Thursday, January 06, 2005

2005 - A Good Idea ?

We have been made aware of a new development in diagnostic testing which may have a place in the fight against Tb.

Readers may have already been aware of a variant of this system known as the Smartcycler, developed in the USA by the late Fred Brown, which was recommended by him (and turned down by Defra) to rapidly diagnose FMD on site in a very short time. Defra preferred to complete a contiguous cull of adjacent cattle and sheep, while they developed their own machine.

Developed by the Ministry of Defence's research arm, the UK system was originally designed to search for biological agents in the battlefield. We would comment that it's use in our countryside as over 5000 farms are now under Tb movement restriction , our 'Animals and Animal products '- as yet undefined- subject to a potential Russian trade ban which feeds back to the farm of origin and infected wildlife are left to maintain a substantial threat to other species including human beings, could not be more aptly described.

'Identify biological agents in the Battlefield' - we like that.

Described in the Veterinary Times at its launch late last year, this new diagnostic tool could allow vets to test for bovine Tb in the field. Scientists at the Defense Science and Technology Laboratory (DTSL) used technology called the Polymerase Chain Reaction (PCR) originally to diagnose biological warfare agents but its wider potential is now recognised and spun out to include the food industry and veterinary and human medicine.

DSTL is launching a joint venture with industry to produce more 'mini labs' which they hope to have available very soon. Enigma Diagnostics, funded by £5 million from a consortium of investors led by Porton Capital (a spin off from the MOD) and the treasury, and including private venture capital will launch fully automated diagnostic machines encapsulating the PCR process which will allow:

* field tests for animal diseases, including FMD and Tb within 30 minutes, rather than sending samples to a far flung laboratory and awaiting their analysis
* detect food contamination such as salmonella, e.coli and listeria.
* fast diagnosis of meningitis etc.

A single machine currently costs around £40,000 but that figure is expected to drop to about £10,000 once mass production kicks in.

Now that the UK has its own PCR cycler machine available, it has been suggested that although this technology can only be used as complementary to the primary intradermal skin test in cattle, there may be a place for it to give rapid identification of Tb in badgers. We have spoken before of the appalling sensitivety of the so called 'Brock' ELISA test on a negative reading, (40.7 percent) and this tool could refine diagnosis with much more accuracy.

The potential advantage of the PCR over gamma interferon in cattle, is that it should be able to differentiate between bovine Tb (m.bovis) and avian (m.avium) particularly in cases where wildlife interface is not identified as a cause, and speed up clearance of movement restrictions.

Of course, if a wildlife reservoir of Tb is allowed to flourish then as we have seen, none of these diagnostic tools will halt its spread.

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