Tuesday, March 28, 2006

Tb spillover - sheep.

That can't be right. In 1997, John Bourne told a questioner on the subject that sheep do not get Tb. He's quite wrong on that - as with many other pronouncements, but we won't dwell on that - and the disease has been found in New Zealand sheep. And now in Worcestershire. But in which sheep, lamb or ewe, and from where is not yet clear.

After FMD, body piercing for sheep became mandatory, with a tag inserted in very small fragile ears at birth, and then every time it changed home. So when it finally made it to the abattoir, the last tag it carried should have enabled Defra to trace it from the unique holding number on its eartag. Immediately. And certainly before any disease spread. A mound of movement forms accompany all consignments of sheep and the top copies are lodged with Trading standards departments of the local councils. All done in the name of tracebility. Simple. Well that's the theory.

So why are Worcs. SVS contacting consignees of the almost 20 batches of sheep sold through Worcester cattle market three months ago, trying to identify the owner of just one sheep which turned up at an abattoir with 'something' looking a tad suspicious, so that a test can arranged for any cattle they may have?

Duty vets at the abattoir sent this 'something' off to VLA, presumably labelled 'something odd from a Worcester sheep' but somewhere along the line the sheep's identity was - errr lost. We'll give them the benefit of the doubt in this case and assume it actually was from a sheep, and that they originally did label its identity. (Remember the 3 year fiasco into sheep BSE that turned out to be experiments on cattle brains? We haven't.) Anyway, the sample was positive for m.bovis and now the fun and games start as a notifiable zoonosis has to be traced to source.

A couple of points here. Firstly the sheep identity tracking system, involving a new ear ring every time it blinks and a mound of paper work, has not exactly covered itself in glory. And secondly, when John Bourne noted in his report to Bern 2004 that 76 percent of badgers culled in Hereford / Worcs area during the last few years of the Interim strategy were confirmed with clinical tuberculosis, that this should spill into anything else which had the misfortune to fall over it should not come as any great surprise to anyone. Even if the good Professor assured his audience during that question and answer session that "Sheep do not get Tb".

Then again the sample could have been from a cow.......


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Anonymous said...

Re: Ear tags (aka traceability)
Are sheep the same as cattle?
ie. Their heads are the first things to be chopped off, as soon as they get to the abbatoir? ... and the carcass is processed & tested devoid of individual ID.

Matthew said...

Anon 5.49

With cattle there is a link between cattle identity and the number on the kill line, thus weight info, carcass grading and disease info are tracked back to the eartag number.
With sheep consigned direct ex farm, this happens too. But it is our understanding that the sheep in this instance was sold ex market, and its individual identity weight or grading was not transferred to anyone.
Defra then did a round-robin of owners of all sheep sold that day and asked 'have you got cattle as well, and if so please test them'.