A potential TB hotspot is an area of variable size in the Low Risk Area (LRA) of England where the Animal & Plant Health Agency (APHA) initiates enhanced TB surveillance measures for a limited period due to the emergence of one or more culture-positive TB herd breakdowns of uncertain origin. Enhanced measures include post-mortem surveillance for TB in potential wildlife reservoirs and changes to cattle testing and controls.
If this enhanced surveillance uncovers Mycobacterium bovis infection in the local wildlife that is linked to the development of cattle breakdowns in the area, the potential hotspot becomes a confirmed hotspot.
Identification of potential hotspot areas
In the LRA, all new TB breakdowns of uncertain origin resulting in Officially TB Free (OTF) herd status being withdrawn (OTFW) are carefully assessed by APHA vets to determine whether they satisfy the criteria for declaration of a potential hotspot area. The TB breakdown(s) triggering the potential hotspot area are known as the index case(s).
How is the origin of infection assessed in the index case(s)?
To determine whether an index case should trigger a potential hotspot area, APHA vets will try to establish the likely origin of infection for the affected herd or cluster of herds. If the origin of the index case is likely to be the introduction of TB-infected cattle into the herd, then APHA will not instigate a potential hotspot area and the standard procedures for a normal OTFW breakdown in the LRA are followed, including radial surveillance testing. Otherwise, the area around the index OTFW breakdown will be considered for a potential hotspot area declaration (see flow chart below). To determine the most likely origin of infection, APHA will carry out several actions.
Disease investigation visit (DRF) of the index OTFW breakdown. This is completed by an APHA vet, primarily to gather information about the source of the TB breakdown.
The index case may be linked to introductions of TB infected cattle if the lesion/culture positive cattle have been detected at a post-movement test, or if the WGS clade of the M. bovis isolate matches that commonly found in the region of origin of the infected animal(s). Index cases can be linked to:
- Cattle purchases from herds in higher risk areas of England or Wales
- Hired bulls
- Spread from other OTFW herds
- Cattle imports from Ireland
- Cattle taken to agricultural shows
- Cattle returning from common or rented grazing
What happens when a potential hotspot area is identified?
Enhanced cattle controls and testing
Once a potential hotspot area has been declared and its boundary delineated, APHA will increase the TB testing frequency of cattle herds inside the potential hotspot area boundary (as per the normal LRA breakdown procedure), which will normally include the 3km radial zone(s) around the index case farm(s).
All cattle keepers in the radial zone(s) of the index case(s) will be issued with a TB test notification letter from APHA, informing them that their herd requires a series of three radial tests.
Surveillance of local wildlife
Once a potential hotspot area has been set up, APHA will carry out enhanced TB surveillance of local wildlife. The aim of enhanced wildlife surveillance is to determine whether the potential hotspot area is home to infected wildlife and, if so, whether infected wildlife is linked to the development of cattle breakdowns in the area. Typically, surveillance of wildlife is carried out by collecting carcases of badger and wild deer ‘found dead’ in the potential hotspot area (for example, carcases found on roads).
Carcases that are suitable for collection by APHA field staff will be sent to the laboratory for post-mortem examination (PME) and bacteriological culture of suitable tissue samples. If any carcases are positive for M. bovis on culture, WGS will be carried out to find links between wildlife infection and local cattle breakdowns. If the WGS of M. bovis isolates from wildlife matches that of the local cattle breakdowns, the potential hotspot area will be declared a confirmed hotspot area.
Local stakeholder engagement
The collection of badger and deer carcases for TB post-mortem surveillance relies on the engagement and cooperation of local stakeholders. It is local stakeholders who report the carcases for collection by APHA field staff. Stakeholder engagement is crucial to the success of wildlife surveillance and the more carcases collected, the better APHA can understand the infection risk posed by wildlife and inform next steps for controlling disease and managing the hotspot area.
All cattle keepers in the hotspot area will be issued with a Potential Hotspot Notification Letter which provides guidance on how to inform APHA of any found-dead badger or deer carcases. Carcases can also be reported through the Defra Rural Services Helpline (03000 200 301).
Other stakeholders informed of the establishment of a potential TB hotspot area are:
Once a potential hotspot area is declared, how soon will all cattle herds inside the hotspot have to be tested?
Breakdown herds in the potential hotspot area will have more frequent testing scheduled and individual restrictions will be put in place. All cattle keepers in the 3km radial zone of the index breakdown(s) will be issued with a test notification letter informing them that their herd requires an immediate radial skin test. Other herds within the potential hotspot area may additionally be placed onto the same radial testing schedule.
Individual animals from cattle herds in the LRA that are undergoing enhanced radial and hotspot surveillance testing must also be pre-movement tested unless destined for slaughter or an Approved Finishing Unit. It is important for cattle keepers to arrange the required tests as soon as possible, as delays to testing will slow down the gathering of evidence and may unnecessarily prolong the duration of increased surveillance in potential hotspot areas.
For an individual cattle herd in a hotspot, what is the quickest possible return to normal (routine) testing frequency?
In a potential hotspot area, testing frequency will return to routine once the radial testing regime has finished. In a confirmed hotspot, the decision to return to the normal four-yearly routine herd testing frequency for the LRA will be taken for the hotspot as a whole and will be handled on a case-by-case basis. Increased testing frequency will continue for all herds in the area until the hotspot is officially closed.
What is the duration of a TB hotspot?
The duration of a hotspot depends on the emerging disease situation in cattle and wildlife in the area and will be different for every hotspot. Hotspot measures will continue until there is clear evidence that the disease risk has been controlled in cattle (all increased testing completed with negative results) and no evidence of M. bovis infection has been found in wildlife.
If all cattle herds are timely tested with negative results, and no infection is found in wildlife carcases submitted for PME, then the shortest realistic duration might be 2.5 years from establishment of the potential hotspot area. However, there are many variables that determine the duration of a hotspot, including:
- Existing TB herd breakdowns continuing
- New TB herd breakdowns detected
- The same strain of bovis being found in any new herd breakdowns and/or in any wildlife carcases submitted for PME
What is the difference between a potential and confirmed TB hotspot area?
In a potential hotspot area, wildlife involvement in herd breakdowns is suspected, but has not been confirmed by PME, bacteriological culture and (if applicable) WGS of found dead wildlife carcases.
Confirmed hotspot areas
Confirmed TB hotspot areas may qualify for the following measures.
Licensed TB control measures in wildlife
Badger TB control has been licensed in confirmed hotspots in the LRA since 2018. Badger control is carried out in so-called ‘badger control intervention areas’, which are defined by expert epidemiologists and ecologists. Hotspot wildlife controls are known as ‘adaptive disease control’ licences and are subject to an annual evidence review by APHA epidemiologists, ecologists, and the Chief Veterinary Officer (CVO) to ensure the ongoing suitability of badger control.
Typically, the badger control intervention areas in the LRA are made up of:
This area is based on the location of confirmed infected badger carcases, farms with associated genotypes and herd breakdown areas.
The CVO may approve badger vaccination in confirmed hotspot areas (or sections thereof) where all badger carcases collected have been free from infection with M. bovis for at least two consecutive years.
Enhanced cattle measures
It may be necessary in confirmed hotspot areas for OTF herds to undergo six-monthly TB testing, which will be funded by the Government.
Keepers of cattle and non-farmed bovine animals can request free, bespoke advice on implementation of biosecurity measures from the TB Advisory Service (TBAS). In hotspot area HS21 (Cumbria), local private vets were trained to give advice to farmers and provided information packs covering biosecurity.
Enhanced TB surveillance of camelid, goat and captive deer herds
Herds of South American camelids (alpacas and llamas), goats and farmed/park deer contiguous to or co-located with cattle TB breakdown herds in the hotspot area may be subject to a comparative skin test followed (in the case of camelids) 10 to 30 days later with a serum antibody test.
Where can I learn more about existing TB hotspots?
At the time of writing this guidance, two confirmed hotspot areas remain active in the LRA:
- Hotspot 21, Cumbria
- Hotspot 23, Lincolnshire
For more information on Hotspot 21 and Hotspot 23 and the TB surveillance measures carried out every year, visit gov.uk
Closing a TB hotspot area
It is important to note that the duration of a hotspot depends on the TB surveillance results in cattle and wildlife in the area and will be different for every hotspot. Closure of a potential hotspot area will only be considered when:
- All required TB tests in cattle herds have been completed and no further TB infected cattle with a strain of bovis linked to the Hotspot are found; and,
- All wildlife survey culture results have been completed with negative results.
The decision to close a confirmed hotspot will be handled on a case-by-case basis, reflecting the evolving disease situation in cattle and wildlife in the area and the results of licensed badger TB controls (usually including four years of vaccination after two consecutive years of culling with no infected badgers found).