April 2023: potential TB hotspots in the Low Risk Area of England
Updated 11 April 2024
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Introduction
As part of the 2014 Strategy to achieve Officially Bovine Tuberculosis Free (OTF) status for England by 2038, 3 management areas were established: High Risk Area, Edge Area and Low Risk Area (LRA). Overall, the LRA has a very low and stable incidence of infected herds. The current strategy seeks to rapidly control infection when it arises through high sensitivity testing of affected herds and temporarily enhanced local TB surveillance through radial and hotspot testing, with the aim of preserving the favourable disease status of this area.
Within the LRA there are 2 types of TB hotspots: potential hotspots and confirmed hotspots. These areas are defined by local Animal and Plant Health Agency (APHA) teams, along with the type of enhanced TB surveillance undertaken within them.
A potential hotspot is an area in England or Wales of historically low TB incidence 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, increased frequency of cattle surveillance testing and a survey of ‘found dead’ wildlife (badgers and wild deer).
If Mycobacterium bovis infection in the local wildlife is identified in a potential TB hotspot area via the ‘found dead’ wildlife survey, and it can be epidemiologically linked to the local cattle TB breakdowns through genetic analysis of bacterial isolates, it then becomes a confirmed hotspot area. Information regarding confirmed hotspots in the LRA can be found in a separate publication (Defra (2022) Confirmed TB hotspots in the Low Risk Area of England).
At the time of writing, there were 5 potential TB hotspot areas (Table 1) and 2 confirmed TB hotspot areas (HS21 in Cumbria and HS23 in Lincolnshire) active in the LRA of England.
Locations
Table 1. Open potential TB hotspot areas in the Low Risk Area of England
| Potential hotspot area | Location | Size |
|---|---|---|
| PHA24 | West Sussex | 143.8 km sq |
| PHA26 | Cumbria | 197.8 km sq |
| PHA27 | Lancashire-North Yorkshire border | 140 km sq |
| PHA28 | Lincolnshire | 780.4 km sq |
| PHA29 | Cumbria | 353.8 km sq |
Surveillance in wildlife
Collection of ‘found dead’ wildlife carcases (badgers and deer) is conducted in potential hotspots with the aim of identifying, if present, M. bovis in the local wildlife population. This relies on the engagement and cooperation of local stakeholders reporting carcases to the Defra Rural Service 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. This is done to establish how similar it is to the strains of the bacterium found in the neighbouring cattle herds affected by TB breakdowns.
Table 2. Number of wildlife carcases collected in potential TB hotspot areas in the Low Risk Area of England to 18 January 2023
| Potential hotspot area | Badgers: Negative | Badgers: Pending | Deer: Negative | Deer: Pending |
|---|---|---|---|---|
| PHA24 | Not applicable | Not applicable | Not applicable | Not applicable |
| PHA26 | 4 | 0 | 3 | 0 |
| PHA27 | Not applicable | Not applicable | 1 | 0 |
| PHA28 | 43 | 0 | 5 | 0 |
| PHA29 | Not applicable | 1 | Not applicable | Not applicable |
Notes:
- no carcases have been submitted in PHA24
- PHA29 was established late 2022
It is important that as many carcases as possible are reported to inform epidemiological investigations. APHA is continuing to test ‘found dead’ badgers and deer carcases within hotspots reported through the Defra Rural Service Helpline (03000 200 301).