“Mad Cow Disease” actually refers to bovine spongiform encephalopathy (BSE), a disease first described in 1996 in cattle, which is related to a disease in humans called variant Creutzfeldt-Jakob disease (vCJD). Both disorders are universally fatal brain diseases caused by a prion--a protein particle that lacks nucleic acid (DNA) and is believed to be the cause of various infectious diseases of the nervous system. The link between the agent that causes human deaths from vCJD and outbreaks of BSE in cattle appears to be dietary consumption of infected cattle products, including beef.
Nonvariant forms of Creutzfeldt-Jakob disease (CJD), which was described before 1996, still exist and may have one of three causes: unknown (sporadic form); genetic mutation; or contaminants introduced during a medical procedure (conventional sterilization methods may not remove the prion that transmits the infection). According to the World Health Organization, less than 5 percent of nonvariant CJD cases are introduced through medical procedures. Nonvariant CJD is also universally fatal.
BSE is a progressive, fatal neurological disorder of cattle resulting from infection by a prion. A total of 217 patients with vCJD have been identified since 1996. The majority are from the United Kingdom (170) and other countries in Europe (41). Three have been reported in the U.S., but all three are thought to have acquired the disease overseas.
In addition to the cases of BSE reported in the United Kingdom (78 percent of all cases were reported there) and the U.S., cases have also been reported in other countries, including France, Spain, Netherlands, Portugal, Ireland, Italy, Japan, Saudi Arabia, and Canada. Public health control measures have been implemented in many of the countries to prevent potentially BSE-infected tissues from entering the human food chain. These preventative measures appear to have been effective. For instance, Canada believes its prevention measures will eradicate the disease from its cattle population by 2017.
Creutzfeldt-Jakob Disease (CJD) is a rare, fatal brain disorder that causes a rapid, progressive dementia (deterioration of mental functions), as well as associated neuromuscular disturbances. The disease, which in some ways resembles BSE, traditionally has affected men and women between the ages of 50 and 75. The variant form, however, affects younger people (the median age of onset is 28) and has atypical clinical features as compared with CJD.
Currently this risk appears to be very small, perhaps fewer than one case per 10 billion servings--if the risk exists at all. Travelers to Europe who are concerned about reducing any risk of exposure can avoid beef and beef products altogether, or can select beef or beef products, such as solid pieces of muscle meat, as opposed to ground beef and sausages. The solid pieces of beef have a reduced opportunity for contamination with tissues that may harbor the BSE agent. Milk and milk products are not believed to transmit the BSE agent. You cannot acquire vCJD or CJD by direct contact with a person who has the disease. Three cases acquired during transfusion of blood from an infected donor have been reported in the United Kingdom. Consult your doctor for more information.