THE DISCOVERY, in Ireland, of the NOR98 strain of scrapie previously only found on mainland Europe has led researchers to conclude it could be more widespread than previously thought.
Reporting the discovery in Vet Record, scientists from Dublin”s Central Vet Research Lab say these findings are unlike the Norwegian cases, where the disease is sporadic. But it also shows the disease is not confined to the Continent.
However, scientist Hanne Onnasch doubts it has implications for the rest of Ireland’s sheep population. “I don”t think it would be missed at farm level because it manifests itself as scrapie and can be picked up by routine diagnostic tests,” she says.
A spokesman from Britain’s Vet Lab Agency also believes NOR98 is not a worry for UK sheep producers. “It’s probably a common phenomenon that has been missed in the past,” he says.
Meanwhile, new evidence from the National Vet Institute in Oslo, Norway suggests sheep with a specific allele could have a higher risk of developing scrapie NOR98.
Scientists have identified a variation on allele 141 which they have labelled F141.
Sheep with the allele AF141RQ have a higher risk of developing NOR98 than those with genotypes containing AHQ, but the effect of the two alleles is additive. In addition, the earliest onset of NOR98 seems to be at about 30 months of age.
These two factors have led scientists to think that NOR98 is probably a spontaneous prion disease resembling sporadic CJD in humans, but further research is needed.