Accredited official statistics

Quarterly TB in cattle in Great Britain statistics notice: September 2024

Updated 11 December 2024

Applies to England, Scotland and Wales

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Key points

  • In England overall, herd incidence between October 2023 and September 2024 was 7.5, an increase of 0.4 from the previous 12 months. Between September 2023 and September 2024, herd prevalence decreased in England (Table 1.1).

  • In Scotland, which has had officially TB-free (OTF) status since 2009, herd incidence and herd prevalence remain very low.

  • In Wales overall, herd incidence between October 2023 and September 2024 was 6.7, a decrease of 0.3 compared to the previous 12 months, while herd prevalence rose by 0.2 of a percentage point.

  • Total animals slaughtered due to a TB incident in England between October 2023 and September 2024 increased 12% from the previous 12 months to 21,864. In Wales the number slaughtered was 12,278, a increase of 27% (Table 1.6). The number of reactors slaughtered in Wales between October 2023 and September 2024 was the most over a 12 month period since 2009.

  • Download the datasets used in these statistics.

This release is produced in accordance with the Code of Practice for Statistics. The purpose of this statistical notice is solely to report the latest available data relating to the ongoing bovine TB situation in Great Britain. It does not provide comment on the effectiveness of any disease control policy.

Short term changes in these statistics should be considered in the context of long-term trends. Comparisons between different areas should take-into-account differences in policy between those areas. A more detailed breakdown of the appropriate use of this statistical release is provided along with the other supplementary material.

1. Key tables summarising key bTB data to September 2024

1.1 Herd incidence and herd prevalence

Herd incidence is a measure of the rate at which new bTB incidents are being detected in an area. It is calculated by dividing the total number of new incidents by the total amount of time (in 100s of years) that tested herds were unrestricted and at-risk of infection since the end of their last TB incident or negative herd test, rather than the total number of tests carried out on those herds. The terms “herd incidence” and “herd incidence rate” are often used interchangeably in bTB-related literature, with both referring to the same measure, but “herd incidence rate” is not strictly accurate as herd incidence is already itself a rate. A document describing the herd years at risk measure is available at this link.

Herd incidence in the High Risk Area of England was 13.6 during the 12 months October 2023 to September 2024, which means for every 1000 unrestricted herds undergoing bTB surveillance in that period, APHA detected on average 136 new breakdowns.

Herd prevalence is defined as the percentage of all registered herds which were not Officially TB-Free (OTF) due to a TB incident. Table 1.1 compares the percentage of non-OTF herds at end of September 2024 with end of September 2023. Prevalence in England decreased by 0.1 of a percentage point.

In Wales overall, herd incidence decreased from 7.0 to 6.7, while herd prevalence rose from 5.4% to 5.6%.

Figure 1: Longterm view of new herd incidents per 100 herd years at risk of infection during the year - GB

View the data for this chart. Charts for Herd Incidence split by England risk areas and Wales TB areas are available to download in the statistical charts file accompanying the downloadable datasets.

Figure 2: Longterm view of number of herds which were non-OTF at the end of the period due to a TB incident as a percentage of registered and active herds - GB

View the data for this chart. Charts for Herd Prevalence split by England risk areas and Wales TB areas are available to download in the statistical charts file accompanying the downloadable datasets.

Table 1.1: Herd incidence and herd prevalence

Region Herd incidence October 2022 to September 2023 Herd incidence October 2023 to September 2024 Herd prevalence at 30 September 2023 Herd prevalence at 30 September 2024
England (All) 7.1 7.5 4.1% 4.0%
England - HRA 13.1 13.6 7.9% 7.6%
England - Edge 7.2 7.2 4.2% 4.4%
England - LRA 1.0 0.9 0.4% 0.3%
Scotland (All) 0.7 0.5 0.1% 0.1%
Wales (All) 7.0 6.7 5.4% 5.6%
Wales - High East 8.1 8.1 5.2% 5.2%
Wales - High West 11.5 12.6 10.8% 11.7%
Wales - Intermediate Mid 3.6 2.8 1.9% 1.9%
Wales - Intermediate North 7.3 6.4 5.6% 5.6%
Wales - Low 2.5 1.4 1.1% 0.8%

1.2 New herd incidents and non-OTF herds

The number of new TB herd incidents from October 2023 to September 2024 compared to the previous 12 months (Table 1.2):

  • decreased by 1 incident in England, as slight increases in the HRA and Edge offset a decrease in the LRA.

  • decreased by 9% in Wales, with decreases in all five TB areas.

  • decreased by 12 in Scotland.

Table 1.2: New herd incidents annual

Region October 2022 to September 2023 October 2023 to September 2024 Year-on-year change
England (All) 2,465 2,464 -0%
England - HRA 1,871 1,885 +1%
England - Edge 451 456 +1%
England - LRA 143 123 -14%
Scotland (All) 36 24 -33%
Wales (All) 645 586 -9%
Wales - High East 174 170 -2%
Wales - High West 283 272 -4%
Wales - Intermediate Mid 59 44 -25%
Wales - Intermediate North 87 75 -14%
Wales - Low 42 25 -40%

The number of herds under restriction due to a TB incident at the end of September 2024 compared to the end of September 2023 (Table 1.3):

  • decreased by 4% in England, despite an increase in the Edge.

  • decreased by 2 herds in Wales, with the High West TB area being the only such area to show a year-on-year increase.

  • in Scotland there was a decrease of 6 herds.

Table 1.3: Non-OTF herds - Herds not officially TB free at the end of the period due to a bovine TB incident

Region September 2023 September 2024 Year-on-year change
England (All) 1,850 1,781 -4%
England - HRA 1,444 1,375 -5%
England - Edge 338 346 +2%
England - LRA 68 60 -12%
Scotland (All) 13 7 -46%
Wales (All) 618 616 -0%
Wales - High East 141 137 -3%
Wales - High West 330 343 +4%
Wales - Intermediate Mid 37 36 -3%
Wales - Intermediate North 86 84 -2%
Wales - Low 24 16 -33%

In Scotland the number of non-OTF herds is very low and approximately 62% of cattle herds are now exempt from routine TB surveillance testing. In Scotland, the England LRA, and the Low TB area of Wales, there are proportionately more false positive results to the tuberculin skin test than elsewhere in GB. For example see articles in the Veterinary Record. Consequently it is also important to consider the number of new herd TB incidents where officially TB free (OTF) status is withdrawn (OTFW) following confirmation of TB by post-mortem examination or laboratory culture of tissue samples.

In the Low Risk Area of England:

  • between October 2023 and September 2024 there were 32 OTFW incidents, 10 fewer than the previous 12 months. OTFW herd incidence did not change (Table 1.4 and Table 1.5).

In Scotland:

  • There were 6 OTFW incidents between October 2023 and September 2024, 15 fewer than the previous 12 months.

  • OTFW herd incidence was 0.1, a decrease of 0.3 from the previous 12 months.

In the Low TB area of Wales:

  • There were 23 OTFW incidents between October 2023 and September 2024, 15 fewer than the previous 12 months.

  • OTFW herd incidence was 1.4, compared to 2.5 over the previous 12 months.

Table 1.4: OTFW new herd incidents annual - New herd incidents where OTF status is withdrawn (OTFW)

Region October 2022 to September 2023 October 2023 to September 2024 Year-on-year change
England (All) 1,079 1,042 -3%
England - HRA 827 790 -4%
England - Edge 210 220 +5%
England - LRA 42 32 -24%
Scotland (All) 21 6 -71%
Wales (All) 590 544 -8%
Wales - High East 167 165 -1%
Wales - High West 264 251 -5%
Wales - Intermediate Mid 55 38 -31%
Wales - Intermediate North 66 67 +2%
Wales - Low 38 23 -39%

Note: from 2011, the figures presented for OTFW incidents in Wales are not directly comparable to England or Scotland. This is previously due to Wales classifying some incidents as OTFW for epidemiological reasons only, and since January 2022 classifying all incidents as OTFW by-default.

Table 1. 5: OTFW herd incidence - New herd incidents OTFW per 100 herd years at risk

Region October 2022 to September 2023 October 2023 to September 2024
England (All) 3.2 3.2
England - HRA 5.9 5.7
England - Edge 3.5 3.4
England - LRA 0.3 0.3
Scotland (All) 0.4 0.1
Wales (All) 6.8 6.7
Wales - High East 8.1 8.1
Wales - High West 11.5 12.6
Wales - Intermediate Mid 3.6 2.8
Wales - Intermediate North 5.8 6.4
Wales - Low 2.5 1.4

Note: in Wales, the different definition of OTFW applies to the new herd incidents in the herd incidence calculation. Therefore OTFW incidence in Wales is approximately the same as overall herd incidence in Wales since January 2022, and the values for OTFW incidence in Wales are not directly comparable with England or Scotland.

1.3 Animals Slaughtered as a result of a TB incident

Between October 2023 and September 2024 there was a 12% increase in the number of cattle slaughtered due to a TB incident in England compared to the previous 12 months. For county trends see the datasets.

Table 1.6: Total animals slaughtered annual

Region October 2022 to September 2023 October 2023 to September 2024 Year-on-year change
England (All) 19,499 21,864 +12%
England - HRA 15,312 17,093 +12%
England - Edge 3,573 4,119 +15%
England - LRA 614 652 +6%
Scotland (All) 970 194 -80%
Wales (All) 9,666 12,278 +27%
Wales - High East 1,428 1,899 +33%
Wales - High West 5,861 8,216 +40%
Wales - Intermediate Mid 574 514 -10%
Wales - Intermediate North 1,493 1,404 -6%
Wales - Low 310 245 -21%

Table 1.6 Includes skin test reactors, antibody test positive animals, gamma test positive animals, and direct contacts. Since April 2017 it also includes inconclusive reactors for Wales only.

In Wales overall there was a increase of 27% in the number of animals slaughtered between October 2023 and September 2024 compared to the previous 12 months. 11,224 of the cattle slaughtered in Wales between October 2023 and September 2024 were TB test positive - the most slaughtered over a 12 month period in Wales since 2009.

In Scotland, 194 cattle were slaughtered.

2. What you need to know about this release

2.1 Contact details

Email address: TBStatistics@Defra.gov.uk

Public enquiries:

Defra TB Statistics
Mallard House, Kings Pool
Peasholme Green
York
YO1 7PX

Media Enquiries: 0208 225 7318 (Press Office)

2.2 Accredited official statistics status

Accredited official statistics are called National Statistics in the Statistics and Registration Service Act 2007. An explanation can be found on the Office for Statistics Regulation website.

Our statistical practice is regulated by the Office for Statistics Regulation (OSR). OSR sets the standards of trustworthiness, quality and value in the Code of Practice for Statistics that all producers of official statistics should adhere to. The continued designation of these statistics as accredited official statistics was confirmed in December 2017 following a compliance check by the Office for Statistics Regulation. The statistics last underwent a full assessment against the Code of Practice in 2012 Assessment Report 240. You are welcome to contact us directly with any comments about how we meet these standards (see contact details at 2.1 above). Alternatively, you can contact OSR by emailing regulation@statistics.gov.uk or via the OSR website.

Since the latest review by the Office for Statistics Regulation, we have continued to comply with the Code of Practice for Statistics, and have made the following improvements:

  • added more value by providing more detailed breakdowns of TB areas in Wales

  • included a glossary of key terms and a mapping of English counties to TB regions

  • introduced quarterly overview documents for England and Great Britain

  • from Q4 2019 included an interactive dashboard of measures

  • redesigned the release and datasets to achieve compliance with accessibility regulations (Q2 2020)

  • new groupings in the dataset of English counties by TB Risk Area (Q2 2020)

  • provided county-level values for herd incidence (Q4 2020)

  • amended the datasets to achieve enhanced accessibility (Q3 2021)

  • included antibody tests and animals slaughtered after receiving a positive antibody test (Q4 2021)

  • conducted additional quality control checks on registered herd counts, to remove registered herds showing no activity (Q1 2022)

  • changed the reporting of OTFW and OTFS New Herd Incidents in Wales to align with national policy backdated to Jan 2012 (Q4 2023)

  • provided additional supplementary material on the differences between TB eradication policies in England, Scotland and Wales (Q3 2024).

2.3 Feedback on this release

We encourage our users to engage with us so we can improve our Accredited Official Statistics and identify gaps in the statistics that we produce. See also our response to our 2020 user survey.

This document has been designed to meet the accessibility requirements outlined in WCAG 2.1:

  • all figures included in this release have accompanying alt-text descriptions

  • the release content has been adapted for easier processing by screen-readers

  • all text and figures use a high contrast colour scheme, and all figures use colour palettes that are visible to colourblind readers

  • publishing in HTML format in order to maximise compatibility

Should you have any comments on this statistical release and how to improve it to meet your needs please contact us by email to tbstatistics@defra.gov.uk

3. About these statistics

3.1 Notes on the data

These statistics are obtained from the Animal and Plant Health Agency (APHA) work management IT support system (SAM), used for the administration of TB testing in GB. They are a snapshot of the position on the date on which the data was extracted.

These statistics may be subject to small revisions until all test results are available. In particular, figures for the previous two calendar years and the current year will be subject to further revision as test and incident records are completed. The herd incidence figures are revised quarterly.

Data for Northern Ireland is not presented alongside the GB figures and is not produced on a comparable basis.

Data from 1996 onwards is available to download for GB countries, Wales TB areas and England risk areas.

England Bovine Tuberculosis (TB) Quarterly Overview and Great Britain Bovine Tuberculosis (TB) Quarterly Overview are available to download as visual representations of four key measures.

An interactive dashboard has been introduced to allow online interrogation of the statistics.

3.2 Future publications

A release calendar is available at least 12 months in advance.

4 Background Information on Bovine Tuberculosis

4.1 What is bovine tuberculosis?

Bovine tuberculosis (bTB) is a chronic infectious disease of cattle. The risk bTB poses to human health is low, largely due to milk pasteurisation. The disease is detected either on farms (through mandatory skin tests of cattle herds for bTB at regular intervals) and at slaughterhouses (through post-mortem meat inspection of cattle carcases).

4.2 What are the impacts of bTB?

Bovine TB presents serious challenges to the food and farming industries and has economic and social impacts. The economic costs of a bTB breakdown are shared by farmers and government.

Defra and Welsh Government commissioned research was published on 28 August 2020 on the financial impact of TB on beef and dairy farmers. The report shows the cost of a TB breakdown directly borne by cattle farms varies significantly, with a median value of around £6,600 across all farms in the survey. Across England and Wales median costs for herds of more than 300 cattle are around £18,600 whilst those for herds up to 50 cattle are around £1,700. Median costs for chronic breakdowns over 273 days are around £16,000.

Costs are incurred for a number of reasons:

  • Cattle which are found (or are highly likely) to have bTB are slaughtered. This loses the farmer the value of the animal and its output. Government pays farmers compensation for slaughtered animals which is based on the market value of cattle.

  • There are costs associated with testing animals for bTB. Farmers incur costs from gathering animals together, such as paying workers for their time, and government pays the vets’ fees for carrying out tests on the herd (and in the event of a breakdown on herds in neighbouring farms).

  • When an animal in a herd tests positive for the disease, the whole herd is put under movement restrictions until all the remaining animals are tested repeatedly with negative results. This presents costs to farmers, for example because they are unable to move their cattle to market or buy in replacements for animals that are slaughtered.

Other impacts of high bTB levels can include:

  • Restrictions on international trade in cattle and cattle products.

  • Significant stress amongst famers, their families, and local communities. See for example research report SE3120 for Defra, 2008.

  • The infection spilling over to domestic and wild animals. For example Broughan, J. M., Downs, S. H., Crawshaw, T. R., Upton, P. A., Brewer, J. & Clifto-Hadley, R. S. (2013) Mycobacterium bovis infections in domesticated non-bovine mammalian species. Part 1: review of epidemiology and laboratory submissions in Great Britain 2004-2010. Veterinary Journal 198, 346-35.

More information on bovine TB controls in Great Britain can be found for England, Wales and Scotland.

The TB Hub contains practical advice for farmers on dealing with bovine TB on their farm, covering everything from biosecurity measures to understanding trading rules.

5 - Narrative on incidence and prevalence of TB in Cattle in Great Britain

5.1 Why monitor statistics about bTB?

Defra policy is to achieve OTF status for England by 2038, and Welsh Government policy is to achieve OTF status between 2036 and 2041. Scotland achieved OTF status in September 2009. bTB statistics are used in England and Wales to measure progress towards this target, and to support the annual case for Scotland to retain its OTF status, as the qualification is based on herd incidence.

Monitoring policy effectiveness

Statistics on the incidence of bTB in cattle herds and the number of cattle slaughtered as a result of bTB are used by policymakers to monitor the spread and concentration of the disease and to inform decisions around the potential approaches to controlling it.

5.2 Factors affecting statistics on incidence and prevalence of TB in cattle

Short term changes in these statistics should be considered in the context of long term trends. Variation in the monthly and quarterly statistics can occur for a number of reasons, including:

  • Disease: an increase in the trend can be the result of a higher proportion of herds experiencing a breakdown because of an increase in the underlying incidence of bTB.

  • Surveillance policy (including the frequency of testing): Cattle herds in high risk areas are tested six monthly or annually and cattle herds in low risk areas are usually tested every four years. In Scotland 62% of cattle herds are now exempt from routine TB surveillance testing. If cattle herds in a low prevalence region are tested more frequently than every four years, the increase in the number of bTB tests will not necessarily be followed by a similar increase in the detection of infected cattle, in which case it would result in a decline in herd incidence.

  • Seasonality: more animals are tested when they are housed, during winter months, compared with when they are grazing outdoors in summer months. This is simply because it is easier to gather and test the cattle when they are already contained within a building.

  • Number of testing days in a given month: tests tend to be carried out at the beginning of the working week and the results collected and entered into the data system towards the end of the week. Months containing five Fridays may therefore have more positive test results than months containing four.

There has been no stable time series because of surveillance and testing changes. For example, there have been different herd testing frequencies in each parish over time, ranging from annual to four-yearly and changing every year until those frequencies were unified in Wales in 2010 (annual) and in England in 2013 (annual and four-yearly), later changing to six-monthly, annual, and four-yearly.

Between 1996 and 2013 there was a general increase in herd incidence in both England and Wales. England’s herd incidence remained stable until 2017 and has shown a generally decreasing trend since. Wales saw a general decline in herd incidence between 2013 and 2020, and it has remained stable since. Herd incidence in Scotland has remained low and stable since 1996.

Herd prevalence in England generally increased between 1996 and 2013, then remaining stable until 2019, and has been generally decreasing since. Herd prevalence in Wales generally increased between 1996 and 2008 and has remained largely stable since aside from two short-term spikes peaking in 2009 and 2012. Herd prevalence has remained low and stable in Scotland since 1996.

Aside from the period between 2001-2002 where bTB testing was reduced due to the large outbreak of FMD, the number of bTB cattle tests increased over time since 1996.

The number of cattle slaughtered for bTB reasons is a time series with few clear trends and a lot of long-term variability. In England the number of slaughters generally increased between 1996 and 2018, including a sharp increase in the aftermath of FMD. Since 2018 the number of slaughters has generally been decreasing in England. In Wales the number of cattle slaughtered for TB reasons has generally increased since 1996, but has been highly variable over that time. Relatively few cattle are slaughtered for TB reasons in Scotland and so this time series shows no clear trends.

5.4 bTB Surveillance policy in GB

Bovine TB surveillance and control policy — including how frequently animals are tested for bTB — varies between England, Wales and Scotland, and has changed over time.

Timeline

1990s: most herds in GB tested every four years and background testing intervals determined on a parish basis. Herds in parishes with a high incidence of bTB breakdowns (in the South West of England and in parts of Wales) are tested on an annual or biennial basis, with a smaller number of three-yearly testing herds.

2004 to 2010: the proportion of parishes and herds in England and Wales with annual testing increases gradually as the disease spread, with a corresponding decrease in the proportion of parishes with four-yearly testing.

2005 to 2006: mandatory pre-movement skin testing of cattle in annually tested herds was introduced. First in Scotland in September 2005 followed by England in June 2006 and Wales in May 2006.

October 2009: the European Commission designates Scotland as an officially bTB free region of the UK.

January 2010: In England, a core annual testing area is established, spanning entire counties in the South West and West Midlands (the high risk area) and surrounded by a “buffer” of two-yearly testing parishes. Most of the rest of England remains on background four-year testing. The Welsh Government puts all cattle herds in Wales on annual bTB testing (with herds in the small Intensive Action Area of West Wales put on 6-monthly bTB testing).

2011 and 2012: further expansion of the annual testing area in England to the east and north.

January 2013: herd testing intervals are determined on a county basis and England is split into annual testing and four-yearly testing counties. Annual testing of herds is extended to all the counties at the edge of the high risk area. Three- and two-yearly testing is abolished.

January 2015: all cattle herds in the edge area of Cheshire are put on six-monthly testing.

April 2016: mandatory post-movement skin testing of cattle was introduced in the Low risk area of England

October 2017: regionalised approach to TB eradication applied in Wales with the introduction of Low, Intermediate and High TB Areas. Cattle in the Low TB area are exempt from pre-movement testing, barring some exceptions.

January 2018: annual testing of cattle herds replaced with six-monthly herd testing in the higher incidence regions of the expanded Edge Area and annual herd testing supplemented with targeted (“radial”) testing of herds located within a 3km radius of new OTFW incidents detected in the rest of the Edge Area.

2020: The IDEXX antibody test was approved as a “relevant test” under Part 2 of the Tuberculosis (Wales) Order 2010 (as amended). Any animal giving rise to a positive reaction to the to the antibody test will be considered a reactor and removed, with compensation being provided to the owner.

September 2020: 6-monthly testing introduced in Staffordshire and Shropshire in the High Risk Area of England with first additional tests starting in March 2021. Further extended to the entirety of the High Risk Area in July 2021 with additional testing starting from January 2022. Current testing intervals and a map of GB TB areas are published online.

November 2021: Wales TB Areas changed on epidemiology advice so that 3 spatial units that were part of the Low TB Area, will temporarily be part of the Intermediate North TB Area. See frequently asked questions

January 2022: In Wales all TB incidents identified from skin testing are classed as Officially TB Free Withdrawn (OTFW), meaning two clear tests, with the first being at severe interpretation are required, before movement restrictions are revoked.

August 2023: mandatory post-movement skin testing of cattle was introduced in the 12-monthly testing part of the Edge area of England.

February 2024: Pre-movement testing is reintroduced for cattle in the Low TB area of Wales, and post-movement testing is introduced for cattle arriving in the Intermediate TB areas of Wales from higher-risk areas of England or Wales.

5.5 Current differences in surveillance policy in GB

The regional and county-level statistics published as part of this statistical notice show that there are considerable differences in the distribution and frequency of bovine TB across GB.

Since 2011, the trends for herd incidence with officially TB-free status withdrawn (OTFW) per 100 herd years at risk of infection during the year are not directly comparable for Wales and the other countries of GB. In Wales the number of incidents includes those where there is no confirmation of TB via post mortem examination or bacteriological culture, but where the herd’s OTF status is withdrawn for epidemiological reasons.

Scotland

Scotland has had officially TB-free (OTF) status since 2009 and has relatively few herd breakdowns. The herd incidence is very low and stable and is largely driven by sporadic introductions of infected cattle into Scotland. Scotland has in place a risk-based routine herd testing policy. This targets testing at higher risk herds. Around 62 per cent of herds are considered low risk herds and are exempt from routine testing. These are herds which have 50 or fewer animals, minimal import of animals from high risk areas and send a high proportion of animals to slaughter. Herds that are not exempt are tested every four years.

Wales

Since 2010, all herds in Wales are tested for Bovine TB at least annually. Since January 2011 some herds in Wales have had their OTF status withdrawn for epidemiological reasons only and from 2022 an OTFW by default policy was introduced. From 1 October 2017, a regionalised approach to TB eradication applies in Wales with the introduction of Low, Intermediate and High TB Areas. This means that measures can be tailored to address the varying risks and disease. The TB areas in Wales are established on the basis of epidemiological evidence and risks in each area. See a map of TB Areas. This regionalisation brought some changes to Pre- and Post- movement testing rules. From 1 October 2017 to 1 February 2024 pre-movement testing continued to be a requirement for movements of cattle from holdings in the intermediate and high TB areas of Wales but not from holdings in the Low TB Area. Cattle moved into the Low TB Area from other areas (not including the English LRA) required a post-movement test. See Official Statistics Tuberculosis (TB) in Cattle: Pre-movement and Post-movement Testing in Great Britain.

The strategically located Intensive Action Area (north Pembrokeshire and small parts of Ceredigion and Carmarthenshire) had, when it was set up in 2009, one of the highest incidence rates of bovine TB in Wales. From June 2019, the only additional surveillance measure that continues, which is different from the rest of Wales, is 6 monthly herd skin testing.

England

In England, there are wide geographical variations in the incidence and prevalence of bTB. This is reflected in the division of the country into three different epidemiological areas, with different disease control strategies and herd testing regimes applied in each of them:

  • In the Low Risk Area of the North, East and South East of England, the incidence of bTB is very low and stable and most cattle herds are routinely tested every four years. Similar to Scotland, the majority of breakdowns in the Low Risk Area can be linked to movements of undetected infected cattle from other areas of GB.

  • In the Edge Area, the herd incidence is higher than in the Low Risk Area, although this varies from county to county. Counties in the Edge are tested either every 6 months or every year. Testing intervals have been published.

  • In the High Risk Area of the West Midlands and South West of England, herds are tested every 6 months.

For a description of the data sources and methodology used in the calculation of the TB statistics, together with notes on data revisions policy etc., please refer to the Background and Methodology document.

6. Glossary

Bovine tuberculosis (bTB)

Bovine tuberculosis is caused by the bacterium Mycobacterium bovis (M. bovis). Cattle are the natural host of the bacterium. Many other species, including wildlife such as badgers and less commonly deer, are also susceptible to M. bovis and can develop TB and transmit the infection to other species.

Breakdown

A breakdown is the term used to describe the occurrence in a herd of at least one animal with a positive reaction to the skin test, or the identification of M. bovis in an animal with TB lesions detected at routine slaughter. The affected herd is then placed under restrictions and loses its Officially TB Free (OTF) status.

Direct Contact (DC)

An animal in an OTFW incident that, although not a test reactor, was considered to have been exposed to Mycobacterium bovis and compulsorily slaughtered.

Inconclusive reactor (IR)

An animal showing a positive reaction to bovine tuberculin that was not strong enough for it to be deemed a reactor. Such animals are usually isolated and subjected to a second skin test after 60 days, unless removed earlier as DCs or IFN-γ test reactors or voluntarily slaughtered by their owner.

Headline herd incidence

The incidence of a disease is the disease occurrence in new cases in a defined population over a designated time period. The accredited official statistics use new herd incidents per 100 herd years at risk of infection during the year as herd incidence definition. Herds which were previously OTF but either had cattle that reacted to a tuberculin test or had a tuberculous animal disclosed by routine meat inspection at slaughter, during the 12 months ending the date shown, divided by the amount of time herds tested during that period were unrestricted and at risk of infection. Figures for Wales include incidents where OTF status has been withdrawn for epidemiological reasons only.

Herd-years at risk

The sum of the time (days, months or years) herds in the population are unrestricted and are therefore at risk of a new incident, among the group of herds that have had a herd-level test during the period of interest.

Time at risk

Time spent not under restriction and at risk of having bTB during the observation period.

Herd prevalence

Herds which were not officially TB-free (i.e. herds under movement restrictions with OTF status suspended or withdrawn) due to a TB incident, at the end of the period as percentage of the number of herds registered on the APHA’s Sam (computer) system.

High Risk Area (HRA) of England

In the West Midlands and the South West of England, the incidence and prevalence of infected cattle have increased steadily to relatively high levels. This is partly a result of a reservoir of endemic M. bovis infection in the local wildlife. Herds are tested for bTB annually. Testing intervals and a map of GB TB areas are published.

Edge Area of England

In the Edge Area herd incidence is higher than in the Low Risk Area, although this varies from county to county. Herds are tested for bTB annually or every six months. The Edge boundary was updated in January 2018 to include the parts of the counties of Derbyshire, Warwickshire, Oxfordshire, East Sussex and Cheshire that had been designated HRA. It also spans Nottinghamshire, Leicestershire, Northamptonshire, Buckinghamshire and Hampshire. Testing intervals and a map of GB TB areas are published.

Low Risk Area (LRA) of England

North, East and parts of South East of England, the incidence of bTB is very low and stable and most cattle herds are routinely tested every four years. Similar to Scotland, the majority of breakdowns in the Low Risk Area can be linked to movements of undetected infected cattle from other areas of GB. Testing intervals and a map of GB TB areas are published.

Officially bovine tuberculosis free herd status suspended (OTFS)

New herd incidents where OTF status was suspended because of the detection of at least one TB test reactor, but where conclusive post-mortem evidence of TB could not found in any of those animals. The official TB status of such herds remains suspended until they have completed all the prescribed follow-up testing with negative results. In Wales from January 2022 onwards, no incidents will be considered as OTFS. However, there are incidents recorded as OTFS on Sam which either relate to exemptions to this policy change, or how the administration database is structured.

Officially bovine tuberculosis free herd status withdrawn (OTFW)

New herd incidents where OTF status was withdrawn from the herd due to the detection of typical lesions of TB during post-mortem examination/meat inspection of at least one TB test reactor or inconclusive reactor, or where post mortem tissue samples from at least one test reactor, inconclusive reactor or a slaughterhouse case prove positive for Mycobacterium bovis on PCR testing and/or bacteriological culture (the causative bacterium of bovine TB). In Wales from January 2022 onwards, all herds where skin test reactors (including animals that are inconclusive reactors at consecutive tests) and/or animals positive to gamma or antibody test have been disclosed are classified as OTFW regardless of the result of post-mortem or PCR and/or bacteriological culture results. Also where one or more slaughterhouse cases prove positive for Mycobacterium bovis on PCR testing and/or bacteriological culture.

Officially TB Free (OTF) status of a country or region

“OTF Status” takes its meaning from European law: for a region or Member State of the EU to be considered to be OTF the annual incidence of herds with confirmed M. bovis infection must not have exceeded 0.1% and at least 99.9% of the herds within it must have been free from bTB at the end of the year for at least six consecutive years.

Single intradermal comparative cervical test (SICCT)

The tuberculin skin test: if tuberculin (a purified sterile cocktail of proteins derived from M. bovis cultures) is injected into the skin of an animal infected with M. bovis, this will cause a localised allergic reaction characterised by temporary swelling of the skin, which is measured 72 hours after the injection. The principle is very similar to the skin tests for TB in humans.

Gamma interferon test (γIFN)

Laboratory-based blood test approved as an ancillary diagnostic tool that measures the release of γIFN in whole blood cultures stimulated with tuberculin.

7. Further Reading

This statistical release does not cover all available data relating to bovine TB in Great Britain. Other available data sources on bovine TB include the following:

8. Bibliography

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