Variant CJD was first described in 1996 in the United Kingdom. It has different clinical and pathologic characteristics from classic CJD. Each disease also has a particular genetic profile of the prion protein gene. (See table below). The median age at death for vCJD patients is 28 years, compared with 68 years for patients with classic CJD. The median duration of illness for vCJD is 14 months, compared to 5 months for classic CJD.

Important Note: Classic CJD is a distinct from "variant CJD", a prion disease that is related to Mad Cow Disease (BSE).
Classic CJD is not related to BSE.

Please see the links below for more information.

• Mad Cow Disease, aka Bovine Spongiform Encephalopathy (BSE)
• CJD (Creutzfeldt-Jakob Disease, Classic)

Clinical and Pathologic Characteristics of Classic CJD

Classic CJD characteristics in comparison with variant CJD, are presented in the table below:

Clinical and Pathologic Characteristics Distinguishing Classic CJD from Variant CJD

Characteristic	Classic CJD	Variant CJD
Median age at death	68 years	28 years
Median duration of illness	4-5 months	13-14 months
Clinical signs and symptoms	Dementia; early neurologic signs	Prominent psychiatric/behavioral symptoms; painful dyesthesiasis; delayed neurologic signs
Periodic sharp waves on electroencephalogram	Often present	Often absent
"Pulvinar sign" on MRI*	Not reported	Present in >75% of cases
Presence of "florid plaques" on neuropathology	Rare or absent	Present in large numbers
Immunohitochemical analysis of brain tissue	Variable accumulation	Marked accumulation of protease-resistance prion protein
Presence of agent in lymphoid tissue	Not readily detected	Readily detected
Increased glycoform ratio on immunoblot analysis of protease-resistance prion protein	Not reported	Marked accumulation of protease-resistance prion protein
Source: Adapted from Belay E., Schonberger L. Variant Creutzfeldt-Jakob Disease and Bovine Spongiform Encephalopathy. Clin Lab Med 2002;22:849-62.
*An abnormal signal in the posterior thalami on T2- and diffusion-weighted images and fluid-attenuated inversion recovery sequences on brain magnetic resonance imaging (MRI); in the appropriate clinical context, this signal is highly specific for vCJD.

Evidence for Relationship with BSE (Mad Cow Disease)

Since 1996, evidence has been increasing for a direct relationship between ongoing outbreaks in Europe of a disease in cattle, called bovine spongiform encephalopathy (BSE, or Mad Cow Disease), and vCJD. There is now strong scientific evidence that the agent responsible for the outbreak of the prion disease BSE in cows, is the same agent responsible for the outbreak of vCJD in humans. Both disorders are fatal brain diseases with unusually long incubation periods measured in years, and are caused by an unconventional transmissible agent. However, this evidence also suggests that the risk is low for developing vCJD, even after the consumption of contaminated product. In 1996, because of the emergence of vCJD in the United Kingdom, CDC enhanced its surveillance for CJD in the United States.

On June 24, 2005, the U.S. Department of Agriculture (USDA) announced the receipt of final results from The Veterinary Laboratories Agency in Weybridge, England, confirming BSE in a cow for which conflicting test results had been reported in 2004. Fortunately, no parts of the animal entered the human or farm-animal food supply. As a result of the findings for this BSE-positive animal, the USDA plans to develop a new laboratory testing protocol to evaluate future inconclusive BSE screening test results.

On December 23, 2003, the USDA announced a presumptive diagnosis of BSE in an adult Holstein cow from Washington State. The diagnosis was confirmed by an international reference laboratory in Weybridge, England, on December 25. Preliminary trace-back based on an ear-tag identification number suggested that the BSE-infected cow was imported into the United States from Canada in August 2001. Genetic testing confirmed the Canadian origin of the cow.

Date: November 18, 2005
Content source: National Center for Infectious Diseases