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Pathogenesis of natural goat scrapie: modulation by host PRNP genotype and effect of co-existent conditions
Authors:Lorenzo Gonz??lez  Stuart Martin  Stephen AC Hawkins  Wilfred Goldmann  Martin Jeffrey  and S??lvia Sis??
Institution:1Veterinary Laboratories Agency (VLA-Lasswade), Pentlands Science Park, Penicuik Midlothian EH26 0PZ United Kingdom ;2VLA-Weybridge, Addlestone Surrey KT15 3NB United Kingdom ;3The Roslin Institute and R(D)SVS University of Edinburgh, Roslin Midlothian EH25 9PS United Kingdom
Abstract:After detection of a high prevalence of scrapie in a large dairy goat herd, 72 infected animals were examined by immunohistochemistry with prion protein (PrP) antibody Bar224 to study the pathogenesis of the infection. Tissues examined included the brain and thoracic spinal cord (TSC), a wide selection of lymphoreticular system (LRS) tissues, the distal ileum and its enteric nervous system (ENS), and other organs, including the mammary gland. The whole open reading frame of the PRNP gene was sequenced and antibodies to caprine arthritis-encephalitis virus (CAEV) infection were determined. Unexpectedly, accumulation of disease-associated PrP (PrPd) in the brain was more frequent in methionine carriers at codon 142 (24/32, 75.0%) than amongst isoleucine homozygotes (14/40, 35.0%). The latter, however, showed significantly greater amounts of brain PrPd than the former (average scores of 9.3 and 3.0, respectively). A significant proportion of the 38 goats that were positive in brain were negative in the ENS (44.7%) or in the TSC (39.5%). These results, together with the early and consistent involvement of the circumventricular organs and the hypothalamus, point towards a significant contribution of the haematogenous route in the process of neuroinvasion. Chronic enteritis was observed in 98 of the 200 goats examined, with no association with either scrapie infection or presence of PrPd in the gut. Lymphoproliferative interstitial mastitis was observed in 13/31 CAEV-positive and scrapie-infected goats; PrPd in the mammary gland was detected in five of those 13 goats, suggesting a possible contribution of CAEV infection in scrapie transmission via milk.
Keywords:scrapie  goat  prion neuroinvasion  transmissible spongiform encephalopathy  CAEV
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