Validation of a western immunoblotting procedure for bovine PrP(Sc) detection and its use as a rapid surveillance method for the diagnosis of bovine spongiform encephalopathy (BSE).

In this report we document the results of several independent studies testing the sensitivity, specificity and reliability of the Prionics Western blotting (PWB) procedure to detect bovine and ovine disease-specific, protease-resistant prion protein (PrP(Sc)). Validation of the technique was obtained by blind analysis of samples from cattle affected with bovine spongiform encephalopathy (BSE), clinically normal animals or cattle with neurological diseases unrelated to BSE. Overall, very high sensitivity, specificity and reliability was observed. It became clear that sampling of the correct brain region and the method used for protein extraction are important factors for correct diagnosis. Furthermore, we tested the usefulness of the PWB technique as an instrument for surveillance purposes. We analyzed animals from a culling scheme as well as older animals from abattoirs to determine the number of subclinical BSE cases detectable by histopathological examination, immunohistochemistry for PrP(Sc) and PWB. In both studies, BSE-affected animals with no overt clinical symptoms were detected. These results demonstrate the usefulness of the PWB procedure in surveillance systems serving as a rapid diagnostic tool to identify animals subclinically infected with BSE.