Badger Friday – FluffySciences Plays Shelter Part Four

It’s time for another Shelter episode, where our cuddly badger friends struggle through a forest fire. Mmmm, crispy badger .  . .

 

 

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Badger Fortnight – The Solution?

But Jill, a fortnight is two weeks not three.

Shut up, that’s what.

 

This week I want to discuss two main studies – the first by Torgerson and Torgerson (2010) and the second a 2008 in the Veterinary Record. We have talked about why the disease is a problem, why the cull hasn’t worked, so the question becomes: What now?

The Torgersons start off with the claim that Defra’s continual fight against bovine tuberculosis is a misplaced use of public resources and we should just chill on the whole thing.

What’s their reasoning?

They start by going into the details of the few cases Britain has had of humans developing bovine TB. Between 1993 and 2003 they note that there were only 315 human cases of Bovine TB and only 14 of those were in people born after 1960 and were British Nationals.

Molecular investigation found that only 10 of the 25 spoligotypes of the bovine TB present in infected humans were actually present in contemporary UK cattle. They describe two cases from Gloucestershire where on-farm transmission from cattle to humans was likely. A third case in Cornwall where a veterinary nurse was infected was considered to have more likely come from her dog. (Interestingly, cats and ferrets are also known vectors of bovine TB and I know I’ve had more cats sneeze into my mouth than badgers, and I’ve probably worked with more badgers than most . . . Ragg et al, 1995). The more infamous six cases which sprouted up in Birmingham featured a UK national with a ‘history’ of drinking unpasteurised milk at home and abroad. And four of these six patients were likely immunocompromised.

Historically, Bovine TB did not come from cattle-to-human airborne transmission, but through milk. And as we pasteurise all our milk nowadays, the Torgersons conclude this risk is now negligible. I want to take a  moment to say that I have anecdotally observed a strange counter culture of people who love unpasteurised milk (in fact it is a topic of conversation that seems to leap up whenever I tell people I work with dairy cows). Unpasteurised milk drinkers are a little like foodies who insist you’re using the wrong kind of spice and I’m often asked if I drink unpasteurised milk – once I was fairly certain my optician wouldn’t sell me glasses until I converted to unpasteurised, but I digress – seeing as milk makes me ill at the best of times, the thought of drinking milk unpasteurised ‘gies me the boak’ as we say in Glasgow. Unpasteurised cheese is another matter . . .

Where was I?

Oh yes. The end conclusion of the Torgersons (are they brothers, or did they just think they would be epic scientific partners?) paper is that they believe our hypervigilant position on bovine tuberculosis in the UK is a waste of public resources. They don’t see a reason for spending so much money on a disease which so rarely affects humans.

The Veterinary Record article doesn’t quite agree, but following the randomised badger culling trial in 2007, they too realised that badger culling was not the way forward (yes we were having this discussion seven years ago) . In the article they propose:

  • More frequent testing of cattle using combined tests to detect active disease.
  • Research on post-movement cattle testing.
  • Research into a vaccine for cattle and badgers and immediate usage as soon as its developed.
  • Research into the disease.
  • Get farmers to understand the need for greater on-farm biosecurity.

 

Really, this article back in 2008, was proposing the oldest solution: identify, research, prevent.

So why aren’t we there yet? Well seven years in research and pharmaceuticals is not a lot of time. Defra’s old website has a page on cattle vaccinations and it points out that the EU prohibits vaccinating cattle against TB (because being vaccinated makes some cattle test positive for TB, ergo herds cannot be declared TB free because the vaccine may be masking infection. The EU prohibits trade of TB infected cattle).

The BCG vaccination is not brilliantly effective in cattle, so we either need a better vaccine, or to use that vaccine to protect some of the herd and reduce the number of cattle we need to cull. But it’s expensive and hampers trade with the EU.

This post will be published a week after I voted in the European elections. I can tell you I didn’t vote for UKIP or anything like that, I’m a good left winger who lives in Scotland, you get three guesses on my vote and the first two don’t count, but the role of the EU legislation in our Bovine TB problem can’t be ignored. The Farmers Guardian reports that the European Commission doesn’t expect a vaccine to be around until 2023.

There is definitely something to be said for better biosecurity measures on farms. There are some brilliant farmers, and there are some poorer farmers, and coughs and sneezes spread diseases. We have known this since Koch came up with his postulates. The good farmers resent being told what they already know and the poor farmers resent being told to do better. We come back to my old hobby horse – how do you communicate that science to a varied audience?

And finally the TB test – if we can find a test that can discriminate between infected, active infections, vaccinated and TB free, and do so reliably, we can still trade with the EU. These things all take time, money, and a little bit of luck.

We won’t find the solution to the bovine TB problem on a welfare scientists hobby blog. The answer is not badger culling. It’s not, as the Torgersons suggest, just letting the disease roam free. If we want to trade with the EU we need to deal with it.

 

Just wait till Defra finds out cats transmit TB . . .

 

Badger Friday! Shelter Part Two

I have a host of goodies for you this Fluffy Friday Badger Friday.

We have another Behind the Scenes blog post in our MOOC – remember to sign up for free here!

The Animal Welfare Hub has a new app for assessing horse grimaces and assessing pain in horses – join the Animal Welfare Hub here.

And there’s another Shelter episode. See you next week!

 

Badger Fortnight: TB

For the next couple of weeks I am dedicating Fluffy Sciences to the noble badger. Why, you ask? Well because the other day I ended up reading Defra’s independent panel report on the UK badger cull and the whole thing made me grumpy.

As someone who works both in animal welfare and in the agricultural industry, with a soft spot in my heart for cattle, I have heard a lot about Bovine TB and badgers in the past few years. I’m going to spend the next few posts telling that story, and where better to start but with Bovine TB itself? After all, without this insidious disease, badgers would be fondly remembered from the Animals of Farthing Wood, or the noble lords in Redwall. Instead they’re synonymous with James May and the word ‘cull’. An interesting turn of events.

So. Bovine TB, the villain in our tale. What are you?

When you’re reading or watching some trashy historical drama and the heroine coughs into her handkerchief, staining it gently with blood, you know she’s not long for this world. Satine, I’m looking at you. That disease is Tuberculosis, or consumption, if you’re still feeling gothic.

It’s a famous disease in science because of Robert Koch, who formulated the well known Koch Postulates, a set of rules to identify the causative pathogen of disease. While still very much remembered, they have been supplanted with other rules better capable of identifying things like parasites and even non-active infections.

  1. The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms.
  2. The microorganism must be isolated from a diseased organism and grown in pure culture.
  3. The cultured microorganism should cause disease when introduced into a healthy organism.
  4. The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.

Koch identified the agent of TB, Mycobacterium tuberculosis, and he received a Nobel Prize for his troubles. Interestingly enough, he received his prize even though for years he’d been convinced that Bovine TB and human TB were not similar, and it was his results that forced him to reevaluate this position.

Fast forward a couple of hundred years and this disease which, at one point, was causing 25% of the deaths in the world was now on the run. Almost all Brits have a peculiar little scar on their left upper arm, the BCG (Bacillus Calmette–Guérin) scar. I have had some Americans quiz me about it and it turns out Americans never had a mass BCG immunisation. You guys missed out on some quality arm punching in school.

If you’ll think back to your school days, you’ll remember a thirteen year old you suspiciously watching a nurse inject you just under the skin on your arm. A few days later they inspect the mark and then decree whether or not you will receive the BCG  vaccination.

It’s often said that if you react to the skin test it means you are already immune to TB, but this isn’t quite true. It means that your body reacted to the TB (in a healthy person this means they got a red blister bigger than 15mm in diameter) which may be because you have a previous vaccination or because your body already has an active TB infection.

Regardless, those who escaped the skin blister get called back for the vaccine. The injection goes between the skin (large ulcerated BCG marks are often an indication of an accidental subcutaneous BCG). As vaccinations go, its quite painful (I remember it being more uncomfortable than three successive rabies vaccinations) and not helped by the traditional teenage sport of punching people in the vaccination spot.

Large keloid scars can form, although latterdays these scars are not so prominent due to improved techniques. I did try to take a picture of mine for you but mine is tiny and barely shows up. The mass BCG vaccination program has recently been suspended in the UK as the disease is now considered very rare. Only at-risk groups are vaccinated now.

 

 

Despite the fact that antibiotic resistant TB is on the rise (and that this is frightening) in the UK we manage the disease in humans fairly well. Other countries, such as India, haven’t been as successful as we have in using the BCG vaccinations – and it seems to be that the disease is harder to manage in equatorial regions, for reasons I’ll not speculate about here.

However Bovine TB is caused by the very similar pathogen Mycobacterium bovis, which can cause TB in humans if they drink the unpasteurised milk of an infected animal, or if they inhale aerosol droplets (e.g. cough, spits and sneezes) of a cow.

Being someone who has been coughed, spat and sneezed on by various cows, I’m not particularly worried about this myself, even though Bovine TB can cross the species barrier, TB itself rarely becomes an active infection in the person who has it.

So why do we worry about it in cows? Well we have a strange double standard here. When we test cows, we use a skin test very similar to the one we use in humans. And, like in some humans, there is a reaction to this skin test.

And those cows which react to the skin test must be culled. You’ll remember that only a few paragraphs higher up I mentioned that a reaction doesn’t mean immunity, it just means the animal is reactive. It doesn’t mean there is an active infection, it just means the animal is reactive. Yet we cull those animals specifically to prevent the spread of the disease.

You can sell the meat of the culled animal if you want, because cooking meat kills the Mycobacterium, but you cannot tolerate a TB cow on your farm.

And this isn’t considering false negatives and false positives in the test, as no diagnostic test is perfect.

The fear is that Bovine TB will either infect or reactivate a latent TB infection in people. Because of this fear we cull any cows infected with TB. Defra have also produced what they optimistically call a leaflet (at 21 pages) of ‘What happens if TB is identified in your herd’ which remind me of those Simpsons leaflets ‘So You’ve Ruined Your Life’.

 

The moment a cow reacts to the skin test the herd is classed as suspect and moving cattle out of and into the herd is restricted. Any reacting animals must be isolated from non-reacting animals and culled. The milk is to be dumped.

The reactor cows are tested post mortem, but even if your reactors show no clinical signs of TB, your herd status is still Officially TB Free Suspended. You will need a clear test (or two clear tests if TB was found in your reacting cows) for your Official TB Free status to be reinstated.

If you have a TB farm you also have restrictions on where you can spread your slurry and on what you can do if your cows die on farm.

It is, in short, a huge hassle, resulting in cow deaths and loss of farm profits, as well as posing a health risk to humans.

 

It is with these facts that the government turned its attention to badgers, and that, dear readers, we will discuss next week.