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Mad Cow Disease in Humans

Brain disorder becomes deadly over time

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Updated October 07, 2013

Variant Creutzfeldt-Jakob disease (vCJD) is the "mad cow" disease that humans contract when they are exposed to food contaminated with bovine spongiform encephalopathy (BSE). As of November 2006, 3 individuals with mad cow disease had been identified in the United States. The Centers for Disease Control and Prevention (CDC) monitors the incidence in the US of all types of Creutzfeldt-Jakob disease.

As of November 2006 there were 200 individuals worldwide diagnosed with mad cow disease, including 164 people in the United Kingdom, 21 in France, 4 in the Republic of Ireland, the 3 in the US, 2 in the Netherlands, and 1 each in Canada, Italy, Japan, Portugal, Saudi Arabia, and Spain, according to the CDC. Of these individuals, most (170) had lived in the UK for over 6 months during the years 1980-1996; 20 others had lived in France during that time.

Disease has no cure
The public has good reason to be concerned about the transmission of BSE to humans. Variant Creutzfeldt-Jakob disease, like the other types of Creutzfeldt-Jakob disease, is a brain disorder which becomes deadly over time. There is no cure.

Normally, Creutzfeldt-Jakob disease occurs in a person in one of three ways:

  • About 10 to 15 percent of cases are inherited, resulting from a gene mutation.
  • Most cases seem to appear sporadically, in someone who has no family history of the disease.
  • A small percentage of cases occur through infection, by contact with infected brain tissue. There are documented cases that occurred as an unintended consequence of a medical procedure.
Creutzfeldt-Jakob disease is not contagious in normal ways, like sneezing or coughing--there are no known cases of spouses or family members of an infected person contracting the disease.

Contaminated beef products implicated
Variant Creutzfeldt-Jakob disease seems to have been caused by people eating contaminated beef products in Europe. The same disease, when it occurs in sheep, is called "scrapie." It is believed that scrapie-infected sheep products were used in cattle feed, and thus the cattle became infected.

Scientists have found that what causes BSE, scrapie, and the Creutzfeldt-Jakob diseases is not a virus or bacteria as in other diseases, but a protein agent called a prion. The prion transforms normal proteins into infectious, deadly ones.

Affects the brain
Since Creutzfeldt-Jakob disease affects the brain, the symptoms it produces are neurological. It may start out subtly with insomnia, depression, confusion, personality and behavioral changes, and problems with memory, coordination, and sight. As it progresses, the person rapidly develops dementia and involuntary, irregular jerking movements called myoclonus.

In the final stage of the disease, the patient loses all mental and physical functions, lapses into a coma, and eventually dies. The course of the disease usually takes one year. The disease generally affects people between the ages of 50 to 75 years. Variant Creutzfeldt-Jakob disease is called "variant" because it has affected people at a younger age, even teenagers (the ages have ranged from 18 to 53 years old).

Difficult to diagnose
There is not, as yet, a definitive medical test for diagnosing Creutzfeldt-Jakob disease. Since the disease is rare, some physicians might not even consider it as a diagnosis, and might mistake the symptoms for other brain disorders like Alzheimer's or Huntington disease. Scientists suggest that new, sophisticated laboratory testing will in the future be able to detect the prions in an infected person's blood or tissues.

Sources:
- Collins, S., A. Boyd, A. Fletcher, M. F. Gonzales, C. A. McLean, C. L. Masters. "Recent advances in the pre-mortem diagnosis of Creutzfeldt-Jakob disease." J Clin Neurosci 7(2000): 195-202.
- "vCJD (Variant Creutzfeldt-Jakob Disease)." NCIDOD. 29 Nov 2006. Centers for Disease Control and Prevention. 28 Dec 2006 <http://www.cdc.gov/ncidod/dvrd/vcjd/>. - Will, R., M. Zeidler, G. E. Steward, M. A. Macleod, J. W. Ironside, S. N. Cousens, J. Mackenzie, K. Estibeiro, A. J. Green, R. Knight. "Diagnosis of new variant Creutzfeldt-Jakob disease." Ann Neurol 47(2000): 575-582.
- Wilson, K., C. Code, M. Ricketts. "Risk of acquiring Creutzfeldt-Jakob disease from blood transfusions: Systematic review of case-control studies." BMJ 321(2000): 17-19.

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