Changes

==Diagnosis==

==Diagnosis==

[[File:800px-Scrapie lymph node immunoglobulin labeling.png|thumb|200px|left|Immunoglobulin in normal(a) and scrapie-affected (b)follicles -with light microscopy.]]A pre-emptive diagnosis of scrapie may be made from the above clinical signs and history. There are no serological test available for scrapie, as is does not evoke an immune or inflammatory response.  Diagnosis is confirmed on postmortem and PrP^Sc can be isolated from brainstem or lymphoid tissues by Western immunoblot, immunohistochemistry (IHC) and elisa tests.  Immunohistochemistry usually shows vacuolation and an accumulation of prion proteins in various parts of the CNS (medulla, pons, midbrain, and spinal cord). However vacuolation is not completely diagnostic since it may also be present to a lesser extent in the brains of healthy sheep <ref name="Fraser, 1976"> Fraser H, 1976. The pathology of a natural and experimental scrapie. Frontiers of Biology, 44:267-305.</ref>, <ref name="Zlotnik and Rennie, 1958"> Zlotnik I, Rennie JC, 1958. A comparative study of the incidence of vacuolated neurones in the medulla from apparently healthy sheep of various breeds. Journal of Comparative Pathology, 68:411-415.</ref>. In most instances the abnormal prion is resistant to protein kinase digestion, a feature used in diagnostic techniques. IHC staining of tonsil and lymphoid biopsies have been used for preclinical scrapie testing.  

[[File:800px-Scrapie lymph node immunoglobulin labeling.png|thumb|200px|left|Immunoglobulin in normal(a) and scrapie-affected (b)follicles -with light microscopy.]]A pre-emptive diagnosis of scrapie may be made from the above clinical signs and history. There are no serological test available for scrapie, as is does not evoke an immune or inflammatory response.  Diagnosis is confirmed on postmortem and PrP^Sc can be isolated from brainstem or lymphoid tissues by Western immunoblot, immunohistochemistry (IHC) and elisa tests.  Immunohistochemistry usually shows vacuolation and an accumulation of prion proteins in various parts of the CNS (medulla, pons, midbrain, and spinal cord). However vacuolation is not completely diagnostic since it may also be present to a lesser extent in the brains of healthy sheep <ref name="Fraser, 1976"> Fraser H, 1976. The pathology of a natural and experimental scrapie. Frontiers of Biology, 44:267-305.</ref>, <ref name="Zlotnik and Rennie, 1958"> Zlotnik I, Rennie JC, 1958. A comparative study of the incidence of vacuolated neurones in the medulla from apparently healthy sheep of various breeds. Journal of Comparative Pathology, 68:411-415.</ref>. In most instances the abnormal prion is resistant to protein kinase digestion, a feature used in diagnostic techniques. IHC staining of tonsil and lymphoid biopsies have been used for preclinical scrapie testing and the third eyelid lymphoid tissue can be used for diagnosis in sheep.