The skin test is currently the main approved test under EU regulations. Defra admits it is not perfect and it must be carried out in strict accordance with agreed procedures. However, it would seem that some vets are not adhering to the rules. This farmer is angry. As with many farmers we speak to, his biggest complaint is with the existing testing regime; ‘My biggest complaint is with the institutionalised inaccuracy of the testing regime’. It would seem that the practices he has identified below are typical of tests that are undertaken, as evidenced by our conversations with other farmers.

He has told us that a recent test of over fifty animals (undertaken on 16th and 18th May 2011) was so haphazard (complaints made to AHVLA and RCVS) that the vet has been suspended pending retraining. However, the effects on the farmer have never been considered; ‘the consequences of his cynical abuse of the powers inherent in the bTB control measures will be left with me’. He goes on to say that ‘it seems odd to me that they destroy an animal for resisting the infection. It is even odder that they know so many (up to one in 5 in one estimate) slaughtered are destroyed unnecessarily. My local vets think it takes months or years for bTB to incubate so the test is pointless anyway and animals are killed when they would have been culled in the fullness of time. They also believe the disease will never be eradicated when the wildlife reserve (a euphemism for badgers) is so infected.

This farmer took notes and kept records under five of the six steps Defra recognizes when implanting the standard skin test used in the UK to identify bovine TB among herds. Each are listed below together with details of what happened in this particular test and the consequences of the action.

Each animal is identified (by its ear tag) and its identification recorded.
1. Two animals were injected twice. Two - probably three - were not injected. The third animal was missing from the SCCT check. The non-injected animals could have been reactors or inconclusives. The double injected beasts could have reacted disproportionately.
2. Two injection sites are selected in the middle third of the side of the neck, one above the other, separated by about 130mm. (if it is a small animal, the two sites will be on either side of the neck.)
3. Hair is clipped around the sites to a radius of about 2 centimetres.
No hair clipping took place on any animal. There was no measurement or recording of separate M.bovis or M.avium sites. The vet was unable to determine whether an injected site was reacting or which tuberculin reacted. It would be impossible to locate where the injections occurred without a marker or clipping. Reactions could have appeared in a site unrelated to the SCCT or a M.bovis reaction appear at the M.avium site or vice versa.
4. A fold of skin at both sites is measured with calipers and the measurements recorded.
Only a few animals were held in a crush. Most had the SCCT loose in the crush or in the race or holding pen. Caliper measurements were called out for BOTH sites having been taken from only one site on each animal. No designated clipped sites existed so could not be separately measured. One unmarked piece of skin was measured for both sites. The one site measured for the two animals tested twice differed on each occasion. The margin for variance is tight. The 'standard interpretation' of the skin test results is that if the reaction to M.bovis is more than 4mm greater than the reaction to M.avium the animal is considered to be infected with bTB and is called a ‘reactor’. It is slaughtered. So BOTH sites must be injected and, at the same site, both measured TWICE.
5. Tuberculin is injected into the skin; the upper site is used for the avian tuberculin.
This did not occur. The essential precision was impossible and was not attempted. The two needles were not clearly separated and the application was hurried, and haphazardly aimed. Not all animals had two jabs. The fact is there were no discernible or delineated sites for either injection. The required tuberculin details (batch number, use-by date, etc) for both jabs was withheld. There was no attempt at a correlation between the M.bovis or M.avium injection and the site. A reaction could be in the M.bovis or M.avium site without the vet being able to determine which. The M.bovis injection could have been missed, repeated or placed in the M.avium site and vice versa. The test is therefore compromised and discredited. At the first 60 days re-test if the reaction to the M.bovis tuberculin is between 1 to 4mm greater than the reaction to avian tuberculin, those animals are considered to 'inconclusive reactors' and will be retested after a further 60 days. The opportunity to quarantine or destroy is lost and a further 60 days made inevitable.
If evidence of bTB can be found in skin test reactor by post mortem examination and/or laboratory culture of tissues, the results of other cattle included in the herd test that disclosed the infected animal are re-assessed using the so-called ‘severe interpretation’. By the vets actions the probability of ‘severe interpretation’ is rendered more likely.
6. After 72 hours, the tester returns, confirms the animal identity, measures the same fold of skin at both sites and records the thickness of the skin fold.
No checking of identity was carried out. Other than the sole reactor (to one or other of the two tuberculins or another mycobacterium) no animals were tested or records kept of thickness on either site. Those animals which were seen were cursorily and generally examined (unrecorded) in the field by eye from a distance. Failing to get close enough to a group of cows at the bottom of a field, farm hands herded them towards the shed and they were glanced at in an adjacent field. The reactor’s skin fold was measured where the lump was - there being no sites marked or measured at SCCT. If there were other reactors the opportunity to remove them from the herd was wrongfully denied. Inconclusives may similarly have been overlooked. The opportunity to quarantine was lost.
There was no certainty that all animals had been seen but absolute certainty no comparison was made or recorded between M.bovis and M.avium sites or between the folds at injection and at the test 3 days later.
Severe interpretation is not used in the initial SCCT but is used in the follow-up tests carried out at 60-day intervals before TB restrictions can be lifted.
The lowering of the cut-off for animals to be classed as reactors narrowing the sensitivity threshold of the test may result in further animals being classed as reactors or inconclusive reactors.

Update received from farmer - email 23/7/11

I thought you might like to know, the bTB test on my reactor - the poor slaughtered cow - came back today. Just as there were no lesions found at post mortem, the culture examination proved negative. No sign of disease.

In other words I was closed down unnecessarily. Plus I will still be subject to a test every 6 months and be unable to sell, buy or move anything for the balance of the 120 days. The reaction may have been to the avian tuberculin or to some other cause. My allegation that the test was incorrectly carried out (which would have been a disgrace and true even if the animal was a M.Bovis reactor!) is proven - yet the material inconvenience and financial loss to the farm remains imposed upon us.

My further fear is that the incomplete shoddy test carried out by the vet may still mean there are inconclusives and reactors out there but there are increased tests which will be more likely to expose these - meaning loss of premium, greater chance of loss of sale, enhance probability of continued restrictions. Moreover, I still have the problem of bulls beyond their breeding ‘sell by date’! My profoundly disturbing experience leaves me with a feeling DEFRA and the veterinary profession are either disinterested in the proper control and eradication of bTB or and indifferent to the disease spread and want to close down farms.