Expert advice: What happens if my herd fails a TB test?

TB is a growing threat for cattle farmers, with many farms encountering breakdowns for the first time as the disease spreads further north.

But what does it mean if your herd is placed under restriction? And can you still trade?

Vet Sarah Tomlinson, from Westpoint Farm Vets in Ashbourne, Derbyshire, is a technical board member delivering the new TB advisory service. She is also member of the Defra TB advisory group for England.

See also: Six-hour TB test shows promising early results

Below she answers common questions on TB restriction rules and dispels some common myths associated with disease.

I’ve had positive reactors within my herd. How long will I be placed under restrictions?

A minimum of two months (60 days), depending on your location and TB history. If  the Animal and Plant Health Agency (APHA) considers your breakdown high risk, you will need two clear, consecutive 60-day tests, so you will be under restriction for at least four months.

Is there anyone I am legally obliged to tell that I have been shut down?

Dairy farmers are legally obliged to tell their milk buyer they have been shut down with TB. The milk from reactors while in isolation must not enter the tank, nor be fed to calves.

When will my animal be taken to slaughter?

All reactors should be removed within 10 working days of failing the test. This has important implications, as your next test can only be done 60 days after removal, not 60 days after your last test.

My cow failed its TB test, but its calf passed. What should I do?

The APHA can only take animals for slaughter that fail the skin (or gamma) test. APHA vets can take “direct contacts” at their discretion.

If the cow in this case had TB lesions in its udder at slaughter, the APHA may decide to take the calf. But this does not stop you deciding this calf would be too risky to remain on farm and culling it.

I have had an inclusive reactor (IR). Should I keep it?

As of 1 November, an IR will have to remain on farm and can only move to slaughter or to an AFU/ red/orange market. We know that up to 21% of IRs slaughtered before their second test show visible lesions.

I would advise all IRs are removed from the herd as soon as they have completed their retest. Being a TB IR is a reason to be on your cull list, just like poor fertility or chronic mastitis.

When culled, the reactor didn’t have lesions. Does this mean it doesn’t have TB?

No. The TB skin test is very specific and is 99.97% likely to identify a true positive. So, a TB reactor is telling you there is TB on your farm. Early stages of the disease can have microscopic lesions that can be missed when animals are processed on a slaughter line.

I would see an non-visible lesion (NVL) reactor as good news. You have been warned there is TB in your cattle’s environment, so surveillance testing is increased, but this animal has been removed in the early stages of the disease and hopefully was not yet infectious to the rest of your herd.

When will I be allowed to buy animals in? And how do I know the TB history of the animals I want to buy?

After a breakdown, you will have to wait until you have completed your first 60-day test and you will need APHA permission. Whenever buying in cattle you should think about the chances of buying in infection. Ask for the TB history of the farm.

A recent clear test is good, but the longer the farm has been free of TB, the more reliable this becomes. You can look up whether a farm has a history of TB on the ibTB.co.uk website. This interactive tool maps bovine tuberculosis outbreaks in England over the previous five years.

I have heard the skin test isn’t very sensitive. Are there any other tests I can request my vet uses and will I have to pay for this?

The conventional skin test is approximately 80% sensitive. This means only 80% of the TB-positive animals are correctly identified. So a clear TB test on a herd that has had reactors in the past can’t be trusted to be a true clear test.

The only other government-recognised test is the gamma interferon test. This is a blood test the APHA will do in certain situations – such as new outbreaks in the edge area.

The sensitivity of the gamma test is higher than the skin test, so there is less chance of leaving positive animals behind. Farmers can request this test privately and at their own expense – for example, when purchasing a high-value animal, but will still need APHA permission.

Animals that test positive are likely to be compulsory slaughtered, with statutory compensation paid and the herd put under official restrictions. Some low-risk animals that test positive may be retested at government discretion and expense.

Antibody or serological blood tests have been developed to detect bovine TB, but these are not officially approved to test for TB in cattle in the EU.

What alternative routes for sale do I have for my stock while under restrictions?

You will be sent a general movement licence that will allow animals to go straight to slaughter. You can also apply for a licence to allow animals to move to an approved finishing unit (AFU) or a licensed finishing unit (LFU) – these are in the low risk area. 

These are APHA-approved units that can buy clear tested cattle from a TB-restricted herd or a red (slaughter) market or orange market. Animals from an orange market can go to slaughter or move to an AFU/LFU.

My neighbour has failed their TB test. Does this mean I will have to test my cattle?

In the edge and low-risk area, a positive herd test will trigger radial testing and all herds in a 3km zone will be tested. In the high-risk area and the old high-risk areas of the new edge areas (see below) contiguous tests are triggered. These include herds within a 1km zone.

I graze sheep on tack over the winter. Are they at risk of spreading TB? And what about other species?

Sheep, along with many other species, can become infected with TB. As sheep are relatively short lived and TB has a long incubation period, it is very unlikely sheep on temporary grazing are a big risk when it comes to spreading TB.

Other species such as goats and camelids may be tested on farms where cattle reactors have been disclosed. Deer have also been linked to specific outbreaks, but cattle and badgers still remain the biggest transmitters of the bacteria and therefore are the biggest TB risk to your herd.

Would I be better setting up an isolation unit to help me sell animals sooner?

Isolation units need to be approved by the APHA before there are any TB restrictions applied to a herd. They must be a completely separate unit with its own new CPH number, but still under the same day-to-day management.

Within 30 days of the herd TB test, clear tested cattle can move into the unit over a period of six weeks. The unit must then pass two consecutive 60-day tests. These animals will then be officially TB free, even if the main herd is still under restrictions.

I have two farms. Would it be best to run them as one holding number?

A unit within 10 miles can be added to your main holding as a temporary land association (TLA). This means there is no obligation to register movements with BCMS, nor is there a need to pre-movement test.

The holdings are treated as one unit for TB testing and if either has a reactor, both units would be placed under TB restrictions, but animals can still be moved between the units.

I know I have badger setts on my farm and I think they are spreading infection. What can I do to stop my cows getting TB?

It is illegal to kill badgers and a successful prosecution can result in a prison sentence. To legally cull badgers, you must apply for a government licence. In areas not culling there are many things farmers can do to reduce the risk of TB from badgers.

It is impossible to badger proof your whole farm, but you can look at the biggest risk pathways of them entering your cattle environment. Small things may have a big effect on your risk of TB from badgers.