N. Hunter et D. Cairns, SCRAPIE-FREE MERINO AND POLL DORSET SHEEP FROM AUSTRALIA AND NEW-ZEALAND HAVE NORMAL FREQUENCIES OF SCRAPIE-SUSCEPTIBLE PRP GENOTYPES, Journal of General Virology, 79, 1998, pp. 2079-2082
As natural scrapie occurs only in sheep of specific PrP genotypes, one
proposed aetiology was that scrapie is simply a genetic disease. Howe
ver, Cheviot and Suffolk sheep of scrapie-susceptible genotypes are fo
und in Australia and New Zealand, both generally accepted to be scrapi
e-free countries. A study of more common Australia and New Zealand she
ep breeds (Merinos and Poll Dorsets) was carried out in order to obtai
n more generally applicable estimates of Australia and New Zealand she
ep PrP genotype frequencies. We have confirmed that animals of highly
susceptible PrP genotypes are found in Australia and New Zealand. Inte
restingly, the Poll Dorset sheep, although born in New Zealand, were b
rought to the UK as young adult animals and subsequently remained free
of clinical scrapie despite 21% of the sheep having scrapie-susceptib
le genotypes. These results have implications for the genetic control
of occurrence of the equivalent human diseases.