A NEW test that detects scrapie in sheep a year before the animals show any symptoms of the disease holds out that a similar test might soon be used to diagnose CJD in humans. Doctors could then begin to seek remedies for what is now an untreatable and incurable disease.
The new scrapie test is reported in this week's Nature by scientists working at the Dutch institute for animal health.
Testing for scrapie, BSE, CJD and the other so called "prion diseases" is extremely difficult. The infectious agent that causes the diseases, a rogue form of the naturally occurring prion protein, is found mostly in inaccessible tissues such as those of the brain.
And, because it occurs naturally, it does not provoke any immune response, so there are no tell tale antibodies to test for. Moreover, in people the symptoms can be confused with those of a stroke or Alzheimer's disease, for example.
Despite considerable international research, the only definitive tests available at the moment are a post mortem examination and, in CJD patients, a brain biopsy.
A number of indirect tests are being developed, including one that detects damage to nerve cells, but none is specific to CJD.
The new Dutch technique tests directly for the rogue prions in a sheep's tonsils. It can be used easily on live animals and can detect scrapie up to 15 months before the sheep show any symptoms.
Dr Mark Rogers, a scrapie expert at UCD who helped to develop a new post mortem test for BSE, said the Dutch results were very interesting" and the test might be of use at abattoirs or in a continuous test and retest scheme, like that for bovine TB.
But it is unlikely the new test can be used with cattle one of the many differences between scrapie, CJD and BSE is that in BSE the rogue prions do not appear to be in the cattle's tonsils and therefore are not accessible to the test.
However, it should be possible to use the Dutch approach with CJD.
Meanwhile, the BSE test developed by Dr Rogers, together with a British biotechnology firm, Proteus, has been licensed to an Irish firm, Enfer Scientific. Like the existing test, it is a post mortem brain examination, but the UCD test can screen animals faster and in greater numbers than the current technique.
Enfer Scientific is licensed to develop the test for use in Ireland France, Germany and the Benelux countries.