Inconclusive reactors are animals that have a skin test result that is neither definitively clear nor positive. Once found, they must be isolated from the rest of the herd until they are re-tested. This is to reduce the risk of spreading TB to other cattle. If possible, they should also be kept separate from any TB reactors found at the same test.
When one or more IRs are found, the herd is initially put under automatic whole herd movement restrictions until the test result is reviewed by the Animal & Plant Health Agency (APHA). A restriction notice (TB34) is issued and you need to isolate the IR on farm until it is re-tested. The IR cannot move off the holding except under a licence issued by APHA.
For officially TB free (OTF) herds, when the test results are reviewed by APHA, the need for whole herd movement restrictions is also assessed against the ‘three year rule’ explained below.
If the three year rule applies then whole herd movement restrictions stay in place until the IR is re-tested. If the three year rule does not apply then the whole herd movement restrictions are lifted and restrictions only apply to the IR(s). If whole herd movement restrictions are lifted then you are free to trade and it is only the IR(s) that need to remain isolated and cannot move off the holding.
IRs found in officially TB free herds
APHA assesses the TB history of the herd over the last three years. If there has been a TB breakdown on the holding within the past three years, the three year rule may apply.
IRs found in TB-restricted herds
For IRs found where herd movement restrictions are already in place, a TB34 isolation notice is served on the IR. You must isolate the IR from the rest of the herd promptly. IRs identified at a short interval test (SIT) will be re-tested at the next SIT. If the herd doesn’t require a further SIT, only the IR will be re-tested but the whole herd movement restrictions will stay in place. Animals with an inconclusive result at their re-test (2xIR) are classed as reactors and compulsorily slaughtered.
IRs are re-tested after a minimum of 60 days and there are two possible outcomes.
The animal is known as a ‘resolved IR’ and may re-join the herd. In the High Risk Area (HRA) and Edge Area (and TB breakdown herds in the Low Risk Area), resolved IRs are restricted for life to the holding in which they were found. However keeping resolved IRs in the herd poses significant risks.
If the animal does not test negative (i.e. is either a reactor or an IR again), it is classed as a reactor and compulsorily slaughtered.
On occasions in TB breakdown herds with lesion and/or culture positive animals, IRs may be slaughtered by APHA as direct contacts before they are re-tested, with compensation paid.
Private slaughter of IRs
You can choose to send an IR to slaughter at your own expense before it is re-tested. You must tell APHA, giving as much notice as possible, as they will have to issue a specific TB24 licence allowing the IR to travel to a slaughterhouse of your choice.
IRs can only go direct to an abattoir, they are not permitted to go via a slaughter collection centre. APHA arrange for the IR to undergo post mortem inspection in the slaughterhouse to look for lesions suspicious of TB, and tissue samples are taken for bacteriological culture.
Compensation is not paid for privately slaughtered IRs. Taking this option rather than waiting for the outcome of the IR’s next test could lead to additional testing and/or prolong the movement restrictions on your herd. If you are considering privately slaughtering one or more IRs, please contact APHA to discuss your case so that you are fully aware of the potential consequences and can make an informed decision.
If an IR dies on farm or has to be put down for welfare reasons, you also need to inform APHA. You will not receive compensation for IRs that die on your farm. If an IR dies on farm or is privately slaughtered and post-mortem inspection reveals visible lesions suspicious of TB, APHA applies movement restrictions (unless they are already in place) and test the rest of the herd.
The risks posed by resolved IRs
A resolved IR is an animal that had an inconclusive test result, but then subsequently re-tested clear. Scientific studies in the Republic of Ireland have found that resolved IRs are 12 times more likely to be found as a reactor at their next test. They also found that 11.8% – 21.4% of IRs slaughtered prior to their re-test after their initial disclosure showed visible lesions that were suspicious of TB at their post-mortem inspection.
In light of this, all resolved IRs in the High Risk Area (HRA), Edge Area, and in TB breakdown herds in the Low Risk Area (LRA) must remain restricted for life to the holding in which they were found. The only off movements permitted are to slaughter or to an Approved Finishing Unit (AFU), either directly or via an approved TB gathering. All movements must be under a licence issued by APHA. It is recommended that these animals are physically identified, such as freeze branding, management tag or marking the passport, to prevent them from accidentally moving off the holding.
Resolved IRs can be released from their life-long restrictions by private interferon-gamma blood testing paid for by the keeper with the approval of APHA. If a resolved IR tests negative to the gamma test, the life-long restrictions on the animal are lifted and it can move freely (unless whole herd movement restrictions apply). If a resolved IR tests positive to the gamma test, it is considered a reactor and normal TB breakdown procedures apply.