What are Prions?

Mary McMahon
Mary McMahon

Prions are unique proteins which appear to be responsible for a family of illnesses collectively referred to as Transmissible Spongiform Encephalopathies (TSEs), including scrapie in sheep, kuru in humans, and "mad cow disease" in cows. These prion diseases are all caused by the breakdown of the nervous system, which is readily apparent after autopsy or necropsy. Looking at the tissue of the nervous system, it becomes clear that it has literally been eaten away by these rogue proteins, causing the formation of distinctive holes.

Prion diseases occur when there is a breakdown in the nervous system.
Prion diseases occur when there is a breakdown in the nervous system.

The existence of prions was hypothesized as early as the 1960s, when researchers first formulated the so-called "protein only" hypothesis to explain TSEs. These researchers noted that irradiation of potentially infective tissue did not seem to kill the organism responsible, suggesting that it did not contain nucleic acid, which is susceptible to radiation. The theory met with a great deal of opposition until the 1980s, when researcher Stanley Prusiner coined the term "prion" to describe the highly unusual proteins he had discovered; these proteins did not contain nucleic acid, the backbone of all living organisms on Earth.

Mad cow disease is an example of a prion-associated disease.
Mad cow disease is an example of a prion-associated disease.

The word is taken from the longer term "proteinaceous infectious particle." Despite the fact that prions lack nucleic acid and therefore in theory cannot reproduce, these proteins do, by exhibiting strange folding patterns which subvert otherwise healthy proteins. The protein they're made of is found in many animals, explaining why these diseases strike a wide range of species. Animals and humans can get TSE by ingesting prions in things like infected tissue and through contaminated blood products.

These little proteins are quite stubborn. They resist many techniques used to decontaminate food, raising concerns about the safety of the food supply. Prions cannot be irradiated, and very high temperatures and pressure are required to remove them — temperatures far higher than those consumers would normally use to cook a steak. Fortunately, they appear to lie primarily in nervous system tissue, although consuming meat from an animal with TSE could potentially be dangerous.

These proteins made the news in the 1990s, when numerous cases of Creutzfeldt-Jakob disease (CJD) began to be linked with prions and the consumption of contaminated tissue from cattle and sheep in the United Kingdom. Cases of TSE have clearly been documented in food animals in Europe, and researchers suspect that TSE may also be an issue in the United States as well, perhaps explaining the rising rate of so-called "downer cows," cows which for some reason are unable to stand up for slaughter. Such cattle are not supposed to enter the food supply out of concerns about prion diseases and other conditions which could pose a threat to human health.

Scientists are still researching a cure for mad cow disease.
Scientists are still researching a cure for mad cow disease.
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

You might also Like

Readers Also Love

Discussion Comments


What levels and what types of irradiation have failed to destroy Prions? If anyone knows or if you can tell me a thread, I would appreciate it.


my sister is suffering the exact symptoms as the article.

she was diagnosed and treated for depression, using antidepressants. what advice to you give so that the medics listen diagnose and treat her effectively?


@KittenTucker - I knew someone who had fatal familial insomnia, which is another disease caused by prions. I found out this disease occurs in people aged 35 to 60 years old – my friend was 50 when she was diagnosed. She started out not being able to sleep, and she had panic attacks, paranoia and phobias for the first four months. For five months after that, her hallucinations and panic attacks got worse. Then for three months after that, she was unable to sleep, and as a result she lost a lot of weight. The last six months of her life, her dementia got worse, and she became unresponsive and mute. The good news is, she did find out through genetic testing that she was a carrier of this disease, so her family was able to get her treatment that improved her quality of life while she was suffering with this disease.


@JillT – Good question. Another diseases caused by prions is Gerstmann-Straussler-Scheinker syndrome, or GSS. This disease is extremely rare, but symptoms include difficulty speaking, unsteadiness, and progressive dementia. The disease can occur in people as young as 25 years old, but is more common in people in their 50s or older.


Wow, talk about scary! So other than kuru and Creutzfeldt-Jakob disease, are there any other human diseases are caused by prions?

And how do you even avoid picking up prions when you eat? It sounds to me like one prion-infused steak and you could be a goner. Is this true, or am I just paranoid?

Post your comments
Forgot password?