Bovine Tuberculosis: Disease Control
(asked on 18th April 2023) - View Source
Question to the Department for Environment, Food and Rural Affairs:
To ask the Secretary of State for Environment, Food and Rural Affairs, what assessment her Department has made of the (a) effectiveness of badger culls in tackling bovine TB and (b) reliability of the TB test used to identify cattle for slaughter; and what estimate her Department has made of the (i) annual cost of bovine TB in Shropshire and (ii) level of bovine TB in that county.
Evidence suggests that the badger cull has been effective in reducing bovine tuberculosis (TB) incidence in cull areas by 45% after three years of culling and 50% after four years. TB statistics for England show that disease incidence (i.e., the rate at which new cases or ‘breakdowns’ are detected in officially TB free herds) in the High Risk Area, where approximately 80% of all the TB-affected (breakdown) herds are located, has been decreasing since 2017. The percentage of cattle herds under TB restrictions in England (prevalence) is at its lowest level (4.5%) since 2010 (4.2%), having peaked at 6.4% in March 2018.
The cornerstone of TB control in cattle and other species is the accurate detection and removal of animals infected with the bovine TB bacterium Mycobacterium bovis (M. bovis) before they can spread the disease to other animals. The main screening test for TB in cattle in Great Britain is the single intradermal comparative cervical tuberculin (SICCT) test. This is commonly known as the tuberculin skin test, which is used throughout the world to screen cattle, other animals and people for TB. It is the internationally accepted standard ante-mortem technique for detecting M. bovis infection in most species of mammals, including cattle.
All the official tests used in the ante- and post-mortem diagnosis of TB in cattle are thoroughly validated and evaluated by the Animal and Plant Health Agency (APHA). The SICCT test has a very high specificity, generating on average only one false positive result for every 5,000 - 6,000 uninfected cattle tested. However, it is only moderately (80%) sensitive, with about one in five bTB-infected cattle potentially missed by the test. This is why APHA uses the more sensitive (but less specific) interferon-gamma blood test to supplement the primary skin test in some herds affected by TB incidents. This helps accelerate the detection and removal of all the infected animals in such herds and reduce the risk of repeat (recurrent) breakdowns.
In September 2020 my Department increased the frequency of routine TB surveillance testing for most cattle herds in Shropshire from annually to every six months, with the first additional skin herd tests starting in March 2021.
As a result of the increased frequency of testing, 583,056 animal TB tests were completed in Shropshire in 2022. This resulted in a total of 1,981 cattle being compulsory slaughtered for TB control reasons in 2022 out of 583,056 animal TB tests completed in the county, at an estimated net compensation cost of £1.8M. This was lower than the peak of 2,357 cattle slaughtered in 2011, out of 425,787 TB tests completed in the county.
There were 232 new TB herd incidents detected in Shropshire in 2022, which is the lowest annual figure since 2007 and substantially fewer cases than the peak of 353 in 2013. 11.1% of herds in Shropshire were under TB restrictions at the end of the year.
For the complete and most recent set of official historical statistics for TB in cattle in Shropshire, published by my Department at the beginning of March, please see: