Immunohistochemical detection of scrapie prion proteins in clinically normal sheep in Pennsylvania.
Following diagnosis of scrapie in a clinically suspect Suffolk sheep, 7 clinically normal flockmates were purchased by the Pennsylvania Department of Agriculture to determine their scrapie status using an immunohistochemical procedure. Two of the 7 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 dendrite-like cells, lymphoid cells, and macrophages. These results confirm that immunohistochemical examination of the nictitating membrane can be used as a screen for the presence of scrapie infection in clinically normal sheep at a capable veterinary diagnostic laboratory. In sheep with a PrP-Sc-positive nictitating membrane, the diagnosis of scrapie should be confirmed by histopathology and immunohistochemical examination of the brain following necropsy. Following full validation, immunohistochemistry assays for detection of PrP-Sc in nictitating membrane lymphoid tissues can improve the effectiveness of the scrapie control and eradication program by allowing diagnosis of the disease in sheep before the appearance of clinical signs.
Kim
H
H
Pennsylvania Animal Diagnostic Laboratory System, Pennsylvania Veterinary Laboratory, Harrisburg 17025, USA.
O'Rourke
K I
KI
Walter
M
M
Purchase
H G
HG
Enck
J
J
Shin
T K
TK
D000818:Animals; D001921:Brain / Q000473:pathology; D007150:Immunohistochemistry; D009541:Nictitating Membrane; D010414:Pennsylvania; D018620:PrPSc Proteins / Q000032:analysis* / Q000276:immunology; D012608:Scrapie / Q000175:diagnosis* / Q000276:immunology; D012680:Sensitivity and Specificity; D012756:Sheep
D018620:PrPSc Proteins