Andrew Proud, BVSc, DVSM, MRCVS writes:
It is clear that the Badger Trust thinks we should all be horrified by the figures [....] but any informed veterinary surgeon who pauses to think, will respond otherwise. Twelve percent of new herd incidents were disclosed by a combination of routine meat inspection, and tracing from other herd incidents: my first response is so what?
My second is .. only twelve per cent?
When I read on (from our Trevor's outraged outpourings) and found that "the situation in three and four year parishes is even more serious, with 18 percent of new incidents..." detected at MHO inspection, I responded "No more than 18 percent? What a striking vindication of Government policy!"
This represents no inadequacy in the tuberculin test; clearly, the Badger Trust does not know that in three and four year testing areas, only adult breeding animals are (skin) tested. Cattle being reared for slaughter are screened for Tb only by meat inspection unless they are in a herd in which reactors have been disclosed in breeding animals.
But my third reaction, following some crude arithmetic, is to observe that the Badger Trust has, unwittingly, produced powerful evidence against one of its favourite theses. If the 87 new herd incidents detected at meat inspection, and the 33 detected following tracing from reactor herds represent 12 percent, then the latter category accounts for only 3.3 percent of new incidents.
What the Badger Trust does not seem to understand is that tracing of animals moved off is a key part of the investigation of all herd incidents. A little allowance must be made for the recording periods, but essentially these figures suggest that tracing from the 96 percent of herds where reactors were found not to have been purchased in animals, disclosed reactors in no more than five percent of herds to which these cattle had been moved.
Even ignoring the fact that in most cases where the traced animals react, all other animals in the recipient herd test clear and continue to do so. This is powerful evidence that the spread of bovine tuberculosis by cattle movement is not significant."
The Badger Trust seem to have got in a pretty froth about these figures, but by disecting them in rather more detail and with an overview of the testing / surveillance situation as it exists, Andrew Proud's reaction (and ours) is "Is that all?"