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NPA welcomes roll out of faster test for bovine TB detection

2nd Mar 2022 / By Alistair Driver

Defra has announced the roll out of the polymerase chain reaction (PCR) test for bovine TB (bTB) that will reduce the length of time pig herds are held under restriction due to suspect cases.

carcasesThe PCR test, which has been recently validated, will be used in certain circumstances from March 30 for tissue samples from carcases of:

  • TB slaughterhouse cases in cattle and non-bovines, including animals routinely sent for slaughter with suspicious lesions of TB identified;
  • Non-bovine animals such as pigs, as well as camelids, goats, sheep and farmed deer that are removed as TB test reactors, direct contacts or clinical TB suspects. And cases where suspicious TB lesions are identified on diagnostic post-mortem examination in a veterinary laboratory; and
  • Domestic pets (cats and dogs) and exotic species of animals (e.g. in zoological collections) submitted to APHA for laboratory investigation.

The main benefit of the change for the pig sector is that it will speed up the currently long process of freeing pig herds suspected of bTB outbreaks from restriction.

It will typically take within three weeks to get a PCR test result, compared with six to 22 weeks to obtain a final result from traditional microbiological culture, the current ‘gold standard’ method used.

Defra said: “The PCR test will reduce the time taken by the APHA laboratory to confirm whether M. bovis is present in tissue samples taken from carcases at post-mortem inspection.

“This means that in certain situations (ie slaughterhouse cases), if the PCR test results are negative, and check testing has been completed where required, APHA will be able to lift herd movement restrictions sooner than the existing protocols using microbiological culture, which typically take 6-22 weeks.

“If the PCR test results are positive, APHA will be able to inform the keeper and their private vet quickly, so that further action can be taken as soon as possible to control TB in the affected herd.


What is the PCR test?

The PCR test can detect the bacterium that causes bTB directly from tissue samples collected at post-mortem inspection.

PCR is a molecular-based laboratory technique which identifies tiny amounts of DNA present within M. bovis bacteria and amplifies it (by making millions of copies of a specific sequence of the target DNA) to produce a quantity which is then detectable.

 In the test validation study, the M. bovis PCR test produced equivalent results to the traditional microbiological culture method.

Further information about the M. bovis PCR test is available on the TB hub website.

NPA comment

NPA chief executive Zoe Davies said: “This is good news for pig producers and something we have been calling for for some time. 

“There have been too many examples of pig herds that have been kept under restriction for much longer than is necessary or proportionate due to the length of testing process.

This will ease the burden for those unfortunate enough to have a suspect identified at slaughter. Cases have been rising in recent months causing a lot of pain on farms already bursting at the seams.  

"We put a lot of pressure on Defra to resolve the situation and highlighted the additional impact that restrictions were causing on top of the current pig industry crisis. In recognition of this, Defra have agreed that the focus will be on slaughterhouse samples and non-bovines in the first instance.”