Friday, August 18, 2006

More on 'Going Dutch'.

A surf around the website of the makers of ID Lelystad tuberculin, imported since June 2005 as a 'stopgap' measure when VLA's production facility at Weybridge encountered problems, turned up some interesting kinks in the does-it-work v. doesn't-it-work conundrum.

As you will see from our posts below, the CVO is blaming her vets, both LVI's and SVS for 'testing procedures' which she says are not to the book. That these 'procedures' include such offences as not measuring the skin on jab day or measuring only one site, is included in the critism. I don't think that the basal skin measurement is going to alter too much in 72 hours, and most vets check it again when measuring anyway, so how that invalidates the test, I fail to see, but let that pass. Positioning the needle to deliver the antigen sub cutaneously instead of intradermally may also skew results - but that has not just happened in the last few months.

She has also studiously ignored the 2mm 'tightening' up to the test interpretation chart on oedemous reactions, introduced by her Department in February and certainly she has completely buried the comment in her report, relating to that 2mm difference; that it will "mean 24 per cent of incidents are missed, or detected later".

But on the CIDC Lelystad website, a comment on antigen sensitivety caught our eye - or the eagle eye of our Cornish contributer Matthew 1, to be precise. See Tuberculin Principle

The potency /level of both avian and bovine antigen in the Weybridge produced product was 2,500 iu/dose. And although both bovine antigens originate from UK supplied AN5 strain, the product which VLA imported from CIDC Lelystad was 2500 iu/dose on the avian antigen, but 3000 iu/dose on the bovine. But that isn't the whole story.

According to the Dutch website;

" In eradication programmes (when the prevalence of TBC infected cattle is significant) the use of Bovine Tuberculin PPD 2000 is recommended. In herds free of TBC, the use of Bovine Tuberculin 5000 is recommended, to increase the sensitivity of the test."

So ID Lelystad advise increasing the potency of bovine antigen for more sensitivity. But has that sensitivity at whatever level, been developed to find Dutch bTb strains, or the UK's?

More on the Dutch product at their : page: Tuberculin

On another part of the Dutch Animal Health site is a comment that using just the intradermal skin test and slaughter of reacters, the Netherlands achieved 'official bTb free status' some years ago, and as such, can now just undertake slaughterhouse surveillance only. The report was 2000, but said that Holland now did no routine testing unless a reactor is found at slaughter, and then skin tests are done on the host herd and any contiguous herds, backed up with PCR for speedy results. Well, well, well.

Amazing what the intradermal skin test can achieve, "in the absence of a wildlife reservoir". And not too much sympathy or patience with our troubles I suspect.

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