Scrapie could be eliminated in Iceland after sheep with a rare genotype were found in the country, Iceland news outlet RЪV reported.
The six sheep carrying the gene are the first instances located in the country. Researchers from the Icelandic Agricultural Advisory Centre, Germany, England and Italy said it could be pivotal to fighting the disease that has affected the country since 1878.
The genotype, known as ARR and recognized by the European Union (EU), shows that the gene protects sheep from contracting and transmitting the disease. Consequently, sheep that carry the ARR gene do not need to be culled.
Scientists found another genotype, known as T137, in four ewes but no rams. Guрfinna Harpa Бrnadуttir, chairperson of the National Association of Sheep Farmers, told RЪV the genotype has been found to protect sheep against scrapie in three Italian studies, but it is not recognized by the EU.
“So we have hopes that the same applies to scrapie that has been plaguing us here in Iceland,” Guрfinna said. “It is yet to be confirmed by further research. But it’s very exciting, at the least, to find that genotype.”
The four ewes belonging to Guрfinna have the unusual characteristics of rare coloring and four horns, so researchers are searching for sheep with unique attributes, as this might be an indicator the sheep carry the gene.
According to RЪV, researchers sequenced 4,200 DNA samples from sheep around Iceland and sheep in Greenland of Icelandic origin. The six sheep were found in the Westfjords portion of the country, giving optimism that they could find other sheep with the ARR genome. They plan to sample 15,000 sheep this winter to find more sheep with the genotype for breeding. However, the researchers are cautious that breeding sheep with the genotype might reduce the diversity of Icelandic breeding stock.
Scrapie, transmissible spongiform encephalopathy, is a degenerative and fatal disease with no treatment or cure, resulting in the culling of the flock. Lambs become infected with the disease, but signs of scrapie appear two to five years after infection, with the average age of onset being 3-4 years old. The prion that causes the disease can persist in soils for decades.
The latest outbreak of scrapie in Iceland occurred in October 2021 at three farms in the northern portion of the country, resulting in the culling of 2,000 sheep.
The U.S. government has invested over $200 million into scrapie eradication since the early 2000s, lowering the percentage of scrapie-positive cull sheep at slaughter by 99 percent since 2003.
According to the USDA’s Animal and Plant Health Inspection Service (APHIS) “National Scrapie Eradication Program” report for the fiscal year (FY) 2020, there were no reports of sheep testing positive for classical scrapie.
In FY 2020, two sheep tested positive at slaughter for nonclassical scrapie. Nonclassical scrapie is also referred to as atypical, Nor98 or Nor98-like scrapie. Nonclassical scrapie appears to occur sporadically and has occurred in sheep of all the common genotypes, and it is either not transmissible or poorly transmissible under natural conditions.
One lamb sampled at slaughter in October 2019 was reported as “inconclusive” for classical scrapie. Thus far, for FY 2022, APHIS reported there are no reported cases of classical scrapie. Congress appropriated $19 million in FY 2022 for the National Scrapie Eradication Program. — Charles Wallace, WLJ editor
