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<p>The early detection and removal of tuberculosis (TB)-infected cattle before they
develop advanced pathology and/or clinical signs of the disease (and thus become highly
infectious) is a key element of bovine TB eradication programmes, including England’s
25 Year Bovine TB Strategy. To that effect, we use ante-mortem tests that measure
the animals’ immune response to infection with the bovine TB bacterium (<em>Mycobacterium
bovis – M. bovis</em>), rather than rely on direct detection methods.</p><p> </p><p>The
single intradermal comparative cervical tuberculin (SICCT) test, commonly known as
the ‘skin test’, together with the interferon-gamma release assay (IGRA), is the legal
standard approved in the EU legislation for the diagnosis of TB in live cattle in
the UK. As with cases of TB in humans, only a proportion of those animals infected
with <em>M. bovis</em> and reacting to a tuberculin skin test or IGRA display gross
lesions of TB when subjected to post-mortem meat inspection in the slaughterhouse.</p><p>
</p><p>In 2017 (the last year for which an analysis of post-mortem findings is available),
approximately 60% of the 32,000 cattle compulsorily removed for bovine TB control
reasons in England as skin test reactors or IGRA positives did not have visible lesions
of TB on post-mortem and were also negative for <em>M. bovis</em> on bacteriological
culture (where performed).</p><p> </p><p>Defra and the Animal and Plant Health Agency
(APHA) are constantly striving for new ways to maximise the effectiveness of TB testing
of cattle to achieve the objectives of the Strategy. APHA may exceptionally authorise
the private use of non-validated diagnostic tests for bovine TB in herds where the
disease is persistent, in order to help detect additional infected animals that may
have been missed by the approved official tests (rather than to negate a positive
result to such tests). A policy position paper on non-validated diagnostics for TB
in cattle is now available on the APHA Vet Gateway (<a href="http://apha.defra.gov.uk/vet-gateway/index.htm"
target="_blank">http://apha.defra.gov.uk/vet-gateway/index.htm</a>).</p><p> </p><p>Over
£4 million was allocated to TB research and development in 2018/19, with the anticipation
of a similar spend this financial year. The majority of these finds are being invested
in improving diagnostic tests alongside vaccine development. However, validation for
a new test to World Organisation for Animal Health standards would only lead to official
adoption if it demonstrated proven advantages in the detection of disease alongside
the current test portfolio.</p>
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