Tuesday, July 04, 2006

Latest Tb figures

Defra have published their latest Tb figures for the 4 months up to April. Unusually, they add the following comment:

"There has been a substantial reduction in the number of new TB incidents in January - April 2006 compared to the same period in 2005. The provisional statistics presented here indicate that this reduction is 27%, although this figure will reduce as further test results are input by AHDOs. It is too early to draw any conclusions about whether the decrease is a temporary or a more sustained reduction and further analysis is needed to identify the reasons for the fall. However, it is likely to be caused by a complex combination of factors. There is no evidence at the moment that the switch in tuberculin supply has caused this reduction although further analysis is required before this can be confirmed."


(Sorry readers, the links go to the 'latest' figures and not the ones we are discussing. The Defra comment is scanned in so stands.)

As you can see, Defra's 'reduction' figure is 27 per cent over the same period last year.

But in our post :
when March's figures were published, the drop was over 29 per cent.
(February figures, we were unable to locate, but January's were still onwards and upwards)
So Defra's 'decrease' of 2.5 percent, (that reduction of 27%, which they expect to fall further) we calculate as an increase in tb incidents on March's (3 month average) vertigo inducing fall.

Without being churlish and without wantinf to look gifthorses in the mouth, we report what we see, and hear. And vets are telling us that during late January / February, some practises went through several weeks of cattle testing "without seeing a single lump". SVS officers confirm this. But not in all counties. In Staffs/Derbyshire, Devon and Cornwall cases were in free fall, with some counties recording drops of over 50 percent, while others (Cheshire and Hereford/ Worcs) reported business as usual.

In the good old days, a few avian reactions could usually be expected, just "to show the vet has actually done the test", as our previous vet used to say. But no lumps at all? Not one? Nothing to record? In herds smack in the middle of large area tb breakdowns? But this has not been sustained, (the vets say) and measurable reactions are again being seen, and measured, and cattle slaughtered.

We also note from Defra's April round up, that slaughterhouse cases are rising at an alarming rate, showing 242 suspected and sent for culture, compared with 109 in the same period last year. Most of these cattle have been regularly tested, yet the skin test has failed to record a 'reaction'. While this is a known rare exception to the reliable intradermal skin test, in that if the animal's immune system is so overwhelmed by disease, there is no 'immune response' to flag up, the numbers coming forward now should ring some warning bells as to why no response has been seen. An extra 288 herds are currently under Tb restriction in April than in March 2006.

Further notes on the imported Lelystad tuberculin, to which Defra refer in their explanation:
*It was first imported a year ago, in June 2005.
*It would have been distributed in batches as required by vets, as the UK product ran out. The batches would not have been used in all counties /areas at the same time.
*The bovine part contains 30,000 units compared with 25,000 in the formally used UK serum, (or should do) and initially vets were saying that it was 'more senstive' and flagging up more inconclusive reactors.
*It's original base is the same as the UK product, m.bovis strain AN5 - or was - but whether it has been refined to seek indigenous strains of tb, we have yet to find out.
*It does not have a 'cross border' pan-EU license, and is used under a different section EU license by VMD (Veterinary Medicines Directorate) for the UK's 'short term problems'.
*We understand that VMD have accepted the product on 'manufacturers' data' only.

Vets are telling us that Tb tests are now back to their depressing 'normal'. And from that we assume heaps of dead cattle and the intradermal skin test - behaving as it should.

No comments: