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BSE Fact Sheet

Synopsis of BSE
Bovine Spongiform Encephalopathy (BSE), commonly known as mad cow disease, is a fatal neurodegenerative disease of cattle. Unlike many other kinds of infectious animal diseases, which are spread by microbes, BSE is a type of transmissible spongiform encephalopathy (TSE) that arises in animals via the spread of a specific type of protein referred to as a prion. Prions are self-replicating abnormal proteins and, in the brain of animals, these proteins cause native cellular prion protein to deform into the infectious state which ultimately results in the formation of dense plague fibers in the brain, degeneration of physical and mental abilities, and ultimately death. Scientist originally thought that BSE epizootic in cattle originated in sheep, in which the related prion disease scrapie is common. However, since the sheep and cattle TSEs are quite different, it is now thought more likely that BSE originated with a case of sporadic BSE in a single cow. The practice of feeding cattle rendered meat and bone meal, a high-protein substance obtained from the remnants of butchered animals (including cows and sheep) allowed for the accumulation of prions over many generations. The use of meat and bone meal as a protein supplement was widespread in Europe prior to 1990 and, as more animals became ill, more infectious tissue got into the feed until the number of cases reached epizootic proportions. These disease-causing prions can also be transmitted to humans and is thought to be the cause of variant Creutzfeldt-Jacob disease, a rare and fatal human brain-wasting disease.
  • Transmission:
    • Consumption of tainted tissues from other animals with the disease.
  • Characterized by a long incubation period
    • Incubation period for BSE among cattle ranges from three to eight years.
    • Incubation period for vCJD among humans is unknown but is at least five years and could extend up to 20 years or longer.
  • The disease is invariably fatal and there is no known treatment or cure.
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Clinical Signs and Symptoms
Cattle:
  • Incubation period for BSE among cattle ranges from three to eight years.
  • BSE affects the brain and spinal cord
  • Clinical signs:
    • Characterized by progressive degeneration of the nervous system
      • Changes in temperament, such as nervousness and aggression
      • Abnormal posture
      • Incoordination and difficulty rising
      • Decreased milk production
      • Weight loss despite continued appetite
  • Post mortem:
    • Sponge-like lesions visible in the brain
Humans:
  • Incubation period for vCJD among humans is unknown but is at least five years and could extend up to 20 years or longer.
  • Clinical signs:
    • Prominent psychiatric or sensory symptoms
    • Neurological abnormalities
      • Ataxia
      • Dementia
      • Myoclonus
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Diagnosis and Treatment
Diagnostic Samples:
  • Brain biopsy
  • Preferably whole brain
  • Fresh spinal cord or caudal medulla
  • Frozen as soon as possible after death
Differential Diagnosis:
  • Hypomagnesaemia
  • Nervous ketosis
  • Encephalic listeriosis and other encephalitides
  • Polioenchephalomalacia or cerebro-cortical necrosis
  • Intra-cranial tumors
Clinical Diagnosis:
  • Neurological signs and symptoms:
    • Cattle:
      • Apprehension, fear, increased startle reflex, or depression
      • Hyper-aesthesia or hyper-reflexia
      • Adventitial movements: tremors and myoclonus
      • Ataxia of gait, including hypermetria
      • Autonomic dysfunction: reduced rumination, bradycardia and altered heart rhythm
    • Humans:
      • Suspected consumption of animals contaminated with BSE
      • Neurological abnormalities, such as ataxia, dementia, and myoclonus, especially in young adults.
Laboratory Tests:
  • Laboratory tests for BSE vary considerably as do the regulations in various jurisdictions for when and which cattle must be tested.
    • In Europe, cattle older than 30 months are tested
    • In Japan, all cattle are tested at time of slaughter
  • Tests are also difficult due to the small levels of altered prion protein in blood and urine and no other signal has been found.
  • No diagnostic tests for live animals although tentative diagnosis can be made based on clinical signs.
  • Post mortem examination of brain tissue.
    • Microscopic examination using histopathological examination to detect sponge-like changes in the brain tissues and immunohistochemistry to examine BSE fibrils.
    • These are the "gold-standard" tests and take more than a week to run.
    • More rapid tests (36 to 48 hours) detect abnormal prion in brain and spinal cord tissue of dead animals.
Treatment:
  • There is no treatment for BSE
  • The course of the disease varies form two weeks to 14 months and usually results in death or humane destruction.
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Economic Consequences and Disease Eradication
Economic Consequences:
  • Loss of livestock
  • Costs associated with containment and clean-up
  • Trade embargoes
  • Medical expenses
Disease Eradication:
  • Prevention (worldwide):
    • BSE surveillance
    • Culling of sick animals
    • Banning of specified risk materials from animal feed and human food chains
  • Prevention (US agencies):
    • Prohibited importation of live ruminant animals and most ruminant products from all of Europe (USDA).
    • US cattle that exhibit abnormal neurological behavior are tested for BSE (USDA).
    • In 1997, regulations prohibited the feeding of mammalian byproducts to ruminants such as cows and goats (FDA).
      • However, the byproducts of ruminants can still be legally fed to pets or other livestock and poultry such as pigs and chickens.
    • Guidelines implemented which exclude potential blood donors who have spent six or more cumulative months in the UK between 1980 and 1996 from donating blood (FDA)
    • HHS action plan:
  • BSE viability:
    • Highly stable, resists freezing, drying and heating at normal cooking temperatures.
    • Stable over a wide range of pH.
    • Infectious BSE prion material is not destroyed through normal cooking procedures or irradiation.
    • The OIE recommends sodium hypochlorite containing 2% available chlorine, or 2 N sodium hydroxide, applied for more than 1 hour at 20°C for surfaces or overnight for equipment.
BSE and Bioterrorism:
  • Hundreds of pages of US agricultural documents recovered from the Al Qaeda in Afghanistan are a strong indication that terrorist recognize that our agriculture and food industry provides tempting targets.
  • BSE prions are considered "select agents" under the Bioterrorism Preparedness and Response Act and, as such, require special security arrangements, including background checks on anyone who may have access to this material in the lab.
  • The malicious introduction of prions into the food chain of humans or of cows would cause a terrible scenario.
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Outbreaks
Country BSE cases vCJD cases
Austria 2 0
Belgium 125 0
Canada 5 (plus one pending) 1
Croatia 0 0
Czech Rep 9 0
Denmark 13 0
Falkland Is 1 0
Finland 1 0
France 891 11
Germany 312 0
Greece 1 0
Hong Kong 2 0
Israel 1 0
Italy 117 1
Japan 26 1
Lichtenstein 2 0
Luxembourg 2 1
Netherlands 75 1
Oman 2 0
Poland 21 0
Portugal 875 1
Republic of Ireland 1353 2
Slovakia 15 0
Slovenia 4 0
Spain 412 0
Sweden 1 0
Switzerland 453 0
Thailand n/a 2
UK 183,803 160
US 3 2 (both cases believed to have been contracted in the UK)
Total 188,515 170 (+ 6 results pending)

United Kingdom: BSE among cattle was first described in the UK in November of 1986. Between 1986 and 2002, approximately 181,000 cases of BSE in more than 35,000 herds were confirmed. In 1989, the first case was reported outside of the UK and has since appeared in other European countries, Ireland, Japan, Canada and the US. Between 1989 and 2000, at least 1,642 cases of BSE have been identified among cattle in Belgium, Denmark, France, Germany, Ireland, Italy, Liechtenstein, the Netherlands, Portugal, Spain and Switzerland.

Human Cases: Following an epizootic of BSE in Britain, 157 people acquired and died of a similar neurological disease referred to a variant Creutzfeldt-Jacob disease. Of the 157 cases of vCJD in humans so far, 148 occurred in the UK, 6 in France, 1 in Italy, and 3 in people who had lived in or visited Britain—1 each in Ireland, Canada and the US. For many of the vCJD patients, there is direct evidence that they had consumed tainted beef, which is the assumed mechanism by which all affected individuals contracted it. It is estimated that 400,000 cattle infected with BSE entered the human food chain in the 1980s.

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Sources and Related Articles
Sources:
  1. OIE, 2006. Bovine Spongiform Encephalopathy. Available at http://www.oie.int/eng/info/en_esb.htm.
  2. US Department of Health and Human Services, 2001. Federal Agencies Take Special Precautions to Keep Mad Cow Disease out of the United States. Available at http://www.hhs.gov/news/press/2001pres/01fsbse.html.
  3. USDA Food Safety and Inspection Service, 2005. Bovine Spongiform Encephalopathy – Mad Cow Disease. Available at http://www.fsis.usda.gov/Fact_Sheets/Bovine_Spongiform_Encephalopathy_Mad_Cow_Disease/index.asp.
  4. WHO, 2006. Bovine Spongiform Encephalopathy. Available at http://www.who.int/mediacentre/factsheets/fs113/en/.
    5. Related Articles:
  5. Becker, G. S., 2005. BSE (Mad Cow Disease): A Brief Overview. CRS Report for Congress.
  6. Hanrahan, C. E. and G. S. Becker, 2005. Mad Cow Disease and US Beef Trade. CRS Report for Congress.
  7. Prusiner, S. B., 2004. Detecting Mad Cow Disease. Scientific America.
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