The Food and Drug Administration is holding a public hearing today to discuss whether it should further limit who can donate blood or organs in this country, based upon donors' potential exposure to transmissible spongiform encephalopathy. TSEs encompass the family of diseases that infect cows, humans, sheep, deer, elk, mice and monkeys, all creating similar neurological devastation as mad cow. The agency also will briefly consider the nutritional supplement issue at its meeting. Mad cow disease is thought to be caused by prions, which are as-yet poorly understood infectious agents that eat away brain tissue, giving it a spongy appearance. The human version responsible for more than 80 deaths in Britain is called variant Creutzfeldt-Jakob disease.
Scientists believe victims contracted it by eating infected beef.
The disease presumably spread throughout Europe by cows fed bone meal and beef by-products contaminated by the disease. Glandular material, blood and serum are within the USDA's ban, but some products may have entered the country before restrictions were put into effect, or have very restricted exemptions. Exceptions to the ban exist. But bovine spongiform encephalopathy risk from these sources is deemed very low. Nervous tissue from the brain or spinal cord is considered the most likely prion carrier.