Mad Cow Disease in Humans

Creutzfeldt-Jakob disease made headlines in the year 2000 when an uptick of cases broke out in the United Kingdom. Those cases were linked to food contaminated with bovine spongiform encephalopathy (BSE), a prion disease that causes variant CJD, otherwise known as "mad cow" disease.

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 rapidly progressing, always fatal neurological disorder. But the disease is very rare: It affects about one person in every one million per year worldwide; in the United States there are about 350 cases per year. 

The Centers for Disease Control and Prevention (CDC) monitors the incidence in the United States of all types of Creutzfeldt-Jakob disease.

There is no cure for Creutzfeldt-Jakob disease, which can occur in a person in one of three ways:

• About 10% to 15% of cases in the United States 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.

Cases of variant Creutzfeldt-Jakob disease seems to be linked to 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 that is how 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.

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, however, variant Creutzfeldt-Jakob disease has affected people at a younger age--even teenagers (the ages have ranged from 18 to 53 years old).

There is not, as yet, a definitive medical test for diagnosing Creutzfeldt-Jakob disease, and confirmation of the disease can only be made after death through an autopsy. 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.