Advanced testing methods are finding more cases of atypical scrapie, a fatal disease found in sheep and goats.
So far this year five cases have been found in Quebec, Ontario, Alberta and Saskatchewan. With the exception of Quebec, all were diagnosed as the atypical form in older animals, said Sandra Shearer, a veterinarian with the Canadian Food Inspection Agency’s disease control division.
“Atypical scrapie may have been present all along,” she said. “It was not previously detected until countries started doing regular surveillance of animals that were not showing any clinical signs.”
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Unlike BSE, live tests can be performed on sheep through blood collection, an examination of the third eyelid or most recently, a rectal biopsy where lymph nodes are examined.
“Scrapie will be in the lymphoid tissue before it is in the brain,” Shearer said.
Lymph nodes in BSE-affected cattle cannot be examined without surgery.
Atypical scrapie appears in animals older than one year and affects different portions of the brain. Classical scrapie has a genetic connection, and efforts have been ongoing internationally to test breeding animals and remove those demonstrating susceptibility. The disease can also be transmitted within a flock.
All the cases in Western Canada were found through the national surveillance program, which tests animals that died at sales barns, or through routine sampling at provincial and federal abattoirs.
About 4,000 samples were collected last year.
Suspect cases were traced back to the farms of origin using mandatory identification ear tags. Investigations found atypical cases did not infect other sheep in the flock.
Canadian producers are encouraged to join the voluntary surveillance program as a way to gain scrapie-free
status.
However, the Canadian Sheep Federation wants government to fund a wider surveillance plan to fully report disease prevalence before it works on complete eradication. The World Animal Health Organization won’t classify Canada as scrapie free until it reports no disease for seven years.
“We are putting together a proposal on how much it is going to cost to implement a full surveillance plan for scrapie,” said Jennifer MacTavish of the federation.
“Before we can set a date for eradication, the first thing we need to do is establish the prevalence. That is looking at a year and a half to two years of surveillance,” she said.
A long-term program needs to include a testing and compensation program for farmers who report unusual deaths in a flock.
“I can understand where producers might not find the time or the value in doing that,” she said.
The federation also wants more abattoirs to submit samples and it needs to know if there are regional differences in disease incidence.
In a letter last summer to federal agriculture minister Gerry Ritz, sheep producers said $10 million has gone into programs and initiatives toward eradicating scrapie in Canada since 1999.
Most of that money was spent on ad hoc eradication rather than an organized program.
MacTavish said without sound prevalence information, Canadian breeding stock producers are banned from trading with the United States.
The border cannot open until the U.S. Department of Agriculture writes a rule to allow more trade.
Feeder and slaughter lambs younger than 12 months are eligible for export, but no breeding stock is allowed. Canadians may import U.S. breeding animals.
Since 2004, the sheep industry has seen its breeding flock shrink by 100,000 animals, which means there has been an eight percent drop in the number of lambs processed in Canada.
Scrapie is a 200-year-old disease found everywhere but New Zealand and Australia.
It is part of the family of transmissible spongiform encephalopathies and does not affect humans.
Pregnancy appears to trigger the migration of abnormal prion protein to the reproductive tract. Birthing fluids and tissues from infected females, such as placenta, contain large quantities of the scrapie agent.
Healthy animals eating or licking contaminated materials in the lambing area may be infected, so newborn lambs and kids sharing the same contaminated pens are extremely susceptible to infection. Adult females sharing the same environment are also at risk.
