Brain tissue of a cow with<unk>  showing the typical microscopic "holes" in the grey matter Diagnosis of<unk>  continues to be a practical problem. It has an incubation period of months to years, during which no signs are noticed, though the pathway of converting the normal brain prion protein (PrP) into the toxic, disease-related PrPSc form has started. At present, virtually no way is known to detect PrPSc reliably except by examining post mortem brain tissue using neuropathological and immunohistochemical methods. Accumulation of the abnormally folded PrPSc form of PrP is a characteristic of the disease, but it is present at very low levels in easily accessible body fluids such as blood or urine. Researchers have tried to develop methods to measure PrPSc, but no methods for use in materials such as blood have been accepted fully. The traditional method of diagnosis relies on histopathological examination of the medulla oblongata of the brain, and other tissues, post mortem. Immunohistochemistry can be used to demonstrate prion protein accumulation. In 2010, a team from New York described detection of PrPSc even when initially present at only one part in a hundred billion (10−11) in brain tissue. The method combines amplification with a novel technology called surround optical fiber immunoassay and some specific antibodies against PrPSc. After amplifying and then concentrating any PrPSc, the samples are labelled with a fluorescent dye using an antibody for specificity and then finally loaded into a microcapillary tube. This tube is placed in a specially constructed apparatus so it is totally surrounded by optical fibres to capture all light emitted once the dye is excited using a laser. The technique allowed detection of PrPSc after many fewer cycles of conversion than others have achieved, substantially reducing the possibility of artifacts, as well as speeding up the assay. The researchers also tested their method on blood samples from apparently healthy sheep that went on to develop scrapie. The animals’ brains were analysed once any signs became apparent. The researchers could, therefore, compare results from brain tissue and blood taken once the animals exhibited signs of the diseases, with blood obtained earlier in the animals’ lives, and from uninfected animals. The results showed very clearly that PrPSc could be detected in the blood of animals long before the signs appeared. After further development and testing, this method could be of great value in surveillance as a blood- or urine-based screening test for<unk> . Classification<unk>  is a transmissible disease that primarily affects the central nervous system; it is a form of transmissible<unk><unk> , like Creutzfeldt–Jakob disease and kuru in humans and scrapie in sheep, and chronic wasting disease in deer.
Bovine spongiform encephalopathy
Variant Creutzfeldt–Jakob disease
Creutzfeldt–Jakob disease
Powassan encephalitis
Saint Louis encephalitis
Eastern equine encephalitis
Japanese encephalitis
Viliuisk encephalomyelitis