Q. Is there any meat that is safe from contamination by the “Mad Cow” disease agent, or is there any way to protect against it?
A. Our ignorance about what causes “Mad Cow” disease (BSE or Bovine Spongiform Encephalitis) is almost complete. The leading theory at present states that a small protein called a “prion” represents an unprecedented class of infectious agents, different from bacteria or viruses. Another theory, discussed below, holds that prions are normal mammalian proteins that have been modified by some external factor into harmful proteins.
The term prion was first used to describe the mysterious infectious agent thought to be responsible for several brain diseases found in mammals. Prions are no bigger than the smallest virus and apparently do not have the usual genetic material (DNA and RNA). Scrapie, a brain disease known to sheep farmers for at least 250 years, has symptoms that are much like BSE. Similar diseases have also appeared in pigs, cats, and several zoo animals whose diet included cow-derived protein.
The human prion diseases, including the one called Creutzfelt-Jakob disease, are more obscure. In 1957, a fatal disease marked by loss of coordination and dementia was discovered in Papua New Guinea among the Fore highlanders. Named “kuru,” the affected individuals apparently acquired it through ritual cannibalism. The Fore tribe reportedly honored their dead by eating their brains. The practice has since stopped, and kuru has virtually disappeared. This observation gives considerable comfort to all of us, since the prion is not destroyed by conventional sterilization techniques. If prions are widespread, there is no known way to control their spread.
The animal prion diseases seem to be confined mostly to England and the European community, and the wholesale slaughter of farm animals in those areas has made news recently. No American animals have been proven to harbor the infectious agent, and there are no proven human cases of Creutzfelt-Jakob disease in America arising from consumption of American-raised meat. Although the American meat supply is presumed safe, there are a couple of disturbing thoughts. One is that the incubation period may be up to 40 years, which makes it extremely difficult to track exposure. The second is that cow serum from England, until last year, was used in vaccines given to almost all American children.
A competitor of the prion theory maintains that prions are normal mammalian proteins that may have been damaged by organophosphate insecticides, which are nerve agents developed by Nazi chemists during World War II. Organophosphate insecticides, used extensively in England at high doses to control the warble fly, are applied to the backs of cattle, along the spinal cord. The fear is that the organophosphate insecticides migrate unchecked into nerve tissue and change normal protein into prions. In America, organophosphate insecticides are found not only in farm insecticides but also in the common remedies for head lice.
One of these organophosphate insecticides used in England contains manganese, and there is some evidence that an imbalance between copper and manganese is part of BSE. Cellular energy production and protection of cellular genetic material from free-radical damage depends heavily on the complex interplay of several trace minerals, including copper and manganese.
The symptoms of Alzheimer’s disease are similar enough to symptoms of the prion diseases to raise suspicions of a relationship. Also, the plaques found in the brains of Alzheimer’s disease victims resemble plaques found in Creutzfelt-Jakob disease. The toxic mineral aluminum, suspected to increase the risk of Alzheimer’s disease, is another of the minerals that negatively affects cellular energy production.
The risk of catching a prion disease may be cumulative, and if so, choosing organically grown meats would be prudent. There is so much uncertainty about the nature of the prion diseases and what sort of defense we may be able to mount if the diseases become widespread that further speculation or even overmuch concern at this time is worthless.
This article appears in August 3 • 2001.