Six sheep on the farm Þernunes in Reyðarfjörður, East Iceland, hold the key to eradicating the fatal disease scrapie from the country. RÚV reports that the sheep carry a gene that is recognised by the European Union to protect against the disease. This is the first time the genotype has been found in Iceland, and could be pivotal to winning the fight against the disease, which has plagued Icelandic farms for over a century.
The genotype, known as ARR, has never before been found in Iceland, despite great efforts from researchers. Another genotype known to protect sheep from scrapie, known as T137, was also recently found in at least four Icelandic sheep. Extensive research in Italy has found that T137 protects sheep from scrapie, but it is not officially recognised by the EU as the ARR genotype.
Scrapie is a degenerative and fatal disease that affects sheep. Because it is highly contagious and can persist in flocks for decades, a flock in which the disease is discovered must be culled. Within the European Union, sheep that carry the AAR genotype do not need to be culled, even when scrapie is diagnosed within their flock, as research shows the gene protects them from both contracting and transmitting the disease.
Researchers sequenced 4,200 DNA samples from sheep around Iceland and sheep in Greenland that were of Icelandic origin. The six sheep in Reyðarfjörður that carry the gene trace their lineage to Reykhólasveit and Strandir, in the Westfjords, giving researchers hope the ARR genotype is to be found elsewhere in Iceland. Researchers plan to analyse DNA samples from some 15,000 sheep this winter to determine whether they carry the genotype.
The ARR genotype could eradicate scrapie through careful breeding. Researchers say, however, that it will be a challenge to spread the genotype through the population as quickly as possible without reducing diversity in the Icelandic sheep stock.