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.
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Let's examine the prion hypothesis more closely.