Bovine Spongiform Encephalopathy (BSE) is a transmissible, neurodegenerative, fatal brain disease of cattle. The disease has a long incubation period of four to five years, but ultimately is fatal for cattle within weeks to months of its onset. BSE first came to the attention of the scientific community in November 1986 with the appearance in cattle of a newly-recognized form of neurological disease in the United Kingdom (UK).

Cases of BSE

• 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 3286) have also been reported in native cattle in Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Ireland, Israel, Italy, Japan, Liechtenstein, Luxembourg, Netherlands, Poland, Portugal, Slovakia, Spain and Switzerland. However, all but 206 cases have been reported in six countries - France, Germany, Ireland, Portugal, Spain and Switzerland.
• Since the introduction of monitoring programmes to detect BSE in dead and slaughtered cattle, 12 countries have found their first native case (Austria, Czech Republic, Finland, Germany, Greece, Israel, Italy, Japan, Poland, Slovakia, Slovenia, Spain). Small numbers of cases have also been reported in Canada, the Falkland Islands (Islas Malvinas) and Oman, but solely in animals imported from the UK. The International Office for Epizootic Diseases (OIE) reports these cases on their web site: www.oie.int

Parts of cattle at high risk for harboring the infectious agent for bovine spongiform encephalopathy (BSE), or mad cow disease, include the skull, brain, eyes, vertebral column, and spinal cord of cows at least 30 months of age. The tonsils and a portion of the small intestine of all cattle also may contain the agent. Federal agencies protect public health by prohibiting these cow parts in the human food supply.

(Infographic: FDA/Michael Ermarth)

Transmissible Spongiform Encephalopathies in animals

Transmissible Spongiform Encephalopathies (TSEs) are diseases characterized 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.

Creutzfeldt-Jakob disease

• While several human TSEs exist, Creutzfeldt-Jakob disease (CJD) is the prototype human TSE. CJD occurs in a form associated with a hereditary predisposition (approximately 5-10% of all cases) and in a more common, sporadic form that accounts for 85-90% of cases.
• A small percentage of cases (less than 5%) are iatrogenic (resulting from the accidental transmission of the causative agent via contaminated surgical equipment or as a result of cornea or dura mater transplants). It has also been shown that CJD can be transmitted to humans as a result of treatment with natural human growth hormone. Replacement of natural human growth hormone by recombinant growth hormone has alleviated this risk.

Variant Creutzfeldt-Jakob disease

• A newly recognized form of CJD, variant Creutzfeldt-Jakob disease (vCJD), was first reported in March 1996 in the UK (cf. WHO Fact Sheet N° 180 on variant Creutzfeldt-Jakob disease). 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, six in France and one each in Canada, Ireland, Italy and the United States of America. Insufficient information is available at present to make any precise prediction about the future number of vCJD cases.
• Since few countries have surveillance systems, the geographical distribution of the incidence of vCJD needs to be better defined.
• Similarities observed between the strain of the agent responsible for vCJD and those of BSE and closely related agents transmitted naturally and experimentally to different animal species, are consistent with the hypothesis discussed during two 1996 WHO consultations: that the cluster of vCJD cases is due to the same agent that caused BSE in cattle.

References
http://www.who.int/mediacentre/factsheets/fs113/en/
http://www.fda.gov/fdac/features/2004/304_cow.html
http://www.faqs.org/nutrition/images/nwaz_02_img0179.jpg

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