Transmissible Spongiform Encephalopathies

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What are transmissible spongiform encephalopathies?

Transmissible spongiform encephalopathies (TSEs), also known as prion diseases, are a group of rare degenerative brain disorders characterized by tiny holes that give the brain a "spongy" appearance. These holes can be seen when brain tissue is viewed under a microscope.

Creutzfeldt-Jakob disease (CJD) is the most well-known of the human TSEs. Other human TSEs include:

  • Kuru
  • Fatal Familial Insomnia (FFI)
  • Gerstmann-Straussler-Scheinker Disease (GSS)

A relatively new type of CJD known as variant CJD (vCJD) was first described in 1996. Research suggests that vCJD may have resulted from human consumption of beef from cattle with a TSE disease called bovine spongiform encephalopathy (BSE), also known as Mad Cow Disease. Other TSEs found in animals include:

  • Scrapie, which affects sheep and goats
  • Chronic wasting disease, which affects elk and deer
  • Transmissible mink encephalopathy

In a few rare cases, TSEs have occurred in other mammals such as zoo animals. These cases are probably caused by contaminated feed. CJD and other TSEs also can be transmitted experimentally to mice and other animals in the laboratory.

Research suggests that TSEs are caused by an abnormal version of a protein called a prion (short for proteinaceous infectious particle). Prion proteins occur in both a normal form, which is a harmless protein found in the body's cells, and in an infectious form, which causes disease.

Human TSEs can occur three ways:

  1. Sporadically—Sporadic TSEs may develop because some of a person's normal prions spontaneously change into the infectious form of the protein and then alter the prions in other cells in a chain reaction.
  2. As hereditary diseases—Inherited cases arise from a change, or mutation, in the prion protein gene that causes the prions to be shaped in an abnormal way. This genetic change may be transmitted to an individual's offspring.
  3. Through transmission from infected individuals—Transmission of TSEs from infected individuals is relatively rare. TSEs cannot be transmitted through the air or through touching or most other forms of casual contact. However, they may be transmitted through contact with infected tissue, body fluids, or contaminated medical instruments. Normal sterilization procedures such as boiling or irradiating materials do not prevent transmission of TSEs.

Symptoms of TSEs vary, but they commonly include:

  • Personality changes
  • Psychiatric problems such as depression
  • Lack of coordination
  • An unsteady gait

Individuals also may experience involuntary jerking movements called myoclonus, unusual sensations, insomnia, confusion, or memory problems. In the later stages of the disease, patients have severe mental impairment and lose the ability to move or speak.

There is currently no treatment that can halt progression of any of the TSEs. Treatment is aimed at alleviating symptoms and making the individual as comfortable as possible. TSEs tend to progress rapidly and usually culminate in death over the course of a few months to a few years.

Learn About Clinical Trials
Clinical trials are studies that allow us to learn more about disorders and improve care. They can help connect patients with new and upcoming treatment options.

How can I or my loved one help improve care for people with transmissible spongiform encephalopathies?

Consider participating in a clinical trial so clinicians and scientists can learn more about TSEs and related disorders. Clinical research uses human volunteers to help researchers learn more about a disorder and perhaps find better ways to safely detect, treat, or prevent disease.

All types of volunteers are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races, and ethnicities to ensure that study results apply to as many people as possible, and that treatments will be safe and effective for everyone who will use them.

For information about participating in clinical research visit NIH Clinical Research Trials and You. Learn about clinical trials currently looking for people with TSEs at

Where can I find more information about transmissible spongiform encephalopathies?

Information may be available from the following resources:

Centers for Disease Control and Prevention (CDC)
Phone: 800-311-3435, 404-639-3311 or 404-639-3543

Creutzfeldt-Jakob Disease (CJD) Foundation Inc.
Phone: 800-659-1991

Food and Drug Administration (FDA)
Phone: 301-827-4573 or 888-463-6332

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