Variant Creutzfeldt-Jakob Disease(vCJD)
What is Variant Creutzfeldt-Jakob Disease (vCJD)?
Variant CJD (vCJD) is a rare, degenerative, fatal brain disorder in humans.
Although experience with this new disease is limited, evidence to date indicates
that there has never been a case of vCJD transmitted through direct contact of
one person with another. However, a case of probable transmission of vCJD
through transfusion of blood components from an asymptomatic donor who
subsequently developed the disease has been reported.
As of December 1, 2003, a total of 153 cases of vCJD had been reported in the
world: 143 from the United Kingdom, six from France, and one each from Canada,
Ireland, Italy, and the United States (note: the Canadian, Irish, and U.S. cases
were reported in persons who resided in the United Kingdom during a key exposure
period of the U.K. population to the BSE agent).
Almost all the 153 vCJD patients had multiple-year exposures in the United
Kingdom between 1980 and 1996 during the occurrence of a large UK outbreak of
bovine spongiform encephalopathy (BSE, commonly known as mad cow disease) among
cattle.
There has never been a case of vCJD that did not have a history of exposure
within a country where this cattle disease, BSE, was occurring.
It is believed that the persons who have developed vCJD became infected
through their consumption of cattle products contaminated with the agent of BSE.
There is no known treatment of vCJD and it is invariably fatal.
How does vCJD Differ from Classic CJD?
This variant form of CJD should not be confused with the classic form of CJD
that is endemic throughout the world, including the United States. There are
several important differences between these two forms of the disease. The median
age at death of patients with classic CJD in the United States, for example, is
68 years, and very few cases occur in persons under 30 years of age. In
contrast, the median age at death of patients with vCJD in the United Kingdom is
28 years.
The vCJD can be confirmed only through examination of brain tissue obtained
by biopsy or at autopsy, but a "probable case" of vCJD can be diagnosed on the
basis of clinical criteria developed in the United Kingdom.
The incubation period for vCJD is unknown because it is a new disease.
However, it is likely that ultimately this incubation period will be measured in
terms of many years or decades. In other words, whenever a person develops vCJD
from consuming a BSE-contaminated product, he or she likely would have consumed
that product many years or a decade or more earlier.
In contrast to classic CJD, vCJD in the United Kingdom predominantly affects
younger people, has atypical clinical features, with prominent psychiatric or
sensory symptoms at the time of clinical presentation and delayed onset of
neurologic abnormalities, including ataxia within weeks or months, dementia and
myoclonus late in the illness, a duration of illness of at least 6 months, and a
diffusely abnormal non-diagnostic electroencephalogram.
The BSE epidemic in the United Kingdom reached its peak incidence in January
1993 at almost 1,000 new cases per week. The outbreak may have resulted from the
feeding of scrapie-containing sheep meat-and-bone meal to cattle. There is
strong evidence and general agreement that the outbreak was amplified by feeding
rendered bovine meat-and-bone meal to young calves.
For more information about CJD, please read the Creutzfeldt Jakob Disease
article.
Is CJD monitored in the U.S.?
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, CDC. By 3- or 4-year periods from 1987 through
2001, the average annual death rates of CJD (not vCJD) have remained relatively
constant, ranging from 0.95 cases per 1 million in 1999-2001 to 1.14 cases per 1
million in 1995-1998. In addition, deaths from non-iatrogenic CJD in persons
aged <30 years in the United States remain extremely rare (<5 cases per 1
billion per year). In contrast, in the United Kingdom, over half of the patients
who died with vCJD were in this young age group.
In addition, CDC collects, reviews and when indicated, actively investigates
reports by health care personnel or institutions of possible CJD or vCJD cases.
Also, in 1996-97, CDC established, in collaboration with the American
Association of Neuropathologists, the National Prion Disease Pathology
Surveillance Center at Case Western Reserve University, which performs special
diagnostic tests for prion diseases, including post-mortem tests for vCJD.
What is being done to prevent BSE?
To prevent BSE from entering the United States, severe restrictions were placed
on the importation of live ruminants, such as cattle, sheep, and goats, and
certain ruminant products from countries where BSE was known to exist. These
restrictions were later extended to include importation of ruminants and certain
ruminant products from all European countries.
Because the use of ruminant tissue in ruminant feed was probably a necessary
factor responsible for the BSE outbreak in the United Kingdom and because of the
current evidence for possible transmission of BSE to humans, the U.S. Food and
Drug Administration instituted a ruminant feed ban in June 1997 that became
fully effective as of October 1997.
In late 2001, the Harvard Center for Risk Assessment study of various
scenarios involving BSE in the United States concluded that the FDA ruminant
feed rule provides a major defense against this disease.
For additional information about BSE, please read the Mad Cow Disease
article.
Source: Centers for Disease Control
Last Editorial Review: 8/2/2004
- Mad Cow Disease - Get the facts on mad cow disease (bovine spongiform encephalopathy, BSE) causes (prions), and learn how it's transmitted to people (variant Creutzfelt Jakob disease).
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