Scientists say breakthroughs in BSE testing are on the way.
Last year’s BSE discovery in Canada drew researchers out of their labs to remind governments and the cattle industry that they are still working on rapid, live tests for the disease. Many said they were nearing breakthroughs.
Scientists generally believe BSE is caused by abnormal proteins called prions.
Roger Morris, a professor or molecular neurobiology at King’s College in London, England, one of the world’s foremost prion researchers, said despite the announced new testing systems, little has changed since the disease caused a panic in Europe in the mid-1990s.
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“There have been new antibodies discovered and systems of testing, but so far nearly all have disappeared down the sinks of the labs where they were born,” he said.
Chris Clark of the Western College of Veterinary Medicine at the University of Saskatchewan says many of these companies are likely a few years away from a rapid field or live test.
“But it takes a lot of money to do this research and those companies need the profile to attract (investors),” he said. “It will be a big deal when somebody comes up with a solution.”
Until then, the industry must make do with the tests that are now available, which can be divided into two categories:
- Classical tests look for brain lesions or the BSE prion.
- Rapid tests either look for evidence of the protein prion strand or add antibodies to a prion that emit a light signal that a pathologist can interpret.
Most diseases are caused by viruses or bacteria, which leave telltale signs of their presence when animals and humans try to fight them off. Doctors and scientists use these antibodies to determine the presence of diseases.
However, BSE prion proteins are not known to be present in the blood, which means a piece of brain is required to isolate them.
The fastest rapid test now on the market mixes brain samples with digestive enzymes that break down brain tissue into a soup, which is tested for surviving BSE prion protein fragments.
“Rapid (Western blot) tests still take eight hours and require a highly trained pathologist to carry them out and interpret them,” Clark said.
BSE identification is complicated by a naturally occurring blood-to-brain barrier that helps animals resist disease by preventing blood diseases from entering the brain.
Immunohistochemistry, or IHC tests, are regarded as the gold standard or reference test for BSE and are generally carried out only when rapid tests show positive for BSE prions. They test the brain asa series of prepared slides and require even more time and skillto complete.
As a result, they are done only at federal reference laboratories.
Earlier this year, the U.S. government promised that BSE testing would become more rapid and affordable in the near future, but Andrea McNally of the U.S. Department of Agriculture said while it has licensed “a number of manufacturers’ tests,” there “no live tests so far. We’re still hoping.”
The United States and Canada have expanded testing in keeping with expert panel reports provided to both countries.
Beginning in June, the USDA will sample 268,000 animals a year that are older than 30 months. Scientists say this level of testing should produce a detection rate of one positive animal in 10 million adult cattle.
McNally said the “system will identify BSE if only five animals in the entire country would test positive.”
Canada is sampling at approximately the same rate.
“Live testing will likely come, but it takes time,” Clark said. “This is a very challenging disease.”
