Mad cow disease is a fatal disease that
slowly destroys the brain and spinal cord (central nervous system) in cattle. It also is known as bovine spongiform encephalopathy,
People cannot get mad cow disease. But in rare cases they
may get a human form of mad cow disease called variant Creutzfeldt-Jakob
disease (vCJD), which is fatal.
This can happen if you eat nerve
tissue (the brain and spinal cord) of cattle that were infected with mad cow
disease. Over time, vCJD destroys the brain and spinal cord.
is no evidence that people can get mad cow disease or vCJD from eating muscle
meat—which is used for ground beef, roasts, and steaks—or from consuming milk
or milk products.
People with vCJD cannot spread it to others
through casual contact.
People who have spent a lot of time (at least 3 months) in places where mad cow disease has been found are not
allowed to give blood in the United States or Canada.2, 1 This is to help prevent vCJD from
Experts are not sure what causes mad cow disease
The leading theory is that the disease is caused by infectious
proteins called prions (say "PREE-ons"). In affected cows, these proteins are
found in the brain, spinal cord, and small intestine. There is no proof that
prions are found in muscle meat (such as steak) or in milk.
Another theory is that mad cow disease is caused by a virus that
causes the proteins to change.3
cow is slaughtered, parts of it are used for human food and other parts are
used in animal feed. If an infected cow is slaughtered and its nerve tissue is
used in cattle feed, other cows can become infected.
get vCJD if they eat the brain or spinal cord tissue of infected cattle.
case of vCJD was reported in 1996. Since then, there have been a few cases of
vCJD reported in the world. Most of the cases have been in countries that are
part of the United Kingdom (England, Scotland, Wales, and Northern
In December 2003, mad cow disease was discovered in one
cow in the United States. Before this cow was found to have the disease, the
cow was slaughtered and its muscle meat was sent to be sold in grocery stores.
But its organs and nerve tissue were not used for human food. Although mad cow
disease cannot be spread through muscle meat, the United States Department of
Agriculture (USDA) quickly traced the meat and removed it from grocery stores.
Between 2004 and 2006, only two more cows
in the United States were found to have mad cow disease. When tested, these
cases were found to be different from the first case found in the United
States. There is some disagreement about whether these two cases were mad cow
Creutzfeldt-Jakob disease (vCJD) causes the brain to become damaged over time.
It is fatal. Symptoms include:
If a person does eat nerve tissue from an infected
cow, he or she may not feel sick right away. The time it takes for symptoms to
occur after you're exposed to the disease is not known for sure, but experts
think it is years.
There is no single test to
diagnose vCJD. Doctors may think that a person has vCJD based on where the
person has lived and the person’s symptoms and past health. Imaging tests, such
MRI, may be done to check for brain changes caused by
Researchers are now trying to develop a blood test that
looks for vCJD. But no blood test is available at this time.
brain biopsy is the only way to confirm a diagnosis of vCJD.
There is no cure for vCJD.
Treatment includes managing the symptoms that occur as the disease gets worse.
The following health
organizations are tracking and studying
mad cow disease and variant Creutzfeldt-Jakob disease
(vCJD). Their websites contain the most up-to-date information about these
The Centers for Disease Control and Prevention (CDC) is
an agency of the U.S. Department of Health and Human Services. The CDC works
with state and local health officials and the public to achieve better health
for all people. The CDC creates the expertise, information, and tools that
people and communities need to protect their health—by promoting health,
preventing disease, injury, and disability, and being prepared for new health
The Genetics Home Reference provides information on hundreds of genetic conditions. The website has many tools for learning about human genetics and the way genetic changes can cause
disease. It also has links to additional resources for people who
have genetic conditions and for their families.
The National Institute of Allergy and Infectious
Diseases conducts research and provides consumer information on infectious and
The USDA Food Safety and Inspection Service sees that
the supply of meat, poultry, and egg products in the United States is safe,
wholesome, and correctly labeled and packaged. Its website has extensive
information on food safety, food preparation, food poisoning, and food
labeling. It provides phone numbers and email addresses to use to ask for
information on food poisoning, food safety, and food safety education programs.
The website also allows the public to ask questions through an interactive
feature called "Ask Karen."
CitationsCanadian Blood Services (2005). Deferral policies for vCJD. Available online: http://www.bloodservices.ca/CentreApps/Internet/UW_V502_MainEngine.nsf/page/Deferral+Policies+for+vCJD?OpenDocument.American Red Cross (2009). Eligibility requirements: Donating blood. Available online: http://www.redcrossblood.org/donating-blood/eligibility-requirements.Manuelidis L, et al. (2007). Cells infected with scrapie and Creutzfeldt-Jakob disease agents produce intracellular 25-nm virus-like particles. Proceedings of the National Academy of Science, 104(6): 1965–1970.Other Works ConsultedU.S. Centers for Disease Control and Prevention (2010). Fact sheet: Variant Creutzfeldt-Jakob disease. Available online: http://www.cdc.gov/ncidod/dvrd/vcjd/factsheet_nvcjd.htm.
March 24, 2011
E. Gregory Thompson, MD - Internal Medicine & W. David Colby IV, MSc, MD, FRCPC - Infectious Disease
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