Neuroanatomical Distribution of Disease-Associated Prion Protein in Cases of Bovine Spongiform Encephalopathy Detected by Fallen Stock Surveillance in Japan

Bovine spongiform encephalopathy (BSE) is a fatal neurodegenerative disorder of cattle characterized by accumulation of the disease-associated prion protein (PrPsc) in the central nervous system (CNS). The immunohistochemical patterns and distribution of PrPsc were investigated in the CNS, brains, and spinal cords of 7 naturally occurring BSE cases confirmed by the fallen stock surveillance program in Japan. No animals showed characteristic clinical signs of the disease. Corona] slices of 14 different brain areas in each case were immunohistochemically analyzed using an anti-prion protein antibody. Immunolabeled PrPsc deposition was widely observed throughout each brain and spinal cord. Intense PrPsc deposition was greater in the thalamus, brainstem, and spinal cord of the gray matter than in the neocortices. The topographical distribution pattern and severity of PrPsc accumulation were mapped and plotted as immunohistochemical profiles of the different brain areas along the caudal-rostral axis of the brain. The distribution pattern and severity of the immunolabeled PrPsc in the CNS were almost the same among the 7 cases analyzed, suggesting that the naturally occurring cases in this study were at the preclinical stage of the disease. Immunohistochemical mapping of the PrPsc deposits will be used to clarify the different stages of BSE in cattle.