March 2022: confirmed TB hotspots in the Low Risk Area of England
Updated 11 April 2024
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Summary
TB surveillance was conducted in 2021 in badgers removed from two 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) and Low Risk Area of England (LRA) was established on 1 January 2013, and is part of the strategy for achieving officially TB free (OTF) status for England by 2038.
In Area 32 – Cumbria, both culling and vaccination operations were conducted, where 62 badgers were removed and 111 vaccinated against TB. All badger carcases underwent post mortem examination and were negative for Mycobacterium bovis infection on bacteriological culture.
Area 54 – Lincolnshire underwent its second year of culling operations, where 14 of the 156 badgers removed (9.0%) 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.
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- and/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, that is, 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 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
The boundaries of the badger control intervention areas and the locations of badger carcases are not being released on security grounds.
As in previous years, APHA carried out TB surveillance on 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 17 February 2022 there have been a total of 46 breakdowns across 37 holdings (of which, 22 were OTF-Withdrawn (OTFW) and 24 were OTF-Suspended (OTFS)). Collection of ‘found dead’ badgers and deer is ongoing in the area. From September 2016 to 18 January 2022, a total of 71 badger and seven wild deer carcases have been submitted (not all reported carcases are collected and submitted for PME. Further detail is provided in the introduction). There have been three M. bovis-positive badgers, all of which were identified in 2017.
Badger control operations
The fourth year of badger TB control operations began within Area 32 in June 2021. To reflect the lack of infected badgers in the outer area since 2019, and in the MIA since 2020, ring vaccination of badgers was carried out around the central MIA, while culling continued in the MIA. Further information on the advice to Natural England on setting minimum and maximum numbers of badgers to be controlled in 2021 was published in September 2021. Vaccination was undertaken in June and July over 140km2 (of which, 91km2 was accessible). The rest of the area (74km2) started culling operations in September. The cull was deemed safe, effective, and humane by Defra’s Chief Veterinary Officer (CVO) in the Summary of Operations published in March 2021. Further details of the outcomes of the operations have been published.
In the 2021 culling operations 62 badgers were removed from the badger control intervention area. Of these, 49 were taken by controlled shooting and 13 by cage trapping. All carcases underwent PME and tissue sampling as described previously. In the rest of the area, 111 badgers were vaccinated.
None of the 62 badgers removed during the 2021 operations tested positive for M. bovis on culture. Table 1 shows the prevalence of badger infection across all operational years.
| 2018 | 2019 | 2020 | 2021 | |
|---|---|---|---|---|
| Area 32 | 11.1% (41/369) | 1% (3/313) | 0% | 0% |
| MIA | 21% (38/181) | 14.3% (3/21) | 0% | 0% |
| Outer Area | 1.7% (3/175)** | 0% (0/233)*** | 0% | 0% |
Table 1. Prevalence of 17:z positive badgers in Area 32 between 2018 to 2021
The boundary of the MIA was changed after 2018 and 2019 operations to encompass the location of all known infected badgers and cattle breakdowns with a suspected wildlife source.
** The remaining 13 carcases from parcels that span both the MIA and outer area were negative
*** The remaining 59 carcases from parcels that span both the MIA and outer area were negative
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 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 01 February 2022, a total of 42 new breakdowns have been disclosed across 41 premises (11 in the LRA portion (6 OTFW and 5 OTFS)), of which 18 were OTFW and 24 OTFS. All M. bovis isolates from cattle except one (one isolate was WGS clade B6-62 (spoligotype 10), so not associated with the hotspot) have been part of the WGS clade B3-11 (which encompasses genotype 25:a and 25:b).
To date, a total of 40 ‘found dead’ badger carcases have been submitted for PME (note: not all reported carcases are collected and submitted for PME. Further detail is provided in the introduction). 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 two others were located in the LRA portion. Nine wild deer carcases have also been submitted for PME: all were negative for M. bovis on laboratory culture.
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 second year (2021) were deemed safe, effective and humane by the CVO (Defra advice to Natural England on setting minimum and maximum numbers of badgers to be controlled in 2021). In 2021, 161 badgers were removed from the badger TB control area, all of them by controlled shooting. There were 67 badgers removed from the MIA and 94 from the outer cull area.
A total of 156 (five badgers did not undergo PME due to being missed from collection. These were disposed of through the cull company following standard protocol) badger carcases removed during culling operations underwent PME and tissue sampling as described previously. Of those carcases, 14 (9.0%) were positive for M. bovis across the whole area. Final results were still pending for two carcases at the time of compiling this report. If the two parts of the badger TB control area are considered separately, 17.9% of the carcases removed from parcels within the MIA tested positive (12/67), and 2.2% tested positive (2/89) in the outer cull area.
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.