Research into BSE and similar diseases (nvCJD, CJD, scrapie) have provided three theories about the agent that causes BSE. These theories lead us to believe that it is:
- An unidentified virus or virus-like particle - Although the size of the agent is right, the resistance to heat and chemicals, as well as the absence of any nucleic acids, would make it unlike any known virus.
- A mobile bacterium (Spiroplasma) - Many of the features of Spiroplasma infections are similar to BSE, but there is no direct evidence to tie it to BSE.
- An abnormal protein (prion) - Abnormal prions are found throughout the brains of BSE-infected cows, nvCJD victims, CJD victims and scrapie-infected sheep. The protein is smaller than a virus and not changed by heat or by disinfectants. This hypothesis is the most prevalent in the media, but goes against many accepted theories of biology.
Let's examine the prion hypothesis more closely.