Mad Cow Disease and Humans
From Mary Kugler,
Your Guide to Rare / Orphan Diseases.
Degenerative fatal brain disorder
Variant Creutzfeldt-Jakob disease is the "mad cow" disease that people contract when they are exposed to food contaminated with bovine spongiform encephalopathy (BSE). A case of BSE in the United States was confirmed in 2003. The Centers for Disease Control and Prevention (CDC) monitors the incidence in the United States of all types of Creutzfeldt-Jakob disease.
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 degenerative, fatal brain disorder. 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.
Creutzfeldt-Jakob disease is not contagious--there are no known cases of spouses or family members of an infected person contracting the disease. There are, however, documented cases that occurred as an unintended consequence of a medical procedure.
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's 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.
Information for this article came from the CDC, the National Institute of Neurological Disorders and Stroke, the Creutzfeldt-Jakob Disease Foundation, and the following articles.
- Andrews, N. (2000). Incidence of variant Creutzfeldt-Jakob disease. The Lancet, vol. 356, no. 9228.
- Collins, S., Boyd, A., Fletcher, A., Gonzales, M. F., McLean, C. A., & Masters, C. L. (2000). Recent advances in the pre-mortem diagnosis of Creutzfeldt-Jakob disease. J Clin Neurosci, vol. 7, no. 3, 195-202.
- Will, R. G., Zeidler, M., Steward, G. E., Macleod, M. A., Ironside, J. W., Cousens, S. N., Mackenzie, J., Estibeiro, K., Green, A. J., & Knight, R. S. (2000). Diagnosis of new variant Creutzfeldt-Jakob disease. Ann Neurol, vol. 47, no. 5, 575-582.
- Wilson, K., Code, C., & Ricketts, M. N. (2000). Risk of acquiring Creutzfeldt-Jakob disease from blood transfusions: Systematic review of case-control studies. BMJ, vol. 321, no. 7252, 17-19.
