Canadian sheep and goat breeders have a new tool to fight scrapie, the fatal disease that affects the central nervous system.
By conducting a blood test or collecting a DNA sample, they can determine their animals’ genotype for scrapie susceptibility or resistance.
While there is no clear picture of how prevalent scrapie is in the Canadian flock, each year a few cases of the disease are found.
Last year scrapie, the sheep equivalent of BSE, was identified in two sheep from Manitoba and two from Quebec.
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Since the discovery of BSE in Canada devastated markets for all ruminants, sheep and goat associations have wanted to eliminate the disease from the Canadian flock and ensure access to international markets.
Last year Alberta introduced its voluntary scrapie surveillance and genotyping program to help identify scrapie resistant sheep and get a firm handle on the incidence of scrapie in the province.
“It was a timely project for the industry to do,” said Norine Moore, a member of the Alberta Sheep and Wool Commission’s flock health committee.
To date, 51 flocks representing 4,000 Alberta sheep have enrolled in the program and 25 of the flocks have submitted genotyping or surveillance samples.
More than 1,400 genotyping samples have been submitted and 103 dead animals tested for scrapie, all of them negative.
In Alberta, producers who sign on for the genotyping program make a commitment to take all their dead animals older than a year to the lab for scrapie testing.
In 2005 the European Union passed a law that forced registered purebred flocks to participate in a scrapie genotyping-breeding program.
Few producers enrolled when the program first began in Alberta, Moore said. The cost of blood samples and testing was a deterrent, she added.
Enrolment increased earlier this year after DNA collection replaced blood samples.
“When you put a tag in their ear and when the tag goes in, it pushes a little piece of ear into a tube and you submit that for DNA testing,” Moore said.
“That has been very popular since we changed to that.”
Genotype testing looks for certain combinations of amino acids at three specific sites, or codons, on the genes. Each genotype is associated with relative susceptibility or resistance to scrapie.
The codes of genes QQ are most associated with scrapie. It has never been found in sheep with RR, the most resistant gene pairs. Scrapie has never been found in sheep with the QR pair.
“If people are more aware of what the genotype of their sheep are and try to breed the QQ out of the sheep, then that will help ensure to keep scrapie out of the Canadian flock.”
Genotyping doesn’t guarantee a scrapie-free flock, but it can be used to decrease or manage the risk of scrapie and is one more tool breeders and buyers can use, Moore said.
Sheep breeders have started to use genotype information to breed scrapie resistance into the flock.
After purebred sheep breeder Ian Clark of Bentley, Alta., selects replacement sheep from his four flocks for key traits such as growth rate and milk yield, he looks at the genotype results of each sheep.
“It is possible, the more susceptible ones, if they were more marginal in other ways, then I might decide not to keep them at all,” said Clark, who has genotyped his sheep for two years.
About 15 to 20 percent of his customers ask for genotyping information, mostly from the United States, Quebec and Ontario, where scrapie is most prevalent.
Clark is a keen supporter of the program, which he believes will help sheep producers discover the prevalence of the disease in Canada.
“The most important thing for any country dealing with scrapie is to first of all deal with surveillance.”
