Research and analysis

South East 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 South East of England, which is part of the LRA. In 2023, 31% of all new TB incidents in the LRA were detected in the South East 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

The cattle industry in the South East of England is predominantly beef based, as shown in Appendix 1. Over 60% of the cattle in this region are in Norfolk, Kent, Suffolk, and West Sussex. There is a large proportion of small cattle herds (up to 50 animals per herd) in all counties within the region.

There are 3 livestock markets, located in Norfolk, Essex and Kent. A collection centre operates in Essex. There were no dedicated sales or collections approved by the Animal and Plant Health Agency (APHA) for onward consignment of TB-restricted cattle direct to a slaughterhouse (SLH). Orange markets (TB-restricted cattle sales) for the sale of negative testing cattle from TB-restricted herds are not permitted in the LRA.

There are 5 active Licensed Finishing Units (LFUs) in this region, and all are subject to annual re-approval visits by APHA.

The number of cattle markets in operation in 2023 is captured and maintained centrally by the 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

There were 41 new TB incidents in the region during 2023, a decrease from 46 incidents reported in 2022 (Figures 1a to f). Nine of those were OTF-W incidents (unchanged from 2022), and 32 OTF-S (37 in 2022) (Figures 1a to f).

The 9 OTF-W incidents were disclosed in West Sussex (4), Hertfordshire (3), and one each in Cambridgeshire and Norfolk.

Of the 32 OTF-S incidents, 6 were disclosed in both Kent and West Sussex, and 5 in Surrey. There were 3 incidents in Bedfordshire, Cambridgeshire, Essex and Suffolk. Two incidents were disclosed in Hertfordshire and one in the Isle of Wight. Reductions in the total number of incidents were also seen between 2022 and 2023 in Cambridgeshire (6 to 4), Essex (8 to 3), Kent (8 to 6), Norfolk (2 to one) and Greater London (one to none). The total number of incidents increased between 2022 and 2023 in Bedfordshire (zero to 3), Hertfordshire (2 to 5) and West Sussex (9 to 10). In the Isle of Wight (one), Suffolk (3) and Surrey (5), the total number of incidents was unchanged between 2022 and 2023.

Bedfordshire

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

Cambridgeshire

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

Figure 1a: Annual number of new TB incidents (OTF-W and OTF-S) in Bedfordshire and Cambridgeshire, from 2014 to 2023.

Figure 1a description: Stacked bar chart showing the number of new OTF-W and OTF-S incidents detected in Bedfordshire and Cambridgeshire between 2014 and 2023. OTF-W incidents are shown in blue and OTF-S incidents are shown in green. There was one new OTF-W and 3 new OTF-S incidents in Cambridgeshire, and 3 new OTF-S incidents in Bedfordshire in 2023.

Essex

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

Greater London

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

Figure 1b: Annual number of new TB incidents (OTF-W and OTF-S) in Essex and Greater London, from 2014 to 2023.

Figure 1b description: Stacked bar chart showing the number of new OTF-W and OTF-S incidents detected in Essex and Greater London between 2014 and 2023. OTF-W incidents are shown in blue and OTF-S incidents are shown in green. There were no new OTF-W incidents and 3 new OTF-S incidents in Essex in 2023. There were no new incidents (OTF-W or OTF-S) in Greater London in 2023.

Hertfordshire

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

Isle of Wight

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

Figure 1c: Annual number of new TB incidents (OTF-W and OTF-S) in Hertfordshire and Isle of Wight, from 2014 to 2023.

Figure 1c description: Stacked bar chart showing the number of new OTF-W and OTF-S incidents detected in Hertfordshire and Isle of Wight between 2014 and 2023. OTF-W incidents are shown in blue and OTF-S incidents are shown in green. There were 3 new OTF-W and 2 new OTF-S incidents in Hertfordshire, and 1 new OTF-S incident in the Isle of Wight, in 2023.

Kent

Year	OTF-W	OTF-S	Total
2014	0	1	1
2015	0	3	3
2016	0	3	3
2017	0	1	1
2018	1	5	6
2019	1	2	3
2020	0	8	8
2021	0	3	3
2022	1	7	8
2023	0	6	6

Norfolk

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

Figure 1d: Annual number of new TB incidents (OTF-W and OTF-S) in Kent and Norfolk, from 2014 to 2023.

Figure 1d description: Stacked bar chart showing the number of new OTF-W and OTF-S incidents detected in Kent and Norfolk between 2014 and 2023. OTF-W incidents are shown in blue and OTF-S incidents are shown in green. There was one new OTF-W incident in Norfolk and 6 new OTF-S incidents in Kent in 2023.

Suffolk

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

Surrey

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

Figure 1e: Annual number of new TB incidents (OTF-W and OTF-S) in Suffolk and Surrey, from 2014 to 2023.

Figure 1e description: Stacked bar chart showing the number of new OTF-W and OTF-S incidents detected in Suffolk and Surrey between 2014 and 2023. OTF-W incidents are shown in blue and OTF-S incidents are shown in green. There were 3 new OTF-S incidents in Suffolk and 5 new OTF-S in Surrey in 2023.

West Sussex

Year	OTF-W	OTF-S	Total
2014	2	4	6
2015	4	12	16
2016	3	12	15
2017	6	7	13
2018	3	7	10
2019	1	12	13
2020	0	5	5
2021	1	4	5
2022	1	8	9
2023	4	6	10

Figure 1f: Annual number of new TB incidents (OTF-W and OTF-S) in West Sussex, from 2014 to 2023.

Figure 1f description: Stacked bar chart showing the number of new OTF-W and OTF-S incidents detected in West Sussex between 2014 and 2023. OTF-W incidents are shown in blue and OTF-S incidents are shown in green. There were 4 new OTF-W incidents and 6 new OTF-S incidents in West Sussex in 2023.

The headline cattle TB statistics for the South East of England are summarised in Appendix 2.

Disclosing test type

Figure 2 shows the surveillance methods that detected new TB incidents in 2023 for each county separately. As in 2021 and 2022, 4-yearly routine herd testing (RHT) disclosed the most incidents in the South East (19). This was followed by radial tests (9) and tracing tests (3).

In 2023, post-movement testing disclosed only one incident compared to 9 in 2022. In 2023, 12-month (post-incident resolution) herd tests disclosed one incident compared to 3 incidents in the previous year. There were 2 incidents triggered by slaughterhouse surveillance (laboratory-confirmed slaughterhouse cases), one in Cambridgeshire and one in West Sussex.

Figure 2: Number of new TB incidents (OTF-W and OTF-S) in the South East 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 different test types in the South East of England in 2023. The counties included were Bedfordshire, Cambridgeshire, Essex, Hertfordshire, Isle of Wight, Kent, Norfolk, Suffolk, Surrey and West Sussex. Most incidents were disclosed by routine herd tests (19). More detail on the breakdown of incidents by test type is described in the text.

Duration of TB incidents

A total of 44 TB incidents were resolved during 2023. Of these, 21 were new TB incidents that started in 2023, 21 started in 2022, and 2 started in 2021. 

Of the 44 TB incidents that closed in 2023, 9 were OTF-W incidents, of which 5 were resolved within 240 days and a further 3 within 550 days. One OTF-W incident in Bedfordshire lasted over 550 days (called a persistent incident) before being resolved in 2023, and another persistent incident, also in Bedfordshire, was still open at the end of 2023.

Of the 44 TB incidents that closed in 2023, 35 were OTF-S incidents. Ten of these were resolved within 100 days, and a further 11 within 150 days. A further 13 incidents were resolved within 550 days, and another persistent OTF-S in West Sussex had lasted over 550 days and was still open at the end of 2023.

There were 25 TB incidents that were still open at the end of 2023, including the 2 persistent incidents mentioned above.

Unusual TB incidents

The incident that started in August 2022, following the detection of a clinical case of TB in a bull in Surrey, continued in 2023 and was resolved at the beginning of 2024. The affected herd regained OTF status after a total of 5 short interval skin tests and 2 rounds of interferon gamma testing. A total of 32 test-positive animals were removed, 10 of which had visible lesions of TB at post-mortem meat inspection. Clade B6-11 of M. bovis (with a homerange in the West Midlands and the east of Wales) was isolated from 3 of these reactors.

A beef suckler herd in Essex experiencing a TB incident caused by infection with M. caprae that began in November 2022 concluded its testing programme in November 2023. However, the incident remained open and continued into 2024 because the herd keeper had not returned the declaration of completion of cleansing and disinfection to APHA by the end of 2023.

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.

In 2023 there were 2 laboratory-confirmed incidents of TB caused by M. bovis infection in non-bovine farmed species: one involving goats in Essex and one in sheep in Hertfordshire.

The goat TB incident in Essex involved a mixed dairy herd of goats and sheep with no previous TB history. A suspect lesion of TB was identified during postmortem meat inspection of a cull goat in the slaughterhouse. M. bovis clade B6-62 was identified from the lesion. Whole Genome Sequencing (WGS) phylogeny linked this case to immediate ancestors (0-2 SNPs difference) in 4 different species (bovines, alpacas, cats and humans) in different counties (Cambridge, Berkshire, Hampshire) between 2010 and 2023, none of them close to the geographical area and with no links to this farm through known animal orpeople movements. The most likely source of infection was the purchase of chronically infected animals. The goat unit on the farm was fully depopulated and the co-located sheep flock was still undergoing repeat tuberculin skin testing at the end of the reporting year.

Another incident involved a farm containing sheep, cattle, goats and alpacas in Hertfordshire. A suspect lesion of TB was identified during postmortem inspection of a cull ewe in one of APHA’s postmortem providers. Culture and WGS was carried out, resulting in the identification of clade B6-62 of M. bovis. The most likely source of infection was the purchase of infected animals from holdings with confirmed TB incidents. Less likely but possible is infection through contact with wildlife. This incident was still open at the end of 2023.

There was also one case of M. bovis infection in a cat in 2023 in the south of Essex.

Recurring TB incidents

Three-year recurrence

In the South East of England, 5 of the 32 (16%) herds with a new OTF-S TB incident in 2023, and 3 of the 9 (33%) with an OTF-W incident, had experienced another TB incident in the previous 3 years, as shown in Figure 3a to c. Overall, only 8 (20%) new TB incidents in 2023 were in herds that had experienced a TB incident in the last 3 years, out of a total of 40 herd incidents. This is the third lowest recurrence percentage reported in the regions of the LRA. The percentage of recurrent incidents in the whole of the LRA was 27%.

TB incidents occurred in herds with a history of TB in the previous 3 years in Bedfordshire (2 OTF-S), Hertfordshire (3 OTF-W), Kent (one OTF-S), Suffolk (one OTF-S), and West Sussex (one OTF-S). New TB incidents occurred in herds with no history of TB in the previous 3 years in Cambridgeshire (3 OTF-S and one OTF-W), Essex (3 OTF-S), Hertfordshire (2 OTF-S), Isle of Wight (one OTF-S), Kent (5 OTF-S), Norfolk (one OTF-W), Suffolk (2 OTF-S), Surrey (5 OTF-S), and West Sussex (5 OTF-S and 4 OTF-W).

Bedfordshire

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

Cambridgeshire

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

Essex

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

Greater London

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

Figure 3a: Number of herds with a TB incident (by OTF-W and OTF-S) in Bedfordshire, Cambridgeshire, Essex and Greater London in 2023, with and without a history of any TB incident in the previous 3 years.

Figure 3a caption: Bar chart showing the number of new TB incidents with an history of TB in the last 3 years in green and those without in blue in Bedfordshire, Cambridgeshire, Essex and Greater London in 2023. Only 2 herds had a history of TB out of the 9 shown on the graph – further breakdown by county provided in the text.

Hertfordshire

TB incidents	No history of TB in the last 3 years	History of TB in the last 3 years	Total
OTF-S	2	0	1
OTF-W	0	3	3

Isle of Wight

TB incidents	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

Kent

TB incidents	No history of TB in the last 3 years	History of TB in the last 3 years	Total
OTF-S	5	1	6
OTF-W	0	0	0

Figure 3b: Number of herds with a TB incident (by OTF-W and OTF-S) in Hertfordshire, Isle of Wight and Kent in 2023, with and without a history of any TB incident in the previous 3 years.

Figure 3b caption: Bar chart showing the number of new TB incidents with an history of TB in the last 3 years in green and those without in blue in Hertfordshire, Isle of Wight and Kent in 2023. Four herds had a history of TB out of the 12 shown on the graph – further breakdown by county provided in the text.

Norfolk

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

Suffolk

TB incidents	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	0	0	0

Surrey

TB incidents	No history of TB in the last 3 years	History of TB in the last 3 years	Total
OTF-S	5	0	5
OTF-W	0	0	0

West Sussex

TB incidents	No history of TB in the last 3 years	History of TB in the last 3 years	Total
OTF-S	5	1	6
OTF-W	4	0	4

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

Figure 3b caption: Bar chart showing the number of new TB incidents with an history of TB in the last 3 years in green and those without in blue in Norfolk, Suffolk, Surrey and West Sussex in 2023. Two herds had a history of TB out of the 19 shown on the graph – further breakdown by county provided in the text.

Overall recurrence

In 2023, 9 out of 31 OTF-S and 5 out of 9 OTF-W (14 incidents, 35%, Figure 4a to c) of incidents reported across the region were in herds with a history of TB in the herd’s lifetime. This includes looking back beyond the three-year period mentioned previously. 
In West Sussex, 5 incidents out of 10 were in herds that had had a history of TB in the herd’s lifetime (50%). Three incidents out of 5 (60%) and 2 incidents out of 3 (67%) had had a history of TB in the herd’s lifetime in Hertfordshire and Suffolk respectively. Just one incident in each of the Bedfordshire, Essex, Kent, Surrey counties had had a history of TB in the herd’s lifetime (Figure 4a to c).

There were no recurrent TB incidents in Cambridge, Norfolk or the Isle of Wight.

This compares to 18 incidents which were in herds with a history of TB in the herd’s lifetime (13 out of 37 OTF-S and 5 out 9 OTF-W) in 2022. Counties with increases in the numbers of incidents in herds with a history of TB in the herd’s lifetime were West Sussex, (5 incidents in 2023 from 1 in 2022), Hertfordshire (3 in 2023, 1 in 2022), and Bedfordshire (1 in 2023, 0 in 2022). Counties with decreases were Cambridgeshire (3 in 2022 to 0 in 2023), Essex (3 in 2022 to 1 in 2023), Kent (3 in 2022 to 1 in 2023), Norfolk (1 in 2022 to 0 in 2023), Surrey (3 in 2022 to 1 in 2023), and Greater London (1 in 2022 to 0 in 2023). There was no change to recurrence in Suffolk (2 incidents in 2022 and 2023 with a history of TB in the herd’s lifetime), and no incidents in herds with a history of TB in the Isle of Wight in 2022 or 2023.

Bedfordshire

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

Cambridgeshire

TB Incident	No history of TB within the herd lifetime	History of TB within the herd lifetime
OTF-S	3	0
OTF-W	1	0

Essex

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

Kent

TB Incident	No history of TB within the herd lifetime	History of TB within the herd lifetime
OTF-S	5	1
OTF-W	0	0

Figure 4a: Number of herds with a TB incident (by OTF-W and OTF-S) in Bedfordshire, Cambridgeshire, Essex and Kent in 2023, with and without a history of any TB incident.

Figure 4a caption: Bar chart showing the number of new TB incidents with an history of TB in the herd’s lifetime in green and those without in blue in Bedfordshire, Cambridgeshire, Essex and Kent in 2023. Three incidents were in herds with a history of TB in the herd’s lifetime out of the 15 shown in the chart – further breakdown by county provided in the text.

Norfolk

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

Suffolk

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

Greater London

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

Figure 4b: Number of herds with a TB incident (by OTF-W and OTF-S) in Norfolk, Suffolk and Greater London in 2023, with and without a history of any TB incident.

Figure 4b caption: Bar chart showing the number of new TB incidents with an history of TB in the herd’s lifetime in green and those without in blue in Norfolk, Suffolk and Greater London in 2023. Two incidents were in herds with a history of TB in the herd’s lifetime out of the 4 shown in the chart – further breakdown by county provided in the text.

Hertfordshire

TB incidents	No history of TB within the herd lifetime	History of TB within the herd lifetime	Total
OTF-S	2	0	2
OTF-W	0	3	3

Isle of Wight

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

Surrey

TB Incident	No history of TB within the herd lifetime	History of TB within the herd lifetime
OTF-S	4	1
OTF-W	0	0

West Sussex

TB Incident	No history of TB within the herd lifetime	History of TB within the herd lifetime
OTF-S	3	3
OTF-W	2	2

Figure 4c: Number of herds with a TB incident (by OTF-W and OTF-S) in Hertfordshire, Isle of Wight, Surrey and West Sussex in 2023, with and without a history of any TB incident.

Figure 4c caption: Bar chart showing the number of new TB incidents with an history of TB in the herd’s lifetime in orange and those without in blue Hertfordshire, Isle of Wight, Surrey and West Sussex in 2023. Nine incidents were in herds with a history of TB in the herd’s lifetime out of the 21 shown in the chart – further breakdown by county provided in the text.

Geographical distribution of TB incidents

As in previous years, new TB incidents in 2023 were spread across the South East of England. Figure 5 shows the location of new TB incidents in 2023, overlaid on a map of cattle density. Incidents were generally disclosed in areas with a higher cattle density.

There were 3 new incidents (OTF-S) in Bedfordshire, compared to no incidents in 2022.

There was a cluster of incidents in central Surrey (3 OTF-S), in the same location as an OTF-W incident that occurred in 2022. The clade of that OTF-W incident was undetermined.

One OTF-S incident occurred in the south of Surrey bordering West Sussex, where in 2022 there were 2 OTF-S incidents and one OTF-W incident.

In West Sussex, there were OTF-S and OTF-W incidents throughout the county. In the north of TB hotspot HS24, there was one OTF-W incident with an undetermined clade. In 2022, one OTF-W incident occurred in the same area and the WGS clade of that incident was also undetermined.

Two OTF-W incidents were disclosed with the WGS clade B6-11, which has a homerange spanning the West Midlands and parts of East Wales. One occurred towards the east and the other in the south of West Sussex, between HS24 and the coastline. In the west of the county, there was one OTF-W incident disclosed with WGS clade B6-85. This clade has a homerange in the south-west of England, mainly in Devon and Somerset. In 2022, one OTF-W incident with clade B6-85 occurred on the border with Surrey.

In Cambridgeshire, the 4 new incidents identified in 2023 were spread throughout the centre and north of the county around areas with high cattle density. The one OTF-W incident (clade B4-11, with a homerange in Devon and Somerset) was disclosed in the north-east of the county.

In Norfolk, there was one OTF-W incident (clade B3-11) in the west of the county, bordering Cambridgeshire. This is the first OTF-W incident that has occurred in Norfolk since 2019. The 2019 incident (clade B3-11) occurred north-east of the 2023 incident, towards the border with Lincolnshire. The B3-11 homerange covers Shropshire, Staffordshire, Cheshire and Derbyshire as well as spilling into northern Wales.

One OTF-S incident occurred toward the south-west in the Isle of Wight.

There were 2 OTF-S incidents in the north of Essex and one in the south-west bordering Greater London. Historically, TB incidents (OTF-W and OTF-S) occurred in the east and south of Essex, though in 2022, one OTF-S incident was located in north-west around the border with Hertfordshire.

Two OTF-S incidents were detected in the north of Suffolk and one in the south on the border with Essex.

In Kent, the 6 2023 OTF-S incidents were spread throughout the whole county, with one occurring near the 2022 OTF-W incident. There were no OTF-W incidents in 2023.

There was a cluster of 3 OTF-W and one OTF-S incidents around the town of Tring in the west of Hertfordshire where a hotspot area straddling the border with Buckinghamshire has been established (HS30). This is an area where a small number of TB incidents continue to occur every year. Clade B6-62 was detected as the cause of 2 of the incidents and clade B3-11 in one of the incidents. Clade B6-62 has a homerange spanning the southern Edge counties from Hampshire to south Leicestershire, as well as northern Staffordshire, Gloucestershire and Wiltshire in the High Risk Area (HRA).

Figure 5: Location of cattle holdings in the South East 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 South East of England (which includes Norfolk, Cambridgeshire, Suffolk, Bedfordshire, Hertfordshire, Essex, Greater London, Kent, Surrey, and West Sussex). The map shows areas of higher cattle densities in darker shades of blue, and these are located around the south and north-east of the South East region. OTF-W incidents are shown as triangles on the map – upright triangles if considered introduced (where cattle movements were most likely the source of infection), upside down triangles if not. Colours are used to show the different clades and this is described in more detail in the text. OTF-S incidents are shown as circles. A goat, a sheep and a cat incident are shown on the map, and the cases are described in more detail in the text.

As shown in Figure 6 and Appendix 3 Table 5, OTF-W incidents were attributed to different likely sources of infection. As in 2022, most incidents in 2023 were likely caused by introductions of undetected infected cattle, labelled as a ‘purchased’ DRF source.

In 2 incidents (one in Hertfordshire and one in West Sussex), contact with wildlife were the most likely source of infection.

The source of infection for one of the OTF-W incidents in West Sussex was unknown.

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 South East 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 South East of England (which includes Norfolk, Cambridgeshire, Suffolk, Bedfordshire, Hertfordshire, Essex, Greater London, Kent, Surrey, and West Sussex). This map shows the most likely source of infection for incidents in the South East region – coloured circles are used to represent OTF-W incidents and empty triangles for OTF-S incidents. Orange circles show incidents where the most likely source was unknown. Green circles where the source was wildlife, red where the source was purchased cattle and blue where the source was local cattle. Further detail on the cases is provided in the text.

Radial surveillance zones that were active or completed around OTF-W incidents in the South East of England between 2014 and 2023 are represented in Figure 7. This indicates areas where OTF-W TB incidents have been repeatedly reported in recent years, for example, along the Buckinghamshire border and in central West Sussex.

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

Figure 7 description: A map of the South East of England (which includes Norfolk, Cambridgeshire, Suffolk, Bedfordshire, Hertfordshire, Essex, Greater London, Kent, Surrey, and West Sussex). Map shows the radial surveillance zones around OTF-W incidents that were active, completed or not instigated, coloured by year (green for 2023, blue for 2022, pink for 2021 and orange for 2014 to 2020). In 2023, radial testing zones were in operation in Cambridgeshire, Norfolk, Hertfordshire, and West Sussex. Further details on the radial zones are provided in the text.

TB hotspots

Hotspot 24

This hotspot, launched in 2018 in the western half of West Sussex. Historical review of WGS phylogeny was carried out to ensure that the ongoing hotspot area in West Sussex was not closed prematurely, due to a lack of wildlife surveillance data. HS24 was formally closed in early 2024.

Hotspot 30

A new hotspot area was established in early 2023 around the town of Tring in Hertfordshire, where OTF-W incidents were detected in 2020 and 2021. There were 3 incidents in this area during this period, where genetically identical isolates of M. bovis were disclosed in homebred animals. These isolates belonged to clade B6-62, which has a homerange in the southern Edge Area, including the neighbouring county of Buckinghamshire.

The index incident could not be attributed to recent or distant cattle movements, and there was evidence for a localised source of infection, supported by WGS and other epidemiological evidence. A badger carcase collected in February 2022 as part of the Southern Edge Area Road Traffic Accident survey was confirmed as infected with M. bovis clade B6-62 and genetically identical to the 3 cattle isolates from local cattle incidents. Further information can be found in TB surveillance in wildlife – confirmed hotspots in the Low Risk Area of England.

In 2023, there were 2 OTF-W incidents associated with clade B6-62 and one with clade B3-11.

Skin test reactors and interferon gamma test-positive animals removed

During 2023, a total of 247 bovine animals were removed as TB test reactors from the South East of England. Of these, 143 were skin test reactors and 104 were positive by the supplementary IFN-γ blood test, as shown in Figure 8a to d.

Compared to 2022, this was an increase in the number of skin test reactors (14) and IFN-γ test positive animals (73). The overall increase in IFN-γ test positive animals is due to increases between 2022 and 2023 specifically in Bedfordshire (2 to 18), Essex (zero to 9), Norfolk (zero to 16), Surrey (7 to 14), and West Sussex (7 to 47).

There was a decrease in the number of IFN-γ test positive animals in Hertfordshire between 2022 and 2023 (11 to zero). An increase in the number of positive animals detected by the skin test compared to 2022 occurred in Bedfordshire, Surrey and West Sussex, from 4 to 16, 7 to 32, and 31 to 42, respectively. Whereas decreases occurred in Cambridgeshire and Essex, 17 to 3 and 35 to 23, respectively. The IFN-γ test has a higher sensitivity but lower specificity than the comparative skin test and so is likely to disclose more TB positive animals. It can also detect infection at an earlier stage of infection than the skin test.

Bedfordshire

Year	Skin test reactors	Interferon gamma reactors	Total
2019	1	0	1
2020	1	4	5
2021	7	33	40
2022	4	2	6
2023	16	18	34

Cambridgeshire

Year	Skin test reactors	Interferon gamma reactors	Total
2019	8	21	29
2020	1	0	1
2021	16	0	16
2022	17	1	18
2023	3	0	3

Essex

Year	Skin test reactors	Interferon gamma reactors	Total
2019	14	0	14
2020	1	3	4
2021	12	11	23
2022	35	0	35
2023	23	9	32

Figure 8a: Number of skin test reactors and interferon gamma (IFN-γ) test positive cattle removed for TB control reasons in Bedfordshire, Cambridgeshire and Essex, from 2019 to 2023.

Figure 8a description: Bar chart showing the number of skin test reactors in blue and IFN-y test positive cattle in green that were removed for TB control reasons in Bedfordshire, Cambridgeshire and Essex between 2019 and 2023. The numbers have fluctuated in these counties over the last 5 years. In 2023, Bedfordshire had 16 skin and 19 IFN-y reactors removed, compared to 23 skin and 9 IFN-y reactors removed in Essex. Cambridge had 3 skin test reactors removed in 2023.

Greater London

Year	Skin test reactors	Interferon gamma reactors	Total
2019	1	0	1
2020	1	0	1
2021	0	0	0
2022	2	0	2
2023	0	0	0

Hertfordshire

Year	Skin test reactors	Interferon gamma reactors	Total
2019	6	48	54
2020	5	0	5
2021	24	9	33
2022	11	11	22
2023	9	0	9

Isle of Wight

Year	Skin test reactors	Interferon gamma reactors	Total
2019	3	16	19
2020	1	0	1
2021	0	0	0
2022	1	1	1
2023	1	0	1

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

Figure 8b description: Bar chart showing the number of skin test reactors in blue and IFN-y test positive cattle in green that were removed for TB control reasons in Greater London, Hertfordshire, and the Isle of Wight between 2019 and 2023. The numbers have fluctuated in these counties over the last 5 years. In 2023, Hertfordshire had 9 skin test reactors removed, and the Isle of Wight had one. No reactors were removed in Greater London.

Kent

Year	Skin test reactors	Interferon gamma reactors	Total
2019	5	1	6
2020	11	1	12
2021	5	0	5
2022	13	2	15
2023	12	0	12

Norfolk

Year	Skin test reactors	Interferon gamma reactors	Total
2019	9	1	10
2020	8	1	9
2021	2	0	2
2022	2	0	2
2023	2	16	18

Suffolk

Year	Skin test reactors	Interferon gamma reactors	Total
2019	5	3	8
2020	5	0	5
2021	4	13	17
2022	6	0	6
2023	3	0	3

Figure 8c: Number of skin test reactors and interferon gamma (IFN-γ) test positive cattle removed for TB control reasons in Kent, Norfolk and Suffolk, from 2019 to 2023.

Figure 8c description: Bar chart showing the number of skin test reactors in blue and IFN-y test positive cattle in green that were removed for TB control reasons in Kent, Norfolk and Suffolk, from 2019 to 2023. The numbers have fluctuated in these counties over the last 5 years. In 2023, Norfolk had 2 skin test and 16 IFN-γ reactors removed. In Kent, 12 skin test reactors were removed in 2023, and in Suffolk, only 3 skin test reactors were removed in 2023.

Surrey

Year	Skin test reactors	Interferon gamma reactors	Total
2019	13	0	13
2020	1	17	18
2021	0	0	0
2022	7	7	14
2023	32	14	46

West Sussex

Year	Skin test reactors	Interferon gamma reactors	Total
2019	43	2	45
2020	7	0	7
2021	7	0	7
2022	31	7	38
2023	42	47	89

Figure 8d: Number of skin test reactors and interferon gamma (IFN-γ) test positive cattle removed for TB control reasons in Surrey and West Sussex, from 2019 to 2023.

Figure 8d description: Bar chart showing the number of skin test reactors in blue and IFN-y test positive cattle in green that were removed for TB control reasons in Surrey and West Sussex, from 2019 to 2023. The numbers have fluctuated in these counties over the last 5 years. In 2023, there were 32 skin test and 14 IFN-y reactors removed from Surrey, and another 42 skin test and 47 IFN-y reactors removed from West Sussex.

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, 31 out of 41 (76%) of new TB incidents in the South East 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 driver of the TB epidemic in the South East of England during 2023 was movement of undetected infected cattle.

The movement of cattle with undetected infection continued to be the main pathway of infection for cattle herds in the South East of England in 2023, resulting in a weighted contribution of 49.5% to the likely sources of infection for herds with new TB incidents. Appendix 3 provides the suspected sources of M. bovis infection for all of the new OTF-W and OTF-S incidents identified in the report period.

There was some of uncertainty around the source of incidents in 2023, with other or unknown sources having a weighted contribution of 18.7%. 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). One incident in West Sussex identified exposure to badgers as a likely risk pathway. This resulted in an overall weighted contribution of 13.7% for wildlife in the south east area.

Exposure to fomites could not be ruled out for one new TB incident in 2023. The non-bovine incidents in 2023 are not be included in the totals for the source of infection described in Appendix 3 Table 5 as this contains only bovine data. However, information on the risk pathways identified for these non-bovine incidents was available and is described below.

The goat incident in Essex with M. bovis clade B6-62 had been established for over 40 years and closed with no new stock purchased in over 20 years. WGS analysis linked the incident to ancestors in 4 different species (bovines, alpacas, cats and humans) but none in the local area or with epidemiological links to the farm. The source of infection for this incident therefore remains obscure.

The sheep incident with M. bovis clade B6-62 in Hertfordshire was attributed to the purchase of already infected animals, as all affected sheep were purchased from a farm which had a previous OTF-W incident with the same clade in 2017, the year the sheep were purchased onto the premises. Wildlife was also considered possible in this case, as the premises were located near HS30 where B6-62 is found, and badgers had been spotted on the farm.

Forward look

Current surveillance and incident management measures are keeping the incidence of TB under control in this region of the LRA. Overall, disease incidence remains low. The recommendation would be continuing to utilise all control measures and to encourage herd biosecurity awareness through communications with farmers’ veterinary providers and farming associations. Based on the current trends, the counties in this region are likely to maintain their target of less than 0.1% of OTF-W incidence by 2025.

The new TB hotspot area (HS30) around the town of Tring in the west of Hertfordshire that borders with Buckinghamshire (Edge Area), where a small number of OTF-W incidents associated with clade B6-62 of M. bovis have been detected, is being closely monitored. This highlights the effectiveness of passive surveillance schemes such as the Road Traffic Accident surveys and reporting of suspect TB in wildlife carcasses by the general public.

Appendix 1: cattle industry demographics

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

Size of herds	Number of herds in Bedfordshire	Number of herds in Cambridgeshire	Number of herds in Essex
Undetermined	1	2	1
1 to 50	81	166	209
51 to 100	29	37	44
101 to 200	10	38	29
201 to 350	4	12	16
351 to 500	3	5	7
Greater than 500	3	9	7
Total number of herds	131	269	313
Mean herd size	77	95	82
Median herd size	38	32	24

Size of herds	Number of herds in Greater London	Number of herds in Hertfordshire	Number of herds in Isle of Wight
Undetermined	2	3	1
1 to 50	41	119	54
51 to 100	5	24	21
101 to 200	4	19	23
201 to 350	1	10	7
351 to 500	0	1	3
Greater than 500	0	2	0
Total number of herds	53	178	109
Mean herd size	30	59	83
Median herd size	8	26	50

Size of herds	Number of herds in Kent	Number of herds in Norfolk	Number of herds in Suffolk
Undetermined	3	5	4
1 to 50	332	425	259
51 to 100	88	120	64
101 to 200	50	96	57
201 to 350	36	45	15
351 to 500	21	16	12
Greater than 500	16	23	7
Total number of herds	546	730	418
Mean herd size	94	94	76
Median herd size	29	34	26

Size of herds	Number of herds in Surrey	Number of herds in West Sussex
Undetermined	2	4
1 to 50	178	186
51 to 100	28	50
101 to 200	31	64
201 to 350	16	34
351 to 500	14	8
Greater than 500	10	16
Total number of herds	279	362
Mean herd size	99	111
Median herd size	21	42

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

Breed purpose	Number (and percentage of total) cattle in Bedfordshire	Number (and percentage of total) cattle in Cambridgeshire	Number (and percentage of total) cattle in Essex
Beef	7,526 (75%)	20,543 (80%)	21,437 (83%)
Dairy	2,146 (21%)	4,282 (16%)	3,346 (12%)
Dual purpose	358 (3%)	706 (2%)	1,002 (3%)
Unknown	(0%)	0 (0%)	1 (0.004%)
Total	10,030	25,531	25,786

Breed purpose	Number (and percentage of total) cattle in Greater London	Number (and percentage of total) cattle in Hertfordshire	Number (and percentage of total) cattle in Isle of Wight
Beef	1,005 (63%)	8,525 (81%)	7,461 (82%)
Dairy	294 (18%)	1,607 (15%)	1,471 (16%)
Dual purpose	276 (17%)	318 (3%)	121 (1%)
Unknown	(0%)	2 (0.019%)	(0%)
Total	1,575	10,452	9,053

Breed purpose	Number (and percentage of total) cattle in Kent	Number (and percentage of total) cattle in Norfolk	Number (and percentage of total) cattle in Suffolk
Beef	33,592 (65%)	55,069 (80%)	23,393 (73%)
Dairy	16,590 (32%)	10,532 (15%)	5,294 (16%)
Dual purpose	1,024 (1%)	2,812 (4%)	2,991 (9%)
Unknown	7 (0.014%)	6 (0.009%)	(0%)
Total	51,213	68,419	31,678

Breed purpose	Number (and percentage of total) cattle in Surrey	Number (and percentage of total) cattle in West Sussex
Beef	19,253 (69%)	23,620 (58%)
Dairy	6,966 (25%)	14,989 (37%)
Dual purpose	1,462 (5%)	1,441 (3%)
Unknown	(0%)	6 (0.015%)
Total	27,681	40,056

Appendix 2: summary of headline cattle TB statistics

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

Herd-level statistics	Bedfordshire	Cambridgeshire	Essex	Greater London
(a) Total number of cattle herds live on Sam at the end of the reporting period	160	341	392	75
(b) Total number of cattle herds subject to annual TB testing (or more frequent) at the end of the reporting period (any reason)	11	17	39	10
(c) Total number of whole herd skin tests carried out at any time in the period	49	90	111	22
(d) Total number of OTF cattle herds having TB whole-herd tests during the period for any reason	39	83	88	22
(e) Total number of OTF cattle herds at the end of the report period (herds not under any type of TB movement restrictions)	155	329	382	75
(f) Total number of cattle herds that were not under restrictions due to an ongoing TB incident at the end of the report period	157	338	388	75
(g.1) Total number of new OTF-S TB incidents detected in cattle herds during the report period	3	3	3	0
(g.2) Total number of new OTF-W TB incidents detected in cattle herds during the report period	0	1	0	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?	0	0	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?	0	0	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?	0	0	0	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)?	0	1	0	0
(h.5) Of the new OTF-W herd incidents, how many were first detected through routine slaughterhouse TB surveillance?	0	1	0	0
(i.1) Number of new OTF-S incidents revealed by enhanced TB surveillance (radial testing) conducted around those OTF-W herds	0	0	0	0
(i.2) Number of new OTF-W incidents revealed by enhanced TB surveillance (radial testing) conducted around those OTF-W herds	0	0	0	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)	1	2	2	0
(k) Number of OTF-W herds still open at the end of the period that were on a finishing unit	0	2	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	1 goat and 1 cat	0

Herd-level statistics	Hertfordshire	Isle of Wight	Kent	Norfolk
(a) Total number of cattle herds live on Sam at the end of the reporting period	229	126	661	946
(b) Total number of cattle herds subject to annual TB testing (or more frequent) at the end of the reporting period (any reason)	33	11	37	35
(c) Total number of whole herd skin tests carried out at any time in the period	76	38	192	169
(d) Total number of OTF cattle herds having TB whole-herd tests during the period for any reason	64	37	181	167
(e) Total number of OTF cattle herds at the end of the report period (herds not under any type of TB movement restrictions)	221	125	651	933
(f) Total number of cattle herds that were not under restrictions due to an ongoing TB incident at the end of the report period	226	126	659	945
(g.1) Total number of new OTF-S TB incidents detected in cattle herds during the report period	2	1	6	0
(g.2) Total number of new OTF-W TB incidents detected in cattle herds during the report period	3	0	0	1
(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?	3	0	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?	0	0	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?	0	0	0	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)?	3	0	0	1
(h.5) Of the new OTF-W herd incidents, how many were first detected through routine slaughterhouse TB surveillance?	0	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	0	0	0
(i.2) Number of new OTF-W incidents revealed by enhanced TB surveillance (radial testing) conducted around those OTF-W herds	2	0	0	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)	2	0	0	1
(k) Number of OTF-W herds still open at the end of the period that were on a finishing unit	0	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)	1 sheep	0	0	0

Herd-level statistics	Suffolk	Surrey	West Sussex
(a) Total number of cattle herds live on Sam at the end of the reporting period	517	333	449
(b) Total number of cattle herds subject to annual TB testing (or more frequent) at the end of the reporting period (any reason)	11	58	67
(c) Total number of whole herd skin tests carried out at any time in the period	105	138	181
(d) Total number of OTF cattle herds having TB whole-herd tests during the period for any reason	102	100	135
(e) Total number of OTF cattle herds at the end of the report period (herds not under any type of TB movement restrictions)	506	320	432
(f) Total number of cattle herds that were not under restrictions due to an ongoing TB incident at the end of the report period	514	328	446
(g.1) Total number of new OTF-S TB incidents detected in cattle herds during the report period	3	5	6
(g.2) Total number of new OTF-W TB incidents detected in cattle herds during the report period	0	0	4
(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?	0	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?	0	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?	0	0	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)?	0	0	4
(h.5) Of the new OTF-W herd incidents, how many were first detected through routine slaughterhouse TB surveillance?	0	0	1
(i.1) Number of new OTF-S incidents revealed by enhanced TB surveillance (radial testing) conducted around those OTF-W herds	0	3	2
(i.2) Number of new OTF-W incidents revealed by enhanced TB surveillance (radial testing) conducted around those OTF-W herds	0	0	1
(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	2
(k) Number of OTF-W herds still open at the end of the period that were on a finishing unit	0	0	2
(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 South East of England during 2023.

Animal-level statistics (cattle)	Bedfordshire	Cambridgeshire	Essex	Greater London
(a) Total number of cattle tested with tuberculin skin tests or additional IFN-γ blood tests in the period (animal tests)	8,708	8,805	7,904	676
(b.1) Reactors detected by tuberculin skin tests during the year	16	3	23	0
(b.2) Reactors detected by additional IFN-γ blood tests (skin-test negative or IR animals) during the year	18	0	9	0
(c) Reactors detected during year per incidents disclosed during year	11.33	0.75	10.67	0.00
(d) Reactors per 1,000 animal tests	3.90	0.34	4.05	0.00
(e.1) Additional animals slaughtered during the year for TB control reasons (dangerous contacts, including any first time IRs)	0	0	0	0
(e.2) Additional animals slaughtered during the year for TB control reasons (private slaughters)	0	0	0	0
(f) Slaughterhouse (SLH) cases (tuberculous carcasses) reported by the Food Standards Agency (FSA) during routine meat inspection	1	2	1	0
(g) SLH cases confirmed by M. bovis PCR testing or bacteriological culture	0	2	0	0

Animal-level statistics (cattle)	Hertfordshire	Isle of Wight	Kent	Norfolk
(a) Total number of cattle tested with tuberculin skin tests or additional IFN-γ blood tests in the period (animal tests)	6,691	3,578	15,988	13,810
(b.1) Reactors detected by tuberculin skin tests during the year	9	1	12	2
(b.2) Reactors detected by additional IFN-γ blood tests (skin-test negative or IR animals) during the year	0	0	0	16
(c) Reactors detected during year per incidents disclosed during year	1.80	1.00	2.00	18.00
(d) Reactors per 1,000 animal tests	1.35	0.28	0.75	1.30
(e.1) Additional animals slaughtered during the year for TB control reasons (dangerous contacts, including any first time IRs)	1	0	0	0
(e.2) Additional animals slaughtered during the year for TB control reasons (private slaughters)	0	0	0	0
(f) Slaughterhouse (SLH) cases (tuberculous carcasses) reported by the Food Standards Agency (FSA) during routine meat inspection	0	1	1	2
(g) SLH cases confirmed by M. bovis PCR testing or bacteriological culture	0	0	0	0

Animal-level statistics (cattle)	Suffolk	Surrey	West Sussex
(a) Total number of cattle tested with tuberculin skin tests or additional IFN-γ blood tests in the period (animal tests)	10,986	21,872	28,277
(b.1) Reactors detected by tuberculin skin tests during the year	3	32	42
(b.2) Reactors detected by additional IFN-γ blood tests (skin-test negative or IR animals) during the year	0	14	47
(c) Reactors detected during year per incidents disclosed during year	1.00	9.20	8.90
(d) Reactors per 1,000 animal tests	0.27	2.10	3.15
(e.1) Additional animals slaughtered during the year for TB control reasons (dangerous contacts, including any first time IRs)	0	1	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	0	2	2
(g) SLH cases confirmed by M. bovis PCR testing or bacteriological culture	0	0	1

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, 31 of 41 (76%) of new TB incidents in the South East of England received a preliminary or final APHA veterinary investigation to identify the source of infection.

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 31 new TB incidents that received a veterinary investigation in the South East of England in 2023.

Source of infection	Possible (1)	Likely (4)	Most likely (6)	Definite (8)	Weighted contribution
Badgers	6	8	0	0	13.7%
Cattle movements	3	6	10	4	49.5%
Contiguous	2	1	0	0	3.0%
Residual cattle infection	1	0	2	0	3.7%
Domestic animals	0	0	0	0	0.0%
Non-specific reactor	0	0	0	0	0.0%
Fomites	7	1	0	0	5.6%
Other wildlife	4	3	0	0	5.8%
Other or unknown source	1	0	0	0	18.7%

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.