April 2023: confirmed TB hotspots in the Low Risk Area of England
Updated 11 April 2024
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Summary
Surveillance for tuberculosis (TB) was conducted in 2021 in badgers removed from 2 badger TB control intervention areas in TB hotspots of the Low Risk Area of England, known as ‘Area 32 – Cumbria’ and ‘Area 54 – Lincolnshire’. The High Risk (HRA), Edge and Low Risk Area of England (LRA) were established on 1 January 2013, and are part of the Strategy for achieving Officially TB Free (OTF) status for England by 2038.
In Area 32 – Cumbria, vaccination operations were conducted and 140 vaccinated against TB. Area 54 – Lincolnshire underwent its second year of culling operations, where 6 of the 80 badgers removed (7.5%) were positive for Mycobacterium bovis on culture.
These results, alongside the ongoing surveillance of cattle and ‘found dead’ wildlife, will inform future control measures in both badgers and cattle within the hotspots.
The Animal and Plant Health Agency (APHA) is continuing to collect and test for TB ‘found dead’ badgers and wild deer carcases within hotspots that are reported through the Defra Rural Service Helpline (03000 200 301).
Introduction
A potential TB hotspot is an area in England or Wales of historically low TB incidence defined by APHA, where enhanced TB control measures are carried out following detection of lesion- or culture-positive TB herd breakdowns of uncertain origin. Enhanced measures include, but are not limited to, more frequent cattle surveillance testing and a survey of TB in ‘found dead’ wildlife (badgers and deer).
Collection of ‘found dead’ wildlife carcases (badgers and deer) is conducted with the aim of establishing whether M. bovis is present in the local wildlife population (badgers and wild deer). This relies on the engagement and cooperation of local stakeholders reporting carcases to the Defra Rural Services Helpline for collection by local APHA field staff. Carcases will only be collected if they are intact, meaning not decomposed or too damaged, and they are in a safe place for collection.
Post-mortem examination (PME) is then conducted, with tissue samples taken for bacteriological culture so that if M. bovis can be isolated, it undergoes Whole Genome Sequencing (WGS) analysis to establish if there are links to the local cattle breakdowns. It is important that as many carcases as possible are reported to inform epidemiological investigations. APHA is continuing to test ‘found dead’ badgers and wild deer carcases within hotspots reported through the Defra Rural Services Helpline (03000 200 301).
Badger control has been licensed in the Low Risk Area of England by Natural England since 2018 in ‘confirmed TB hotspots’ (those in which M. bovis-infected badgers have been found). The boundaries of the badger control intervention areas and the locations of badger carcases are not being released on security grounds. The badger control intervention areas are defined by APHA epidemiologists and ecologists and consist of:
- the minimum infected area (MIA), based on:
- the location of the infected badgers, associated farms and contiguous breakdown areas, plus a radius of the estimated average social group territory based on main sett distribution
- an outer area, also based on:
- estimated average badger social group territory size, surrounding the minimum infected area, to take into account the possibility that infection may have already spread in the badger population. The boundary was adjusted to adhere to natural barriers to badger movement as far as practical to minimise the risk of any possible perturbation effects
As in previous years, APHA carried out TB surveillance using culled badger carcases to monitor the prevalence of M. bovis infection and generating information for future operations in the area. Cage-trapped and controlled shot badger carcases removed from the cull areas underwent PME, with suitable tissue samples collected for culture of M. bovis in the laboratory. Genotyping and WGS was then carried out on any isolates of the bacterium.
Area 32 – Cumbria
Background
A cluster of TB cattle herd breakdowns emerged in the Low Risk Area of England in eastern Cumbria from late 2014. A potential hotspot area (HS21) was declared and cattle, some species of non-bovine farmed animals and wildlife were subjected to enhanced TB surveillance from September 2016.
The genotype of M. bovis (17:z) associated with HS21 had not previously been identified in cattle herds in Great Britain. Investigations concluded that disease is most likely to have been introduced by cattle imported from Northern Ireland. The novel genotype identified in both cattle and badgers in this area and the WGS analysis provided evidence that local spread of TB was likely to be occurring within and between both species.
From identification of the index case in November 2014 to 15 February 2023, there have been a total of 57 breakdowns across 48 holdings investigated as part of HS21. Of those, 50 were associated with the hotspot (of which, 22 were OTF-Withdrawn (OTFW) and 28 were OTF-Suspended (OTFS). Collection of ‘found dead’ badgers and deer is ongoing in the area. From September 2016 to 15 February 2023, a total of 74 badger and 8 wild deer carcases have been submitted. There have been 3 M. bovis-positive badgers, all of which were identified in 2017. Not all reported carcases are collected and submitted for PME. Further detail is provided in the introduction.
Badger control operations
The fifth year of badger TB control operations began within Area 32 in May 2022. To reflect the lack of infected badgers identified by post-mortem across the area since 2020, vaccination is now carried out across the whole 218 km2 area. Further information on these decisions was published in September 2022: (Defra (2022) Setting the minimum and maximum numbers in badger cull areas in 2022: Advice to Natural England).
In 2022, 140 vaccinations were administered to badgers trapped by APHA staff. A total of 351 badger vaccinations have been given to date (100 in 2020, 111 in 2021). APHA wildlife experts have used vaccination in this area to develop their knowledge of vaccination operations in a post-cull population, which will assist in the further expansion of vaccination in these areas.
Results from the ongoing enhanced surveillance of cattle and ‘found dead’ wildlife will be considered annually to inform future control measures in both badgers and cattle within HS21.
Area 54 – Lincolnshire
Background
A potential hotspot area (HS23) was established in June 2018, following the disclosure of M. bovis in a cattle herd in south west Lincolnshire. Due to its proximity to, and shared genotype with, a cluster of OTFW breakdowns in north east Leicestershire, this hotspot area straddles the LRA (Lincolnshire) and the Edge Area (Leicestershire). Additional TB surveillance measures have been implemented in cattle and wildlife across the whole hotspot area, including the collection of ‘found dead’ badger and wild deer carcases.
From the disclosure of the index case in December 2017 to 15 February 2023, a total of 104 breakdowns have been disclosed across 99 premises. All M. bovis isolates from cattle except one have been part of the WGS clade B3-11 (which encompasses genotype 25:a and 25:b). One isolate was WGS clade B6-62 (spoligotype 10), so not associated with the hotspot.
To date, a total of 33 ‘found dead’ badger carcases have been submitted for PME. Three badger carcases have been culture positive for M. bovis, all identified pre-2020. One of the positive badgers was located in the Edge Area portion of the hotspot, and the 2 others were located in the LRA portion. Two wild deer carcases have also been submitted for PME: all were negative for M. bovis on laboratory culture. Not all reported carcases are collected and submitted for PME. Further detail is provided in the introduction.
Badger control operations
Badger TB control operations were licensed and began within the LRA portion of HS23 in September 2020, formally known as Area 54 – Lincolnshire. The operations carried out in the third year (2022) were deemed safe, effective and humane by the UK Chief Veterinary Officer (CVO). Further details of the outcomes of the operations have been published (Natural England (2022) Summary of badger control monitoring during 2022). In 2022, 80 badgers were removed from the badger TB control area.
Of those carcases, 6 (7.5%) were positive for M. bovis across the whole area. Final results were still pending for 7 carcases at the time of compiling this report. Table 1 shows the change in prevalence within the sampled culled badger carcases over the 3 years of badger control operations in the area.
Table 1. Prevalence in the sampled badgers in Area 54 – Lincolnshire
| Operational year | Carcases positive for M. bovis | Prevalence |
|---|---|---|
| 2020 | 34 of 139 | 24.5% [95%CI 17.4, 31.6] |
| 2021 | 16 of 156 | 10.3% [95%CI 5.5, 15.1] |
| 2022 | 6 of 80 | 7.5% [95%CI 1.7, 13.3] |
If the 2 parts of the badger TB control area are considered separately, 6.9% of the carcases removed from parcels within the MIA tested positive (4 of 58), and 9.1% tested positive (2 of 22) in the outer cull area. Overall, 7.5% of the removed carcases were positive for M. bovis.
Figure 1. Schematic of the distribution of infected badgers
The results presented here, alongside the ongoing enhanced surveillance of cattle and ‘found dead’ wildlife, will inform future control measures in both badgers and cattle within HS23.