Research and analysis

North West of England (low risk area) year end report 2022

Updated 20 November 2023

Introduction

The Low Risk Area (LRA) of England was established in 2013. In 2014 this area was incorporated into the UK government’s strategy to achieve Officially Tuberculosis-Free (OTF) status for England by 2038. A key action was to recognise the different levels of bovine tuberculosis (TB) in different parts of the country and to vary the approach to control accordingly.

Overall, the LRA has a very low and stable incidence of infected herds. The current strategy seeks to rapidly control infection when it arises through:

• high sensitivity testing of affected herds
• temporarily enhanced local surveillance (radial and hotspot testing)
• mandatory pre- and post-movement testing of cattle entering the LRA from higher risk areas of the UK

The aim 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 2022 in cattle herds in the North West of England, which includes Lancashire, Merseyside, and Greater Manchester, which are all part of the LRA. In 2022, 18% 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 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 individuals involved in the control of TB, both locally and nationally. This includes, but is not limited to farmers, veterinarians, policy makers and 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 2022.

Types of TB incident

Unless otherwise specified, this report includes all new TB incidents detected during the reporting period, 1 January to 31 December 2022. This includes both ‘Officially Tuberculosis-Free Status Withdrawn’ (OTF-W) and ‘Officially Tuberculosis-Free Status Suspended’ (OTF-S) incidents.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, or SICCT test) with either typical lesions of TB identified at post-mortem (PM) meat inspection, or at least one animal with M. bovis-positive culture results from tissue samples collected from carcases during the PM inspection, or both.

OTF-S incidents are triggered by reactors to the skin test, but without subsequent detection of TB lesions or positive 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 size band and breed purpose for each county.

There are 4 livestock markets in the region, all located in northern Lancashire. Of the 4 markets, one is TB exempt. Two collection centres, both situated in Lancashire, handle slaughter cattle. There is one Licensed Finishing Unit (LFU), also located in Lancashire.

New TB incidents

During 2022, there were 26 new TB incidents in the North West of England, a marginal increase from 24 incidents in 2021 (Figure 1). This figure has been increasing since 2020 when there were 13. The total number of OTF-W incidents in the region was 9 (up from 7 in 2021), and the total number of OTF-S incidents was 17 (unchanged from 2021).

As shown in Figure 1, in Greater Manchester, the total number of incidents was 9 (4 OTF-W and 5 OTF-S). This was an increase from 7 total incidents, an increase of one OTF-W and one OTF-S incident compared to 2021.

In Lancashire, the total number of incidents was 17 (unchanged from 2021). The number of OTF-W incidents was 5, which was an increase from 4 in 2021, and there were 12 OTF-S incidents (decreased from 13 in 2021).

There have been no TB incidents in Merseyside since 2018.

There were no incidents of TB reported in non-bovine species in the North West of England during 2022.

Figure 1: Annual number of new TB incidents (OTF-W and OTF-S) in the North West, from 2013 to 2022

County and year	OTF-W incidents	OTF-S incidents	Total
Greater Manchester 2013	3	2	5
Greater Manchester 2014	1	4	5
Greater Manchester 2015	3	3	6
Greater Manchester 2016	1	6	7
Greater Manchester 2017	1	5	6
Greater Manchester 2018	0	4	4
Greater Manchester 2019	4	1	5
Greater Manchester 2020	5	0	5
Greater Manchester 2021	3	4	7
Greater Manchester 2022	4	5	9
Lancashire 2013	6	13	19
Lancashire 2014	6	15	21
Lancashire 2015	2	16	18
Lancashire 2016	3	10	13
Lancashire 2017	4	2	6
Lancashire 2018	0	10	10
Lancashire 2019	1	12	13
Lancashire 2020	2	6	8
Lancashire 2021	4	13	17
Lancashire 2022	5	12	17
Merseyside 2013	1	0	1
Merseyside 2014	1	1	2
Merseyside 2015	0	1	1
Merseyside 2016	0	1	1
Merseyside 2017	2	0	2
Merseyside 2018	1	1	2
Merseyside 2019	0	0	0
Merseyside 2020	0	0	0
Merseyside 2021	0	0	0
Merseyside 2022	0	0	0
Merseyside 2021	1	2	3
Merseyside 2022	0	0	0

The headline cattle TB statistics for North West of England are summarised in Appendix 2.

Unusual TB incidents

In Lancashire, one OTF-S TB incident that closed in February 2022 had been under TB restrictions for over a year (435 days). This incident was in a dairy herd of 306 cattle. Five skin test reactors and 4 inconclusive reactors (IRs) were found at a routine herd test in December 2020. Additional IRs were found at 4 subsequent short interval tests, resulting in the prolongation of the incident. Serial re-testing of these IRs was carried out using the high-specificity format of the interferon gamma blood test in accordance with the non-specific reactor procedure. Negative results were received, and restrictions were lifted.  

Disclosing test type

As shown in Figure 2, in 2022, just over half of new TB incidents in Greater Manchester and Lancashire were disclosed by radial testing (RAD), 56% (5 out of 9), and 53% (9 out of 17), respectively.

For Greater Manchester, this has not changed significantly since 2021, when just fewer than half of new incidents were detected by RAD testing (3 out of 7). For Lancashire, however, this is a significant change compared to 2021 when just 18% of new incidents were disclosed by radial testing.

In Lancashire, routine herd testing (RHT) detected 4 incidents. Both slaughterhouse (SLH) surveillance and movement tests each detected 2 incidents.

In Greater Manchester, RHT, slaughterhouse surveillance, 6-month testing and whole herd testing detected one incident each.

Figure 2: Number of new TB incidents (OTF-W and OTF-S) in the North West, in 2022 according to the surveillance method that detected them

County	6 month test	Pre-movement test	Radial test	Routine herd test	Slaughterhouse	Whole herd test	Total
Greater Manchester	1	0	5	1	1	1	9
Lancashire	0	2	9	4	2	0	17

Duration of TB incidents

A total of 25 TB incidents were resolved during 2022. Of these, 19 were new TB incidents that started in 2022, 5 started in 2021 and one was from 2020.

Consistent with previous years, most OTF-S incidents were quickly resolved in less than 150 days (11 out of 14). Of the remaining 3, 2 resolved within 240 days and one within 550 days (see the ‘Unusual TB incidents section’).

In Greater Manchester, 5 OTF-W cases resolved, one within 150 days and 4 within 240 days. In Lancashire, 6 OTF-W cases resolved, 4 within 240 days and 2 within 550 days. These findings are also largely consistent with 2021 when most OTF-W incidents closed within 240 days.

There were no persistent incidents (under movement restrictions for more than 550 days) in the region.

Of the 26 new TB incidents in 2022, 7 were still ongoing at the end of 2022 and their duration will be assessed when they are resolved.

Geographical distribution of TB incidents

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 3).

Whole genome sequencing (WGS) replaced genotyping of M. bovis isolates at APHA in 2021. There was one OTF-W incident (labelled 3 in Figure 3) in the east of Lancashire near Burnley, which was culture negative and therefore clade information was unavailable. A further 3 OTF-S TB incidents were disclosed in this area. The 4 new TB incidents in this area in 2022 occurred near 2 OTF-W incidents disclosed in 2021 with clade B3-11. Clade B3-11 is usually detected in the south-east of the region (Stockport area of Greater Manchester) bordering Cheshire and Derbyshire, where clade B3-11 has it’s homerange.

Around the higher cattle density area in central Lancashire and towards the west of the region, there were 3 new OTF-W incidents. Two of these (labelled 2 and 5 in Figure 3) were due to clade B6-11. Clade B6-11 is widespread across the West Midlands and parts of Wales. The other OTF-W in the central area (labelled 4 in Figure 3), was due to clade B6-82, which has a small homerange in Avon. Incident number 2 occurred near another OTF-W incident that was disclosed in 2021. However, the 2021 incident was due to a different clade (B6-62, which has a homerange in the southern Edge Area, including neighbouring county Buckinghamshire). Three OTF-S incidents were also detected in this central area in 2022.

Towards North Lancashire there were 4 OTF-S incidents and one OTF-W incident (labelled 1 in Figure 3). Clade B5-11 was detected in the OTF-W incident.

In Greater Manchester, 3 OTF-W incidents (labelled 7 to 9 in Figure 3) were all clade B3-11. They occurred near previously detected OTF-W incidents, one OTF-W incident in 2021 and one OTF-W incident in 2020, both with clade B3-11. One new OTF-S incident was also detected in this area in 2022.

The other new OTF-W incident in Greater Manchester in 2022 (labelled 6 in Figure 3) was detected in the north-east, near Oldham. This also had clade B3-11 detected and was in the same area as previous clade B3-11 incidents from 2020 and 2021. There were 4 OTF-S incidents spread across the north of the county.

Figure 3: Location of cattle holdings in the North West of England with new TB incidents (OTF-W and OTF-S) in 2022, and cattle holdings with pre-2022 OTF-W incidents still ongoing at the beginning of 2022, overlaid on a cattle density map. Note that ‘OTF-W Introduced 2022’ refers to OTF-W incidents in which cattle movements were the most likely source of infection.

As can be seen from Figure 4 and Appendix 3 Table 5, OTF-W incidents in the North West of England in 2022 were attributed to different sources of infection.

In Lancashire, 2 incidents were attributed to possible exposure to wildlife. One of these is in the Burnley area and the other one is in the north of the county. Of the 3 incidents around the centre of Lancashire in 2022, one was attributed to fomites (inanimate objects or material contaminated with the bacterium transferred between farms), one to the introduction of undetected infected cattle, and one remained unknown.

In Greater Manchester, for all 4 OTF-W incidents, exposure to infected wildlife was found to be a likely risk pathway.

Figure 4: 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 2022. 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 5 shows the hotspot areas and radial surveillance zones around OTF-W incidents since 2012.

In Lancashire, new OTF-W incidents were clustered towards the centre of the county in recent years. In the east, near Burnley, 3 OTF-W incidents have occurred in the last 2 years (2 in 2021 and one in 2022). Further west of Lancashire, new incidents have been occurring each year since before 2019, as shown in Figure 5.

No new OTF-W incidents have occurred in the Lancashire side of Potential Hotspot Area 27 (PHA27) since before 2019.

Only one new OTF-W incident has occurred towards the north of Lancashire since 2019.

In Greater Manchester, new OTF-W incidents have continuously occurred since before 2020 in the south-east of the region, bordering Cheshire and Derbyshire. This area is subject to further investigation.

There have also been OTF-W incidents in the Oldham area, to the north-east of Manchester, for the last 3 reporting periods.

New incidents have also been detected towards the east and the west of the region since 2020.

Figure 5: Hotspot areas and radial surveillance zones around OTF-W incidents that were active, completed or not instigated in the North West of England during 2022, by year of initiation.

Potential or confirmed TB hotspots

Potential Hotspot Area PHA27

PHA27 covers parts of Lancashire and North Yorkshire and can be seen in Figures 3 to 5. This potential hotspot was established in January 2020 due to clade B6-23 (genotype 17:z) and is described in more detail in the 2020 Yorkshire and Humberside Epidemiological Report.

There were no new OTF-W incidents or active radial zones in the Lancashire part of this area in 2022.

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 6, the number of reactors removed for TB control purposes in 2022 in the North West of England decreased compared to 2021 (from 78 to 59). Of the total 59 cattle that were removed for TB control purposes, 30 were skin test reactors (down from 35 in 2021) and 29 were positive on the interferon gamma (IFN-γ) test (down from 43 in 2021).

In Greater Manchester, there were 12 skin test reactors (compared to 9 in 2021), and 2 IFN-γ test positive animals (down from 20 in 2021).

There were 18 skin test reactors in Lancashire (down from 26 in 2021), and 27 IFN-γ test positive animals (increased from 23 in 2021).

In Merseyside, there have been no skin test reactors since 2018 and no IFN-γ test positive animals since 2017.

Figure 6: Number of cattle that tested positive to the skin test or interferon gamma test and were removed by APHA for TB control reasons in the North West, from 2017 to 2022

County and year	Skin test	Interferon gamma test	Total
Greater Manchester 2017	6	1	7
Greater Manchester 2018	4	0	4
Greater Manchester 2019	11	6	17
Greater Manchester 2020	8	6	14
Greater Manchester 2021	9	20	29
Greater Manchester 2022	12	2	14
Lancashire 2017	12	58	70
Lancashire 2018	21	0	21
Lancashire 2019	17	1	18
Lancashire 2020	20	0	20
Lancashire 2021	26	23	49
Lancashire 2022	18	27	45
Merseyside 2017	6	4	10
Merseyside 2018	1	0	1
Merseyside 2019	0	0	0
Merseyside 2020	0	0	0
Merseyside 2021	0	0	0
Merseyside 2022	0	0	0

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 2022, 14 of the 26 (54%) 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 2022.

The key drivers of the TB epidemic in the North West of England during 2022 were identified as follows:

• exposure to probable infected badgers
• exposure to other probable infected wildlife
• purchase of undetected infected cattle

Exposure to probable infected badgers appears to be the main pathway of infection for cattle herds. As can be seen in Appendix 3, this pathway had an overall weighted contribution of 36%. This figure is derived from 13 instances of risk pathways involving exposure to infected badgers, 2 of which were associated with the same incident (exposure to at grazing and exposure at housing both selected). Of these, 6 were ranked as possible, 6 were ranked as likely and one was ranked as most likely. Four of those ranked as likely or very likely were clustered in the Stockport area. The other 3 were in separate locations.

It therefore appears that the shift towards exposure to infected badgers as a key risk pathway is being driven by findings in the Stockport area. This relative increase in importance should also be considered in the context of only 54% of DRFs being carried out.

Wildlife excluding badgers (15%), movement of undetected infected cattle (11%), and exposure to fomites (11%) were also selected as a potential source of infection for some new TB incidents in 2022.

There was a moderate degree of uncertainty around the source of incidents in 2022, with other or unknown sources having a weighted contribution of 24%. This category is added to those incidents in which there was high uncertainty around the selected pathways (see explanatory supplement for methodology).

Forward look

The sustained number of new TB incidents in Lancashire and increase in Greater Manchester are a concern. However, the predominance of OTF-S incidents in the area suggest TB is being found early and reduces the risk of onward lateral spread. Furthermore, most of the OTF-S incidents were resolved swiftly, in under 150 days.

As mentioned previously, the North West has a historically low level of TB, but the south-east area of Greater Manchester, around Stockport and Manchester Airport, is of concern due to its proximity to the Cheshire and Derbyshire Edge Area. Furthermore, areas around Oldham in Greater Manchester and Burnley in Lancashire will require careful monitoring in case the situation deteriorates further in these areas.

The apparent increase in the relative importance of exposure to infected badgers as a risk pathway is also concerning and this is predominantly driven by the Stockport area. This needs to be considered in the context that just under half of the new TB incidents in 2022 did not receive a risk pathway investigation.

Appendix 1: cattle industry demographics

Table 1: Number of cattle herds by size category in the North West of England at 31 December 2022 (RADAR data)

Size of herds	Number of herds in Greater Manchester	Number of herds in Lancashire	Number of herds in Merseyside
Undetermined	4	9	2
1 to 50	270	718	22
51 to 100	43	277	11
101 to 200	41	243	8
201 to 350	15	185	4
351 to 500	2	98	1
Greater than 500	2	87	2
Total number of herds	377	1617	50
Mean herd size	55	141	96
Median herd size	24	62	55

Table 2: Number (and percentage of total) of animals by breed purpose in the North West of England at 31 December 2022

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	12,581 (60%)	83,159 (36%)	3,229 (67%)
Dairy	7,643 (37%)	131,162 (57%)	1,513 (31%)
Dual purpose	411 (1%)	14,074 (6%)	59 (1%)
Unknown	0%	8 (0.0035%)	0%
Total	20,635	228,403	4,801

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 2022

Herd-level statistics	Greater Manchester	Lancashire	Merseyside
(a) Total number of cattle herds live on Sam at the end of the reporting period	475	1,966	67
(b) Total number of cattle herds subject to annual TB testing (or more frequent) at the end of the reporting period (any reason)	130	463	7
(c) Total number of whole herd skin tests carried out at any time in the period	199	723	18
(d) Total number of OTF cattle herds having TB whole herd tests during the period for any reason	170	632	16
(e) Total number of OTF cattle herds at the end of the report period (herds not under any type of Notice Prohibiting the Movement of Bovine Animals (TB02) restrictions)	446	1,932	65
(f) Total number of cattle herds that were not under restrictions due to an ongoing TB incident at the end of the report period	473	1,961	67
(g.1) Total number of new OTF-S TB incidents detected in cattle herds during the report period	5	12	0
(g.2) Total number of new OTF-W TB incidents detected in cattle herds during the report period	4	5	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
(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 2 time inconclusive reactors (2xIRs) at routine herd tests?	3	4	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	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	2	7	0
(i.2) Number of new OTF-W incidents revealed by enhanced TB surveillance (radial testing) conducted around those OTF-W herds	3	2	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	0	1
(k) Number of OTF-W herds still open at the end of the period that are within a finishing unit	0	0	0
(l) New confirmed (positive M. bovis culture) incidents in non-bovine species detected during the report period (indicate host species involved)	0	0	0

Table 4: Animal-level summary statistics for TB in cattle in the North West of England during 2022

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.

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)	12,280	134,330	1,538
(b.1) Reactors detected by tuberculin skin tests during the year	12	18	0
(b.2) Reactors detected by additional IFN-γ blood tests (skin-test negative or IR animals) during the year	2	27	0
(c) Reactors detected during year per incidents disclosed during year	1.56	2.65	0
(d) Reactors per 1,000 animal tests	1.14	0.33	0
(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) SLH cases (tuberculous carcases) reported by the Food Standards Agency (FSA) during routine meat inspection	2	5	0
(g) SLH cases confirmed by culture of M. bovis	1	2	0

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 2022, 14 of the 26 (54%) new TB incidents in the North West 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 2022.

Table 5: Suspected sources of M. bovis infection for all new OTF-W and OTF-S incidents identified in the North West of England in 2022.

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.

Source of infection	Possible (1)	Likely (4)	Most likely (6)	Definite (8)	Weighted contribution
Badgers	6	6	1	0	36%
Cattle movements	2	1	1	0	11%
Contiguous	0	0	0	0	0%
Residual cattle infection	1	0	0	0	1%
Domestic animals	1	0	0	0	1%
Non-specific reactor	0	0	0	0	0%
Fomites	1	3	0	0	11%
Other wildlife	6	2	0	0	15%
Other or unknown source	2	1	0	0	24%