A blood test has been developed by Canadian researchers that can diagnose fatal chronic wasting disease in elk, and may provide an inexpensive approach to screening for mad cow disease.
According to the researchers, the test looks for damaged cells in the blood, and may also provide a way to diagnose Creutzfeldt-Jakob disease in humans.
The report appears in the journal Nucleic Acids Research.
“We can now take a blood sample from a live animal and look at the DNA patterns in the blood and predict six months ahead of time whether an animal is infected with chronic wasting disease,” said Christoph Sensen of the University of Calgary.
The secret, according to Sensen, is that they look for circulating nucleic acids which are released by dying cells instead of searching for the prions that cause mad cow disease.
Researchers discovered three patterns in these circulating strands of DNA that appeared three months prior to elk showing symptoms of disease. Each pattern could be linked to a genetic mutation that puts the animal at risk of catching the disease.
Transmissible spongiform encephalopathies (TSEs) such as mad cow disease, chronic wasting disease, and CJD destroy the brain, and can be transmitted when an animal eats another’s infected tissue.
In the 1980s, mad cow disease swept through Britain infecting herds and people who ate contaminated beef products.
Fewer than 200 people globally have died by contracting the disease in this manner.
Outbreaks of mad cow disease can halt a nation’s beef exports, so governments and breeders are enthusiastic about an inexpensive way to test for mad cow disease.
According to Sensen, the test they have developed is a simply polymerase chain reaction (PCR) that intensifies the DNA so it may be sequenced.
The researchers suggest pooling the blood of several animals for traces of BSE. If traces are found, then individual tests can be performed.
Sensen and his team tested their methods on 19 elk and two BSE-infected cattle from Germany. The researchers were able to identify the infected animals each time.
It may take up to four years to replicate the findings in cattle, said Sensen.
“There is currently no reliable way to tell if an animal may have a prion infection before it becomes obviously sick,” said Kevin Keough of the Alberta Prion Research Institute.
“If there were a reliable way to know, it would be of great benefit to producers, processors and wildlife managers.”
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