THE DISTRIBUTION OF SCRAPIE-ASSOCIATED FIBRILS IN NEURAL AND NONNEURAL TISSUES OF ADVANCED CLINICAL CASES OF NATURAL SCRAPIE IN SHEEP

The distribution of scrapie-associated fibrils (SAFs) throughout four brain regions, the pituitary gland, along the whole length of the spin al cord and in the sciatic nerve was assessed in 10 sheep terminally a ffected by scrapie and in four control sheep. Tonsils, retropharyngeal , broncho-mediastinal and mesenteric lymph nodes, the distal ileum, pr oximal colon and spleen were also examined for fibrils in all 14 sheep . Fibrils were detected in all four brain regions and throughout the l ength of the spinal cord in nine of the scrapie affected sheep. SAFs w ere not detectable in any of the sciatic nerve samples tested. In one of the 10 clinically affected sheep only minimal lesions were found by histopathology and fibrils were detected only from the cerebrum and o ne spinal cord region (taken at the C1 C2 vertebrae). Fibrils were not detected in the tonsils or retropharyngeal lymph nodes but were detec ted in other non-neural tissues of some of the scrapie-affected sheep. These tissues included pituitary gland, broncho-mediastinal and mesen teric portal lymph nodes, distal ileum, proximal colon and spleen. Fib rils could not be detected in any of the tissues taken from the four c ontrol sheep.