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Prion diseases or transmissible spongiform encephalopathies (TSEs) are a family of rare progressive neurodegenerative disorders that affect both humans and animals. They are distinguished by long incubation periods, characteristic spongiform changes associated with neuronal loss, and a failure to induce inflammatory response.

The causative agents of TSEs are believed to be prions. The term "prions" refers to abnormal, pathogenic agents that are transmissible and are able to induce abnormal folding of specific normal cellular proteins called prion proteins that are found most abundantly in the brain. The functions of these normal prion proteins are still not completely understood. The abnormal folding of the prion proteins leads to brain damage and the characteristic signs and symptoms of the disease. Prion diseases are usually rapidly progressive and always fatal.

Identified Prion Diseases

Listed below are the prion diseases identified to date. CDC does not currently offer information on every prion disease listed below.

Human Prion Diseases

Animal Prion Diseases

This tissue slide shows sponge-like lesions in the brain tissue of a classic CJD patient. This lesion is typical of many prion diseases

CJD (Creutzfeldt-Jakob Disease, Classic)

Classic CJD is a human prion disease. It is a neurodegenerative disorder with characteristic clinical and diagnostic features. 

Image of a scientist performing a test.

vCJD (Variant Creutzfeldt-Jakob Disease)

vCJD has a different clinical and pathologic characteristics from classic CJD. Each disease also has a particular genetic profile of the prion protein gene.

image of a cow

BSE (Bovine Spongiform Encephalopathy)

BSE also known as Mad Cow Disease is a progressive neurological disorder of cattle that results from infection by an unusual transmissible agent called a prion.

Image of elks.

CWD (Chronic Wasting Disease)

CWD is a prion disease that affects North American cervids (hoofed ruminant mammals, with males characteristically having antlers.

BSE/TSE Action Plan

BSE/TSE Action Plan of the Department of Health and Human Services (DHHS) has four major components:

For additional information, see the August 23, 2001 HHS press release, HHS Launches Expanded Plan to Combat "Mad Cow Disease".