strongly linked to exposure, probably through food, to BSE. Recent studies have confirmed that vCJD is distinct from sporadic and acquired CJD.
- from October 1996 to November 2002, 129 cases of vCJD have been reported in the UK, 6 in France and one each in Canada, Ireland, Italy and the United States of America;
- Feb 2003: predicted deaths from vCJD slashed - a new analysis reduces the extent of the worst-case epidemic to 7,000, following two years of falling figures;
- May 2004: new tonsil tests reveals that nearly 4,000 Britons aged between 10 and 30 may be harbouring prions that cause vCJD;
- recently, the worst case-scenario for the deaths caused by vCJD has been revised downwards from 50,000 (2002) to 540 UK cases between 2003 and 2080. Researchers at Imperial College, London indicate that the vCJD epidemic is now in decline. Their short-term projections point out that 40 cases are expected in the second half of this decade.
|Deaths from definite vCJD (confirmed) || 107|
|Deaths from probable vCJD (without neuropathological confirmation) || 42|
|Deaths from probable vCJD (neuropathological confirmation pending) || 1|
|Number of deaths from definite or probable vCJD|| 150|
|Number of definite/probable vCJD cases still alive|| 6|
|Total number of definite or probable vCJD cases (dead and alive) || 156|
(1) The positive cases in bovine animals were considered as BSE cases, while those in ovine and caprine animals as scrapie.
(2) The Independent, 10 October 2002.
(3) CJD surveillance unit in Edinburgh, updated 6 June 2005.