Variant Creutzfeldt-Jakob disease and bovine spongiform encephalopathy ("mad cow disease")

Variant Creutzfeldt-Jakob disease (CJD) is a degenerative neurologic disease acquired by eating beef from cows with a related illness known as bovine spongiform encephalopathy (BSE) ("mad cow disease"). The disorder was initially described in the United Kingdom. As of June 2005, there were 155 definite or probable cases of variant CJD reported from the United Kingdom, as well as a small number of cases from France, Italy, and the Republic of Ireland. "Mad cow disease" has also been identified in Austria, Belgium, Czech Republic, Denmark, Finland, Germany, Greece, Liechtenstein, Luxembourg, the Netherlands, Portugal, Slovak Republic, Slovenia, Spain, Switzerland, Israel, Japan, and the United States, but human cases have not been reported from these countries to date.

Bovine spongiform encephalopathy appears to be caused by abnormal proteins called prions, which do not resemble bacteria, viruses, or other conventional causes of human and animal disease. The agent that causes BSE is transmitted when meat and bone meal feed prepared from the carcasses of infected animals is fed back to other cattle. (This practice has been banned within the European Union and many other countries). The infection is not transmitted directly from animal to animal within herds. A new case of BSE arising within a country is therefore much more significant than an imported case, because it implies that recycled ruminant protein is still being used within that country as animal feed, against all current recommendations.

The agent that causes BSE is concentrated in nervous tissue, such as brain and spinal cord. Since this agent has never been found in skeletal muscle, which is the source of most quality meat, the current thinking is that most cases of variant CJD are caused by contamination of meat by nervous tissue during slaughter and processing. Careful slaughter practices can therefore markedly reduce the risk of acquiring variant CJD, even in a country where BSE is known to occur.

The incubation period of variant CJD appears to be several years or longer. Initial symptoms may be psychiatric, similar to depression or (less often) psychosis. Patients may complain of unusual sensory symptoms, such as "stickiness" of the skin. Later symptoms include unsteady gait, involuntary movements, dementia, and mutism, progressing inevitably to death within 1-2 years. There is no treatment.

Variant CJD can only be acquired by eating beef or beef products; i.e if you do not consume beef or beef products while visiting a country which has reported "mad cow disease", you cannot become infected. There is no evidence of any risk from pork, lamb, milk or milk products. The Centers for Disease Control does not advise against eating European beef, but suggests that travelers who wish to reduce their risk may either abstain from beef completely while in Europe or eat only solid pieces of muscle meat, such as steak, rather than products like sausage or chopped meat that might be contaminated during processing. Cooking, drying, or freezing does not inactivate the agent that causes new variant CJD or prevent its transmission.

In December 2003, a single case of transfusion-acquired variant CJD was reported from the United Kingdom. Since the time of the transfusion, which took place in early 1996, a number of measures have been instituted to protect the blood supply, including depletion of white blood cells, which are thought to be a potential source of infection. Procedures for blood transfusions in the U.K. are currently under review. For further information, go to Eurosurveillance.

From the World Health Organization (WHO)

Understanding the BSE Threat

Variant Creutzfeldt-Jakob Disease

Surveillance and Response

From the Centers for Disease Control (CDC)

Creutzfeldt-Jakob Disease (Variant) and Bovine Spongiform Encephalopathy (Prion Diseases)

Risk for Travelers

BSE (Bovine Spongiform Encephalopathy, or Mad Cow Disease)

vCJD (Variant Creutzfeldt-Jakob Disease)

From Emerging Infectious Diseases

Bovine Spongiform Encephalopathy and Variant Creutzfeldt-Jakob Disease: Background, Evolution, and Current Concerns