Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/27/2000
Publication Date: N/A
Interpretive Summary: The Agricultural Research Service of USDA has developed a preclinical test for sheep scrapie. Using this test, infected sheep can be identified years before clinical signs develop. Early identification and culling of infected sheep will reduce the incidence of scrapie in infected flocks. The test methodology is readily adaptable to use in state and veterinary diagnostic laboratories. In this publication, the Pennsylvania state diagnostic laboratory used the test to examine sheep in an infected flock. This publication represents the first reported use of the USDA test by a state diagnostic laboratory.
Technical Abstract: Scrapie was diagnosed in a flock of seven 4-year-old Suffolk sheep with a history, but no symptoms of the disease. Because of their history and in order to take them out of the food chain, the seven sheep were purchased by the Pennsylvania Department of Agriculture to determine their Scrapie status using an immunohistochemical procedure. Two out of seven euthanized healthy sheep had positive immunohistochemical staining of the prion protein of Scrapie (PrP-Sc) in their brains, nictitating membranes and tonsils. The PrP-Sc was localized in the areas of the brain where, histopathologically, there was neurodegeneration and astrocytosis. The PrP-Sc occurred within germinal centers of the affected nictitating membranes and tonsils and was located in the cytoplasm of the dentritic-like cells, lymphoid cells and macrophages.