Elisa testing of brain and spleen homogenates for transmissible spongiform encephalopathy/scrapie of sheep

A diagnosis of TSE / scrapie in sheep is based on a positive ELISA of the obex, which is confirmed by confirmation tests, such as histopathology, immunohistochemistry, electronmicroscopy ( scrapie associated fibrils (SAF)) and Western blot. However, preclinical scrapie cases may only be detected 3 months before the onset of symptoms based on a positive ELISA of the obex, while a 1.5 year preclinical diagnosis can be obtained based on a positive immunostaining of the lymphoid tissue ( tonsil, spleen, lymph node, third eyelid) with other tests on the brain tissue still being negative. The brain tissue and spleen of positive ( clinical and preclinical) and negative scrapie sheep were examined with immunohistochemistry, ELISA and Western blot. In most cases, all tests were consistent for the same tissue. It can be concluded that with minor adaptations of the ELISA technique, ELISA on the lymphoid tissue of sheep are as reliable, easier and quicker to perform than immunohistochemistry. This can be of importance in epidemiosurveillance, i.e. the detection of infected ( clinical cases and preclinical cases), and the eradication and spread of the disorder within the population.