Research and analysis

North West of England (Low Risk Area) year end report 2023

Published 19 September 2024

Applies to England

Introduction

The Low Risk Area (LRA) was established in 2013, along with the Edge and High Risk Areas of England. In 2014 the 3 bovine tuberculosis (TB) risk areas were incorporated into the UK government’s strategy to achieve Officially TB-Free (OTF) status for England by 2038. A key action was to recognise the different levels of TB in different parts of the country and to adjust the approaches to TB surveillance and control in each risk area accordingly. Overall, the LRA has a very low and stable incidence of TB-infected herds. The current strategy for the LRA seeks to mitigate the risk of TB incursions via cattle movements and rapidly contain and eradicate any foci of infection through:

• mandatory pre- and post- movement testing of cattle entering the LRA from higher risk areas of the UK
• more sensitive testing of infected herds
• temporarily enhanced TB surveillance (radial and hotspot testing) in the vicinity of herds experiencing lesion and/or Polymerase Chain Reaction (PCR) test (or culture)-positive incidents of TB

The aim of this combined approach is to preserve the favourable disease status of this area so that its counties can be declared OTF as soon as possible.

This report describes the frequency and geographical distribution of TB in 2023 in cattle herds in the North West of England, which is part of the LRA. In 2023, 13% of all new TB incidents in the LRA were detected in the North West of England.

TB in cattle and other mammals is primarily caused by infection with the bacterium Mycobacterium bovis (M. bovis) and the disease is subsequently referred to as ‘TB’ in this report. Although other sources may refer to TB ‘breakdowns’, this report will use the term ‘incidents’ throughout.

This report is intended for those involved in the control of TB, both locally and nationally. This includes, but is not limited to:

• cattle farmers
• government and private veterinarians
• policy makers
• the scientific community

Details of the data handling methodology used in this report, a glossary of terms, and the TB control measures adopted in the LRA, can be found in the explanatory supplement for the annual reports 2023.

Types of TB incident

Unless otherwise specified, this report includes all new TB incidents detected during the reporting period, 1 January to 31 December 2023. This includes both ‘Officially Tuberculosis-Free Status Withdrawn’ (OTF-W) and ‘Officially Tuberculosis-Free Status Suspended’ (OTF-S) incidents.

OTF-W incidents are those involving at least one skin test reactor (an animal positive to the Single Intradermal Comparative Cervical Tuberculin [SICCT] test) with either:

• typical lesions of TB identified at post-mortem (PM) meat inspection
• and at least one animal with M. bovis-positive PCR test or bacteriological culture results in tissue samples collected from carcasses during the PM inspection

OTF-S incidents are triggered by reactors to the skin test, but without subsequent detection of TB lesions or positive PCR test (or culture) results in any of those animals.

Cattle industry

Most cattle herds in the North West region are found in Lancashire. Cattle herds in Lancashire are mainly of the dairy type, whereas in Merseyside and Greater Manchester they are predominantly beef herds. Appendix 1 provides the number of cattle premises by herd size band and breed purpose for each of the 3 counties.

There are 4 livestock markets in the region, all located in northern Lancashire. One of those can operate as an ‘exempt’ market for the exceptional sale of cattle that are moved without a mandatory TB pre-movement test, for onward consignment to slaughter or to a TB approved finishing unit (AFU). Two collection centres, both situated in Lancashire, handle slaughter cattle. There is also one Licensed Finishing Unit (LFU) in Lancashire.

The number of cattle markets in operation in 2023 is captured and maintained centrally by the Animal and Plant Health Agency (APHA) TB Customer Service Centre. Where possible, this data is then subject to further validation by APHA veterinarians subject to their best knowledge of the local area. Some small discrepancies may therefore exist where changes to markets were not captured in time for this report.

New TB incidents

During 2023, there were 17 new TB incidents in the North West of England, a 35% decrease from 26 incidents in 2022 (Figure 1a and b). This follows a steady rise in the number of incidents in the region, from 12 in 2020 to 26 in 2022, and was driven by a fall in the number of OTF-W incidents (4 in 2023, down from 9 in 2022). The total number of OTF-S incidents was 13 (down from 17 in 2022).

As shown in Figure 1a and b, in Lancashire, the total number of incidents was 11, a decrease from 17 in 2022. The number of OTF-W incidents was 2, down from 5 in 2022, and there were 9 OTF-S incidents, down from 12 in 2022.

In Greater Manchester, the total number of incidents was 5 (2 OTF-W and 3 OTF-S). This was a decrease from 9 total incidents, a drop of 2 OTF-W and 2 OTF-S incidents compared to 2022.

In Merseyside, a single OTF-S incident was disclosed, the first recorded in the county since 2018.

Greater Manchester

Year	OTF-W	OTF-S	Total
2014	1	4	5
2015	3	3	6
2016	1	6	7
2017	1	5	6
2018	0	4	4
2019	4	1	5
2020	5	5	0
2021	3	4	7
2022	4	5	9
2023	2	3	5

Lancashire

Year	OTF-W	OTF-S	Total
2014	6	15	21
2015	2	16	18
2016	3	10	13
2017	4	2	6
2018	0	10	10
2019	1	12	13
2020	2	6	8
2021	4	13	17
2022	5	12	17
2023	2	9	11

Figure 1a: Annual number of new TB incidents in the Greater Manchester and Lancashire of England, from 2014 to 2023.

Figure 1a description: Bar chart showing the number of OTF-W and OTF-S incidents in Greater Manchester and Lancashire between 2014 and 2023. There are more OTF-S incidents than OTF-W in both counties throughout all 10 years. In 2023, there were 2 OTF-W and 3 OTF-S in Greater Manchester, and 2 OTF-W and 9 OTF-S in Lancashire.

Year	OTF-W	OTF-S	Total
2014	1	1	2
2015	0	1	1
2016	0	1	1
2017	2	0	2
2018	1	1	2
2019	0	0	0
2020	0	0	0
2021	0	0	0
2022	0	0	0
2023	0	1	1

Figure 1b: Annual number of new TB incidents in Merseyside, from 2014 to 2023.

Figure 1b description: Bar chart showing the number of OTF-W and OTF-S incidents in Merseyside between 2014 and 2023. There were no incidents in Merseyside between 2019 to 2022. In 2023, there was one OTF-S incident.

The headline cattle TB statistics for the 3 counties are summarised in Appendix 2.

Disclosing test type

As shown in Figure 2, in 2023, just under half of new TB incidents in Greater Manchester and Lancashire were disclosed by targeted surveillance around OTF-W incidents, commonly known as ‘radial testing’ (RAD): 40% (2 out of 5) and 45% (5 out of 11) respectively.

In Lancashire, 4-yearly routine herd testing (RHT) detected 3 incidents. Pre-movement testing detected 2 incidents and whole herd testing detected one incident.

In Greater Manchester, this was similar to the trend seen in the county over the last 2 years, when just under half of new incidents were detected by RAD testing in 2021 (43%), and over half in 2022 (55%). In Lancashire, this is a slight decrease compared to 2022 when 53% of new incidents were disclosed by radial testing.

In Greater Manchester, RHT, pre-movement testing and 12-month testing detected one incident each.

In Merseyside, the single OTF-S incident in the county in 2023 was detected through RHT.

Location	12M Test	Pre-Movement Test	Radial Test	Routine Herd Test	Whole Herd Test	Grand Total
Greater Manchester	1	1	2	1	0	5
Lancashire	0	2	5	3	1	11
Merseyside	0	0	0	1	0	1

Figure 2: Number of new TB incidents (OTF-W and OTF-S) in the North West of England, in 2023 according to the surveillance test that detected them.

Figure 2 description: Bar chart showing the number of new TB incidents disclosed by TB test type in 2023. In Greater Manchester, 5 incidents occurred, with 2 from radial tests, and 1 each from 12-monthy post-incident (12M) testing, routine testing, and pre-movement testing. In Lancashire, 11 incidents occurred, with most incidents (5) disclosed by radial testing, followed by routine testing (3). In Merseyside, 1 incident was disclosed from a routine herd test.

The headline cattle TB statistics for each county are summarised in Appendix 2.

Duration of TB incidents

A total of 18 TB incidents were resolved during 2023. Of these, 11 were new TB incidents that started in 2023 and 7 had started in 2022.

Consistent with previous years, most OTF-S incidents which resolved in 2023 were quickly resolved in less than 150 days (10 out of 13). The other 3 were resolved within 240 days.

All OTF-W incidents which resolved in 2023 in Greater Manchester (3) and Lancashire (2) were resolved within 240 days. These findings are also largely consistent with the previous 2 years.

There were no herds with persistent incidents (not under TB movement restrictions for more than 550 days) in the region.

Of the 17 new incidents in 2023, 6 were still open at the end of the reporting year and continued into 2024 (5 OTF-S and 1 OTF-W).

Unusual TB incidents

One of the OTF-W incidents in Lancashire involved a raw milk producer-retailer. The sale of raw milk had to cease due to the loss of OTF herd status, to protect public health. Milk from cows in a herd under TB movement restrictions must not be used for human consumption unless it has been heat treated.

TB in other species

There is no statutory routine TB surveillance of non-bovine species, apart from Post-Mortem Examination (PME) of animals slaughtered for human consumption, or carcasses submitted to veterinary laboratories for diagnostic investigations. Targeted TB testing takes place in non-bovine herds under TB movement restrictions due to laboratory-confirmed incidents of M. bovis infection, and in specific herds of camelids, goats and captive deer at an elevated risk of infection. There were no TB incidents in other susceptible species in the North West in 2023.

Recurring TB incidents

Three-year recurrence

In the North West of England, 4 of the 13 (31%) cattle herds with a new OTF-S TB incident and one of the 4 (25%) with an OTF-W incident had experienced another TB incident in the previous 3 years, as shown in Figure 3. This was the second highest percentage of recurrent incidents among the regions within the LRA. In the whole of the LRA, 27% of the new TB incidents recorded in 2023 were considered recurrent.

Greater Manchester

TB incident	No history of TB in the last 3 years	History of TB in the last 3 years	Total
OTF-S	2	1	3
OTF-W	1	1	2

Lancashire

TB incident	No history of TB in the last 3 years	History of TB in the last 3 years	Total
OTF-S	6	3	9
OTF-W	2	0	2

Merseyside

TB incident	No history of TB in the last 3 years	History of TB in the last 3 years	Total
OTF-S	1	0	1
OTF-W	0	0	0

Figure 3: Number of herds with a TB incident (by OTF-W and OTF-S) in the North West of England in 2023, with and without a history of any TB incident in the previous 3 years.

Figure 3 description: Bar chart showing the number of herds with a TB incident (OTF-W and OTF-S) in Greater Manchester, Lancashire and Merseyside in 2023, with a history of TB in the last 3 years in green and without a history of TB in blue. Most TB incidents did not have a history of TB in the last 3 years in any of these counties in 2023. In Greater Manchester, 2 herds out of 5 had a history (one OTF-S and one OTF-W herd), and in Lancashire it was 3 OTF-S herds out of 11 total herds.

Overall recurrence

In 2023, 75% of incidents reported in the region were in herds with a history of TB at any point in the herd’s lifetime. This includes looking back beyond the 3-year period mentioned previously (7 out of 13 OTF-S and 2 out of 4 OTF-W), as shown in Figure 4. The recurrence of TB incidents in herds in 2023 was greatest in Greater Manchester (4 incidents out of a total of 5) followed by Lancashire (16 incidents out of 65). There was no recurrence in Merseyside.

Overall recurrence of TB increased compared to 2022 (31%, 6 out of 17 OTF-S and 2 out of 9 OTF-W). This was due to recurrence increasing in Greater Manchester (56% in 2022 to 80% in 2023) and Lancashire (18% in 2022 to 45% in 2023).

Greater Manchester

TB Incident	No history of TB within the herd lifetime	History of TB within the herd lifetime
OTF-S	1	2
OTF-W	0	2

Lancashire

TB Incident	No history of TB within the herd lifetime	History of TB within the herd lifetime
OTF-S	4	5
OTF-W	2	0

Merseyside

TB Incident	No history of TB within the herd lifetime	History of TB within the herd lifetime
OTF-S	1	0
OTF-W	0	0

Figure 4: Number of herds with a TB incident (by OTF-W and OTF-S) in the North West of England in 2023, with and without a history of any TB incident in the herd’s lifetime.

Figure 4 description: Bar chart showing the number of herds with a TB incident (OTF-W and OTF-S) in Greater Manchester, Lancashire and Merseyside in 2023, with a history of TB in the herd’s lifetime in green and without a history of TB in the herd’s lifetime in blue. Most TB incidents did have a history of TB during the herd’s life time in Greater Manchester (4 out of 5 herds). In Lancashire, most OTF-S incidents had a history of TB in the herd’s lifetime (5 out of 9 OTF-S herds). Merseyside had no herds which had a TB incident in 2023 with a history of TB in the herd’s lifetime.

Geographical distribution of TB incidents

As in previous years, most new TB incidents in Lancashire continued to occur in areas of higher cattle density, though some occurred in regions where the cattle density was comparatively lower (Figure 5).

Around the higher cattle density area in central Lancashire, there was one new OTF-W incident attributable to clade B6-84 of M. bovis. This clade is widespread across the West Midlands and parts of Wales. An OTF-W incident with WGS clade B6-84 was previously detected on a farm in Lancashire in 2021. The 2 farms are about 8 miles apart and no epidemiological links had been identified between the 2 isolates. They have also been found to be genetically unrelated.

There have been previous OTF-W incidents in central Lancashire in 2021 and 2022, but these yielded isolates with clades B6-62 (homerange in the southern Edge Area and east Gloucestershire and east Wiltshire in the High Risk Area (HRA) LFU) and B6-11 (homerange in the west of England, from south Cheshire to Avon and Wiltshire, and in parts of Wales). One OTF-S incident was disclosed in this area in 2023.

The other OTF-W in Lancashire was located to the west towards the border with Merseyside. This incident was associated with clade B6-86. This clade is very uncommon in Great Britain (England, Scotland and Wales (GB)) and does not yet have a homerange, although it has been previously found in Scotland.

There were 2 new OTF-S incidents in south Lancashire towards the border with Greater Manchester. There have been no OTF-S incidents in this area since 2019 and there have been no OTF-W incidents recorded at least since 2015.

In Greater Manchester, there was one OTF-W incident with clade B3-11 in the southeast of the county near Stockport. Small numbers of OTF-W incidents caused by this clade of M. bovis have continuously occurred in this area since 2020 (one in 2020, one in 2021, and 3 in 2022). There was also one OTF-S incident in this area in 2023. APHA is considering setting up a formal hotspot area of enhanced cattle and wildlife TB surveillance in this section of Greater Manchester.

The other new OTF-W incident in Greater Manchester in 2023 was detected in the north-east, north of Mossley. This incident had clade B1-11 of M. bovis detected , however the sample was contaminated and this clade result is therefore unreliable. There have been no previous OTF-W incidents detected in this area, although in 2018 there was one OTF-S incident nearby.

The one OTF-S incident detected in Merseyside in 2023 was located towards the west of the region, where a previous radial testing zone was triggered before 2020.

Figure 5: Location of cattle holdings in the North West of England with new TB incidents (OTF-W and OTF-S) in 2023, and cattle holdings with pre-2023 OTF-W incidents still ongoing at the beginning of 2023, overlaid on a cattle density map. Note that ‘OTF-W Introduced 2023’ refers to OTF-W incidents in which cattle movements were the most likely source of infection.

Figure 5 description: A map of the North West showing the cattle density, the geographical location of cattle holdings with new TB incidents (OTF-W and OTF-S) in 2023, and OTF-W incidents pre-2023. Dark blue areas represent higher cattle density and light blue represent lower cattle density. New OTF-W incidents detected in 2023 are shown as triangles and colour-coded based on the WGS clade that was detected in the incident. Pink triangles represent clade B3-11, blue triangles represent clade B6-51, brown triangles represent clade B6-62, red represents clade B6-84, orange triangles represent clade B6-86 and white triangles represent incidents where the WGS clade was undetermined. OTF-S incidents in 2023 are shown as circles. OTF-W incidents detected pre-2023 are shown as squares. The geographical location of TB hotspots are shown as ‘yellow lines’. The new OTF-W incidents in 2023 was located in central and west Lancashire, and the south and east of Greater Manchester. New OTF-S incidents were located throughout the county in 2023 and are described in more detail in main body of text.

As can be seen from Figure 6 and Appendix 3 Table 5, it was not possible to define a clearly predominant risk pathway for 3 of the OTF-W incidents in the North West of England. One OTF-W incident in the southeast of Greater Manchester was found to have exposure to infected wildlife as the most likely risk pathway.

The OTF-W incident with clade B6-84 in the centre of Lancashire remains obscure but exposure to infected wildlife and movement of undisclosed infected cattle are possible risk pathways.

Investigation of the OTF-W incident with clade B6-86 to the west of the county showed that the isolate was 5 Single Nucleotide Polymorphism (SNPs) away from a cattle isolate from a TB incident detected in Scotland in 2020 and 4 SNPs away from a 2022 sheep isolate in Wales. However, there were no obvious epidemiological links, which could explain either of these genetic relationships. Exposure to infected wildlife was also considered possible, however due to a lack of evidence, the likely source of infection for this pathway remained undetermined.

Investigation of the OTF-W incident to the east of Greater Manchester found that the origin was uncertain, but exposure to infected wildlife and purchase of contaminated feed or bedding were considered possible risk pathways.

Exposure to infected wildlife was considered the most likely risk pathway for the OTF-W incident near Stockport due to a small number of previous OTF-W incidents in this area associated with the same clade of M. bovis, its proximity to the endemic TB areas of north-east Cheshire and north-west Derbyshire in the Edge Area, and reports of local badger activity. TB infected badgers have previously been identified in the Stockport region (view the 2016 Edge Report), and a study of the road killed badger carcasses collected identified strong co-localisation of genotype 25:a (as the study occurred prior to WGS) for both the badger carcasses infected with M. bovis and incidents in cattle herds.

Figure 6: Map of the source of infection pathway recorded with the highest level of certainty, for OTF-W incidents, and the location of OTF-S incidents in the North West of England which started in 2023. Local cattle refer to residual infection and contiguous cattle risk pathways. Purchased refers to cattle movement risk pathways. Wildlife refers to both badger and other wildlife risk pathways.

Figure 6 description: A map of the North West showing the geographical location of cattle holdings with new OTF-W incidents in 2023 and the most likely source of infection. OTF-W incidents are shown as circles in different colours which represent the source of infection. Blue represents local cattle, brown represents purchased cattle, and green represents wildlife. New OTF-S incidents in 2023 are shown as triangles. The geographical location of TB hotspots are shown as ‘yellow lines’. The source of infection of 3 OTF-W incidents in 2023 were attributed to wildlife, and for one the source was unknown.

Figure 7 shows the hotspot areas and radial surveillance zones around OTF-W incidents since 2014.

In Lancashire, there were 2 active radial zones in 2023. One was triggered by an incident with clade B6-84 in the centre of the region, in the same area as an active radial zone from 2022 (clade B6-11) and another that began in 2021 (clade B6-62). The radial zones in this area have been triggered by incidents with different clades and are therefore not indicative of locally spreading disease. The other radial zone in Lancashire was triggered by an incident with clade B6-86 and located south of a radial zone triggered in 2021 by the aforementioned incident with clade B6-84. Similarly, these radial zones have been triggered by incidents with different clades and are therefore not indicative of locally spreading disease.

No radial zones have been triggered in the Lancashire side of potential Hotspot Area 27 (HS27) since before 2019.

In Greater Manchester, OTF-W incidents and associated radial zones have continuously occurred since before 2020 in the south-east of the region near Stockport, bordering Cheshire and Derbyshire. Clade B3-11 has been isolated from several of these. In 2023, one radial zone was triggered in this area, associated with a single B3-11 incident. As described above, this area is under consideration for enhanced measures.

For the previous 3 reporting periods, OTF-W incidents triggered radial zones in the Oldham area to the north-east of Manchester. These were all associated with clade B3-11, but isolates were separated by at least 17 SNPs, suggesting that they are genetically unrelated. This area continues to be monitored. There were no OTF-W incidents disclosed in this area in 2023.

There was one radial zone pending in 2023 triggered by an incident to the east of Greater Manchester. The incident was attributed to clade B1-11, but as described earlier, the sample was contaminated and the clade result cannot be relied upon.

Figure 7: Hotspot areas and radial surveillance zones around OTF-W incidents that were active, completed or not instigated in the North West of England during 2023, by year of initiation.

Figure 7 description: A map of the North West showing the geographical location of hotspots and radial surveillance zones around OTF-W incidents in 2023. The radial zones are shown as circles. Active radial zones are shown as solid line circles, completed radial zones are shown as dotted line circles, and radial zones that were not instigated are shown as orange triangles. The colour of the circles represents the year in which the radial zone was instigated: 2023 is green, 2022 is blue, 2021 is pink and 2014 to 2020 is orange. The geographical location of TB hotspots are shown as ‘yellow lines’. In 2023, there were new active radial zones located in central Lancashire and the south of Greater Manchester which are described in the text.

TB hotspots

Hotspot 27

Potential hotspot 27 (HS27) spans a small area of Lancashire and north Yorkshire as shown in Figures 5 to 7. This hotspot was established in January 2020 due to the detection of clade B6-23 (genotype 17:z) and is described in more detail in the 2020 Yorkshire and Humberside Epidemiological Report. Further information can be found in TB surveillance in wildlife – confirmed hotspots in the Low Risk Area of England.

There were no new OTF-W incidents or active radial zones in the Lancashire part of this area since 2020.

Since its implementation, only one wild deer carcase has been submitted to APHA for examination, with negative culture results for M. bovis.

Skin test reactors and interferon gamma test-positive animals removed

As presented in Figure 8a and b, the number of reactors removed for TB control purposes in 2023 in the North West of England decreased to 32 from 59 in 2022. Of the total 32 cattle that were removed for TB control purposes, 23 were skin test reactors (down from 30 in 2022) and 9 were positive on the interferon gamma (IFN-γ) test (down from 29 in 2022).

There were 16 skin test reactors in Lancashire (down from 18 in 2022), and 24 IFN-γ test positive animals (decreased from 27 in 2022).

In Greater Manchester, there were 5 skin test reactors (compared to 12 in 2022), and 5 IFN-γ test positive animals (increased from 2 in 2022).

In Merseyside, there were 2 skin test reactors from the single OTF-S incident declared in the west of the county, the first removed since 2018. There have been no IFN-γ test positive animals since 2017.

Greater Manchester

Year	Skin test reactors	Interferon gamma reactors	Grand total
2018	4	0	4
2019	11	6	17
2020	8	6	14
2021	9	20	29
2022	12	2	14
2023	5	5	10

Lancashire

Year	Skin test reactors	Interferon gamma reactors	Grand total
2019	17	1	18
2020	20	0	20
2021	26	23	49
2022	18	27	45
2023	16	4	20

Figure 8a: Number of skin test reactors and interferon gamma (IFN-γ) test positive cattle removed by APHA for TB control reasons in the Greater Manchester and Lancashire, from 2019 to 2023.

Figure 8a description: Stacked bar chart showing the number skin test reactors and interferon gamma test positive animals removed from herds between 2019 and 2023 in Greater Manchester and Lancashire. Skin test reactors are shown in blue and interferon gamma test positive animals shown in green. There were 5 new skin test reactors and 5 interferon gamma test positive animals removed from Greater Manchester in 2023. In Lancashire there were 16 skin test reactor and 4 interferon gamma test positive animals removed from herds in 2023.

Mersyside

Year	Skin test reactors	Interferon gamma reactors	Grand total
2019	0	0	0
2020	0	0	0
2021	0	0	0
2022	0	0	0
2023	2	0	2

Figure 8b: Number of skin test reactors and interferon gamma (IFN-γ) test positive cattle removed by APHA for TB control reasons in the Merseyside, from 2019 to 2023.

Figure 8b description: Stacked bar chart showing the number skin test reactors and interferon gamma test positive animals removed from herds between 2019 and 2023 in Merseyside. Skin test reactors are shown in blue and interferon gamma test positive animals shown in green. In Merseyside there were 2 skin test reactors and no interferon gamma test positive animals removed from herds in 2023.

Main risk pathways and key drivers for TB infection

Evidence collected during APHA veterinary investigations into the source of infection within herds was used to inform this understanding. In 2023, 12 out of 17 (76%) of new TB incidents in the North West of England received a preliminary or final APHA veterinary investigation to identify the source of infection.

It can be challenging to retrospectively establish the route of infection for a TB incident herd. Ideally this investigation includes a thorough on-farm investigation and scrutiny of routinely collected data, such as cattle movement records, and the results of WGS where available. Up to 3 hazards and risk pathways were selected for each incident investigated. Each of these potential sources were given a score that reflects the likelihood of that pathway being the true one, based on the available evidence.

Details of the protocol used for these investigations, and the subsequent methodology used to calculate the weighted contribution of the different suspected sources of M. bovis infection can be found in the explanatory supplement to the annual reports 2023.

The key drivers for the TB incidents detected in the North West of England during 2023 were identified as follows:

• movement of undetected infected cattle
• exposure to probable infected badgers

Movement of undetected infected cattle was the most common risk pathway with an overall weighted contribution of 23.5%. This is increased compared to 2022 where cattle movements accounted for 11% of weighted source pathways. This was followed by exposure to potentially infected badgers which had an overall weighting of 21.3%. This figure is derived from the 2 incidents which occurred in the Stockport area of Greater Manchester which had exposure to infected badgers at grazing ranked as most likely and exposure to infected badgers at housing ranked as likely or possible. Several incidents in Lancashire also had high uncertainty regarding origin of infection and exposure to infected badgers was included in potential risk pathways. This overall weighted contribution of this pathway was reduced compared to 2022, where exposure to infected badgers accounted for 36% of weighted source pathways noted for new incidents in the North West of England. This can be partly explained by there being fewer breakdowns in the Stockport area (where exposure to infected badgers carries a higher likelihood) in 2023 compared to 2022.

Exposure to fomites (9.9%) and exposure to wildlife excluding badgers (6.6%) were also selected as potential source risk pathways for some new TB incidents in 2023.

There was a moderate degree of uncertainty around the source of incidents in 2023, with other or unknown sources having a weighted contribution of 31.9%. This category is added to those incidents in which there was high uncertainty around the selected pathways (view the explanatory supplement to the annual reports 2023 for methodology).

Forward look

The total number of incidents in this region, as well as number of OTF-W incidents, decreased in 2023 compared to the previous 2 years. A lower number of reactors was also disclosed overall, and incidents had a relatively short duration. Moreover, the predominance of OTF-S incidents in the area suggests that TB-infected herds are being detected early, which reduces the risk of onward spread. This is a positive trend and demonstrates that current surveillance and incident management measures in the area are effective.

To further reduce the TB incidence and maintain LRA status, farmers in the North West of England need to exercise caution and aim to minimise risk when introducing cattle onto their farms. Purchasing cattle from areas or herds with a higher risk of TB heightens the risk of seeding infection from cattle into the local wildlife, resulting in more potential for local spread of infection and increased numbers of TB incidents in herds. The promotion and use of interactive mapping tools (ibTB) may help to mitigate some of the risk from cattle movements.

Implementation of good herd biosecurity and adherence to TB surveillance measures are also vital in reducing incidence of TB, regardless of the risk pathways involved.

As described above, APHA is considering setting up a formal hotspot area of enhanced cattle and wildlife TB surveillance in the Stockport area of Greater Manchester.

Appendix 1: cattle industry demographics

Table 1: Number of cattle herds by size category in the North West of England as of 31 December 2023 (RADAR data on number of holdings in the report year)

Size of herds	Number of herds in Greater Manchester	Number of herds in Lancashire	Number of herds in Merseyside
Undetermined	4	13	1
1 to 50	246	715	20
51 to 100	43	253	10
101 to 200	42	247	10
201 to 350	15	180	3
351 to 500	2	90	0
Greater than 500	2	101	2
Total number of herds	354	1,599	46
Mean herd size	58	144	97
Median herd size	25	63	64

Table 2: Number (and percentage of total) of animals by breed purpose in the North West of England as of 31 December 2023

Breed purpose	Number (and percentage of total) cattle in Greater Manchester	Number (and percentage of total) cattle in Lancashire	Number (and percentage of total) cattle in Merseyside
Beef	12,815 (62%)	85,984 (37%)	2,909 (65%)
Dairy	7,372 (35%)	130,685 (56%)	1,473 (33%)
Dual purpose	346 (1%)	13,650 (5%)	68 (1%)
Unknown	4 (0.019%)	26 (0.0113%)	0 (0%)
Total	20,537	230,345	4,450

Appendix 2: summary of headline cattle TB statistics

Table 3: Herd-level summary statistics for TB in cattle in the North West of England in 2023. (Sam data showing the number of herds flagged as active at the end of the report year).

Herd-level statistics	Greater Manchester	Lancashire	Merseyside
(a) Total number of cattle herds live on Sam at the end of the reporting period	450	1,890	57
(b) Total number of cattle herds subject to annual TB testing (or more frequent) at the end of the reporting period (any reason)	68	208	7
(c) Total number of whole herd skin tests carried out at any time in the period	178	655	19
(d) Total number of OTF cattle herds having TB whole-herd tests during the period for any reason	155	623	17
(e) Total number of OTF cattle herds at the end of the report period (herds not under any type of TB movement restrictions)	433	1,869	56
(f) Total number of cattle herds that were not under restrictions due to an ongoing TB incident at the end of the report period	449	1,885	57
(g.1) Total number of new OTF-S TB incidents detected in cattle herds during the report period	3	9	1
(g.2) Total number of new OTF-W TB incidents detected in cattle herds during the report period	2	2	0
(h.1) Of the new OTF-W herd incidents, how many occurred in a holding affected by another OTF-W incident in the previous 3 years?	1	0	0
(h.2) Of the new OTF-W herd incidents, how many could be considered secondary to a primary incident based on current evidence?	1	0	0
(h.3) Of the new OTF-W herd incidents, how many were triggered by skin test reactors or twice-inconclusive reactors (2xIRs) at routine herd tests?	1	1	0
(h.4) Of the new OTF-W herd incidents, how many were triggered by skin test reactors or 2xIRs at other TB test types (such as forward and back-tracings, contiguous, check tests)?	1	1	0
(h.5) Of the new OTF-W herd incidents, how many were first detected through routine slaughterhouse TB surveillance?	0	0	0
(i.1) Number of new OTF-S incidents revealed by enhanced TB surveillance (radial testing) conducted around those OTF-W herds	1	4	0
(i.2) Number of new OTF-W incidents revealed by enhanced TB surveillance (radial testing) conducted around those OTF-W herds	1	1	0
(j) Number of OTF-W herds still open at the end of the period (including any ongoing OTF-W incidents that began in a previous reporting period)	0	1	0
(k) Number of OTF-W herds still open at the end of the period that were on a finishing unit	0	0	0
(l) New laboratory-confirmed incidents of M. bovis infection in non-bovine domestic species or captive deer detected during the report period (indicate host species involved)	0	0	0

Note (a) and (f) Cattle herd counts in Appendix 2 Table 3 and Appendix 1 Table 1 differ due to different data sources used. Appendix 1 Table 1 uses data from RADAR, while Appendix 2 Table 3 uses data from Sam.

Table 4: Animal-level summary statistics for TB in cattle in the North West of England during 2023.

Animal-level statistics (cattle)	Greater Manchester	Lancashire	Merseyside
(a) Total number of cattle tested with tuberculin skin tests or additional IFN-γ blood tests in the period (animal tests)	12,568	115,968	3,517
(b.1) Reactors detected by tuberculin skin tests during the year	5	16	2
(b.2) Reactors detected by additional IFN-γ blood tests (skin-test negative or IR animals) during the year	5	4	0
(c) Reactors detected during year per incidents disclosed during year	2.00	1.82	2.00
(d) Reactors per 1,000 animal tests	0.80	0.17	0.57
(e.1) Additional animals slaughtered during the year for TB control reasons (dangerous contacts, including any first time IRs)	0	0	0
(e.2) Additional animals slaughtered during the year for TB control reasons (private slaughters)	0	0	0
(f) Slaughterhouse (SLH) cases (tuberculous carcasses) reported by the Food Standards Agency (FSA) during routine meat inspection	1	7	0
(g) SLH cases confirmed by M. bovis PCR testing or bacteriological culture	0	0	0

Note (c) Reactors detected during year per incidents disclosed during year, reactors may be from incidents disclosed in earlier years, as any found through testing during the report year count here.

Note (g) SLH cases confirmed by culture of M. bovis, not all cases reported are submitted for culture analysis. All cases reported are from any period prior to or during restrictions.

Appendix 3: suspected sources of M. bovis infection for all of the new OTF-W and OTF-S incidents identified in the report period

In 2023, 12 of 17 (76%) of new TB incidents in the North West of England received a preliminary or final APHA veterinary investigation to identify the source of infection. Not all investigations were carried out in 2023 due to the continued impact and diversion of field resource as part of the 2022 to2023 highly pathogenic avian influenza (AI) outbreak which continued into spring 2023, in addition to the bluetongue virus outbreak from summer 2023 onwards.

Each TB incident could have up to 3 potential risk pathways identified. Each risk pathway is given a score that reflects the likelihood of that pathway bringing TB into the herd. The score is recorded as either:

• definite (score 8)
• most likely (score 6)
• likely (score 4)
• possible (score 1)

The sources for each incident are weighted by the certainty ascribed. Any combination of definite, most likely, likely, or possible can contribute towards the overall picture for possible routes of introduction into a herd.

If the overall score for a herd is less than 6, then the score is made up to 6 using the ‘Other or unknown source’ option. Buffering up to 6 in this way helps to reflect the uncertainty in assessments where only ‘likely’ or ‘possible’ sources are identified.

Table 5 combines the data from multiple herds and provides the proportion of pathways in which each source was identified, weighted by the certainty that each source caused the introduction of TB.

The output does not show the proportion of herds where each pathway was identified (this is skewed by the certainty calculation).

WGS of M. bovis isolates can be a powerful tool in identifying a likely source of infection, however WGS clades have not been determined for OTF-S herds. As a result of varying levels of uncertainty, only broad generalisations should be made from these data. A more detailed description of this methodology is provided in the explanatory supplement for the annual reports 2023.

Table 5: Suspected sources of M. bovis infection for the 12 new TB incidents that received a veterinary investigation in the North West of England in 2023.

Source of infection	Possible (1)	Likely (4)	Most likely (6)	Definite (8)	Weighted contribution
Badgers	5	1	2	0	21.3%
Cattle movements	4	1	1	1	23.5%
Contiguous	0	0	0	0	0.0%
Residual cattle infection	1	0	1	0	5.8%
Domestic animals	0	0	0	0	0.0%
Non-specific reactor	1	0	0	0	1.0%
Fomites	2	0	1	0	9.9%
Other wildlife	5	0	0	0	6.6%
Other or unknown source	2	0	0	0	31.9%

Please note each TB incident could have up to 3 potential pathways so totals may not equate to the number of actual incidents that have occurred.