Monday, November 12, 2007

Red Herring?

Researchers at the Institute of Animal Health's Compton laboratory have been awarded a commendation described as "Outstanding Contribution by an Academic or Scientific Institution", at the Animal Health Awards, for their work in developing a diagnostic test for cattle which have been "vaccinated against bovine tb".

But is the vaccination of cattle for Tb a viable solution to a problem which is endemic in wildlife?

The test as Farmers Weekly reports, is said to differentiate between cattle 'vaccinated against bTb' and those infected with the disease.

TB is on the increase in the UK cattle herd, costing more than £90m a year and vaccination is under "active consideration", say the Institute of Animal Health. This would involve using the same vaccination used to immunise humans against the disease, BCG.

However, BCG-vaccinated cattle test positive using the tuberculin skin test. Before a bovine TB vaccination strategy can be implemented, a method of distinguishing between vaccinated and infected animals has to be established.
With all due respect to the researchers at Compton, Tb vaccine has been "under consideration" for as many years as I can remember. On other forums, vaccination of cattle for various disease is under active discussion. Vaccination is used worldwide for some notifiable dieases as an anti- marketing tool, and should countries adopt it, their produce is automatically disqualified from entry into other trading blocs.

The current discussions centre on the midge bourne BTV (bluetongue virus) which had not been reported in the UK before this year. We therefore qualified for "BTV free status zoning". And for years this country excluded exports of breeding stock, embryos, semen etc from parts of the world whose geographic location encouraged BTV midges and whose stock were vaccinated. Vaccination across Europe is now on the cards, but as a compulsory trading bloc, which will probably mean in due course that BTV is "de-listed" from its current notifiable status.

FMD (Foot and Mouth Disease) has similar trading restrictions under OIE and EU trading rules, and the inevitable two tier markets develop between countries with endemic disease and vaccination policies, and those without either.

So why should a cattle Tb vaccine even be considered other than as a reserach project? It's use is strictly limited, and its disadvantages many.

We asked several epidemiologists and also industry leaders who have connections with export markets, and the replies were unequivocal. Unworkable, unnecessary and commercial suicide.

..I doubt very much that this is the prelude to a vaccination programme for cattle. For a start there is currently no effective vaccine for cattle and I rather doubt there will be. Secondly the idea of vaccinating cattle in the face of massive challenge in the field from infected badgers is daft. Yes, vaccination against brucellosis was successful but there was no wildlife reservoir to break down resistance (and the S19 vaccine was a good one) ...
So, if cattle are the only candidate and there is no wildlife reservoir to break down resistance to a vaccine, it would work. But vaccination minimises an immune response to bacterial challenge: it does not stop it altogether. Thus cattle vaccination in the face of exposure from disease endemic elsewhere would be pointless.

And on trade, as we have said an immediate ban would come from the EU - that's if any pharmaceutical company decided with such a limited market, to produce a vaccine at all. Only countries with an uncontrolled wildlife reservoir of Tb would be remotely interested. Manufacturers are demanding a 100 million dose underwrite across the EU for BTV-8 vaccine, before they'll think of applying for market authorisation, so how viable is a Tb vaccine for the West of GB and Wales?

Another quote on this subject:

If we vaccinated cattle there would be an immediate trade embargo with the rest of the EEC. In fact I reckon they are almost waiting for it! Vaccination for badgers is a long term approach which Ireland are currently trialling (or will very soon be ). But no vaccine can cope with the current weight of infection in the badger population at the moment and strategic culling will be an essential pre requisite.
Now that is interesting. We have expressed support for vaccination for badgers, if only to protect them from their infected sett mates, but vaccination + disease = death, was always the mantra. And it would appear that for any vaccination programme to succeed, the candidate must be uninfected at the time of vaccination. So how would the Badger Trust sell the concept of a badger cull as a prerequisite of a badger vaccination programme to its members?

But we digress. The test which IAH Compton have developed, relies on the information that immune cells of cattle previously infected with TB contain more of the protein gamma interferon than those vaccinated for TB. They describe the test as able to provide:

.. same day, on farm diagnosis of TB and identify which are vaccinated and which are infected.
That sounds suspiciously like PCR. And if it is, good. Especially if it is rt-PCR and we're not still lagging 6 years behind the plot on this stunning technology. Next step, use it to identify bTb in the environment and that is progress.

The researchers at Compton comment: "The ultimate benefit of accurate diagnosis of disease, in the light of vaccination, would be a reduction in the incidence of TB with associated improvements in animal health and welfare, and the livelihood of farmers."

Don't think so. Vaccination in the face of an endemically infected wildlife, would be ineffective and vaccination per se would destroy the livlihoods of all cattle producers, by creating a two tier market - or even no market, for their goods. Archaic, that may seem but it is the reality of global trading.

And what about the cats? And llamas? And free range pigs? ...


Anonymous said...

I'm curious as to the figures for meat imports/exports.

What would the supply situation if all imports and exports of cattle and cattle products were banned?

It would be environmentally sound to reduce 'food miles' in this way, and if there were a shortfall we could always eat fish - red herrings of course!

Matthew said...

Anon: 8.53

"What would the supply situation if all imports and exports of cattle and cattle products were banned?"

Quite simply, our population would starve.

We have over 60 million people in the UK, and have steadily increased the balance of payments deficit on imported food.
We are now very reliant on imports.

We export top end value products like Stilton cheese and bottom end aged cattle which for some reason continental Europe appear to favour. The difference in price on old cow prices with no carcass export, (as now with FMD restrictions) is about £200 / head.

So a ban on exports would be a death blow to the cattle industry -as we found during BSE. This filters right down through commodity products like dried milk crumb, and gelatin which finds its way into confectionary on the continent, and pharmaceutical coatings.
The production processes which use all this type of by product, including skins, leather etc, have been exported long ago. So the 5th quarter 'bits' now have to be exported to join them. Either that or incinerated at great cost and no value.

Current UK government thinking is to let the global retailers provide. Their trust in that supply may be misplaced - but that's a whole new blog.

And Russian factory ships are hoovering up the herrings - red or otherwise!

Anonymous said...

"Quite simply, our population would starve."
Not so. Meat, and especially beef (even cattle milk) is not essential in great quantities for a healthy population, indeed we'd be healthier eating less meat - I'm not a veggie, btw. It is the carbohydrate staples (wheat, rice, potatoes etc ) that govern whether we starve or not, and one can argue that growing more food crops and fewer livestock (for home consumption, as in the past) is more efficient anyway and strategically more sensible.

An effective strategy for dealing with this problem has to be multi-faceted and prepared to break the moulds of (quite recently) established farming practice - as every other industry has had to do. Vaccines should be part of the approach, as is the need to reassess the wisdom of import/export of meat in general and the current market/business models and concepts in agriculture. There are alternatives; after all, unlike cattle and badgers, we have the capacity for creative problem-solving, if we are brave enough to do so. Change will be forced on us anyway, we can choose to be proactive or pessimistically reactive - the former is the harder, but happier, route.

Matthew said...

You're right anon: 8.38, when you say we "have the capacity for creative problem solving".
That would be 'we' as in the human race?

The governor on food production is a) space to grow it and b)water. Supply should be driven by demand for the product. But increasingly the demand for food of any sort, crops or animal protein is dictated by governments, and supply is limited by the two things I've mentioned above, combined with population increase + the commitment to bio fuels and industrial crops.

Disease status will always be used as a trading tool, and if reports of Cyprus's FMD problems v. imports of Brazilian/ S. A beef are correct, with good reason. With BTV, it is imperative to achieve reasonable success with the disesae (and to avoid trading implications) that vaccination occurs across the EU trading area, and extends into N. America.

Vaccines will / are playing a more important role, but in the context of TB are not necessary for cattle, if the wildlife reservoir of the disease is controlled. I don't believe that continental Europe vaccinated it's population against rabies, but left feral sources?

We would support vaccinating badgers to try and control this disease before it becomes completely endemic in them, but from a comment on the post above, that too requires a cull of infected populations as a pre - requisite.

With a single species disease problem, it is possible to vaccinate out of trouble. But b.tuberculosis is multi species, with zoonotic implications, and a maintenance reservoir in badgers.

The 'non-strategy' coming from the 'creative problem solvers' - in this case government, amounts to an annual cull of sentinels.