T for the dreaded TB

TB is at the centre of all cattle farmers’ nightmares, and is a very real, living nightmare for hundreds of them.

Bovine Tuberculosis – A chronic disease caused by a bacteria called Mycobacterium Bovis, which is related to the bacteria that causes human and avian tuberculosis. Practically all mammals can be affected by it and can therefore spread it, including wildlife.

Here in the UK, this devastating disease meant almost 40,000 cattle had to be killed in England and Wales during just the last 12 months. Scotland’s the only country here to have an Officially TB Free Status.

We’re incredibly lucky to farm in what’s called a Low-Risk Area.

The country is split into risk areas, based on the number of incidences of TB infection found in that area and its wildlife. There are 3 categories – Low-Risk Area, High-Risk Area and Edge Area (the buffer zone between Low and High), and they all have different testing regimes to keep the disease controlled in cattle.

Being in the Low-Risk Area means our cattle have to be tested once every 4 years.

TB Test days are terrifying. Even though the risk is low here, there’s still the knowledge in the back of your mind that it might spread further, and one day, arrive on our doorstep, just like it has with countless other farms further south and west. And you might not know until one of your beloved cows fails the TB Test and has to be culled.

In the Edge and High-Risk areas, testing frequency varies from annually to every 6 months, depending on the level of risk. And in Wales, all herds are tested at least annually. If you have a confirmed breakdown (positive cases), then testing is a lot more frequent.

Pre and Post Movement Tests also have to be done when cattle move farms in some areas, especially when moving from higher risk areas to lower ones.

Should we be tested more than every 4 years? I think so, if only for piece of mind.

4 years is a really long time, and you do continually wonder if it’s made it here yet. Every time you see a dead badger on the side of the road, your mind jumps straight to worrying about whether they died of TB (badgers have been found to be a major source of infection in wildlife here).

Although, regardless of where you are in the country, post mortem meat inspections are carried out to check for TB, to make sure all meat is safe to enter the food chain, so the disease wouldn’t go undetected for long.

So, how does a TB Test go?

The standard test is a skin test, and is spread over 4 days. (There’s also a blood test, used in certain scenarios in known infected herds.)

On day 1, the skin thickness of two sites on the cow’s neck is measured and recorded by a vet. Then, those sites are injected with two types of tuberculin antigens. One of them is injected with a small amount of Bovine tuberculin and the other with Avian tuberculin.

Then, on day 4, the skin thickness of both sites is measured again to see what, if any, immune response the cow has had to the injections. If the Bovine site has had a bigger reaction (a swelling or a lump) to the Avian site, then depending on the amount of size difference, the cow is either classed as a reactor and has to be culled, or an inconclusive reactor and has to be retested.

Because there are many different types of mycobacteria found in the environment that don’t cause bovine TB, the two different injections are used to compare the animal’s immune response to each of them, and so be better at telling those infected with Bovine TB apart from those who have simply been exposed to similar bacteria in the environment.

It’s nerve-wracking waiting for them all to be checked, I can’t imagine how worrying it must be if you live in a higher risk area. Or how utterly heart-breaking it is seeing seemingly healthy cows condemned as reactors and taken away, especially if they’re carrying unborn calves. Sometimes multiple generations of meticulous breeding are lost in just one test, something no generic compensation can replace.

There’s no option for treatment, anything deemed to be infected or at risk of infection has to be culled.

If you have a reactor, you’re whole herd is put under TB restrictions, where you can’t sell or move any cattle except for when they’re only going for slaughter, and there’s also rules about how you can sell milk. You remain under restrictions until you’ve had a specific amount of clear tests- the restrictions can put entire livelihoods on hold indefinitely.


I really hope one day soon we can say things have changed and bTB is fully under control. There’s a cattle vaccine in trials which could potentially save a lot of herds, one day, but how many will be gone before that gets here?

It’s also important to mention that alpacas and other camelids, and also deer, can carry and spread bTB, but there’s no legal requirement to test them, unlike with cattle. It’s up to their keeper to choose whether or not to test, which certainly has to change if this disease is ever going to be controlled. You surely can’t expect to eradicate it if you aren’t testing all the sources?

One thought on “T for the dreaded TB

  1. In the days before nationwide TB testing, infected cattle gave us humans some protection against human TB. I remember being tested at school and reacting sufficiently that I did not need vaccination !!

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