Last year in answer to the exponential rise in Tb cattle slaughterings, our Ben - bless him he's back with the poisoned chalice again after the election - set up a couple of committees. One was the Pre-Movement testing committee, which had a remit from Defra to discuss - just that, 'Pre Movement Testing'.. Not whether pre movement testing worked or was effective as a disease control method - just do it. Sounds good though doesn't it? And cost didn't enter because the farmer was going to pay. Generously, our Ben agreed to pay for the tuberculin. That's 25p against the farmer's share of about £25 for the vet - twice.
We've told you several times on this blog, about severe cattle measures applied both in Ireland and the UK which have made not a dent in cattle Tb, if the reservoir in wildlife was not tackled simultaneously. And we (as ever) are most grateful to Captain Ben for the answers to Parliamentary Questions (archived) which confirm that "in the absence of a wildlife reservoir, regular testing (of cattle) and slaughter (of reactors) is all that is necessary".
But reporting to Defra this week the Pre Movement Testing Group, having cogitated, pondered and meditated their extraordinarily restrictive remit, expect Defra to implement some type of pre movement test next year.
Speaking at the launch of Defra's Animal Health 2004 report (not doing too well at that are they - cattle slaughterings up 30%? Not very well at all.) Chief Veterinary Officer Debbie Reynolds said "Tb is a regional problem and we need to keep clean areas clean. This depends on rigourous implementation of cattle controls and pre-movement testing would play a fundamental part in this".
That's easy then. Rigourous cattle controls and all the tb just - goes away? Errr no. It does not, as Ireland found in the 'Downie' era and certain DVM's found to their cost in the UK. (see posts and comments below)
But pre movement testing can be downright dangerous as farmers purchasing cattle so tested will assume, quite wrongly that they are 'clear' of tb. The skin test is not at fault, its implementation in this situation, combined with the expected industry 'exclusions' is.
We will explain;
1. The skin test has a latency of 30 - 50 days from exposure to m.bovis to the provoking of a skin reaction from that exposure.
2. The industry is likely to want at least an 8 week window from a pre movement test to selling, in which to arrange sales.
3. The industry is likely to ask for exemption for calves under 8 weeks, and slaughter stock which is probably OK, but also for store animals up to 15, 18 or even 20 months - which is risky.
4. The skin test is an 'excellent herd test' - John Bourne says so, so it must be. But on a single animal tested just once it's accuracy falls to under 70%.
So what have we got so far? 1 + 2 + 3 + 4 = a whole lot of 'missed' potential reactors.
The latency and 8 week exemption window add up to 4 months. That's 30 percent of reactors missed on an annual testing regime. Store animals exempt up to some 'teenage' cut off point, even though SVS tell us that 50 percent of reactors are in such young stock, would leave only a third of the animals tested reasonably covered by any pre movement test - and that compromised by the 'single animal' factor. Under conditions described above, we reckon about 60 percent of potential reactors would be missed.
But from Defra's Page Street disease control centre - it sounds good, and of course Defra isn't planning to pay.