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By Adele Waters & Josh Loeb
The Welsh government has given the go ahead for the use of unvalidated tests on cattle herds affected by TB breakdowns.
Last week, approval was given for vets to use of the interferon gamma test, the IDEXX ELISA antibody test and the Enferplex (bovine serum) test.
The decision means that these so-called ‘novel’ tests can be used privately in exceptional circumstances as a supplementary approach to managing problem herd breakdowns, subject to some terms and conditions (see box).
Rules for novel testing
A clear plan must set out:
1. What animals will be tested
2. What type of samples will be taken (eg, blood, milk, faeces, bulk milk), what test(s) will be used, and when
3. What will be done with the results
4. How the Welsh government and the APHA will be kept informed as required
5. Additional diseases in the herd, eg, Johnes/bovine viral diarrhoea, which may be affecting the TB status of bovine animals, and a plan as to how these diseases are being, or are to be controlled
Under current rules, any new diagnostic technique must be validated to the standards required by the World Organisation for Animal Health (OIE), even if it is not actually listed by the OIE.
Since novel tests have not undergone this level of evaluation, officials have prepared a document that sets out conditions under which private vets can use the new tests.
The document, ‘Use of non-validated tests in cattle herds’, requires vets to make a case for the use of any novel test and advises that any proposed test should, ideally, contribute to development work, in collaboration with the relevant manufacturer. Any data generated can contribute to the evidence needed for the candidate test to be validated.
The conditions also require that both the vet conducting the test and the animal keeper agree to the terms and conditions in writing.
The terms stipulate that the new tests cannot be used on any animals that have been confirmed as test-positive and are awaiting slaughter (including DC or ‘Direct Contact’ animals, regarded as high risk) or any inconclusive reactor animals.
Animals identified as positive via a non-validated test will need to be kept isolated from other animals (those not testing positive and those identified as reactors or inconclusive reactors during official Welsh government tests).
It is not clear how many farmers will agree to the new tests given that the Welsh government is not automatically liable to pay farmers compensation for animals killed after being identified as positive by any novel test.
However, Wales’s chief veterinary officer Christianne Glossop suggested last week that greater sensitivity may in fact lead to fewer animals having to be removed.
Fine-tuning this approach actually would be win-win
‘We feel [at the moment] as if we’re removing animals that are definitely infected, but it’s possible that we’re also taking some animals in that process that we, maybe, don’t need to take,’ Glossop told a Welsh Assembly committee. ‘So, fine-tuning this approach actually would be win-win, because we would be taking fewer animals – everyone would be happier with the numbers – and we’d be paying less compensation.’
The Welsh government has confirmed it cannot pay compensation for animals that test positive to non-validated tests.
A spokesperson said: ‘Farmers wishing to use non-validated tests in consultation with their vet will do so in the full knowledge that compensation cannot be paid before they sign the agreement.’
However, they went on to say that the APHA could potentially class animals that test positive to such tests as DC animals, and that this ‘may lead to the removal with full compensation.’
Gaining a true picture of the scale of infection is regarded as a vital first step to controlling bTB.
Devon-based vet Dick Sibley said: ‘If you use the suite of tests, what you can do is identify animals that the skin test is missing that are actually infected, and also that are infectious.’
BVA junior vice president James Russell said: ‘We welcome this decision by Welsh government to align with APHA in England in sharing this responsibility with the farmers’ own vet where there is both a need and a desire to undertake testing in addition to that required by statutory guidelines.
‘The appropriate placement of these tests in a disease control strategy is best identified at farm level through close collaboration between government, farmer and vet.’
The British Cattle Veterinary Association also welcomed the decision to allow private vet surgeons (PVS) in Wales to apply to use alternative bTB tests.
However, the association said it should be remembered that non-validated tests have not undergone the rigorous OIE approval process ‘and as such our preference would be to also use the OIE-validated tests currently available’. •
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