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Derivation of a scrapie-free sheep flock from the progeny of a flock affected by scrapie
  1. J. Foster, BSc1,
  2. C. McKenzie, HDA, DipSurv, MBA1,
  3. D. Parnham, HNC, AIB1,
  4. D. Drummond1,
  5. W. Goldmann, PhD1,
  6. E. Stevenson, BSc2 and
  7. N. Hunter, BSc, PhD, DIC1
  1. 1 Institute for Animal Health, Neuropathogenesis Unit, West Mains Road, Edinburgh EH9 3JF
  2. 2 Institute for Animal Health, Compton Laboratory, Compton, Newbury, Berkshire RG20 7NN


The Cheviot flock at the Institute for Animal Health's Neuropathogenesis Unit (npu) has endemic scrapie, which affects primarily vrq/vrq sheep and at high frequency. A new flock with a full range of PrP genotypes, including the highly susceptible vrq/vrq, has been produced on a separate site, from animals in the npu breeding flock, and it remains scrapie-free after eight years. In contrast, in a parallel flock at the npu farm, scrapie has reappeared after five years, although the animals were kept in separate accommodation from the scrapie-affected sheep. During this time the npu breeding flock continued to have scrapie cases. Although it is known that highly susceptible sheep can remain free of infection in a clean environment, this is the first report of the infection being removed successfully from the bloodlines of scrapie-affected sheep. The results confirm that scrapie is not a genetic disease dependent only on the PrP gene sequence, but requires both genetic susceptibility and an infectious agent.

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