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Vet. Res.
Volume 40, Number 6, November-December 2009
Number of page(s) 13
Published online 18 August 2009
How to cite this article Vet. Res. (2009) 40:65
How to cite this article: Vet. Res. (2009) 40:65
DOI: 10.1051/vetres/2009048

High prevalence of scrapie in a dairy goat herd: tissue distribution of disease-associated PrP and effect of PRNP genotype and age

Lorenzo González1, Stuart Martin1, Sílvia Sisó1, Timm Konold2, Angel Ortiz-Peláez2, Laura Phelan2, Wilfred Goldmann3, Paula Stewart3, Ginny Saunders2, Otto Windl2, Martin Jeffrey1, Stephen A.C. Hawkins2, Michael Dawson2 and James Hope1

1  Veterinary Laboratories Agency (VLA-Lasswade), Pentlands Science Park, Penicuik, Midlothian EH26 0PZ, United Kingdom
2  VLA-Weybridge, Addlestone, Surrey KT15 3NB, United Kingdom
3  Roslin Institute Neuropathogenesis Division, Roslin, Midlothian EH25 9PS, United Kingdom

Received 8 April 2009; accepted 14 August 2009; published online 18 August 2009

Abstract - Following a severe outbreak of clinical scrapie in 2006–2007, a large dairy goat herd was culled and 200 animals were selected for post-mortem examinations in order to ascertain the prevalence of infection, the effect of age, breed and PRNP genotype on the susceptibility to scrapie, the tissue distribution of diseaseassociated PrP (PrP$^{\rm d}$), and the comparative efficiency of different diagnostic methods. As determined by immunohistochemical (IHC) examinations with Bar224 PrP antibody, the prevalence of preclinical infection was very high (72/200; 36.0%), with most infected animals being positive for PrP$^{\rm d}$ in lymphoreticular system (LRS) tissues (68/72; 94.4%) compared to those that were positive in brain samples (38/72; 52.8%). The retropharyngeal lymph node and the palatine tonsil showed the highest frequency of PrP$^{\rm d}$ accumulation (87.3% and 84.5%, respectively), while the recto-anal mucosa-associated lymphoid tissue (RAMALT) was positive in only 30 (41.7%) of the infected goats. However, the efficiency of rectal and palatine tonsil biopsies taken shortly before necropsy was similar. The probability of brain and RAMALT being positive directly correlated with the spread of PrP$^{\rm d}$ within the LRS. The prevalence of infection was influenced by PRNP genetics at codon 142 and by the age of the goats: methionine carriers older than 60 months showed a much lower prevalence of infection (12/78; 15.4%) than those younger than 60 months (20/42; 47.6%); these last showed prevalence values similar to isoleucine homozygotes of any age (40/80; 50.0%). Two of seven goats with definite signs of scrapie were negative for PrP$^{\rm d}$ in brain but positive in LRS tissues, and one goat showed biochemical and IHC features of PrP$^{\rm d}$ different from all other infected goats. The results of this study have implications for surveillance and control policies for scrapie in goats.

Key words: scrapie / goat / prion disease / transmissible spongiform encephalopathy

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© INRA, EDP Sciences 2009