Aging Begins at 30

Mad Cows, Scrapie Sheep and the Human Nervous System

Ian Maclean Smith, M.D.
Emeritus Professor
Department of Internal Medicine
University of Iowa Hospitals and Clinics
Creation Date: May 2001
Last Revision Date: May 2001
Peer Review Status: Internally Peer Reviewed

Prion diseases occur in sheep, goats, mink, mule deer, elk, cats and cows. The disease is transmitted to cows from sheep with Scrapie by feeding sheep carcasses to cows. This was banned in Britain in 1988. Scrapie causes intense itching of the skin and loss of wool, hence its name, and was first noticed in Scottish border flocks.

In humans, prion diseases are Kuru in New Guinea transmitted by honoring the dead by eating the brains of ancestors. Creutzfeldt-Jakob disease described in 1920 and 1921 is a spontaneous disease and variant Creutzfeldt-Jakob disease is produced by eating meat from animals with mad cow disease or by injecting growth hormone or tissue derived from infected animals. Other human diseases that might be caused by prions are Alzheimer's disease (4 million cases in the United States), Parkinson's disease (1 million), amyotrophic lateral sclerosis or Lou Gherig's disease, and possibly others. They all have dementia, uncoordinated movements (ataxia), sleeplessness, paraplegia, paraesthesias, deviant behavior and they have a material called amyloid in their brains that resembles a breakdown product of PrPSc. Ten percent or less of these diseases are inherited. Most of them cause death in a few to ten years. The annual cost of Alzheimer's disease alone is over $200 billion.

Techniques to destroy all nucleic acid were used but still infection occurred in animals inoculated with mad cow disease brain material. There is a normal prion protein in brain cells called PrP, for prion protein. The amino acid sequence of PrPc was determined. It was found in two forms and the second one was called PrPSc. The first has three regions where the amino acids are arranged in corkscrew fashion and in the abnormal PrPSc this area changes into a bed-sheet shape but there is no other change. This can be shown in a test tube. In the body it occurs inside a nerve cell or neuron. When a change occurs, a domino refolding type change in neighboring PrPc proteins increases it as if the first abnormality was a template for further change.

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See related Patient Topics Brain and Nervous System or Creutzfeldt-Jakob Disease.

See related Provider Topics Brain and Nervous System or Creutzfeldt-Jakob Disease.

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