Monday, May 30, 2005

Cattle / Cattle : A Critical Analysis.

In the same edition of 'Nature' as the work by the Oxford team, (see post below) is a critical analysis in rather more readable form by Mark Woolhouse of the University of Edinburgh's Centre for Infectious Diseases, who concludes;

" In a further analysis, (of Spatial multiple logistic regression), Gilbert et al, found that cattle movements played a more obvious role outside the 'core' areas where bTb is already established, implying that movements are more important for the spread of disease than for its persistence. Indeed there are regions where bTb occurs only sporadically despite regular imports of cattle from infected areas. Some other necessary factor seems to be missing - which brings the discussion round to wildlife reservoirs and especially the badger".

At the risk of being disrespectful, we would also flag up the another apparently 'missing factor', referred to and reported by Matthew 4 in the post below. That is the collective brain cell of the Oxford team in totally ignoring the obvious.
A point so eloquently picked up by Mark Woolhouse who continues:

"Badgers are known to carry bTb, but Gilbert and colleague's study is equivocal (that's a a polite way of saying dubious, of double meaning, questionable etc.) on the animal's role in the epidemiology of the disease in British cattle. Proximity to known badger locations does appear in their analysis - but it is not prominent".

"To better understand the role of badgers in the persistence of bTb, we need to turn to experimental studies such as the Four Counties trial in Ireland, the results of which were published this year. (and Offaly, and Thornbury, Steeple Leez and Hartland)

Mark Woolhouse concludes that the Four County trial with a reduction of up to 95 percent in cattle Tb relative to its reference areas "is the clearest demonstration to date of a link between badgers and bovine tb in cattle. Given the incidence of bovine tb in Britain is expected to remain high, or even increase further, the sooner that effective control measures are introduced, the better. "

We agree. But would add a caution; that any attempt to clamp down on cattle movements by either pre / post movement testing must be for disease control reasons and not political expediency, and run concurrent to and simultaneous with the clearance of bTb from all known wildlife reservoirs.

Infectious bacteria do not respond to political bullying - they just spread..................

7 comments:

Anonymous said...

This work looks like it was 'done in a hurry'. Commissioned after FMD, and the input data sketchy, unknown or 'assumed' in some cases. Some cattle on restocked farms which moved from the south into Cumbria did move with tb infection on board. The point here is that it did not establish, as the report says. You have already pointed out the weaknesses of pre-movement testing alone, but a post movement test on these herds picked up the problem before it amplified. Again the report picks up on this, but does not question it. (lack of persistence)
You are correct to point out that although the headline indicated cattle / cattle, the work could also be interpreted as an indication of a parallel and persistent infection source in core areas which the Oxford team missed.

Anonymous said...

There would be no need for the movement controls if the problem in the bad areas was sorted.

Matthew said...

Exactly.
Our worry is that Defra will do one ahead of the other - that is completely hamstring cattle movement, and do absolutely nothing about the core problem in the wildlife, which as we've seen will expand and expand and....

Frank said...

A more useful study, would have been to examine how many herds who had no 'ON' movements registered on CTS database were restricted with bTb. This site has mentioned a few already and there must be more.

Matthew said...

Matthew 2 is on the case!
When we hear back from BCMS we'll post it. Meanwhile any farmers logging on who qualify ...

Anonymous said...

The important point is 'there are regions where bTb occurs only sporadically despite regular imports of cattle from infected areas'. If cattle to cattle spread was common this would not happen. But the disease is found by testing the cattle and thats it. Without the constant re-infection from a source outside the herd it does not persist.

Matthew said...

The editors of this site agree. Dr. John Gallagher agrees.
David Denny, and 405 other members of the RCVS agree.
SVS vets agree.
Parliamentary Questions confirm.
Our NZ contributer is aghast.
In fact most of the thinking world looks on in amazemment, at the politically contrived antics of the 'Flat Earth' society, aided and abetted by John Bourne and Co. in leaving to fester, a source of tuberculosis in one of our best loved wildlife species.
But while politically motivated vets are being 'equivocal' in their comments, and others challenge the accuracy of the skin test, Defra's Chief Vet is happy to do - nothing.