Newspapers have printed many articles on "mad cow disease." They have described the possible risk to humans of eating beef from sick cows, as well as the impact of the disease on farmers and the slaughtering industry in Great Britain. I would like to know more about the human disease thought to result from eating beef from infected cows.
Bovine spongiform encephalopathy, aka mad cow disease, is a neurological disease first recognized by British veterinarians in 1985. The present panic was initiated when British physicians recognized 10 people, all under age 42, with symptoms similar to those of a human form of this disease, called Creutzfeldt-Jacob (C-J) disease, or subacute spongiform encephalopathy.
C-J disease is a rapidly fatal disorder caused by rather mysterious infectious agents called prions. It is not clear how most individuals acquire C-J disease; in 5 to 10 percent of cases, however, it is inherited. The cardinal features of C-J disease are rapidly progressive dementia and myoclonus (brief, involuntary jerky muscle contractions).
The doctors' findings were alarming for several reasons. First, the victims' illness developed at an earlier age than typical C-J disease. Second, 10 cases over a short period is a high rate because C-J disease is usually quite rare, occurring in only about one in a million people. Third, while not contagious in the usual sense, C-J disease has been transmitted from affected humans to unaffected ones via corneal transplants taken from C-J patients, from improperly cleaned neurosurgical instruments contaminated during surgery on patients with C-J disease, and from injections of growth hormone purified from huge numbers of pituitary glands obtained from human cadavers. In those developing C-J disease from the growth hormone injections, the disease also occurred at an early age more than 5 to 10 years after getting the growth hormone.
None of these transmissions of C-J disease resulted from the intake of infected material by mouth.
Nevertheless, there is understandable concern that C-J disease could result from eating beef from infected cows although it will take a long time to determine whether mad cow disease was responsible for the illnesses reported in the 10 Britons. People in this country are not affected by the threat in Britain since the U.S. has banned the import of British beef since 1989.
Dr. Margolis is professor of medicine and biological chemistry at the Johns Hopkins School of Medicine.
Pub Date: 4/09/96