Live scrapie test
AMERICAN scientists have developed a technique for diagnosing scrapie in live sheep, raising hopes that a live BSE test for cattle might also be possible.
In the UK, scrapie – a form of spongiform encephalopathy – is confirmed by microscopic examination of the brain at post-mortem.
But the US scientists have discovered that the scrapie disease agents, prion proteins, are present in the third eyelid of infected sheep. The test, which has been patented, involves taking a biopsy from the eyelid, sectioning it, and incubating it with an antibody.
. This antibody specifically binds to prion proteins within infected sections, and an associated coloured stain indicates the presence of the disease.
The new assay is an improvement on current blood tests, which only determine whether an animal will be susceptible if exposed to the disease.
"This test will allow producers and vets to detect scrapie in sheep before the animals show signs of disease," says Dan Glickman, the secretary of State for Agriculture.
It is also hoped that the test could be adapted to detect BSE in cattle before the onset of clinical symptoms. But Don Knowles, one of the researchers involved in the study, explains that, to date, research has not extended to cattle. To address this question, the research team from Washington State University and the National Animal Disease Centre in Ames, Iowa, are beginning to collaborate with UK scientists.
Chris Bostock, Head of the Institute of Animal Health, Compton, admits the test is promising.
But Dr Bostock urges caution, as the UK and US scrapie strains may have a different disease pattern. And he says that not all forms of scrapie may accumulate in the third eyelid tissue.
"There is research work to be done to validate the test as a general diagnostic test for infection," he says.