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Comparison of tests

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Sandhusker

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From the Cattle Report;

BSE TESTS

RAPID TEST
This test, referred to as ELISA, is fast. taking only a few hours to identify whether abnormal prion proteins are present in an animal's brain tissue sample. Misfolded prions are believed to be the cause of BSE, which slowly disintegrates neural tissue and is always fatal. To test an animal carcass using the rapid test, scientists snip off a small amount of the brain stem for testing. A reagent mixture consisting of digestion enzymes is used to isolate the BSE-specific prion protein in the sample. Antibodies are then added to the sample to detect the prions. A chemical is then added to the sample that enables it to emit light, and the light is measured by a computer. In general, a negative sample is white and a positive is yellow.

IHC TEST
The immunohistochemistry test, or IHC, involves a staining technique to determine whether the brain sample has the BSE agent. After placing antibodies on a suspect brain sample, the test causes a chemical reaction that can detect the abnormal form of the prion protein found in BSE. The test, considered the "gold standard" by the USDA, requires two to three days to complete. This test has been used to confirm the Rapid Test and generally is done in the lab at Ames Iowa.

WESTERN BLOT TEST
The test is more complex than the IHC test. It homogenizes a suspect brain sample and treats it with a protease enzyme that destroys normal prion proteins, but not the abnormal protein. The sample is then run through a gel-type separation using specific antibodies that will give you bands. The USDA said the molecular weight of those bands are used to determine the outcome of the test.
 
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