Scrapie epidemic in a fully PrP-genotyped sheep flock

M Baylis, W Goldmann, Fiona Houston, D Cairns, A Chong, A Ross, Allister Smith, N Hunter, A R McLean

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

In scrapie-affected sheep flocks, host PrP genotype plays a vital role in determining which sheep will succumb to scrapie and the incubation period. Consequently, within-flock scrapie dynamics is best understood within the context of the genotype profile of the flock. Here we describe a 17 month epidemic of scrapie in a commercially farmed flock of 230 genotyped Texel sheep. At the start of the study, 70% of the sheep were of three genotypes only: ARR/ARQ, ARH/ARQ and ARQ/ARQ. Only 15% of sheep encoded the disease-associated VRQ allele and only a single sheep (0.4%) was of the most susceptible VRQ/VRQ genotype. For susceptible genotypes there was a marked deficit (P or =3 years), implying that some cases of scrapie had occurred previously. In the ensuing 17 months, 18 sheep of known genotype were confirmed positive for the disease: seven VRQ/ARQ, six VRQ/ARH, two VRQ/ARR, three ARQ/ARQ. Median ages at death were 2.7, 2.8, 4.2 and 3.8 years respectively. Mortality rates were 55, 86, 13 and 3% respectively. Survival analysis revealed a highly significant effect of genotype on survivorship, but no difference between VRQ/ARQ and VRQ/ARH, or between VRQ/ARR and ARQ/ARQ. There was no difference in the survivorship of middle- and older-age cohorts of susceptible sheep. Scrapie risk group (as defined by PrP genotype) was not associated with submission as a scrapie suspect but later found to be negative, or with dying of unknown causes on the farm.
Original languageEnglish
Pages (from-to)2907-14
Number of pages8
JournalJournal of General Virology
Volume83
Issue numberPt 11
Publication statusPublished - Nov 2002

Keywords / Materials (for Non-textual outputs)

  • Age Factors
  • Animals
  • Disease Outbreaks
  • Female
  • Genotype
  • Male
  • Prions
  • Scrapie
  • Sheep
  • Survival Rate

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