Veterinary Times 27th Sept '04
"Battlefield technology deployed in fight against bovine TB"and BBC News 4th Oct '04
The obvious potential of a portable PCR cycler machine is to give a rapid identification of TB and the spoligotype of TB present in badgers. If one animal from a sett is found to have TB of a type causing infection in nearby cattle, then that sett could be treated with carbon monoxide with less nervousness by Ministers who would be able to give a better explanation to the general public. There are 29 strains or spoligotypes of bovine TB, of which 17 are found very infrequently. In the UK the most common is type 9 with type 11 being more common in Devon, type 21 and 9 more common in Somerset and Dorset, and Cornwall being higher in types 9 and 15. The geographical distribution of spoligotypes of bovine TB in badgers has a high level of correlation with the distribution of spoligotypes in cattle. Spoligotype 35 has recently been identified in farmed deer near Ulverston, Cumbria, and linked to a spread to cattle there. The samples for multiplication in the PCR machine can be from any source and could merely be from a small amount of cattle blood or badger sputum or urine. Samples from several animals can be put in each of the glass testing tubes within the machine. A single case of infection in one animal would show up, allowing immediate rechecking of the animals in that batch.
The suitability of the portable PCR cycler machine for testing cattle for TB obviously depends on finding cattle that are shedding TB bacilli - either in milk, saliva, dung or urine - or which have bacilli in their blood.
The potential advantages of the PCR cycler over the gamma interferon test is that it should be able to differentiate between bovine TB and avian TB in blood and can be used on farm and give a result within 30 minutes. In the case of cattle this would save the wait of 3 days to read the skin test and the further wait of 6 to 12 weeks for confirmation of TB by culture test.
However the PCR cycle seems potentially to be of even more use in identifying bovine TB in badgers - which no other test can currently do satisfactorily. The sensitivity of the current (brock) ELISA blood test for badgers is only 40.7 per cent, and needs to be done 3 times at 28 to 42 day intervals, which entails keeping wild badgers in captivity for at least 84 days for a result. I
A further attraction of using this PCR technique is that it may be accurate enough to distinguish the TB status of individual badgers within a sett. If a half hour test can reveal this, then the targeted cull of badgers that we propose might be refined even further.