This TB cattle control enhancement is being introduced by Defra in November 2017 following a public consultation in 2016.

Background

The main test used in Great Britain for detecting TB in cattle is the single intradermal comparative cervical tuberculin test (SICCT), more commonly known as the tuberculin skin test .

The skin test in cattle relies on detecting and measuring the immune response of the animal to tuberculin, a protein produced by Mycobacterium bovis, the bacterium that causes TB in cattle.  The skin test is comparative as the animal’s immune reaction to injections of both bovine and avian (bird) tuberculin is measured and compared.  Cattle infected with Mycobacterium bovis tend to show a greater response to bovine tuberculin than avian tuberculin.

Depending on the degree of reaction to the skin test, the animal is classified as;

  • Clear (negative result)
  • Fail (reactor or positive result)
  • Inconclusive reactor (IR) – the animal shows a reaction to bovine tuberculin greater than the avian, but not strong enough to be classified as a reactor

IRs are placed under movement restrictions and must be isolated until they are re-tested. The soonest an IR can be re-tested is 60 days after the injection date of the previous test. If the IR tests clear at the re-test, it is known as a ‘resolved IR’.  If the IR fails the re-test (i.e. it has a positive result or an inconclusive result for a second time), the animal is compulsorily slaughtered and movement restrictions are placed on the whole herd if that has not already happened.

In severe TB breakdowns, IRs may be compulsorily slaughtered at the discretion of APHA as ‘direct contacts’ (DCs) without a re-test with compensation paid.

The risk posed by resolved IRs

Scientific studies looking at resolved IRs in the Republic of Ireland1,2 where bovine TB is widespread, have demonstrated that such animals have significantly higher odds of becoming reactors at a subsequent test in the same or another herd.  The studies concluded that;

  • Resolved IRs that moved out of the herd after passing their re-test were 12 times more likely to be disclosed as a reactor at the next test compared to all other animals in the national herd
  • Between 11.8% and 21.4% of IRs slaughtered prior to re-test showed visible lesions suspicious of TB at post mortem meat inspection, compared with less than 0.5% of non-IR animals

These studies provided evidence for the introduction of a new policy for resolved IRs in the Republic of Ireland in 2012. After reviewing the evidence, Defra is now introducing a similar policy in England.

Analyses of cattle herds in England in 2015 showed that all IRs have a substantial likelihood of being infected at the time they are found, except in herds in the Low Risk Area (LRA) without a prior history of TB3.

Why not just compulsorily slaughter all IRs?

Compulsory slaughter of all IRs would increase the probability of rapidly removing all TB-infected animals in herds. However it would be at a disproportionate cost, as increased numbers of TB-free cattle would be slaughtered resulting in additional herds being unnecessarily placed under movement restrictions.

This is why the government has adopted the alternative approach of restricting resolved IRs to the holding in which they were found for the rest of their life. This contains the potential disease risk to that holding and reduces the risk of spread of disease.  Cattle keepers have the option to slaughter resolved IRs, effectively removing the risk from the herd.

The new measure

All IRs in the High Risk Area (HRA) and Edge Area (and in TB breakdown herds in the LRA) that have a negative result on re-testing will remain restricted for the rest of their life to the holding in which they were found. The only permitted off movements for such animals will be to slaughter (either directly or via an Approved Finishing Unit).

To release resolved IRs from life-long restrictions, the option of interferon gamma blood testing (paid for by the animal owner) will be available to cattle keepers, subject to securing prior approval from APHA. If a resolved IR tests negative to the gamma test, the movement restrictions on the animal will be lifted and it could move freely (unless whole herd movement restrictions apply).  Cattle keepers wishing to take up this option should contact their private vet who would need to secure permission from APHA to carry out the test.  It is important to note that if the test result is positive the animal will be compulsorily slaughtered (with compensation paid), movement restrictions will be placed on the whole herd (if not already in place) and the standard TB breakdown procedures will then be followed.

Identification of resolved IRs

It is the cattle keeper’s responsibility to ensure resolved IRs are restricted for life to the holding in which they were found. Although not a mandatory requirement we recommend that such animals are physically identified to prevent accidental movement off the holding.  This could be achieved by using a management tag or freeze branding, and/or marking the animal’s passport.

Restriction of resolved IRs

Resolved IRs will be automatically restricted following their clear re-test, and keepers will receive a restriction notice in the post.

Resolved IRs will be restricted for life to the holding in which they were found, and this holding must have a permanent County Parish Holding (CPH) number.  If a resolved IR is residing at temporary grazing when it re-tests clear, it will be restricted to the permanent CPH associated with the temporary grazing.  Once the resolved IR moves back to the permanent CPH, it must be restricted to that CPH and cannot move back to a temporary CPH.

For more information on livestock movements, temporary CPHs and Temporary Land Associations, see the Defra guidance on GOV.UK.

Timing of implementation

This measure will be applied to all IRs disclosed from 1st November 2017 that subsequently test clear at re-test.  This means that if the injection date (TT1) of the test that found the IR is on or after 1st November 2017 the animal will be restricted for life if it re-tests clear.

Q&A

What is the policy change?

All IRs in the HRA and Edge Area (and in TB breakdown herds in the LRA) that have a negative result on re-testing remain restricted for the rest of their life to the holding in which they were found. The only permitted off movements for such animals will be to slaughter (either directly or via an Approved Finishing Unit).

Why is this measure being introduced?

Resolved IRs have a significantly higher likelihood of becoming reactors than clear tested animals, and as such present an increased risk of spreading TB. Restricting resolved IRs for life to the holding in which they were found prevents transfer of this risk to other herds.

When will this control measure be introduced?

On 1st November 2017

Why doesn’t the government just slaughter all IRs and pay compensation?

Slaughtering all IRs would be disproportionately costly. Increased numbers of TB-free cattle would be slaughtered resulting in additional herds being unnecessarily placed under movement restrictions.  Accepting that risk can never be completely eliminated, the policy aims to reduce the risk to an acceptable level with the resources available to the government.

Do resolved IRs need to be physically identified?

It is the keeper’s responsibility to ensure resolved IRs are restricted for life to the holding in which they were found. If a keeper intends to retain resolved IRs in their herd it is advisable, but not mandatory, to physically identify them to prevent their accidental movement off the holding.  This could be achieved by using a management tag or freeze brand and/or marking the animal’s passport.  It is also advisable to keep a record of any resolved IRs in the herd register.

How will resolved IRs be restricted for life?

A restriction notice will be issued explaining the conditions of the restrictions and the keeper’s obligations.

Is there a way of lifting restrictions on a resolved IR?

Potentially, yes. Cattle keepers may be able to commission interferon gamma blood testing of resolved IRs at their own cost, within 40 calendar days of the injection date (TT1) of the clear skin test.  The keeper must first seek permission from APHA through their private vet.  For more information about private gamma testing see the guidance for private vets on the APHA website.

If the resolved IR tests negative to the gamma test, the animal would be free to move off the holding, unless it is subject to any other whole herd movement restrictions.  If the animal tests positive it would be compulsorily slaughtered (with compensation paid), movement restrictions would be applied to the whole herd (if not already in force) and standard TB breakdown procedures followed.

What happens if a resolved IR is not eligible (too young) to undergo private gamma testing, but the keeper still wishes to test?

Animals less than six months of age are excluded from gamma testing as their immune systems are still developing and this can interfere with the test, leading to false positive results. If a resolved IR is too young for a gamma test, the keeper may apply to APHA to defer the test until the animal becomes old enough.  The keeper or their private vet must contact APHA to discuss the situation; all cases will be assessed on an individual basis.  If permission to test is granted by APHA the keeper will have 40 calendar days from when the animal reaches six months of age to undertake the test.

What happens to resolved IRs in TB restricted herds undergoing government funded mandatory gamma testing?

A resolved IR in a TB-restricted herd undergoing government funded mandatory gamma testing will automatically be included in any whole herd testing as long as it is over six months of age. If the resolved IR tests negative to the gamma test then the restrictions on the animal will be lifted, though it would continue to be subject to whole herd movement restrictions.  If the resolved IR tests positive to the gamma test it would be compulsorily slaughtered with compensation paid, just like any other reactor.

Can resolved IRs be moved to slaughter?

Yes. Resolved IRs are permitted to move to slaughter either directly or via an Approved Finishing Unit (AFU) under a licence issued by APHA.

Movements of resolved IRs to AFUs can occur directly or via a TB Dedicated Sale (Orange Market).  Movements of resolved IRs to slaughter can occur directly or via an Approved Slaughter Gathering.

Please contact APHA if you are considering this option.

What about resolved IRs at temporary land?

Temporary CPH (tCPH) Resolved IRs found at a tCPH will be restricted for life to the permanent CPH associated with the tCPH.  The resolved IR will only be permitted to move back to the permanent CPH associated with the tCPH, or to slaughter either directly or via an AFU.  Once back at the permanent CPH, the animal will be restricted for life to that CPH.

Temporary Land Association (TLA) If a resolved IR is found at a TLA it will be restricted to the permanent CPH associated with the TLA.  Subsequent movements of the resolved IR to the TLA will be permitted, as by definition the land falls within 10 miles of the permanent CPH.

For more information on livestock movements, tCPHs and TLAs see the Defra guidance on GOV.UK.

What happens with resolved IRs found at common grazing?

If a resolved IR is found whilst at common grazing it will be restricted for life to the keeper’s home holding which must have a permanent CPH number. The resolved IR will not be permitted to move to common grazing again because of the increased risk it potentially presents to other herds that use the common land.

Can resolved IRs move off the holding to agricultural shows?

No. Resolved IRs will be restricted to the holding in which they were found for the rest of their life and cannot move off to agricultural shows.

Can resolved IRs move off the holding for veterinary treatment?

Yes. Resolved IRs can move off the holding for veterinary treatment under a licence issued by APHA.  After treatment the animal must return directly to the home holding or to slaughter.

What happens if a keeper is non-compliant?

APHA will carry out percentage checks of resolved IRs to ensure that they remain restricted for life. Non-compliance will be referred to the relevant Local Authority for investigation and any enforcement action they deem appropriate.

References

  1. Clegg, T. A. et al. Shorter-term risk of Mycobacterium bovis in Irish cattle following an inconclusive diagnosis to the single intradermal comparative tuberculin test; Preventive Veterinary Medicine 102(4):255-64 http://www.sciencedirect.com/science/article/pii/S0167587711000614
  2. Clegg, T. A. et al. Longer-term risk of Mycobacterium bovis in Irish cattle following an inconclusive diagnosis to the single intradermal comparative tuberculin test; Preventive Veterinary Medicine 100 (3-4):147-154 http://www.sciencedirect.com/science/article/pii/S0167587711000614
  3. Epidemiology report – bovine tuberculosis in England in 2015 (Animal & Plant Health Agency) https://www.gov.uk/government/publications/bovine-tb-epidemiology-and-surveillance-in-great-britain-2015