The prion that causes mad cow disease is an abnormal (misfolded) form of the bovine prion protein, commonly referred to as the BSE prion (from bovine spongiform encephalopathy).

Quick Scoop: Short Answer

Mad cow disease (bovine spongiform encephalopathy, BSE) is caused by a misfolded, infectious prion protein often simply called the BSE prion or abnormal prion protein.

It is a pathogenic version of the normal prion protein found in cattle, which changes shape and triggers a chain reaction of misfolding in the brain.

What Is This Prion?

Scientists describe the agent behind mad cow disease as an unusual transmissible prion , meaning an infectious protein rather than a virus or bacterium.

It’s a modified form of the normal prion protein in cattle that, once misfolded, accumulates and damages the central nervous system.

Key points:

  • It is not a separate organism but a misfolded version of a normal protein (prion protein) in cows.
  • When misfolded, it’s called the pathogenic BSE prion and is responsible for mad cow disease.
  • This same family of abnormal prion proteins can, in rare cases, cause variant Creutzfeldt–Jakob disease (vCJD) in humans who consume contaminated beef.

How It Causes Mad Cow Disease

Mad cow disease is a progressive, fatal neurological disorder of cattle caused by infection with this misfolded prion protein.

The abnormal prion builds up in the brain and spinal cord, leading to sponge‑like holes in brain tissue and severe nervous system symptoms.

Typical features:

  • Damage mainly in the brain and nervous system, causing behavior changes and movement problems in cows.
  • Very long incubation period — it takes years after infection before symptoms appear.
  • Once clinical signs start, the disease is always fatal and there is no effective treatment or vaccine.

Name Usage in Research and News

In scientific and public health sources, you’ll usually see the agent described as:

  • “Prion causing bovine spongiform encephalopathy (BSE)” or “BSE prion.”
  • “Abnormal prion protein” or “pathogenic prion protein” in cattle.

So, while lay summaries often just say “a prion,” the more precise name is the BSE prion , the abnormal bovine prion protein responsible for mad cow disease.

Information gathered from public forums or data available on the internet and portrayed here.