English

Cristina Santos Sotomaior,David Driemeier,Vanete Thomaz-Soccol,Juliano Leal,Rüdiger Daniel Ollhoff

doi:10.14393/bj-v31n4a2015-26231

Abstract

Scrapie in sheep is associated with at least three polymorphisms in the prion protein gene (PRNP) on codons 136, 154, and 171. Countries where scrapie is endemic have been using breeding programs based on selection for the most resistant alleles. There are some PRNP genotyping data on sheep in Brazil, and scrapie has sporadically been observed since 1978. Parana is the Brazilian state where most of the cases of scrapie have been diagnosed. A flock that had three clinical scrapie cases in 2003 and 2004 was genotyped (128 sheep: 53 pure Hampshire Down and 75 crossbred) and slaughtered (111 sheep: 47 pure Hampshire Down and 64 crossbred) in 2006. Samples of lymphoid and central nervous tissues were examined by immunohistochemistry (IHC) for altered prion protein (PrP Sc ). Six genotypes were detected in the 128 genotyped animals: ARR/ARQ was the most frequent (45.3%), followed by ARQ/ARQ (28.1%), ARR/ARR (14.1%), and ARQ/VRQ (8.6%). ARR/VRQ and ARQ/AHQ showed less than 2.5% genotype frequency. IHC identified 16 positive sheep. Palatine tonsil tissue had the highest percentage of reactive samples: 81.25% of the total positive samples. Of these 16 positive animals, nine (56.25%) had genotype ARR/ARQ, five (31.25%) had genotype ARQ/ARQ, and the remaining two (12.5%) had genotype ARQ/VRQ. All the positive animals were clinically healthy, and therefore represented 14.14% of pre-clinical cases of scrapie in this flock.

Highlights

Scrapie is a fatal, neurodegenerative disease that affects sheep and goats and belongs to the group of transmissible spongiform encephalopathies (TSE) or prion diseases
For sheep exposed to the scrapie infectious agent, allelic variation at codons 136, 154, and 171 of the prion protein gene (PRNP) is associated with an increased risk of disease development (HUNTER et al, 1989, 1997a,b; BELT et al, 1995; DAWSON et al, 1998)
The purpose of this study was to retrospectively analyze the PRNP polymorphisms found in an ovine flock in which three animals had been diagnosed in 2003 and 2004 with the classical form of scrapie, and to determine if these polymorphisms are associated with the presence of PrPSc

Summary

Introduction

Neurodegenerative disease that affects sheep and goats and belongs to the group of transmissible spongiform encephalopathies (TSE) or prion diseases. In these prion diseases the normal cellular form of the prion protein (PrPC) undergoes a conformational change to the infectious form (PrPSc). For sheep exposed to the scrapie infectious agent, allelic variation at codons 136 (alanine, A/valine, V), 154 (histidine, H/arginine, R), and 171 (histidine, H/glutamine, Q/arginine, R) of the prion protein gene (PRNP) is associated with an increased risk of disease development (HUNTER et al, 1989, 1997a,b; BELT et al, 1995; DAWSON et al, 1998). In ARR/VRQ sheep, there is little or no involvement of the lymphoid tissue in agent replication (ANDRÉOLETTI et al, 2000; VAN KEULEN et al, 2008)

Objectives

Methods

Results

Conclusion