BSE was already a European problem, and Switzerland was experiencing a small, but significant, epidemic. Collaboration between the Swiss authorities and an embryonic company called Prionics, led to the application of a hitherto research tool for the testing of fallen stock and casualty cattle. The test, a western blotting method, had been validated with assistance from colleagues at VLA Weybridge. By 1998/99 significant numbers of additional cases were detected by this approach and, following publication of the results, the European Commission (EC) decided to apply similar methods in all member states. This would help to determine the size and geographical spread of the European BSE epidemic.

VLA’s Regional Laboratory in Newcastle

The EC began by publishing a call for expressions of interest from companies that believed they had tests that were virtually ready for the market place. Using positive control samples supplied from the Transmissible Spongiform Encephalopathy (TSE) Archive at VLA, four potential tests were evaluated in 1999. Three were eventually approved, and subsequently became the basis of the active surveillance programme in Europe.
This officially began in 2001, but some countries pushed ahead independently in 2000, leading to the recognition of more cases in France, and first home-bred cases in several others, including Germany and Spain.

The rest, as they say, is history.

The three tests to be approved in 1999 were the Enfer ELISA, the BioRad Platelia ELISA and the Prionics-Check Western Blot test. Following a further round of evaluations in 2001 and 2002, the Commission approved two more tests, the Prionics LIA (ELISA) and the InPro Biotech CDI (also an ELISA) in 2003. Following the introduction of the first three tests in 2000/01 it was clear that none were quite as ready for the market place as had been hoped. Consequently the 2001/2 evaluation required thousands of additional samples to be tested in field conditions before approval was given. This included the testing of poor quality material from fallen stock.

Currently VLA carries out approximately half of the tests done in Great Britain. Both VLA Carmarthen and VLA Newcastle had gained experience in the use of the Dissociation Enhanced Lanthanide Fluoro Immunoassay (DELFIA) test in 2000, testing approximately 10,000 samples between them. Before embarking on larger scale surveillance, VLA decided after a tendering exercise and test evaluation to use the Prionics Check Western Blot method. The new work was concentrated at VLA Newcastle, although VLA Carmarthen also did a significant amount of testing during 2001 before turning their hands to the testing of scrapie in sheep in 2002.

All the techniques are based on the detection of abnormal prion protein, the unique identifier for TSE, in the central nervous system of both cattle and sheep. The protein is distinguished from normal prion protein, both by its protease resistance and molecular size.

In scaling up testing capacity, the VLA Newcastle team faced major obstacles.

• logistics - problems posed by the receipt, preparation and testing of large numbers of samples
• quality - issues of maintaining traceability of samples and testing standards
• safety - issues associated with large- scale rapid preparation of samples containing the prion agent

To manage the whole process effectively, individual samples were allocated a unique reference number, reagents were validated before use, metal instruments were replaced with plastic equipment and all primary and secondary sample preparation was carried out in containment level 2 and 3 facilities respectively.

This regime worked well but by the end of 2001 the testing unit at Newcastle was facing the prospect of testing 200,000 samples a year. Additional staff were recruited and trained and resources were increased accordingly. A decision soon had to be taken in this rapidly changing environment as to whether we were now using the most appropriate test. VLA evaluated the options and decided to adopt the BioRad Platelia ELISA method for rapid testing in September 2002.

This decision to ‘change horses in midstream’ meant that staff had to be re-trained and a new system put in place by November 2002.

Processing samples using the BioRad Platelia ELISA

The experience of moving through essentially three different testing methodologies has been enormously useful for VLA in facing the TSE testing demands of the future. Large scale testing for scrapie is now more realistic.

Strong links with colleagues at other EU laboratories carrying out rapid TSE testing have been forged and VLA Newcastle has demonstrated that we have the flexibility to respond to future changes in the testing requirement.