Bovine Spongiform Encephalopathy�
(BSE; Mad Cow Disease)
AS-1206 (Revised), March 2004
Greg Lardy, Ph.D. Beef Cattle Specialist, NDSU Extension Service
Charlie Stoltenow, DVM Veterinarian, NDSU Extension Service
Julie Garden-Robinson, Ph.D. Food and Nutrition Specialist, NDSU Extension
Service
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What is BSE?
How is BSE spread?
Where does BSE occur?
What is the status of BSE in North America?
What should livestock
producers do?
What feeds have been banned by FDA?
What rendered products are cleared
for feeding to ruminant animals?
Should consumers be concerned about eating
beef?
Suggested Resources for Further Information
Bovine spongiform encephalopathy (BSE) is a disease condition
in cattle which is thought to have originated in Great Britain. It occurs in
cattle between two and eight years old and is always fatal. The most plausible
cause of the disease is a prion, a "self-replicating" protein, rather
than a bacterium or virus. BSE causes a portion of the brain to become sponge-like.
Brain, central nervous system tissue, and the distal ileum (portion of the small
intestine) can carry the infective agent, and measures have been taken to exclude
those parts known to carry the infective agent (primarily brain and central
nervous system tissue) from the food and feed supply.
BSE is often referred to as "mad cow"
disease, because animals infected with the disease are often irritable and
can react in a somewhat violent or threatening fashion when approached by
humans.
BSE is similar to other transmissible spongiform encephalopathies
(TSEs) present in man and animals. In animals the TSEs include scrapie (sheep
and goats), chronic wasting disease (deer and elk), transmissible mink encephalopathy
(mink), and feline spongiform encephalopathy (felines). In humans, Creutzfeldt-Jakob
disease (CJD), variant-CJD (v-CJD), Gerstmann-Sträussler-Scheinker syndrome
(GSS), fatal familial insomnia (FFI), and Kuru are all transmissible spongiform
encephalopathies.
BSE it thought to be linked to v-CJD. Pathological similarities
exist between the two conditions, which has lead scientists to speculate that
the two conditions are related.
How is BSE spread?
There is still much debate in the scientific community
regarding how BSE is spread. At the present time, BSE is thought to be spread
in tissue from the central nervous system (brain, spinal cord) as well as distal
ileum, some of which can be present in meat and bone meal. BSE is not spread
by animal-to-animal contact. In other words, an animal infected with BSE cannot
infect another animal with which it is penned or pastured. Little is known regarding
the minimum amount of prion material that can cause an infection.
Where does BSE occur?
BSE was first observed in Great Britain in April 1985
and was officially diagnosed in 1986. By June 1990, some 14,000 cases were confirmed
(out of an estimated population of 10 million cattle) in Great Britain.
Since 1986, more than 185,000 cases of BSE have been
confirmed in Great Britain. The epidemic peaked in 1992-93 at almost 1,000 new
cases per week. Control measures have since reduced incidence of the disease,
and currently fewer than 100 new cases are reported per week.
What is the status of BSE in North
America?
In May 2003, BSE was diagnosed in a cow in central Alberta.
This was the first native-born case of BSE reported on the North American continent.
On Dec. 23, 2003, the U.S. Department of Agriculture
(USDA) announced that a Holstein cow in Washington had been diagnosed with BSE.
The subsequent epidemiological investigation revealed that the cow originated
in Canada.
Since 1989, the U.S. has prohibited importation of ruminants
and most ruminant products from countries affected by BSE. A total of 496 cattle
were imported from the United Kingdom and Ireland between January 1, 1981, and
July 1989. None of these animals remain alive. The animals that could be identified
and located in 1989 were put under quarantine and monitored by USDA Animal and
Plant Health Inspection Service (APHIS) personnel. The animals were allowed
to die of natural causes or were euthanized. None of the identified animals
entered the food or rendering system.
The APHIS has also conducted a trace-back effort to locate
each of the cattle imported from BSE-affected countries between 1980 and the
implementation of the importation ban in 1989. No evidence of BSE has been found
in any of these animals.
As a precautionary measure, the Food and Drug Administration
(FDA) implemented a ruminant-to-ruminant feeding ban for meat and bone meal
in December 1997. Following the announcement of the case of BSE in Washington,
FDA announced additional measures to further safeguard the feed supplies for
cattle in the United States.
Also in December 1997, APHIS banned importation of live
ruminants and most ruminant products from other European countries.
Since May 1990, the United States has had an aggressive
surveillance program to ensure timely detection and response in the unlikely
event that BSE is ever detected in the U.S. The surveillance program is based
on sampling brains of cattle with suspicious neurologic symptoms. Based on the
current understanding of BSE, the U.S. must sample 224 brains from cattle with
suspicious neurological signs per year to detect an occurrence of 100 cases
of BSE per 1,000,000 head of cattle. In 2003, USDA tested over 20,000 animals
for BSE. It expects surveillance efforts to increase in 2004 in response to
the BSE case in Washington. Regularly updated numbers of bovine brain samples
tested as part of the nationwide BSE surveillance program are available on the
World Wide Web at: www.aphis.usda.gov/lpa/issues/bse/bse-surveillance.html
What should livestock producers do?
Livestock producers who feed ruminant animals must comply
with the following requirements under the law:
- Maintain copies of all invoices for all feeds received
that contain animal protein.
- Maintain copies of labeling for all feeds containing
animal protein by-products.
- Make copies of invoices and labeling available for
FDA inspection and copying.
- Maintain records for a minimum of one year.
- Producers who mix feed for both cattle and non-ruminant
animals (such as hogs and poultry) and use prohibited material in the non-ruminant
feed must use a completely separate mixer for the cattle feed.
- Producers who do not mix their own feed but purchase
feed for both cattle and non-ruminants must take steps to make sure that any
prohibited material intended for non-ruminant animals is not accidentally
fed to cattle.
More information regarding feeding regulations can be found on the following web site:
Food and Drug Administration: http://www.fda.gov/cvm/index/bse/bsetoc.html�
Several major meat packers have announced that they will now require cattle
producers to certify that they do not include ruminant meat and bone meal in
cattle feed.
What feeds have been banned by FDA?
The following feeds cannot be fed to ruminant animal:
- Ruminant meat and bone meal
- Blood meal and blood by-products
- Inspected meat products cooked and offered for human
consumption and further heat processed including plate waste and food casings
- Poultry litter (because of the possibility of spilled
feed which may contain ruminant meat and bone meal)
What rendered products are cleared for feeding to ruminant
animals?
- Feather meal
- Porcine meat and bone meal
- Equine meat and bone meal
- Gelatin
- Poultry by-product meal
- Tallows, fats, oils, grease, amino acids, dicalcium
phosphate
Media reports about the human form of "mad cow disease,"
v-CJD, in Europe may cause fear among consumers in the U.S. The risk of acquiring
v-CJD from eating beef in the U.S. is extremely low due to the safeguards in
place. To date, there has been one probable case of v-CJD identified in a U.S.
resident; however, this person had lived in the United Kingdom for an extended
period of time before emigrating to the U.S.
More than 99 percent of v-CJD cases from 1986 to 2000
have been linked to the United Kingdom. Despite these statistics, even in the
United Kingdom, the risk is considered very low, at perhaps one case per 10
billion servings of beef. Control measures put in place have reduced the incidence
of new cases. According to the Centers for Disease Control and Prevention (CDC),
Americans traveling to Europe can further reduce their risk of contracting the
disease by choosing whole muscle cuts of beef (eg. roasts, steaks) instead of
ground meat (eg. hamburgers, sausage). This would reduce the chances of consuming
a product possibly contaminated with tissues containing the prion. Another option
for travelers is to avoid eating European beef altogether.
Suggested Resources
for Further Information:
NDSU Extension BSE Frequently Asked Questions:
www.ext.nodak.edu/pubs/ansci/beef/bse-faq.pdf
NCBA's BSE Web Site:�
www.bseinfo.org�
USDA/APHIS Veterinary Services:�
www.aphis.usda.gov/lpa/issues/bse/bse.html�
Centers for Disease Control and Prevention:�
www.cdc.gov/ncidod/diseases/cjd/cjd.htm�
Food and Drug Administration:�
www.fda.gov/cvm/index/bse/bsetoc.html�
Council for Agricultural Science and Technology:�
www.cast-science.org/cast/src/cast_top.htm
United Kingdom Ministry of Agriculture Fisheries and Food�
www.defra.gov.uk/animalh/bse/index.html
For more information about food safety, contact your local county office of
the NDSU Extension Service or visit the website: www.ag.ndsu.nodak.edu/food.htm�
For more information on this and other topics, see:�
www.ag.ndsu.nodak.edu
�
AS-1206 (Revised), March 2004
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