Transmissible Spongiform Encephalopathies (TSEs) are a family of diseases occurring in man and animals and are characterised by a degeneration of brain tissue giving a sponge-like appearance leading to death. The family includes diseases such as Creutzfeldt Jakob Disease (CJD) and Kuru in humans, Bovine Spongiform Encephalopathy (BSE) in cattle, Scrapie in small ruminants (sheep and goats), Chronic Wasting Disease (CWD) in cervids and Transmissible Mink Encephalopathy (TME) in minks. The commonly accepted cause of the TSE disease is a transmissible agent called prion (PrPres), which is an abnormal form of a protein.
Bovine Spongiform Encephalopathy (BSE) in bovine animals
Bovine Spongiform Encephalopathy (BSE) is a TSE disease of cattle. The common symptoms of BSE include behavioural changes, lack of coordination, difficulty in walking or standing up, decreased milk production and weight loss. However, the disease has also been detected in animals showing no symptoms or atypical signs of the disease. The average incubation period of BSE in cattle is 4-6 years, but it can be much longer. BSE was first diagnosed in the UK in 1986, and reached epidemic proportions due to cattle being fed with processed animal protein, produced from ruminant carcasses, some of which were infected. BSE is considered to be transmissible to humans, see vCJD below.
See archives concerning Questions and Answers on BSE (dated 28 September 2007)
TSEs in sheep and goats
Scrapie is a TSE in small ruminants (sheep and goats) and it can be divided into classical (typical) scrapie and atypical scrapie. It has been known for centuries. It is assumed that scrapie can be transmitted horizontally, from one animal to another or via environmental routes, or vertically, from ewe to lamb / from goat to kid. The clinical signs of scrapie are predominantly in animals aged from 2 to 5 years and include weight loss, salivation, pruritus and associated hair loss and skin abrasions, incoordination of hind limbs and altered behaviour such as observed nervousness, depression, excitability or aggressiveness. On the basis of the available scientific data scrapie is not considered to be transmissible to humans.
BSE has once been detected in a goat in the EU wide surveillance programme designed to detect suspicious TSE strains in sheep and goats. The case was confirmed in January 2005 by the Community Reference Laboratory (CRL) for TSEs
and it concerned a goat slaughtered in France in 2002. The goat was disposed of after slaughtering as well as its entire herd and did not enter the food chain. In addition, retrospective testing of a Scottish goat culled in 1990s gave results indicative of BSE and the CRL for TSEs concluded in May 2009 that BSE cannot be excluded.
See http://www.defra.gov.uk/vla/science/docs/sci_tse_rl_steg.pdffor more information. Following the French BSE case detected in a goat, the European Commission advised no change in the current consumption of goat milk, cheese and meat. EU food safety rules ensure that only products from healthy animals are allowed to enter the food chain and the food placed on the market is safe. As an additional safety measure the specified risk material (the tissues most likely to carry infectivity if TSE is present) are also removed from all goats. See the related EFSA statements,
press releases IP/04/1324, IP/05/105, IP/05/132 and CRL statement on BSE in a goat.
See archives concerning Questions and Answers on TSE in sheep(dated 9 March 2006) and Questions and Answers in TSE in goats (dated 28 January 2005)
Chronic Wasting Disease (CWD)
Chronic Wasting Disease (CWD) is a TSE disease of cervids (deer, elk and moose). The symptoms of CWD are a loss of body condition ("wasting") and behavioural abnormalities such as staggering and poor standing posture. CWD has never been detected in Europe, but is quite common in North America ( USA and Canada). Though CWD belongs to the same family as BSE and scrapie, there is no known relationship between CWD and other TSEs in animals or humans under natural conditions.
Variant Creutzfeldt-Jakob Disease (vCJD)
Variant Creutzfeldt-Jacob Disease (vCJD) is a TSE disease in humans. vCJD was first diagnosed in 1996. It is now generally assumed to be caused by the transmission of the BSE agent to humans by the oral route. vCJD occurs mostly in young people and most cases have occurred in the UK, although there have been cases also in France, Ireland, Italy, the Netherlands, Portugal and Spain in the EU and in the USA, Canada, Saudi-Arabia and Japan in third countries. Due to the uncertainty and complexity of the epidemiology of this disease it is difficult to predict the future, although future cases are expected to occur due to past exposure to infective material before the current stringent control measures against BSE were implemented. See www.cjd.ed.ac.uk/vcjdworld.htm for more information on vCJD.
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