Invasive Species Compendium

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Abstract

Immunohistochemical detection of prion protein in lymphoid tissues of sheep with natural scrapie.

Abstract

The localization and distribution of the scrapie-associated form of the prion protein (PrPSc) was studied in various lymphoid tissues collected at PM examination from 55 sheep with clinical scrapie. Samples collected from the spleen, palatine tonsil, ileum, and 5 different lymph nodes were immunohistochemically stained for PrPSc. PrPSc was deposited in a reticular pattern in the centre of both primary and secondary lymphoid follicles. In addition, granules of PrPSc were seen in the cytoplasm in macrophages associated with the lymphoid follicles. In 54 (98%) of the 55 scrapie-affected sheep, PrPSc was detected in the spleen, retropharyngeal lymph node, mesenteric lymph node, and the palatine tonsil. However, only in the palatine tonsils was PrPSc present in a consistently high percentage of the lymphoid follicles. PrP was not detected in any of the lymphoid tissues of 12 sheep that had no neurohistopathological signs of a scrapie infection. It is concluded that the tonsils are the best-suited lymphoid tissue to be biopsied for the detection of PrPSc in the diagnosis of clinical scrapie in living sheep.