email received 17th Augustv 2011 from Dr Ruth Watkins
Thanks for updating on Hallmark Boxster and linking to his page.
Though the false positive might be related to the mixing of blood from 2 animals (the other having been infected with bovine TB) or the contamination with Staph aureus by the non-sterile mixing (Staph aureus protein is used to give a positive control in the test) it is most likely that it is the non-repeatability of low positives in this test, which is flawed for several reasons - as well as being demanding to do, as Prof Torgerson pointed out; he did such tests in triplicate to try to arrive at a reliable result.
DEFRA never repeat any positive results no matter how low, but hasten such cattle immediately to be killed.
In the case of Step Farm, so many were killed on the basis of low gamma interferon results that were not skin test positive (like Hallmark Boxster) and none had any lesions PM nor were the sample of animals from whom they cultured normal tissues found to be positive for M bovis on culture.
The replacement of the bovigam test by the DIVA test for cattle when they vaccinate them will be much more specific and I hope give cleaner results. Peptides or recombinant antigens will be used rather than a complex mix of whole proteins as used in the Bovigam test that are likely to evoke non-specific reactions, particularly from Natural Killer cells whose job it is to recognise pathogens never encountered before.
There is no reason why they should not use the DIVA test now for cattle instead of the Bovigam test.
It is also great that you are commenting on the giant intensive pig and dairy farms being proposed.
It is partly to do with individuals having large amounts of money to invest advantageously in such enterprises and believing they make a return on tax, subsidy and other benefits they can have.
The absolute stench in the intensive poultry houses and the intensive pig and dairy facilities proposed in itself is cruel. It would be like us spending all our life in a sewage works processing human faeces and urine and never allowed to go outside and breathe fresh air free of the overwhelming stench even once in our whole lives.
There are other reasons too why I think it is cruel to deny the animals all the natural behaviours and experiences that their evolution has fitted them for as though they were not living beings.
Small farms will in the end be only for a niche market, the hobby of the rich, and for environmental reasons. I guess I fall into the latter.