Variant Creutzfeldt-Jacob Disease (vCJD)
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Variant Creutzfeldt-Jacob Disease (vCJD)

Variant Creutzfeldt-Jakob disease (vCJD) is a new variant of Creutzfeldt-Jakob disease (CJD) which is a type of rare and ultimately fatal degenerative brain disease. They both form part of a group of diseases called Transmissible Spongiform Encephalopathies (TSEs) that affect humans and animals. TSEs are thought to be caused by the build up in the brain of an abnormal form of the naturally occurring 'prion' protein. 

Variant CJD (vCJD) was first identified in 1996. Variant CJD is strongly linked to exposure, probably through food, to a TSE of cattle called Bovine Spongiform Encephalopathy (BSE) which is a progressive neurological disorder of cattle that results from infection by an unconventional transmissible agent. In fact there has never been a case of vCJD that did not have a history of exposure within a country where the 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 or in three cases, each reported from the United Kingdom, through receipt of blood from an asymptomatic, infected donor. Although there have been no reported cases of vCJD having been transmitted as a result of surgical procedures, the possibility cannot be ruled out. Precautionary measures have been taken to reduce such a risk by improving the standards of decontamination services for surgical instruments.

Incubation Period
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.

Signs and Symptoms
In contrast to the classic form of CJD, the variant form in the United Kingdom predominantly affects younger persons (median age at death around 28 years) and has atypical clinical features.

These atypical features include prominent psychiatric or sensory symptoms at the time of clinical presentation or early in the course of the illness, delayed onset of neurologic abnormalities including ataxia within weeks or months, dementia and myoclonus late in the illness, duration of illness of at least 6 months, and a diffusely abnormal non-diagnostic electroencephalogram.

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.

Is there evidence directly linking this newly recognized variant of CJD to BSE exposure?
There is some strong epidemiologic evidence for a causal association between variant CJD and BSE. The absence of confirmed cases of variant CJD in other geographic areas free of BSE supports a causal association.

In addition, the interval between the most likely period for the initial extended exposure of the population to potentially BSE-contaminated food (1984-1986) and onset of initial variant CJD cases (1994-1996) is consistent with known incubation periods for CJD.