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Prions are abundantly found in the brain. There are two different forms of prion proteins, a normal form and an abnormal form. The abnormal form of the prion protein can push the normal prions to change into an irregular misfolded shape. This process can damage normal prions by converting them to the abnormal shape. The normal form protein is found on nerve cells, but when it changes into its abnormal form, it combines into materials that affect the normal functioning of the brain. These proteins resist many techniques used to decontaminate food. They need very high temperatures and pressure. It is also not possible to irradiate prions. Because these processes do not easily destroy prions, they can be transmitted by consumption of infected meat, transfusions of blood, cannibalism and organ transplants. Other ways of acquiring the disease includes mutations in the prion gene, which is transmitted from parent to child, or they can arise spontaneously. Prion diseases are called transmissible spongiform encephalopathy - transmissible because they can infect others, spongiform for the sponge resemblance, and encephalopathy, which is the general term for brain disease.

When the abnormal protein is ingested or accidentally gets into the blood, it can cause a severe disease. Even a small dose of abnormal prions can infect an entire organism. Prions are not counted as bacteria or viruses and are not recognized by the body as something dangerous and that is why they do not cause an immune response. An example of a Human prion disease is variant Creutzfeldt-Jakob which is believed to be caused by a prion which typically infects cattle, causing Bovine spongiform encephalopathy or commonly called as mad cow disease and is transmitted through infected meat.
Prions can cause diseases to humans by building up materials that cause cell death. When this happens in the central nervous system, it can alter normal brain functions, causing symptoms like muscle weakness, personality and behavior changes, convulsions, coma, and eventually death. The symptoms will depend on which parts of the brain are affected. Prion diseases actually have incubation period of months to decades during which there are no symptoms. Once the symptoms are present, the disease state of the patient is already severe.
Presently there is no method qualified of confirming the presence of BSE in the live animal. When an animal is suspected to have a prion related disease, it is killed and tissue samples are gathered to identify the abnormal protein (PrPSc). Current diagnostic methods are based on the appearance of this protein. One test called conformation-dependent immunoassay (CDI), can identify infected cattle before symptoms appear, helping to prevent the spread of the disease to humans. According to UC San Francisco scientists who developed the test, it uses high-affinity antibodies molecules to identify abnormal prions in brain tissue by locking on to the exact shape of the molecules. Researchers are still looking for more accurate ways to detect prions because identification and control of Prion infected animal is very crucial for the human health.

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