Mad Cow Disease
Are humans susceptible?
What is Mad Cow Disease?
• Mad Cow Disease is scientifically known as
Bovine Spongiform Encephalopathy (BSE).
• BSE affects the central nervous system of
cattle, destroying brain tissue and eventually
causing dementia and death.
• The nature of the transmissible
agent is unknown.
• There is no known cure.
• The disease is carried in nervous system
tissue.
What is Mad Cow Disease?
• The infectious agent that is widely thought to cause
disease is the prion (although that is speculative – there
is a lack of evidence), a particle of clumped-up protein.
• In its normal form, the prion protein is found in a wide
variety of tissues throughout the body, including the
brain, immune system, blood, gut, and liver, and causes
no disease. But mutations in the protein can cause it to
fold abnormally and clump up to form infectious prions.
• Researchers also believe that new prions can form when
a normal prion protein comes into physical contact with
an abnormally shaped prion protein. For reasons that are
still unknown, the bad protein makes the good protein
turn bad.
What causes Mad Cow
Disease?
• Although the cause is unknown, Scientists
speculate that the disease has spread among
cattle primarily through "animal recycling" -the use of bone meal and other ground animal
parts in feeds.
• Mad cow disease was first identified in Britian
in 1985.
• BSE does not
spread from
cow-to-cow contact
What is being done
about it?
• The European Union implemented new rules
Jan. 1, 2001 requiring all cattle over 30
months old to be tested for the disease.
• The FDA prohibits all material from nonambulatory cattle in human food, removing
certain cattle tissues
from the human food,
and banning certain
nervous system tissues
in meat products.
Source: FDA
Source: Rutgers Poll 2.2.04
What is the human
variant of Mad Cow
Disease?
• The human form of Mad Cow disease,
Creutzfeldt-Jakob disease (CJD) is a rare,
degenerative, invariably fatal brain disorder.
• Typically, onset of symptoms occurs at about age
60.
•There are three major categories of CJD: sporadic
CJD, hereditary CJD, and acquired CJD
What causes CJD?
• In sporadic CJD, the disease appears even though the person
has no known risk factors for the disease. This is by far the
most common type of CJD and accounts for at least 85 percent
of cases.
• In hereditary CJD, the person has a family history of the
disease and/or tests positive for a genetic mutation associated
with CJD. About 5 to 10 percent of cases of CJD in the United
States are hereditary.
• In acquired CJD, the disease is transmitted by exposure to
brain or nervous system tissue, usually through certain medical
procedures. There is no evidence that CJD is contagious
through casual contact with a CJD patient. Since CJD was first
described in 1920, fewer than 1 percent of cases have been
acquired CJD.
Source: http://www.mydna.com/health/diseases/madcow
How is it detected?
• There is currently no one diagnostic test for CJD.
• First it is important to rule out treatable forms of
dementia such as encephalitis or chronic meningitis.
• The only way to confirm a diagnosis of CJD is by brain
biopsy or autopsy by removing a small piece of brain
tissue to be examined by a neurologist.
• Early symptoms in humans
include insomnia, memory
loss, and depression.
Brain tissue infected with prions
has a spongy appearance.
Image courtesy NEJM.
What is the treatment
and prognosis?
• Due to the lack of knowledge of what causes it,
there is no treatment that can cure or control CJD
• Around 90 percent of patients die within the first
year. In the early stages of disease, patients may
have failing memory, behavioral changes, lack of
coordination and visual disturbances. As the
illness progresses, mental deterioration becomes
pronounced and involuntary movements,
blindness, weakness of extremities, and coma
may occur in the patient.
What link is there
between bse and cjd?
• “We don’t know much about how the disease is transmitted or why only
certain people appear susceptible,” says Richard Johnson of Johns
Hopkins University in Baltimore, Maryland, who headed a recent Institute
of Medicine panel to study mad cow and related diseases. “There are too
many questions and not enough answers.”
• An experimental study reported in June 1996 showed that three
cynomologus macaque monkeys inoculated with brain tissue obtained
from cattle with BSE had clinical and neuropathological features
strikingly similar to those of variant CJD.
• A study published in 1996 indicated that a Western blot analysis of
infecting prions obtained from 10 variant CJD patients and BSE-infected
animals had similar molecular characteristics that were distinct from
prions obtained from patients with other types of CJD (Nature
1996;383:685-90).
Source: http://www.mydna.com/health/diseases/madcow
What do most americans
believe?
Of those who had heard of the disease, 65
percent believe the nation’s beef supply is
safe, 24 percent believe it is unsafe and 10
percent are unsure.
Source: Rutgers Poll 2.2.04
How does this affect the
economy & beef market?
•The EU has set aside about $1 billion for the tests, which cost about
$100 per animal. The European Commission estimates the cost of
incinerating slaughtered animals at $3.3 billion.
• Nearly 1 in 5 (19.5 percent) of those who knew about mad cow
disease say they have since reduced their beef consumption.
About 9 percent say they eat somewhat less beef, 5 percent say
they eat much less and nearly 5 percent say they have stopped
eating beef altogether. As such, about 4 percent of the total
population claims to have stopped eating beef.
Source: Rutgers Poll 2.2.04
How does this affect the
economy & beef market?
• Nearly a quarter (24 percent) of 19.5
percent of those who have claimed to
have stopped eating beef say they will
never resume eating it.
Source: Rutgers Poll 2.2.04
Should you avoid
hamburgers?
• The average annual CJD death rate in the United States
has remained relatively stable at about one case per
million population per year. In addition, CJD deaths in
persons aged <30 years in the United States remain
extremely rare (<1 case per 100 million per year).
Source: http://www.mydna.com/health/diseases/madcow
Where did I get this
information?
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http://www.pbs.org/newshour/bb/health/mad_cow.html
http://www.mad-cow-facts.com/News-Commentary/rutgers_poll_2-204.htm
www.genomenewsnetwork.org/. ../01/23/mad_cow.php
http://www.fda.gov/fdac/features/2004/304_cow.html
http://www.mydna.com/health/diseases/madcow
http://www.ninds.nih.gov/disorders/cjd/detail_cjd.htm