Research and analysis

Bovine TB in cattle: background information for badger control areas monitoring data up to 2025

Published 10 September 2026

Background and purpose of the monitoring data

Bovine tuberculosis (TB), caused primarily by Mycobacterium bovis (M. bovis), is an infectious, zoonotic bacterial disease of cattle and other mammals. Badgers are the principal wildlife host in England (Delahay et al., 2002) and are present in large areas of the country.

Licensed industry-led badger culling was carried out in the High Risk Area (HRA) and Edge Area of England from 2013 to 2025 as part of a Badger Control Policy. Culling has also been licensed in parts of the Low Risk Area (LRA) since 2018. The aim of culling is to decrease the badger population in order to reduce the risk of M. bovis transmission from badgers to cattle.

The Badger Control Policy was informed by evidence generated from the Randomised Badger Culling Trial (RBCT) conducted in England between 1998 and 2005 (Donnelly et al., 2007; Jenkins et al., 2010). Further information about the rationale and aims of the policy can be found in the previously published policy on Bovine TB and badger control in England and Strategy for achieving Officially Bovine Tuberculosis Free status for England. In June 2026, a refreshed Bovine TB control strategy for England, developed and recommended by a steering group of the Bovine TB Partnership, was published.   

In 2024, the government announced that the Badger Control Policy would conclude before the end of the parliament and announced its intention to increase the delivery of badger vaccination as a non-lethal alternative to culling. Industry-led culling in the HRA and Edge Area of England permanently ceased operations in January 2026 upon expiry of the respected licences. Natural England revoked the final remaining badger control licence in the LRA following the transition to badger vaccination in 2026, bringing licenced badger culling in England to an end.

APHA is commissioned by Defra to monitor the levels of TB in cattle in geographic areas where badger control has taken place under the Badger Control Policy (referred to as “badger control areas” in this report). Since 2016, APHA has therefore published monitoring data showing the incidence and prevalence of TB in cattle herds in each badger control area that has at least one year of follow-up after at least one period of culling.

The monitoring data are derived from TB tests conducted during routine surveillance and control of TB in cattle. The data do not demonstrate whether the Badger Control Policy has reduced bovine TB in cattle. Evaluation of the effect of the Badger Control Policy requires consideration of other factors that could affect cattle TB incidence in addition to culling. This has been subject to separate independently reviewed and published analytical studies (Brunton et al., 2017; Downs et al., 2019, Birch et al., 2024). The data also do not take account of changes to the nature of badger control across the different areas over time arising from changes to the Badger Control Policy itself, including the end of culling and the introduction of vaccination.

The data are provided in an accessible format in OpenDocument Spreadsheets (ODS). This document provides background information and methodological details to accompany these data.

The Badger Control Policy

The Badger Control Policy involved licensed, industry-led badger culling from 2013 and provision of biosecurity advice to farmers in licensed areas from 2014. After the policy was first implemented, changes to other TB surveillance and control policies were made which applied to cattle in badger control areas. These are outlined in the section: Changes to TB surveillance that may influence cattle TB incidence and prevalence.

The policy involved the use of 3 types of badger culling licence in England, as described below.

1. Badger Disease Control (BDC) licence: Four-year duration and applicable to the HRA and Edge Area of England. The period of badger culling under these licences is referred to as the “intensive” cull period.
2. Supplementary Badger Disease Control (SBDC) licence: Variable duration from 2 to 5 years and applicable to areas that had already completed at least four years of culling under a Badger Disease Control licence. The period of badger culling under these licences is referred to as the “supplementary” cull period.
3. Low Risk Area Badger Disease Control (LRABDC) licence: Applicable to the LRA of England and typically associated with TB control within defined TB hotspots.

All badger culling licences are issued by Natural England (NE) under the Protection of Badgers Act 1992. No new BDC licences have been issued since 2022. No new SBDC licences have been issued since 2024. LRABDC licences are subject to an annual evidence review by APHA epidemiologists, ecologists, and the UK Chief Veterinary Officer (CVO) to ensure the ongoing suitability of badger control within TB hotspots.

All badger culling licences apply to pre-defined badger control areas, the boundaries of which are defined by NE. Badger control areas in the HRA and Edge area were proposed by the farming industry and had to meet government licensing criteria. In 2013, areas were required to be greater than 150km² with at least 70% of land accessible for culling (note that ‘accessible land’ comprises land parcels participating in the cull). Following a consultation on guidance to Natural England on licences to control the risk of bovine tuberculosis from badgers in 2015, the licence criteria were adjusted to 100km² minimum area size with at least 90% of land accessible for culling, or within 200m of land accessible for culling (Defra, 2021). Badger control areas in the LRA are defined by expert epidemiologists and ecologists according to established criteria for managing TB hotspots.

Under an active BDC or LRABDC licence, culling took place for a period of approximately 6 weeks each year between late August and early November. Culling operations under an active SBDC licence were authorised to take place over a longer period each year, generally from June to the following January. More detailed information relating to culling operations in badger control areas up to the end of 2025 can be found at:

• Summary of 2025 badger control operations
• Summary of 2025 supplementary badger control operations
• Bovine TB: hotspots in the Low Risk Area of England

Badger control areas included in the latest monitoring data

The latest monitoring data extend to the end of 2025 and include all areas licensed up to and including 2024. There are 73 areas in total. Forty-seven areas are entirely in the HRA, 15 areas straddle the HRA and Edge Area, and eight areas are entirely in the Edge Area. Three areas are in the LRA.

A detailed overview of annual badger control operations in each of the 73 areas is provided in the accompanying ODS spreadsheet, Badger Control Areas Overview.

HRA and Edge Area

The first two Badger Disease Control licences were issued in 2012 (although badger culling began in 2013). Further licences were issued in 2015 (1), 2016 (7), 2017 (11), 2018 (10), 2019 (11), 2020 (10), 2021 (7) and 2022 (11).

Each badger control area has a unique identifier, which relates to the year when the area was first licensed for culling and the county where it is predominantly located. Area boundaries were defined by NE and shared with APHA. Area sizes when licences were first issued ranged from 100 km² to 1,551 km² (median: 404.5 km²).

For 40 areas, boundaries remained stable over time. However, NE revised the boundaries of 30 areas, usually in the second (and occasionally also in the third) year of the licence. These revisions resulted in an overall increase in area ranging from 0.30% to 45.9% compared with the original size (median: 6.0% increase). Once approved, a revised boundary was first implemented operationally during the subsequent badger cull season. Details of boundary changes for each area are shown in Table 1. Boundary revisions made up to and including 2024 are reflected in the current monitoring data.

By the end of 2025, each area had been subjected to between four and nine annual rounds of culling under a combination of BDC licence and SBDC licence. Culling operations remained active in 20 of these areas in 2025 (Summary of 2025 badger control operations and Summary of 2025 supplementary badger control operations). All other areas were between one and four years post-cull by this time, with the final year of culling having taken place in 2021 (2 areas), 2022 (11 areas), 2023 (13 areas) or 2024 (24 areas).

LRA

Three areas are within TB hotpots (HS). Culling operations began in different years and varied in duration across the areas, as detailed in Bovine TB: hotspots in the Low Risk Area of England:

• Area 32 (within HS21) was first licensed in 2018, underwent 4 annual rounds of culling (2018 to 2021) and was 4 years post-cull by the end of 2025
• Area 54 (within HS23) was first licensed in 2020, underwent 5 annual rounds of culling (2020 to 2024) and was one year post-cull by the end of 2025
• Area 73 (within HS29) was first licensed in 2024 and had undergone 2 rounds of annual culling by the end of 2025

When first licensed, all three areas were less than 200km² in size (Table 1). Some revisions to area boundaries were made over time, reflecting the established adaptive management approach to managing TB infection in TB hotspots. Area 32’s boundary was revised in 2019, increasing its size by 12.9%. Area 54’s boundary was revised in 2021 and 2023, resulting in a total size increase of 42.9% from its original extent. Boundary revisions made up to and including 2024 are reflected in the current monitoring data.

Table 1: Initial area sizes (km²) and percentage area changes to badger control areas across the HRA, Edge and LRA licensed up to and including 2024

Areas linked to LRA hotspots are identified by ‘HS’ number in parentheses. Initial area size (including accessible and inaccessible land) on the date each area was first issued with a licence is shown. Percentage changes to the size of badger control areas over time due to boundary revisions are also shown, along with the dates these boundary revisions were approved.

Badger control area	Year of first cull	Initial area size (km2)	Percentage area changes
Area 01 - Gloucestershire	2013	311	No change
Area 02 - Somerset	2013	256	No change
Area 03 - Dorset	2015	223	No change
Area 04 - Cornwall	2016	393	No change
Area 05 - Cornwall	2016	272	No change
Area 06 - Devon	2016	567	No change
Area 07 - Devon	2016	431	No change
Area 08 - Dorset	2016	416	+ 3.2% in April 2017
Area 09 - Gloucestershire	2016	649	No change
Area 10 - Herefordshire	2016	285	No change
Area 11 - Cheshire	2017	292	No change
Area 12 - Devon	2017	563	No change
Area 13 - Devon	2017	433	+ 9.4% in May 2018
Area 14 - Devon	2017	249	No change
Area 15 - Devon	2017	206	+ 0.6% in May 2018
Area 16 - Dorset	2017	1030	No change
Area 17 - Somerset	2017	280	No change
Area 18 - Somerset	2017	198	No change
Area 19 - Wiltshire	2017	623	+ 3.5% in May 2018
Area 20 - Wiltshire	2017	546	+ 1.3% in May 2018
Area 21 - Wiltshire	2017	332	No change
Area 22 - Cornwall	2018	1272	No change
Area 23 - Devon	2018	594	No change
Area 24 - Devon	2018	510	+ 6.1% in February 2019
Area 25 - Devon	2018	311	No change
Area 26 - Devon	2018	303	No change
Area 27 - Devon	2018	210	No change
Area 28 - Devon	2018	194	No change
Area 29 - Gloucestershire	2018	431	No change
Area 30 - Somerset	2018	622	No change
Area 31 - Staffordshire	2018	1180	No change
Area 32 – Cumbria (HS21)	2018	190	+12.7% in January 2019
Area 33 - Avon	2019	480	No change
Area 34 - Cheshire	2019	515	+19.8% in August 2020
Area 35 - Cornwall	2019	1021	+0.3% in August 2021
Area 36 - Staffordshire	2019	289	No change
Area 37 - Devon	2019	548	+0.3% in August 2020
Area 38 - Devon	2019	509	No change
Area 39 - Dorset	2019	390	No change
Area 40 - Herefordshire	2019	1119	+0.3% in August 2020
Area 41 - Staffordshire	2019	455	No change
Area 42 - Wiltshire	2019	1076	No change
Area 43 - Wiltshire	2019	547	No change
Area 44 - Avon	2020	561	+24.2% in August 2021
Area 45 - Derbyshire	2020	761	No change
Area 46 - Gloucestershire	2020	222	+4.6% in August 2022
Area 47 - Herefordshire	2020	557	+11.5% in August 2021
Area 48 - Leicestershire	2020	392	No change
Area 49 - Oxfordshire	2020	607	No change
Area 50 - Shropshire	2020	1551	+1.1% in August 2021 and +1.2% in August 2022 Overall 2.3% increase from original area
Area 51 - Somerset	2020	606	+3.0% in August 2021 and +1.3% in August 2022 Overall 4.4% increase from original area
Area 52 - Warwickshire	2020	607	+11.8% in August 2021
Area 53 - Wiltshire	2020	251	+4.6% in August 2021 and +1.1% in August 2022 Overall 5.8% increase from original area
Area 54 - Lincolnshire (HS23)	2020	102	+19.1% in August 2021 and +20.0% in August 2023 Overall 42.9% increase from original area
Area 55 - Shropshire	2021	181	+9.8% in August 2022
Area 56 - Hampshire	2021	450	+3.5% in August 2022
Area 57 - Berkshire	2021	133	+0.5% in August 2022
Area 58 - Staffordshire	2021	234	+0.8% in August 2022
Area 59 - Worcestershire	2021	117	No change
Area 60 - Shropshire	2021	547	+31.5% in August 2022
Area 61 - Oxfordshire	2021	324	+23.4% in August 2022
Area 62 - Buckinghamshire	2022	252	+45.9% in August 2023
Area 63 - Cornwall	2022	103	+23.2% in August 2023
Area 64 - Cornwall	2022	104	No change
Area 65 - Derbyshire	2022	258	+12.0% in August 2023
Area 66 - Devon	2022	151	+28.5% in August 2023
Area 67 - Hampshire	2022	153	No change
Area 68 - Northamptonshire	2022	501	+13.1% in August 2023
Area 69 - Oxfordshire	2022	211	+18.5% in August 2023
Area 70 - Somerset	2022	100	No change
Area 71 - Warwickshire	2022	252	No change
Area 72 - Warwickshire	2022	534	+2.6% in August 2023
Area 73 – Cumbria (HS29)	2024	182	No change

Badger vaccination against M. bovis in England

Vaccination of badgers against M. bovis has been carried out across parts of England since 2010. The aims of badger vaccination are to reduce the spread of the pathogen in the badger population, thus reducing the risk of transmission between badgers and cattle.

Trapping and marking badgers for vaccination is licenced by Defra and NE and only permitted between 1 May and 30 November each year. By the end of 2025, a variety of vaccination projects had been carried out in England, including larger scale government-led projects (delivered by APHA) and projects delivered by a variety of non-government groups, usually at a much smaller scale.

More than 4,000 badgers were vaccinated in 2024 and 2025, the highest numbers ever vaccinated in England. Delivery is expected to expand further with the introduction of a new Badger Vaccination Field Force from 2026.

Further details of the rationale, approach and extent of badger vaccination in England to date are available on the TB Hub. The total number of badgers vaccinated per county across England in 2025 can be found on: Summary of badger vaccination in 2025.

APHA-delivered badger vaccination in badger control areas

The nature of wildlife disease control within the boundaries of some badger control areas has changed over time. APHA-delivered vaccination has taken place in parts of some badger control areas in the LRA since 2020 as part of targeted TB hotspot management. As a result of an expansion of vaccine deployment across England in general, APHA has also delivered vaccination in parts of some badger control areas in the HRA and Edge Area since 2021. Some vaccination has also taken place completely outside of any badger control area, but this is not considered further here.

The ODS spreadsheet, Badger Control Areas Overview, provides a summary of the badger control activities occurring in each area up to the end of 2025. This includes the years in which badger culling took place and the extent of APHA-delivered badger vaccination within each area in those years. The extent of vaccination is measured as the square kilometres of land (rounded up or down to the nearest whole number) where landowners had signed up for APHA-delivered badger vaccination by 31 December each year. This includes land where vaccination did not subsequently take place due to an absence of badger activity. Vaccination coverage within a badger control area is not necessarily static over time. Coverage can increase if additional land is enrolled in later years but can also decrease where land has reached the end of the typical four-year delivery programme.

Badger vaccination cannot take place on land that is actively involved in badger culling. Therefore, vaccination within a badger control area either took place on land where culling had concluded or on land where culling had never taken place. Furthermore, due to differences in licence conditions, vaccination and culling that took place in the same badger control area during the same calendar year will have generally taken place at different times of year.

Vaccination in badger control areas in the LRA

By the end of 2025, APHA had delivered badger vaccination in two badger control areas in the LRA: Area 32 and Area 54. Full details are available at: TB hotspots in the Low Risk Area of England.

• Area 32: Vaccination was first introduced in 2020 while culling under an LRABDC licence was still taking place elsewhere within the area. At that time, 103km² of land was signed up to vaccination within a total area of 214km². Culling was subsequently phased out and vaccination delivery increased to cover the entire area two years later. Since 2022, vaccination has been the sole method of badger disease control. However, vaccination was only delivered across 41km² in 2025 as the outbreak was considered to be contained.

• Area 54: Following an assessment by the CVO, culling ended in this area in 2024 and vaccination began for the first time the following year. The extent of land signed up for vaccination in 2025 was 52km², which compares to the total area size of 146km².

Vaccination in badger control areas in the HRA and Edge Area

Up to the end of 2025, APHA had delivered badger vaccination covering at least 1km² in parts of 17 badger control areas in the HRA and Edge Area.

In some cases, contiguous vaccination activities may have extended beyond the boundaries of the relevant badger control area; however, only the vaccinated land parcels falling within badger control area boundaries are included here.

The extent of land signed up to vaccination within the boundary was relatively small for 11 of the 17 areas but was more extensive (more than 10km²) in 6 areas.

APHA-led vaccination was carried out in the following areas, but only once culling operations had ended:

• Area 01: Vaccination began in 2022. The extent of land signed up to vaccination in 2022 was 75km², increasing to 92km² in 2023 onwards. This compares to a total area size of 311km².
• Area 02: Vaccination began in 2022. The extent of land signed up to vaccination in 2022 was 80km², increasing to 105km² in 2023 onwards. This compares to a total area size of 256km².
• Area 20: Vaccination began in 2023. The extent of land signed up to vaccination in 2023 was 347km², increasing to 356km² in 2023 and 357km² in 2024. This compares to a total area size of 553km².

In the following areas, APHA-led vaccination began while badger culling operations were still ongoing:

• Area 19: Vaccination first took place in 2021 while culling under SBDC licence was still taking place in other parts of this area. At that time, the extent of land signed up to vaccination was relatively small, covering 25km² compared with the total area of 645km². Following the end of culling, vaccination continued and expanded, reaching 154km² of signed-up land in 2024. However, the extent of vaccination subsequently decreased in 2025.
• Area 30: Vaccination first took place in 2022 while culling under SBDC licence was still taking place in other parts of this area. At that time, the extent of land signed up to vaccination was small, covering 15km² compared with the total area of 622km². Vaccination continued following the end of culling, although the extent of land signed up remained unchanged.
• Area 70: Vaccination first took place in 2022 while culling under BDC licence was ongoing in other parts of this area. However, vaccination covered less than one square kilometre of land at this time. The extent of land signed up to vaccination increased in 2024 but was still relatively small, covering 11km² compared with the total area of 100km². Culling continued in 2025 and the extent of vaccination also remained unchanged.

Badger vaccination delivered by non-government organisations in badger control areas

Licensed badger vaccination projects delivered by non-government organisations have also been carried out in parts of England since 2010. Activity has taken place across all TB risk areas, including within the boundaries of some badger control areas. However, most of this activity has been small scale. Detailed information about which land was signed up to badger vaccination by non-government organisations is not currently routinely available to APHA. Data on the occurrence of non-APHA-delivered badger vaccination are therefore not included with the data presented here. This may result in a slight under-estimate of the overall land area that was signed up for badger vaccination in some badger control areas.

Changes to TB surveillance that may influence cattle TB incidence and prevalence

Reported TB incidence and prevalence reflect not only the background force of infection but also the impact of surveillance and control policies, which influence disease detection. These policies, including the frequency of routine cattle testing and the types of tests used, vary across TB risk areas and therefore also between badger control areas.

The principal changes to TB surveillance and control policies affecting cattle in badger control areas up to the end of 2025 are set out below.

Further information about TB tests and surveillance and control policies can be found on the TBhub.

1. Prior to 2013, when the badger control policy started, most cattle herds in counties now in the HRA were subject to routine annual field surveillance for TB. Most counties in the Edge Area, as it is now known, were subject to field surveillance every 2 years, although there was some variation in this.
2. In 2013 all herds in the Edge Area became subject to routine annual surveillance.
3. In 2015 part of Cheshire in the Edge Area became subject to routine 6-monthly testing because it was recognised as having a particularly high risk of TB infection.
4. In 2018 routine 6-monthly testing was applied to all of Cheshire, Oxfordshire and Warwickshire, and parts of Berkshire, Hampshire and Derbyshire in the Edge Area (Expansion of the Edge Area and cattle testing arrangements).
5. In September 2020 routine 6-monthly testing was applied to the HRA counties of Staffordshire and Shropshire.
6. In July 2021 routine 6-monthly testing was applied to the remainder of the HRA (Animal and Plant Health Agency, 2021a; Six-monthly surveillance testing of cattle herds in the HRA). Herds in counties subject to 6-monthly testing can revert to annual testing upon meeting criteria which demonstrates a lower risk of infection (Earned Recognition).
7. From 2017 to 2021, mandatory interferon (IFN) gamma testing to detect and remove infection was applied to persistent confirmed TB incident herds in all risk areas, and to all new confirmed TB incidents in the LRA and Edge Area. In the HRA, IFN gamma testing was also applied to herds with a new confirmed TB incident where cattle-to-cattle transmission was considered the most likely route of infection or when herds were located in areas that had been subject to 2 or more years of badger culling.
8. Since July 2021, the gamma testing policy has changed in the HRA and 6-monthly testing Edge Area. IFN gamma testing is now applied to all herds experiencing a new confirmed TB incident within 18 months of the herd regaining OTF status following a previous incident (Refinements to the IFN gamma testing policy in the HRA and Edge Area). The policy remains unchanged for the annual testing Edge Area and the LRA.
9. From 23 March 2020, skin testing for select purposes was not mandatory for cattle under 180 days old due to the COVID-19 outbreak (Animal and Plant Health Agency, 2020a). Short interval tests, which are required to restore a herd’s OTF status, were not originally included in this derogation. However, herds were considered on a case-by-case basis with extensions granted to time windows to perform short interval tests (Animal and Plant Health Agency, 2020b). These temporary amendments to TB skin testing due to COVID-19 were discontinued over July and August 2021 (Animal and Plant Health Agency, 2021c).
10. During the winter of 2022 to 2023, a large-scale outbreak of highly pathogenic avian influenza (HPAI) meant that substantial numbers of APHA personnel were redeployed from usual TB surveillance activities to help control the outbreak. However, there were established contingency plans in place to minimise disruption to TB control activities in England (Delivery of TB surveillance & controls during the HPAI outbreak (England)).
11. From 1 August 2023, post-movement TB testing became compulsory for cattle moved to annual surveillance testing parts of the Edge Area from higher TB incidence areas of England, and from Wales. A small number of exemptions apply (Post-movement testing in annual surveillance testing parts of the Edge Area).

Monitoring methods

Data source and quality

TB data are extracted from Sam, the APHA database, which records the results from TB tests conducted in cattle herds throughout Great Britain. Data were downloaded on 20 May 2026.

These data are compiled from TB surveillance activities and control policies, and historical data may be updated or corrected over time. Corrections may include removal of a herd that has become inactive, inclusion of a herd that has become active, and revisions to the geographical location of the herd. Herd TB incident designation may also change from unconfirmed infection (Officially Tuberculosis Free- Suspended, OTF-S) to confirmed infection (Officially Tuberculosis Free- Withdrawn, OTF-W) due to confirmatory information about the presence of M. bovis infection becoming available since the previous report was published. Data corrections and routine validation can affect the counts of incidents and the calculated time at risk. The corrections in the past have generated minor differences in statistics between annual reports, particularly in relation to the year prior to the most recent year in the report. The most recently published monitoring data contain the most accurate current and historical data known to the project team.  

Time period

Monitoring data are provided for calendar years and intervention years. Each badger control area has its own associated baseline date, which is the start date of the first cull in that area. An intervention year is the period of 12 months starting from the same day and month of the baseline date for each year in the reporting period and is defined separately for each area. Note that intervention years are always based on the start date of culling and are not influenced by the occurrence of any badger vaccination occurring in an area.

The starting year reported, and the number of follow-on years, is dependent on the start date of the first cull in that area. Data up to 4 years prior to the baseline date for each badger control area are also included.

Monitoring herd populations

Data are reported for 2 different cattle populations: cohort and herds in existence (HIE). The populations represent alternative definitions of cattle herds exposed to badger culling. Each is subject to potential sources of bias.

Cohort

Cohort herds are herds recorded as active in badger control areas on the baseline date for that area. The number of herds in the cohort population is affected by changes in the active status of herds in the original cohort over time, for example, the loss of herds from farms that are no longer operating. This means the number of herds in the cohort can decrease but not increase between years following the first year of culling in that badger control area. The cohort population is not affected by changes to cull area boundaries.

By their definition, we can assume that cohort herds are exposed to badger control operations for the full follow-up period whilst they remain active. However, loss of herds from the cohort population over time appears to be non-random and may be a substantial source of bias, as herds most likely to cease to exist tend to have lower TB incidence rates than herds that remain in the cohort (Birch et al., 2024).

Herds in existence (HIE)

HIE provides an annual snapshot of active herds located within each badger control area in each reporting year. This group of herds includes active cohort herds plus other herds recorded as active within an area each year based on contemporary herd location map reference data. The size of the HIE population may therefore fluctuate over time and herd identity is not static. HIE may therefore include herds that were not in a badger control area for the entire follow-up period (for example, if they only became active after the baseline date), or at all (for example, if they were only active before the baseline date).

When the annual monitoring data are compiled, HIE are retrospectively redefined for each reporting year for each area to account for ongoing data validation (see Data Source and Quality). In addition, HIE for all reporting years is based on the most up-to-date boundary information provided by NE so that it always includes active herds located within the maximum area to have been culled under licence for each badger control area. This means that HIE for all years are also retrospectively redefined annually at the time of data compilation to account for any changes to badger control area boundaries that may have occurred up to the preceding year. Note, however, that updates to HIE resulting from a boundary extension are not implemented in the dataset until one season of badger culling has taken place within the extended area. These retrospective changes may result in minor differences in the HIE data reported between data releases.

HIE aims to represent all herds currently exposed to badger control operations at a given point in time. However, herds included in HIE each year were not all active on the baseline date for the area. Some herds may therefore have not been exposed to badger control operations for the entire follow-up period and the inclusion of herds that only recently became active may be a source of bias.

Individual area monitoring data

The monitoring data include the following metrics, calculated for each badger control area:

• total number of incidents
• number of OTF-W incidents
• number of herds
• herd years at risk
• total TB incidence rate
• OTF-W incidence rate
• total TB prevalence
• OTF-W prevalence
• numbers of reactors

Each metric is calculated for two different annual surveillance units: intervention years and calendar years. Each metric is calculated for two different cattle populations: cohort herds and HIE. 

Values in cells representing data for areas with fewer than 10 herds in total have been omitted to ensure the confidentiality of individual herd owners. This cut-off value is used by the Office for National Statistics (ONS) (Office for National Statistics, n.d.; Welpton, 2019).

Glossary of definitions for the monitoring data

Baseline date 

The baseline date is the start date of the cull in each area.

All incidents and OTF-W incidents

All incidents refer to the total number of new TB incidents in a herd during the reporting period, that is the intervention year or calendar year. It is the sum of Officially Tuberculosis Free-Withdrawn (OTF-W) and Officially Tuberculosis Free-Suspended (OTF-S) incidents detected. Both OTF-W and OTF-S are incidents of TB in a herd that have been disclosed through TB surveillance. However, in OTF-W incidents, M. bovis infection has been confirmed through post-mortem tests in at least one animal from the herd. For incidence rate data, incidents refers to the number of incidents detected throughout the reporting period. For prevalence data, incidents refers to the number of incidents on the last day of the reporting period (intervention year or calendar year).

Number of herds

The number of herds refers to the number of active herds in a badger control area for each group (cohort or HIE) at either the start (for incidence rate) or end (for prevalence) of each reporting period (intervention year or calendar year).

Time at risk (TAR)

The TAR is the total period of time the herds in a badger control area were considered at risk of TB infection (Defra, 2015; Downs et al., 2013). Herds are considered to be at risk of infection when they are not under trading restrictions due to a TB incident in the herd. The TAR is reported in years and is calculated from day one of the reporting period to the final day of the reporting period.

Total TB incidence rate and OTF-W incidence rate

The total TB incidence rate is the rate of occurrence of all TB incidents (OTF-S and OTF-W) over the reporting period. The OTF-W incidence rate is the rate of occurrence of new OTF-W incidents over the reporting period. The rates are calculated as the number of new TB incidents or OTF-W incidents, respectively, divided by the TAR and is reported as incidents per 100 herd years at risk (Defra, 2015; Downs et al., 2013). OTF-W incidence rate is typically used as the primary outcome for monitoring rather than total TB incidence rate. OTF-W incidence rate is less sensitive to variation in surveillance intensity than OTF-S incidence rate. Temporal changes to OTF-W incidence rate are also countered to some extent by linked and opposite changes to OTF-S incidence rate and monitoring total incidence rate disguises these underlying dynamics.

Total TB prevalence and OTF-W prevalence

The total TB prevalence and the OTF-W prevalence are point prevalence measurements indicating the proportion of herds under trading restrictions due to any TB incident (OTF-S or OTF-W) or an OTF-W incident, respectively, on the last day of each reporting period. Prevalence data provides an indication of the burden of disease in a badger control area.

Skin test reactors

Skin test reactors are cattle that reacted to the Single Intradermal Comparative Cervical Tuberculin (SICCT) test.), which is the primary screening test for TB in cattle in the UK. The yearly count of reactors relates to the date reactors were detected, not necessarily the year the incident started. Therefore, the count can include reactors from incidents which started in previous years.

The data do not include any cattle removed as “Direct Contacts (DC)”. These are non-reactor animals which are slaughtered because they are considered to be at high risk of being infected, normally as a result of contact with infected cattle.

Interferon (IFN) gamma reactors

IFN gamma reactors are cattle that tested positive to the IFN gamma assay, which is a rapid whole blood in-vitro assay detecting cell-mediated immune response to M. bovis infection, similar to the SICCT, for the diagnosis of TB.

Antibody test reactors

Antibody test reactors are cattle that tested positive to an antibody detection assay, which detects whether the animal is generating a humoral immune response to M. bovis infection.

Reactors to multiple test types are rare, as a reactor to one test type will usually be removed from a herd before a different test is carried out. However, for clarity, reactors to multiple test types are included just once in the dataset according to the following rules. Reactors to the SICCT test are always included in this category. Reactors to the IFN gamma assay are only included in this category if not also a SICCT test reactor. Reactors to the Antibody test are only included in this category if not also a reactor to the SICCT test and/or IFN gamma assay. The number of reactors include all reactors detected during an incident, including any at a short interval skin test.

Changes to the monitoring data and background information over time

1. Since the 2018 publication, no data from unculled comparison areas are included because of the loss of land (to culling) which might have been used to compare TB incidence rates in cattle to rates in badger control areas.
2. Since the 2021 publication, TB and herd data are no longer reported for buffer areas surrounding central badger control areas. This is because over time the proportion of the buffer area remaining around badger control areas has decreased, with substantial deductions in some areas (see Table 1 in Animal and Plant Health Agency 2021b) due to the licensing of new badger control areas. Additionally, remaining buffer is often comprised of small, separated areas of land which contain small numbers of herds. The overall reduction of available buffer land and the division of remaining buffer into small segments diminishes its value in an analysis of effects from culling.
3. Since the 2022 publication, graphs are no longer included to display the monitoring data due to the large number of areas now reported. All data which were displayed in the graphs are still available in the OpenDocument Spreadsheets.
4. Since the 2022 publication, 95% confidence intervals are no longer provided with the monitoring data. This is to allow data users to calculate confidence intervals using their preferred method.
5. Since the 2024 publication, an additional OpenDocument spreadsheet has been provided to give an overview of the different badger control operations (badger culling and APHA-delivered badger vaccination) that have occurred in each area over time.
6. Since the 2025 publication, total TB incidence rate and total TB prevalence data have been provided in addition to OTF-W incidence rate and prevalence. This is to align the data provided here with the TB data provided in other TB epidemiology surveillance reports and statistics.

Bibliography

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