General Information
Bovine spongiform encephalopathy (BSE) was first observed in the United Kingdom in April 1985, and specifically diagnosed in November 1986. BSE has been found in native cattle in Austria, Belgium, Canada, Czech Republic, Denmark, Finland, France, Germany, Greece, Ireland, Israel, Italy, Japan, Luxembourg, Liechtenstein, the Netherlands, Northern Ireland, Poland, Portugal, Slovakia, Slovenia, Spain and Switzerland. BSE also has been detected in cattle exported to Oman, the Falkland Islands, and the Azores. In December, 2003 a single case of BSE was observed in the United States.
BSE is a chronic, degenerative disorder that affects the brain and central nervous system in adult cattle after a long incubation period. The disease is progressive and always fatal. The disease is not caused by a virus or bacteria, but thought to be a pathological change in structure of a naturally occurring brain protein, the prion protein. The change makes the prion protein very resistant to degradation, thus enabling transmission of the disease. BSE is one of several known transmissible spongiform encephalopathies (TSE), which include scrapie (affecting sheep and goats), chronic wasting disease or CWD (affecting deer and elk), transmissible mink encephalopathy (TME) and feline spongiform encephalopathy (FSE). The human forms of these diseases are CreutzfeldJakob Disease (CJD), variant CJD, Gerstmann-Straussler-Scheinker syndrome (GSS), fatal familial insomnia (FFI) and Kuru.
In naturally occurring cases, BSE has only been detected in the brain, spinal cord and retina in affected cattle. No BSE agents have been detected in muscle tissue/meat, milk or blood. Extensive testing on BSE-infected cattle also has shown that their milk products do not contain the infective agent.
BSE is primarily transmitted between cattle by their consumption of rendered by-products or ruminant-derived meat-and-bone meal. Maternal-to-fetal transmission may occur, but would be a secondary route of transmission.
According to the Animal and Plant Health Inspection Services (APHIS) of the United States Department of Agriculture (USDA), prior to December, 2003, BSE had not been detected in the United States, despite more than 12 years of active surveillance efforts. Since 1990, over 57,000 cow brains had been examined by USDA National Veterinary Services Laboratory pathologists, and no evidence of BSE was found.
The United States was early to implement stringent feed and import bans. In 1989, the U.S. banned the importation of live ruminants and at-risk ruminant products (such as meat-and-bone meal) from all countries where BSE had been found. In 1997, the U.S. banned the importation of live ruminant animals and most ruminant products that could carry the BSE infectious agent from all European countries. Any products excluded from the ban have been scientifically determined not to have a risk of carrying the BSE infectious agent. This includes products such as milk, milk products, semen and hides. The USDA continues to take stringent measures to monitor and test for BSE. In December 2000, the USDA banned imports of all rendered animal protein products, regardless of species, from all European countries.
BSE Questions and Answers
What is BSE?
BSE, or bovine spongiform encephalopathy, is a chronic, degenerative disorder that affects the brain and central nervous system in adult cattle after a long incubation period. The disease is progressive and always fatal. The disease is thought to be caused by an abnormal brain protein (a prion) rather than a bacterium or virus.
Is eating beef, drinking milk and consuming dairy products safe?
Yes. BSE only has been detected in the brain, spinal cord and retina in affected cattle. No BSE infectivity has been detected in muscle tissue/meat or milk.
Are other food products made from cattle products safe?
Gelatin, a clear, jellylike substance, is extracted from the bones and hides of animals used for food. The gelatin manufacturing process is extensive and produces a product that is now thought to be of lower risk of BSE. Beef tallow, which also undergoes high-temperature refining, would also be considered safe for human consumption. The World Health Organization has stated that all food, cosmetic or pharmaceutical products containing gelatin or tallow are safe and can be used with confidence.
What is CJD?
CJD (Creutzfeld-Jakob Disease) is an extremely rare, progressive, fatal disease of the brain of humans. It affects approximately one in one million people per year. Most cases of CJD are sporadic and show no relation to regional, ethnic, economic or other factors. CJD has been identified around the world.
Is there monitoring of the incidence of Creutzfeld-Jakob Disease in the United States?
Yes. The possibility that BSE can spread to humans has focused increased attention on the desirability of national Creutzfeld-Jakob Disease (CJD) surveillance. The Centers for Disease Control and Prevention (CDC) monitors the trends and current incidence of CJD in the United States by analyzing death certificate information from U.S. multiple cause-of-death data, compiled by the National Center for Health Statistics. A summary of these data was published in the Journal of the American Medical Association on November 8, 2000 (Volume 284, No. 18, pp. 2322-3; available at http:// jama.ama-assn.org/issues/ v284n18/ffull/jIt1108-6.html).
What is the difference between the new variant CJD (vCJD) and the classic CJD?
In contrast to the classic form of CJD, the new variant form in the United Kingdom predominantly affects younger persons (median age at death: 27.5 years as of October 2000), has different clinical features, with prominent psychiatric or sensory symptoms at the time of clinical presentation, and delayed onset of neurological abnormalities. Recently published data show an increasing trend for the new variant CJD in the United Kingdom. Cases of vCJD have been reported in Europe. The vCJD is still more rare than CJD.
Is there evidence that this newly recognized variant of CJD is caused by BSE exposure?
There is compelling epidemiological and laboratory evidence that the new variant CJD is BSE. The absence of confirmed cases of new variant CJD in other geographic areas free of BSE supports a causal association. In addition, the interval between the most likely period for the initial extended exposure of the population to potentially BSE-contaminated food (1984-1986) and onset of initial vCJD cases (1994-1996) is consistent with known incubation periods for CJD.
Has CDC initiated increased surveillance efforts to determine whether the newly recognized variant of CJD occurs in the United States?
Yes. In addition to the ongoing review of national CJD mortality data, CDC conducted active CJD surveillance in its four established Emerging Infections Program areas (Minnesota, Oregon, Connecticut, and the San Francisco Bay area, California) and in a metropolitan Atlanta site during April and May 1996. These surveillance efforts have not detected evidence of the occurrence of new variant CJD in the United States.
Can other transmissible spongiform encephalopathies (TSE) be transmitted to humans?
Species variation in prion protein creates some barrier to transmission. Some species are more susceptible than others, and some TSEs are more transmissible than other forms. Human do not develop scrapie, for example, but the answer is not clear for other TSEs such as CWD, chronic wasting disease.
At what age do cattle contract BSE?
BSE has been confirmed in cattle as young as 20 months. Most cases are in cattle over 30 months of age.
Are all TSEs caused by the same thing?
There are several prion "strains" that damage different areas of the brain, and result in different pathology. Strain properties are transmissible and are thought to be the result of structural variations between prion proteins. Some TSEs are caused by abnormal synthesis of prion proteins. BSE, scrapie, and CWD are different diseases.
BSE Timeline
1985 - BSE first observed in United Kingdom.
1986 - First official diagnosis of bovine spongiform encephalopathy (BSE) is made in the United Kingdom.
1988 - Britain prohibits feeding meal containing ruminant products to other ruminants.
1989 - U.S. prohibits importation of live ruminants and at-risk ruminant products (such as meat-and-bone meal) from the United Kingdom and subsequently countries where BSE had been found.
1994 - European Union prohibits use of cattle feed containing cattle meat and bone meal.
1995 - First human death from what was later identified as human variant of BSE, also called new variant Creutzfeld-Jakob Disease (vCJD).
1997 - U.S. bans the importation of live ruminant animals and most ruminant products that could carry the BSE infectious agent from all European countries. U.S. bans mammalian-to-ruminant feed sources.
2000 - USDA bans imports of all rendered animal protein products, regardless of species, from all European countries. Japan bans beef imports from Europe.
2001 - Livestock and meat industries call for strict compliance, and U.S. regulators order animal-feed industry to maintain stringent controls. U.S. regulators ban blood donations from anyone who has lived in France, Portugal or Ireland for a total of 10 years since 1980.
2001 - Canada, Mexico and the U.S. temporarily ban Brazilian beef products after Brazil failed to comply with a tricountry request for information to complete a BSE risk assessment. No cases of BSE have been found in Brazil, to date.
2003, May – Canada reports finding BSE in a single beef animal. The U.S. closes its Canadian border to the importation of all ruminants and most products derived from ruminants.
2003, October – USDA proposes a rule to allow the importation of certain live ruminants and ruminant products from minimal risk regions under specific conditions. The proposed rule placed Canada on a list of countries considered a minimal risk for BSE.
2003, December – USDA announces a positive case for BSE. Major trade partners ban importation of U.S. beef.
Summary
The volume of science-based information about BSE has grown rapidly in the pest ten years. As knowledge has increased, the North American food industry has been able to work with government agencies to implement sound measures to effectively prevented the spread of the disease. At the same time, policies ere in place which will effectively contain an outbreak end limit human exposure, should the disease ever be found in North America.
The international scientific community continues to diligently expend the knowledge base concerning the disease, particularly in the diagnosis, treatment end cure of infected organisms.
At present, the risk presented to the U.S. food supply by BSE is still effectively non-existent. U.S. consumers should be reassured that their food supply continues to be the safest in the world.