Prions found in the brain are in the PrP^C^. Form, when altered to the PrP^Sc^ form it can cause disease. In the disease causing form, the prion can also induce other prions to become misfolded. In the disease form, the prions can accumulate and form fibrils in nerve cells. This causes the transmissible spongiform encephalopathies.

Prion Misfolding and Disease Onset

Common signs of transmissible spongiform encephalopathies are memory loss, personality cahnges, blurred vision, and lack of coordination. These issues accumulate over time and can lead to coma or death.

Signs and Symptoms of Transmissible Spongiform Encephalopathies

Prions are acellular proteins that do not contain DNA or any other genetic material, and they are not viruses. Because they are acellular and do not fit neatly into any particular category of microbe, they are excluded from the tree of life. They are exceptionally small, measuring approximately $${}1/10$$ the size of a typical virus. While normal prions are found in healthy brain tissues, they cause diseases when their folded state is changed into an abnormal protein.

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Transmissible spongiform encephalopathies is a disease caused by prions. There are multiple transmissible spongiform encephalopathies that cause neurological infections. 

Transmissible Spongiform Encephalopathies

- Opportunistic pathogen
- Primary pathogen

Types of Pathogens

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Prions

Creutzfeldt-Jakob disease (CJD) is an extremely rare and universally fatal transmissible spongiform encephalopathy (TSE) caused by prions. Diagnosed in only about $${}300$$ patients in the United States each year, the disease induces rapid cognitive decline. There is currently no approved treatment, and roughly $${}90\%$$ of affected individuals succumb to the disease within $${}1$$ year of diagnosis.

Creutzfeldt-Jakob Disease (CJD)

A primary pathogen can cause disease in a host regardless of the host’s microbiota or immune system.

Primary Pathogen

An opportunistic pathogen can only cause disease in situations that compromise the host’s defenses, such as skin, immune system, or normal microbiota.

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