From the submissions to this conference on surveillance for BSE and scrapie it became clear that histological examination is the primary diagnostic method used worldwide. It is certainly the method for which most experience has accumulated over the years. Histological examination is accepted by the European Community and worldwide. The appropriate areas of the brain have to be examined for the typical lesions by an experienced pathologist, thus each tissue sample has to be examined for lengthy times under the microscope.
Tissue samples have to be fresh to avoid autolysis.
It appears that quite frequently immunocytochemistry is applied as a confirmatory method in various countries. This seems to be logical because a histology laboratory is normally able to perform immunocytochemistry and formalin-fixed tissues can be used for histology and immunocytochemistry. A well-characterised antibody is necessary for this test which may be not readily available. To my knowledge immunocytochemistry is not accepted by the European Community yet, but the method is under evaluation at present. The method has the advantage of showing colour for positive tissue samples and therefore positives should be identified more easily than with histology.