TB Testing: From validation to eradication

Of all the scares and scandals around meat farming practices in the UK, few have been as persistent as been bovine TB. While we're nowhere near the 1930s estimate of the number of cattle infected, it's never really gone away. Why is that?

Dr. Neil Watt of MV Diagnostics joins us to cover where bovine TB has been hiding between outbreaks, how changes in testing may help pin it down, and why now might be the turning point on the management, maybe even eradication, of bovine TB in the UK.

Read the original paper: https://doi.org/10.1002/vetr.4241

Read more : https://www.mvdiagnostics.co.uk/

Transcript

Hello, I'm Will Mountford. Welcome to Research Pod.

As a child of the 90s, I have lived through a fair few scares and scandals around meat farming practices in the UK. There was foot-and-mouth disease, pig flu, a couple of bird flus, a bout of which recently prohibited the existence of free-range eggs in the UK due to quarantining practices keeping all of the birds indoors, and probably a few more that escape my memory.

A persistent one, though, has been bovine TB.

While we're nowhere near the 1930s estimate of the number of cattle infected, it's never really gone away. So what's to blame for that?

Is it the poor performance of testing currently available? Is there resistance to the take-up of vaccines? Is it the impact of pasteurisation on milk safety?

Or badgers? Or deer? Or even, in one case, the farm cat?

What will it take to break the seeming inevitability of a TB outbreak at a UK farm given enough time?

Today I'm speaking with Dr. Neil Watt of MV Diagnostics to cover where bovine TB has been hiding between outbreaks, how changes in testing may help pin it down, and why now might be the turning point on the management, maybe even eradication, of bovine TB in the UK.

And joining me from MV Diagnostics is Dr. Neil Watt.

Neil, hello.

Hi there Will, glad to be talking to you

Could you tell me a bit of yourself, your background, your work and what brings us here today?

Okay, I'm a vet. I qualified from the University of Glasgow in 1977, a long time ago. I’m 71 so probably not that long to go! Better crack on with TB!

I was in practice for a year or so down in North Yorkshire, in the next practice up from James Herriot's place at Thirsk.

And we were a totally large animal practice, no small animals apart from the odd farm dog and cat.

I then went back to Glasgow to do a PhD on calf respiratory disease and then moved over to the Edinburgh Vet School (I became a ‘Dick’!) to work on a disease called Maedi Visna, which is a sheep disease related to HIV.

More recently, a colleague and I, Gordon Harkiss who is an immunologist, set up a company, MV Diagnostics, in order to commercialise the test we developed for Maedi Visna, which we did, and we now sell that.

And then we've also developed other tests for Caseous Lymphadenitis and Chlamydia abortus.

What got us into TB was that we were working with a company over in Ireland, Enfer Scientific, who have a very clever way of combining tests into one well, called a multiplex test.

So one well in an ELISA plate will test for several diseases.

And their main effort at the time was on tuberculosis in cattle.

We had a look at the test and we thought, this looks really interesting, but we didn't think it had enough antigens in it.

So Gordon worked his immunological magic on the test, and we eventually developed it to an extent where it was much more sensitive, much more specific, and we got it validated internationally for use in cattle.

And that's really what we've been focusing on mostly for the last quite a long period, actually, for the last probably 10 years, is trying to get the tuberculosis tests up and running.

We're already using them in alpacas, and we have used them in goats and camels and deer and pigs and dogs.

I mean, in principle, they'll work in all of the species if you just sort of fiddle about and adapt them. So that's really our main topic.

And the way it all works is that I'm a vet pathologist, Gordon's an immunologist, so we do the design of the test. We then get the antigens, these are reagents that you use in the test, made commercially and then we send them over to Enfer. They put them onto their multiplex system.

And then once they've got the test up and running, we help them to get it validated and work with the labs that use it in order for them to get the best out of it.

And you mentioned this was an Irish partnership. I understand your work takes you much further afield than that.

It does indeed. Recently I've been in Mexico, Kenya, Saudi Arabia and my colleagues are working with a group in New Zealand and others in South America

So potentially we're pretty much global. Most of that work is on TB, but not just TB.

We also work on other diseases of interest in all of these countries and we have various multiplexes put together to service their needs.

And with that kind of global view and the decades-long work in mind, what is it, I suppose, that you see is the problem that we're going to be talking through today and what makes it such a timely discussion that we have it?

Well, I think it's essentially that the way we're trying to control TB in this country, Gordon and I just don't think it'll work because the way the tests have been developed, they focus on only one part of the immune response and to get the best sensitivity out of a test, you need both parts of the immune response, the cell mediated response and the antibody response.

And we can maybe go into that a bit later.

But also we're working directly with farmers and there are political and social difficulties about dealing with TB, particularly in the areas of the country where it's relatively high prevalence and the farms have had TB several times.

It can be very difficult to persuade them to introduce a new, more sensitive test because they just lose more cattle and put them under restrictions longer.

They can't trade.

And there's all the mental health issues as well of having to cope with the stresses and strains of having TB.

To set the stage for some of this discussion and a lot of your work, let's start off by thinking about farms as a whole. Farms in England and TB, so far as I know, has been a problem my entire life.I came of age during the foot and mouth crisis.

So holistic picture over the last 10, 50, maybe even 20 years, what is the state of health on the farms?

Yeah, well, the situation varies between the different countries within the UK.

In Scotland, they are officially TB free. That doesn't mean they don't get TB. It just means that they have a very low prevalence. And when it gets into a herd, they tend to know where it came from.

In England, England is divided into 3 areas, a high risk area where they have relatively a lot of TB, a low-risk area where they don't have much, and an edge area where it's either spreading or receding.

In Wales, they have divided the country a bit more rigorously, if you like. They have high risk, low risk and intermediate risk areas, and they're sort of intermingled.

Whereas in England, it's essentially the north and east of the country is low risk, the south and west is high risk, and the middle up by Birmingham is the edge area.

In Northern Ireland, their problems are even worse. They have a very high prevalence of infection.

And the problems that we have are that we trade a lot of animals from Ireland, both parts of Ireland, the south and the north, and they tend to spread a bit of infection into this country.

We then have a lot of trade between herds. It's just a characteristic of English and Welsh farming, but there's a lot of trading of animals between herds.

And with an insensitive group of tests for the disease, it's very easy to have undetected infection which gets traded between farms in animals which are not positive in the official tests.

How does TB get into a herd?

It's generally introduced by animals from other herds, which are infected, but they're officially TB-free. And this sounds ridiculous, but an officially TB-free herd is not necessarily an uninfected herd.

And in fact, nearly 80% of the new infections in some parts of Wales are introduced by bringing infected animals with undetected infection into the herd.

The other mechanism is from badgers or other wildlife which are infected. But according to a report in 2007, this is actually a relatively rare event. Maybe only about 5% of outbreaks are due to bringing infection in badgers or from other wildlife.

But of course, once it's in the herd, then it spreads round. So In essence, you really do need to control badgers and wildlife in order to get full control of TB.

But the main route of infection into a herd is by bringing infected cows in.

So 95% of TB infections are due to just moving the same reservoir of TB around?

Essentially, yes. Yeah.

Some of that's coming from Ireland, some of them from the south of Ireland. Some from trading from the high risk to the low risk areas. 

A lot of it is local trading. I mean, we have a very good example of a herd in Cumbria, which has a relatively low prevalence of TB, where he broke down in 2020. We did one of our methods of analysis of the herd, the RiskRate on him, and it was clear that he'd got infection in 2015.

By that time, we knew that the local strain of M. bovis was from Cheshire. So I asked him if he'd ever brought any animals in from Cheshire and he'd bought a British blue cow in 2015. I looked back at the herd that it came from and it had TB in 2014 and 2016.

So the strongest likelihood is that he bought TB in that cow but it took four or five years before the herd was officially positive in the official tests.

During that period, he was trading locally to farms, a few miles down the road, and then they started going down with the same Cheshire strain of TB as well.

And what are the consequences of a TB infection in a herd, either if it is caught and managed or if it goes undiagnosed and enters, you know, food chains, that kind of thing?

Yeah. In fact, the entry into the food chain isn't really an issue because TB is a very easy organism to kill. The most problematic source of TB would be if it were in milk, but because we've pasteurized milk, that's effectively taken that out of the game altogether.

The health consequences for the animals are pretty minimal as well, because we tend to catch them quite early before they've developed severe disease. We do see health issues with the animals we detect in our test, but they're usually not specifically TB.

They maybe have mastitis or lameness or other conditions going on. The main problem for the farmer is that it puts them under restrictions so that they can't trade their animals.

If you're on a dairy farm, for example, you're producing calves, some of which you can't actually use as your own replacements. So you very quickly get overcrowded with too many animals and you can't get rid of them.

So our farmers are desperate to have at least periods of officially TB free so they can move animals on and replenish the stock.

And what does that mean then for testing in terms of a typical schedule? Is it just like an annual, biannual thing?

Yeah, good question. I mean, it depends on which part of the country you're in. If you're in the very low risk area, you only get tested once every four years. If you're in Scotland, you get tested even less frequently in that and only on a risk basis. So they test the most risky herds and a lot of others never get tested.

However, if you do have an outbreak, then you're being tested every 60 days.

And that means that the animals are being gathered in, injected with tuberculin, and then three days later, gathered together again to measure the size of the lumps. And that goes on every 60 days until you're ‘officially  free’ of infection.

So some herds would have been under these restrictions for maybe 2, 3, 4, 10, 15 years. And it's an incredible stress on the farmer and on the animals to have to be gathering them in, administering these tests every 60 days.

In 60 days, it's only two months. You know, if you're on a schedule like that, it's hugely demanding of time and resources.

And that does that come at cost to the farmer as well for, you know, per test per animal?

They don't actually pay for the official testing, and they do get compensation for animals that are positive in official tests, but the compensation doesn't cover all of the farmer's costs.

So if it, for example, it costs DEFRA £10,000 to control infection on a farm, it'll be costing the farmer another £10,000 at least as well.

That varies quite a lot between farms because of the management systems.

But yes, it is very expensive.

Could you tell me about the BTB partnership?

The TB partnership came about after the Godfrey report and they were trying to get together a group of vets, farmers, scientists to advise the government on how to control TB.

But it's a pretty secretive organization. It produces reports that go to DEFRA, but the general public and vets in practice don't ever get to see these reports.

The only one I've managed to dig out of them was the report on the task and finish group report on increasing test sensitivity.

And it took two Freedom of Information questions to get that one out of them.

However, that is actually a very good report. It's very comprehensive. Dick Sibley, a Devon vet in practice, was the chair for it.

He was under a lot of constraints as to what he could say and do and what aspects he could look at. But I think he produced an excellent report.

But then Dick was ‘not required back’ for the TB partnership and the report just seemed to go underground until I asked the freedom of information question.

And then they said, they were using some of Dick's ideas to start a trial of some of the more sensitive tests.

I further asked for more information on this, but really got nothing. I mean, there is a sort of quite a culture of control of information and almost secrecy within DEFRA.

And I think it particularly seems to me to particularly apply to TB.

They just don't want us to know what going on behind the scenes, what they're thinking of, what they're saying to each other, what they're advising each other.

And a lot of people who are on these groups, they're acting as individuals. They're not necessarily representative of the organisation they're from. So it's even very difficult to get, I mean, for example, there are members of the British Cattle Veterinary Association on the TB partnership, and they report back to the BCVA board but the BCVA board don't report that on to practitioners and members like me.

So I don't really know what the TB Partnership is actually doing.

And it looks to be a similar situation developing in Wales, where they have a technical advisory group, which does essentially the same sort of thing. But it seems to be very constrained by confidentiality agreements as well.

But Dick's report was very good.

The only weakness I would say was that it used the IDEXX test rather than the Enferplex test.

And we'll probably go into this later, but IDEXX and Enferplex measure the same thing. They measure antibodies, but the Enferplex does it a lot more sensitively than the IDEXX test.

Something that we'll link to in the show notes for this episode is a letter putting forward your position and some of the critique that you have about the current testing regime, deployment, sensitivity, kind of just the whole approach.

It's in Veterinary Record. Josh Loeb has just written an excellent three-part report on the state of bTB in the UK and he’s taken a lot of input for this, from right across the spectrum of thinking on bTB 

I think that's the right journal title. For anyone who doesn't have the time to go read it, could you give me a quick summary about your position from that paper?

Essentially what we're arguing is that in order to control TB, you need more sensitive tests. You need to use Enferplex and tests like it, but you need to use it in a policy environment which is sustainable for the farmer.

Currently the Catch-22 is that if the farmer uses Enferplex, he/she'll find a lot of positive animals, which he/she can't then easily get rid of to get officially TB-free status back. So in business terms, it's better not to use the Enferplex test and just tosuffer the fact that you might have another breakdown at some point in the future, and many do.

And I have a very good example of that from Wales, a dairy farmer called Abi Reader, who is now President of the NFU in Wales. She would desperately like to use the Enferplex test for her herd, but we know from the work that we have done with it, that she's likely to find maybe 20 or 30% of the herd positive.

And it would be really difficult for her to get rid of those animals to run the business.

So she needs OTF status so that it can trade the calves that are built up in the meantime while she has broken down with TB.

So there's a Catch 22 that if a test is almost too good, it can be a big disintentive to use it unless the policy is right to support that use.

And at the moment it isn't.

You mentioned, yes, the schedule and that there's different tests available.

How many tests are there for TB that farmers or government testers have to choose from?

What's the market like for that?

Well, there are four tests. The official one, main official one is the skin test. This is where you inject tuberculin into the skin and three days later you come and measure the lump. They use that for all of their animals that are in susceptible or infected herds.

They then take a subset of those animals and use a Gamma interferon test, which is measuring the same part of the immune response. It's still measuring cell-mediated immunity, but it does it by a different mechanism, and it's more sensitive.

They then use the IDEXX test, which is an antibody test, but they only use that on a subset of the animals, a smaller subset even than the Gamma.

So the antibody tests are used very infrequently.

You can use the Enferplex test on a private basis, but the rules as to what you can test with it, very restrictive. We can't go and test new infections in herds. We can only detect, we can only test herds that have already had a Gamma test.

It's not certain that we'll get permission if we do ask. And the consequences are more serious for the farmer if we find positives because he/she doesn't get any compensation and has to get rid of the positives before officially TB free test status is granted.

There are other tests, non-validated, the Actiphage test, which detects the bacterium directly rather than its immune response, but I don't think anybody's using that now.

And then there are ways of screening at the slaughterhouse for visible lesions. These are lesions which are caused by the immune response to TB, but they only occur in about 3% of infected animals. So it's not very sensitive.

And then the other one is the culture of M. bovis itself, but that needs the presence of VLs, visible lesions, for you to be able to culture the bacterium. So it's not very sensitive either.

Now, you mentioned that you and your colleagues have been involved in the development of Enferplex and its sensitivity. So if you break down just a little bit of the molecular biology of how it works.

Yeah, well, the Enferplex test is what we call a multiplex test. So it uses 11 antigens from Mycobacterium bovis, different types of antigens. One of them is a synthetic peptide, which we make in a machine. Others are proteins, which we grow in bacteria and then purify. And the other one is the standard diagnostic reagent for TB, which is PPDb, purified protein derivative type B from M bovis.

And then we print these individual antigens onto the surface of a microtitre plate in 50 or 30 nanolitre spots, so tiny, tiny spots. And then we block the plate and then we put the serum or the milk or the bulk milk on, then we wash it, then we develop it.

And what we get is chemiluminescence, so light output from any spot where there are antibodies to the antigen. And we will measure the amount of light output, put it through a program which identifies to the farmer which animals are infected and which are not.

And it also, because it has 11 antigens, it identifies the most risky animals because the most risky ones will have responses to most of the antigens. And we give the farmer a traffic light system, red, amber, yellow.

There are the reds. These are the ones you want to get rid of as quick as you can.

The ambers, you need to get rid of them maybe at the end of a lactation if they're a dairy cow.

The yellows, you can maybe afford to monitor them, but if you've got any reason to get rid of them for other reasons, maybe you've got mastitis or lameness, then take that opportunity.

The diagnostic specificity of the Enferplex test is 98.4% at its high sensitivity setting.

I think what people need to realize is that we can vary the cutoffs on the test in order to optimize either the sensitivity or the specificity. So in its most sensitive form, the specificity is 98.4%. And at that, the diagnostic sensitivity is 94.2%.

But we can vary that in order to meet particular needs, whether we're doing surveillance on a large scale or we're actually working on a particular farm to reduce the level of infection.

The sensitivity does vary between the different classes of infected animals.

So in an animal with visible lesions, the sensitivity is 95.8%. But in an animal which is positive by the Gamma test, it's 86.7%.

What this really means is that the more criteria you have for an animal being truly infected, the better the sensitivity is.

The Gamma test is a little bit difficult because its specificity isn't 100%. So you've got to be quite careful how you interpret these things.

But essentially, compared to any of the other tests or test combinations, both the specificity and the sensitivity of the Enferplex and skin test combination are really better than any others.

And we've mentioned some of the other tests and how they work. So to kind of hold them in a direct comparison between Enferplex, you mentioned IDEXX, Actiphage have different mechanisms of action. But in terms of just straight accuracy, what is the best approach with a single test.

And then if they're double testings, which you mentioned that you use Enferplex as a second confirmation, happens if you get 2 positives, 1 negative, 1 positive, 2 negatives, like how much confusion is added by additional testing?

Yeah, Will, it's a very good point because Mycobacterial infections are very difficult. And if you're expecting all the tests to agree with each other, they never will. So the combination that we use is the skin test first, and then 5 to 30 days after the skin test, we take the sample for Enfiplex.

And the reason for that is that when you do a skin test, you inject tuberculin into the animal's skin. If the animal, and ONLY if the animal, is already infected with Mycobacterium bovis, that injection of tuberculin boosts the antibody response.

So it goes much higher. So it increases the sensitivity of the test quite dramatically.

So the best combination to use is the skin test and then the Enferplex test

IDEXX does the same thing, but it's not as sensitive a combination.

Gamma, there may be a role for Gamma in clearing up some residual infection, but although it's a sensitive test, it's still working by the same mechanism as a skin test, and it does have a problem with specificity, so you will get relatively more false positives in a herd.

And the one thing that farmers hate the most is false positive animals, which they're having to get rid of, and which just don't have TB at all.

There was a farm that was in Somerset, and he'd had a long-term problem with TB and did make really assiduous efforts on his own, but to get rid of it by doing a lot of private testing with the Gamma test and the IDEXX test. And he got to the point where in 280 animals, he had no Gamma positives and he only had  4 IDEXX positives….and we thought, great, we'll go in with Enferplex, we'll find four or five more infected animals, get rid of them, job done.

But When we went in, we found 140 Enferplex positives. So because of his farming system, he was able to split the herd into 140 Enferplex positives and then 140 Enferplex negatives. Over the next 15 months, all of his official reactors came from the Enferplex positives.

Now, 15 months isn't really long enough, would have loved them to go on longer. But by that time, he was fed up with the whole process and he decided to change his business model and he got out of dairying and we weren't able to follow the animals up for whatever reason.

But it does in principle show that there could be more or less a one-step eradication if you're vigorous enough with the Enferplex test.

And we're certainly going to try this in Mexico, where the herd structure is such that we can maybe test 5 herds and put all of the Enferplex negatives onto one farm and all the Enferplex positives onto the others, then keep testing the negatives to see if they go positive, move them over to the positive farm if they do, and then maybe achieve eradication relatively quickly.

So we're looking forward to starting that project. They're ready to go. We just need to go over very soon to do the validation for them and then we're off.

And with all these different options on the market, I think leads into the concern about, between that and how secretive the TB partnership is being, are there any kind of figures moving behind the scenes? Is there any concern of vested interests or undue influence onto which test gets picked up for deployment? Because you said there being, you know, 10s of thousands of pounds sent around hundreds and thousands of animals being tested. I can imagine that all adds up to someone getting paid quite a lot, quite quickly.

Yeah, it does. Well, DEFRA seem to have a big affinity for cell-mediated response tests, so the skin test and the Gamma test.

The skin test has been around for donkeys years, but quite a lot of the DEFRA people do believe that it's a very good test.

Unfortunately, the work that we've done shows that at best its sensitivity is 80%, so it'll detect 80% of animals with visible lesions, but they're only 3% of all infected animals.

And at worst it's 0%, because if a herd is going officially TB free, but it's still infected, as many are, then the skin test has failed to detect any of the infected animals.

The IDEXX test has a longer history than Enferplex. It was first validated, I think, in 2012. The tests do differ in the actual cost of production and the ease of interpretation, if you like.

And for our test, the Enferplex test, we have to have a special reader, which costs about £20,000, which the lab needs before it can run the test at all. There only are, I think, 2 readers in the country at the moment.

One's in the APHA lab in Weybridge or Starcross, and the other one's just been set up in Wales. I'm going down there next week to help set it up.

We're using that in Wales more for sheep diseases, for which we have a multiplex as well, but we're hoping eventually we will be able to get on to use the Enferplex TB test in that lab as well.

That sounds like a lot of investment in terms of developing the test. I mean, developing the test, but also developing the reader. Is it something that, will pay off in time or is it enough for farmers to take the more inaccurate route for a longer period and what's the cost risk calculation there?

I think if you really did the cost benefit properly, you'd find that you could get rid of infection with Enferplex much more quickly than with any of these other test combinations.

So although your initial costs might be higher, your longer term costs will be lower.

And I have sort of estimated, it's a bit of a back of a fag packet calculation that at the moment DEFRA is spending £100 million per year on TB. A lot of that is going in compensation to the farmers.

If you were to use the combination of tests that we are suggesting, you'd probably need to up that to £300M, maybe £400M, maybe £500M, but you'd probably only need to do it for five years.

So the options are you continue on forever, spending £100M a year, or you spend a lot more per year, but over a relatively period of time, and you eradicate the infection.

If you had to pick any one of the options out, would you say the main problem facing farmers currently then is microbial, ecological, financial or political?

I think it's a combination of the tests and strategy which are being used, which comes down to the politics of it. The microbial thing is important too, because there are different strains of M. bovis and they don't all interact with the host in the same way.

And we don't really understand all of the ins and outs of how the host microbe interaction goes on. And we're trying to better understand that.

Ecological, well, that's where the badgers and the wildlife come in. Particularly badgers, but also deer, which can get infected with M. bovis.

In fact, any warm blooded mammal can get infected.

And on some farms, it's the cats that are a problem as well.

But I think really the main thing is it's the politics of it, actually getting DEFRA to change policy when they're very reluctant to.

And the sustainability issues for the farmers, the way to really deal with this infection is not to test and cull it out, but it's to test and manage it out.

But in order to do that, you need a bit more time and you need a policy which is flexible enough to allow you to continue to trade even when you're managing the infection out.

And that is the difficulty that we're having at the moment.

People are not using the tests we’d like them to use because they don't want the trade restrictions that using the test would bring.

Is this something that, you know, some magic single super test would be a solution too?

No, there isn't such a thing. The immune response is very clever at adapting to an organism.

And you do need to measure both the cell mediated and the antibody side of the test to get good sensitivity.

Detecting the organism itself sounds great, but it's present in such low quantities and in such hidden away parts of the body but it's very difficult to get at.

I mean, there will be infection in the bone marrow, but that's very rarely looked at and you have to kill the animal to get the bone marrow. It's also present in the eyes in cattle.

So that gives you a lot of technical difficulties with the test for the bug. So there'll never be a, you know, a magic bullet test that will do everything.

It's got to be a combination used sensibly with the right strategy. And I think that's where we're heading.

And in the right policy environment that allows farmers to manage infection out of their herds sustainably.

That's the key.

These farmers are businessmen/women. They cannot afford to lose too much milk production. They're already running on very fine margins.

So to lose 20 or 30 cows on a test and cull system, just not sustainable.

What would you say to any incoming MP, councillor even, anyone who might be in a position of importance or local influence for farming communities in those areas or trafficking with the infected herds up into Scotland from the Northern Ireland, as you say.

Come and speak to me! I think there will be a significant change if the current Labour government listens and acts on what we are telling them. I don't think their heart is really in culling badgers. Nor does it need to be.

And that will throw the emphasis, I think, back on residual infection in herds, which is not being detected by the current tests, so I think there maybe is an opportunity to move on with the recent change of government.

And change of governments tend to introduce changes of people in the civil service at various levels. And I think that'll help too. I’ve met some very good DEFRA/APHA people recently.

I mean, in my view, a lot of the civil service thinking on TB is based in the 1950s. I mean, it's still not moved on into the modern scientific environment.

So we need to get a few more people in there who really understand the modern science and are able to apply the modern techniques in a much better way.

We've done all this already with another mycobacterial disease called Mycobacterium avium paratuberculosis, it's called Johne's disease.

It's very similar to TB in a lot of ways, but the way we manage that out is by detecting antibody and then culling on the basis of risk, how many times the animal's been antibody positive. And it's very efficient.

You can get the levels down to 1% or less of the herd, at which point you can go in with a test and cull and just cull the remaining positive animals.

So we've done it all before, but for regulatory and international trade reasons, it's much more difficult to do that with TB.

If anyone does pick you up on that first point there of come talk to you, where would be the right place to do that? Would it be through the MV Diagnostic site or is there any more useful channels for finding?

Well, I’m down in England and Wales a lot, so let me come and speak to you! Farmers, vets, politicians whatever.

And because TB apparently isn't an issue in Scotland, we're based in Edinburgh, I think I've traveled to them quite happily. Particularly in Wales, we've got a big project going on in Pembrokeshire, which is looking at 15 farms which have had chronic TB problems over the last 15, 20 years.

We're not using Enferplex much down there yet, but we're using the RiskRate system which looks at the skin test results much more sensitively and identifies high risk animals, again on a traffic light type system.

But that project is going to last for two, maybe three years. Hopefully it’ll get refunded.

And I think as we gain more experience with that and more farmer buy-in and vet buy-in, I think that will be a, you know, a very useful project to come down and have a look at.

For anyone listening to this, maybe not in a policy level, but just the public. Should they be worried about the state of farms, farming, farmers, cattle?

Well, in relation to the risks that farms with TB pose to them as public and individuals, I don't think you really need to worry about that at all.

The mechanisms for treating milk and meat are sufficient to mean that the transmission of M. bovis to humans in the UK is absolutely tiny.

However, if you were a Mexican citizen, then you should be very worried because roughly half of the TB in humans in Mexico is due to M. bovis because they don't pasteurize half the milk and that's why we're involved over there.

In terms of effects on the farmers, yeah, I think mentally and financially, TB is a huge, absolutely huge stressor for farmers, particularly in the high-risk areas, but also in the edge or wherever it's spreading, or even in parts of the low-risk area when outbreaks are appearing and loads of restrictions are being put in on.

I think farmers around the country, wherever they are, whichever type of risk area you're in, are really concerned about TB.

It's the biggest disease problem which DEFRA hasn't really solved effectively.

And I think that is sort of pressure that should be put on whatever Government there is to actually get their act together and really make some progress on this disease.

There is an official plan to eradicate it, by which they don't mean get rid of it altogether, but get the whole country officially TB free by 2038.

But our calculations suggest that is just absolutely impossible. And 2083 might be a bit more realistic, but even then we don't think that's going to happen.

And it's because the residual infection that's being left is of a type which the current Official tests can't detect and somebody has got to get their head around that and start looking at the antibody responses, dealing with animals on that basis, but in a way that's sustainable for the farmers.

This has all been fascinating. Thank you so much for talking with us today and I look forward to seeing how this translates into a change in agricultural policy locally, maybe even nationally sometime soon.

It's been a pleasure speaking to you as well, Will. My take home message is that bTB can be eradicated….truly eradicated….but not in the way DEFRA are trying to do it. Give my team a square go at it, using our tests and strategy and involving farmers in a way that’s sustainable for their businesses and working with their private vets….job done! 

It won’t be easy, it won’t be quick, but we will get there. Trust me!