Figures to December 2021 (published 9 March 2022)

Question 1

Key points

Accepted Answer

In England overall, the herd incidence rate for the 12 months to end December 2021 was 8.8, a decrease of 0.6 from the previous 12 months. Between December 2020 and December 2021, the herd prevalence rate decreased in all three risk areas of England (Table 1.1).
In Scotland, which has had officially TB-free (OTF) status since 2009, herd incidence and herd prevalence remain very low and stable.
In Wales herd incidence increased by 0.5 compared to the previous 12 months, and herd prevalence increased slightly between December 2020 and December 2021.
Total animals slaughtered due to a TB incident in England in 2021 decreased 1% from the previous year to 27,581. In Wales the number slaughtered was 10,641, an increase of 1% (Table 1.6).

Short term changes in these statistics should be considered in the context of long-term trends. The charts in this statistical notice give the latest indication of how trends in bovine TB have changed since 1996.

Question 2

1.  Key tables summarising key bTB data to December 2021

Accepted Answer

1.1 Herd incidence and herd prevalence

The headline measure of herd incidence is the rate of new herd incidents per 100 herd years at risk. The rate is based around the total amount of time that herds tested were unrestricted and at risk of infection since the end of their last TB incident or negative herd test, rather than the total number of tests carried out on those herds. The rate in the High Risk Area of England was 14.4 at the end of 2021, which means for every 1000 unrestricted herds undergoing bTB surveillance in that period APHA detected on average 144 new breakdowns. A document describing the herd years at risk measure is available online.

Herd prevalence is defined as the percentage of all registered herds which were not Officially TB Free (OTF) due to a TB incident. Table 1.1 compares the percentage of restricted herds at end of 2021 with end of 2020. Prevalence in England decreased by 0.4 of a percentage point, driven by decreases of 0.4 and 1.3 percentage points in the High Risk Area and Edge area respectively.

In Wales overall herd prevalence has increased from 5.4% to 5.5%.

Figure 1: Longterm view of new herd incidents per 100 herd years at risk of infection during the year - GB

Charts for Herd Incidence split by England risk areas and Wales TB areas, are available to download in the charts file.

Figure 2: Longterm view of number of herds which were non-OTF at the end of the period due to a TB incident as a percentage of registered and active herds - GB

Charts for Herd Prevalence split by England risk areas and Wales TB areas, are available to download in the charts file.

Table 1.1: Herd incidence and herd prevalence

Region	Herd incidence 2020	Herd incidence 2021	Herd prevalence at 31 Dec 2020	Herd prevalence at 31 Dec 2021
England (All)	9.4	8.8	5.0	4.6
England - HRA	16.2	14.4	9.2	8.8
England - Edge	10.1	8.9	5.9	4.7
England - LRA	1.1	1.1	0.4	0.3
Scotland (All)	0.7	0.7	0.2	0.1
Wales (All)	6.6	7.1	5.4	5.5
Wales - High West	10.7	10.9	10.3	10.6
Wales - High East	8.9	7.6	6.2	4.9
Wales - Intermediate North	6.8	10.0	5.3	6.6
Wales - Intermediate Mid	2.9	3.9	1.9	2.5
Wales - Low	1.4	2.1	0.5	1.0

1.2 New herd incidents and non-OTF herds

The number of new TB herd incidents in 2021 compared to 2020 (Table 1.2):

decreased by 10% in England with all risk areas showing decreases.
increased in Wales by 8% to 665, with all TB areas except the High East TB area showing increases.
decreased by 11 in Scotland.

Table 1.2: New herd incidents annual

Region	2020	2021	Year-on-year change
England (All)	3,176	2,851	-10%
England - HRA	2,363	2,150	-9%
England - Edge	674	574	-15%
England - LRA	139	127	-9%
Scotland (All)	38	27	-29%
Wales (All)	613	665	8%
Wales - High West	252	262	4%
Wales - High East	201	171	-15%
Wales - Intermediate North	88	129	47%
Wales - Intermediate Mid	48	67	40%
Wales - Low	24	36	50%

The number of herds under restriction – or more formally herds not officially TB free at the end of the period due to a bovine TB incident is the top line of the herd prevalence calculation used in Table 1.1. The bottom line is the number of registered active herds, which has been subject to data cleansing in recent months. Examining the counts of non-OTF herds can identify particular drivers for trends.

The number of herds under restriction due to a TB incident at the end of 2021 compared to the end of 2020 (Table 1.3):

decreased by 14% in England, driven by decreases in all risk areas.
increased in Wales by 2% to 640, with only the High East area showing a decrease.
in Scotland there was a decrease of 13 herds.
large percentage changes in Scotland and three Welsh TB areas (Intermediate North, Intermediate Mid, and Low) are due to low baseline numbers.

Table 1.3: Non-OTF herds - Herds not officially TB free at the end of the period due to a bovine TB incident

Region	2020	2021	Year-on-year change
England (All)	2,464	2,130	-14%
England - HRA	1,865	1,683	-10%
England - Edge	521	386	-26%
England - LRA	78	61	-22%
Scotland (All)	27	14	-48%
Wales (All)	626	640	2%
Wales - High West	323	328	2%
Wales - High East	171	136	-20%
Wales - Intermediate North	83	104	25%
Wales - Intermediate Mid	39	50	28%
Wales - Low	10	22	120%

In Scotland the number of non-OTF herds is very low and approximately 59% of cattle herds are now exempt from routine TB surveillance testing. In Scotland, the England LRA, and Wales Low area there are proportionately more false positive results to the tuberculin skin test than elsewhere in GB. For example see articles in the Veterinary Record. Consequently it is also important to consider the number of new herd TB incidents where officially TB free (OTF) status is withdrawn (OTFW) following confirmation of TB by post-mortem examination or laboratory culture of tissue samples.

In the Low Risk Area of England:

in 2021 there were 38 OTFW incidents, an decrease of 4 from the previous year. The OTFW herd incidence rate per 100 herd-years remained constant at 0.4 (Table 1.4 and Table 1.5).

In Scotland:

There were 6 OTFW incidents in 2021, compared to 13 in 2020.
The OTFW herd incidence rate of breakdowns per 100 herd-years at risk decreased from 0.3 to 0.2 in 2021.

In the Low TB area of Wales:

There were 12 OTFW incidents in 2021, 7 more than in 2020.
The OTFW herd incidence rate of breakdowns per 100 herd-years at risk was 1.1 at the end of 2021, an increase of 0.4 from the end of 2020.

Table 1.4: OTFW new herd incidents annual - New herd incidents where OTF status is withdrawn (OTFW)

Region	2020	2021	Year-on-year change
England (All)	1,910	1,540	-19%
England - HRA	1,505	1,242	-17%
England - Edge	363	260	-28%
England - LRA	42	38	-10%
Scotland (All)	13	6	-54%
Wales (All)	334	328	-2%
Wales - High West	132	128	-3%
Wales - High East	120	116	-3%
Wales - Intermediate North	54	45	-17%
Wales - Intermediate Mid	23	27	17%
Wales - Low	5	12	140%

Table 1. 5: OTFW herd incidence - New herd incidents OTFW per 100 herd years at risk

Region	2020	2021
England (All)	5.7	4.8
England - HRA	10.3	8.4
England - Edge	5.5	4.1
England - LRA	0.4	0.4
Scotland (All)	0.3	0.2
Wales (All)	5.9	5.8
Wales - High West	10.1	9.8
Wales - High East	8.4	7.0
Wales - Intermediate North	5.9	6.1
Wales - Intermediate Mid	2.1	3.0
Wales - Low	0.7	1.1

Figure 3: New herd incidents with officially TB-free status withdrawn (OTFW) per 100 herd years at risk of infection during the year – GB, per quarter

Note: from 2011, the figures presented in Figure 3 for OTF-W incidents per 100 herd years at risk in Wales are not directly comparable to England or Scotland. This is due to the inclusion of some incidents in Wales that have their OTF status withdrawn for epidemiological reasons only, in the absence of post-mortem confirmation. The figures presented here are not comparable with those for Wales in the dataset downloads.

1.3 Animals Slaughtered as a result of a TB incident

There is a year-on-year 1% decrease in the number of cattle slaughtered due to a TB incident in England. In the High Risk Area and Edge Area fewer animals were slaughtered in the 2021 than in 2020. For county trends see the datasets.

Table 1.6: Total animals slaughtered annual

Region	2020	2021	Year-on-year change
England (All)	27,852	27,581	-1%
England - HRA	22,022	21,849	-1%
England - Edge	5,482	5,193	-5%
England - LRA	348	539	55%
Scotland (All)	261	581	123%
Wales (All)	10,488	10,641	1%
Wales - High West	6,314	6,270	-1%
Wales - High East	2,146	1,653	-23%
Wales - Intermediate North	1,372	1,830	33%
Wales - Intermediate Mid	550	754	37%
Wales - Low	106	134	26%

Table 1.6 Includes skin test reactors, antibody test positive animals, gamma test positive animals, and direct contacts. Since April 2017 it also includes inconclusive reactors for Wales only.

In Wales overall there was an increase of 1% in the number of animals slaughtered in 2021 compared to 2020, despite the High West and High East areas showing decreases.

The 581 animals slaughtered in Scotland in 2021 is the most ever recorded in a calendar year. The reason for the large number of slaughters is a large breakdown involving a single holding in Ayrshire.

Question 3

2.  What you need to know about this release

Accepted Answer

2.1 Contact details

Email address: TBStatistics@Defra.gov.uk

Public enquiries:

Defra TB Statistics
Foss House, Kings Pool
Peasholme Green
York
YO1 7PX

Media Enquiries: 0208 225 7318 (Press Office)

2.2 National statistics status

National Statistics status means that our statistics meet the highest standards of trustworthiness, quality and public value, and it is our responsibility to maintain compliance with these standards. The continued designation of these statistics as National Statistics was confirmed in December 2017 following a compliance check by the Office for Statistics Regulation. The statistics last underwent a full assessment against the Code of Practice in 2012 – Assessment Report 240.

Since the latest review by the Office for Statistics Regulation, we have continued to comply with the Code of Practice for Statistics, and have made the following improvements:

added more value by providing more detailed breakdowns of TB areas in Wales
included a glossary of key terms and a mapping of English counties to TB regions
introduced quarterly overview documents for England and Great Britain
from Q4 2019 included an interactive dashboard of measures
redesigned the release and datasets to achieve compliance with accessibility regulations (Q2 2020)
new groupings in the dataset of English counties by TB Risk Area (Q2 2020)
provided county-level values for herd incidence (Q4 2020)
amended the datasets to achieve enhanced accessibility (Q3 2021)
included antibody tests and animals slaughtered after receiving a positive antibody test (Q4 2021)

2.3 Feedback on this release

We encourage our users to engage with us so we can improve our National and Official Statistics and identify gaps in the statistics that we produce. See also our response to our 2020 user survey.

This document has been designed to meet the accessibility requirements outlined in WCAG 2.1:

all figures included in this release have accompanying alt-text descriptions
the release content has been adapted for easier processing by screen-readers
all text and figures use a high contrast colour scheme, and all figures use colour palettes that are visible to colourblind readers
publishing in HTML format in order to maximise compatibility

Should you have any comments on this statistical release and how to improve it to meet your needs please contact us by email to tbstatistics@defra.gov.uk

Question 4

3.  About these statistics

Accepted Answer

3.1 Revision notices

In November 2021 the boundaries of the three Denbighshire/Conwy Valley spatial units CL1, CL2 and GW1 were realigned from the Low TB area to the Intermediate TB Area North. The data in this release now reflect these new boundaries for the entirety of the historical series. Since this revision covers time periods outside of our ordinary scope for revisions there are minor inconsistencies for some months. These represent modifications to Sam records that have happened since these values were last revised, but their impact on the data is minimal and they do not affect observed general trends.

Due to ongoing quality control checks on pre-Sam herd register data, values for the number of registered herds in the Wales TB areas are only available from June 2011 onwards, and similarly values for herd prevalence in the Wales TB areas are only available for this time period. Once quality control checking is complete we will update these datasets accordingly, and publish the complete historical series for comparison between the old and new boundaries of the Wales TB areas.

3.2 Notes on the data

These statistics are obtained from the Animal and Plant Health Agency (APHA) work management IT support system (SAM), used for the administration of TB testing in GB. They are a snapshot of the position on the date on which the data was extracted.

These statistics may be subject to small revisions until all test results are available. In particular, figures for the previous two calendar years and the current year will be subject to further revision as test and incident records are completed. The herd incidence figures are revised quarterly.

Data for Northern Ireland is not presented alongside the GB figures and is not produced on a comparable basis.

Data from 1996 onwards is available to download for GB countries, Wales TB areas and England risk areas.

“England Bovine Tuberculosis (TB) Quarterly Overview” and “Great Britain Bovine Tuberculosis (TB) Quarterly Overview” are available to download as visual representations of four key measures.

An interactive dashboard has been introduced to allow online interrogation of the statistics.

3.3 Future publications

A release calendar is available at least 12 months in advance.

Question 5

4 Background  Information on Bovine Tuberculosis

Accepted Answer

4.1 What is bovine tuberculosis?

Bovine tuberculosis (bTB) is a chronic infectious disease of cattle. The risk bTB poses to human health is low, largely due to milk pasteurisation. The disease is detected either on farms (through mandatory skin tests of cattle herds for bTB at regular intervals) and at slaughterhouses (through post-mortem meat inspection of cattle carcases).

4.2 What are the impacts of bTB?

Bovine TB presents serious challenges to the food and farming industries and has economic and social impacts. The economic costs of a bTB breakdown are shared by farmers and government.

Defra and Welsh Government commissioned research was published on 28 August 2020 on the financial impact of TB on beef and dairy farmers. The report shows the cost of a TB breakdown directly borne by cattle farms varies significantly, with a median value of around £6,600 across all farms in the survey. Across England and Wales median costs for herds of more than 300 cattle are around £18,600 whilst those for herds up to 50 cattle are around £1,700. Median costs for chronic breakdowns over 273 days are around £16,000.

Costs are incurred for a number of reasons:

Cattle which are found (or are highly likely) to have bTB are slaughtered. This loses the farmer the value of the animal and its output. Government pays farmers compensation for slaughtered animals which is based on the market value of cattle.
There are costs associated with testing animals for bTB. Farmers incur costs from gathering animals together, such as paying workers for their time, and government pays the vets’ fees for carrying out tests on the herd (and in the event of a breakdown on herds in neighbouring farms).
When an animal in a herd tests positive for the disease, the whole herd is put under movement restrictions until all the remaining animals are tested repeatedly with negative results. This presents costs to farmers, for example because they are unable to move their cattle to market or buy in replacements for animals that are slaughtered.

Other impacts of high bTB levels can include:

Restrictions on international trade in cattle and cattle products.
Significant stress amongst famers, their families, and local communities. See for example research report SE3120 for Defra, 2008.
The infection spilling over to domestic and wild animals. For example Broughan, J. M., Downs, S. H., Crawshaw, T. R., Upton, P. A., Brewer, J. & Clifto-Hadley, R. S. (2013) Mycobacterium bovis infections in domesticated non-bovine mammalian species. Part 1: review of epidemiology and laboratory submissions in Great Britain 2004-2010. Veterinary Journal 198, 346-35.

4.3 Links to additional information on bovine TB policy

More information on bovine TB controls in Great Britain can be found for England, Wales and Scotland.

The TB Hub contains practical advice for farmers on dealing with bovine TB on their farm, covering everything from biosecurity measures to understanding trading rules.

Question 6

5 -  Narrative on incidence and prevalence of TB in Cattle in Great Britain

Accepted Answer

5.1 Why monitor statistics about bTB?

Legal requirements

Defra policy is to achieve OTF status for England by 2038, and Welsh Government policy is to achieve OTF status between 2036 and 2041. Scotland achieved OTF status in September 2009. bTB statistics are used in England and Wales to measure progress towards this target, and to support the annual case for Scotland to retain its OTF status, as the qualification is based on herd incidence.

Monitoring policy effectiveness

Statistics on the incidence of bTB in cattle herds and the number of cattle slaughtered as a result of bTB are used by policymakers to monitor the spread and concentration of the disease and to inform decisions around the potential approaches to controlling it.

5.2 Factors affecting statistics on incidence and prevalence of TB in cattle

Short term changes in these statistics should be considered in the context of long term trends. Variation in the monthly and quarterly statistics can occur for a number of reasons, including:

Disease: an increase in the trend can be the result of a higher proportion of herds experiencing a breakdown because of an increase in the underlying incidence of bTB.
Surveillance policy (including the frequency of testing): Cattle herds in high risk areas are tested six monthly or annually and cattle herds in low risk areas are usually tested every four years. In Scotland 59% of cattle herds are now exempt from routine TB surveillance testing. If cattle herds in a low prevalence region are tested more frequently than every four years, the increase in the number of bTB tests will not necessarily be followed by a similar increase in the detection of infected cattle and so this may result in a decline in the incidence rate.
Seasonality: more animals are tested when they are housed, during winter months, compared with when they are grazing outdoors in summer months. This is simply because it is easier to gather and test the cattle when they are already contained within a building.
Number of testing days in a given month: tests tend to be carried out at the beginning of the working week and the results collected and entered into the data system towards the end of the week. Months containing five Fridays may therefore have more positive test results than months containing four.

5.3 Trends in TB since 1996

There has been an overall long-term upward trend in the incidence of TB in cattle herds in England and Wales since these statistical series began in 1996 although there is evidence that the rate of new incidents is levelling off in most areas of the country.

There was a fairly steady increase in the herd incidence rate until early 2001 when there was an outbreak of foot and mouth disease (FMD) from February to October. During this period TB testing was suspended. In the meantime, new bTB breakdowns continued to be detected on farms through routine post-mortem meat inspection of cattle carcases in slaughterhouses. Following the 2001 FMD outbreak there was a gradual resumption in TB testing. This led to an unusually high incidence rate for 2001 and 2002, when effectively two years’ worth of breakdowns were identified in one year when the normal testing regime resumed.

There appears to be a three-year cycle in the bTB herd incidence rate from 2001 onwards. This can be observed in figures 1 and 3, with peaks in 2005, 2008 and (to a lesser extent) 2013, and troughs in 2006 and 2009. This pattern has stabilised somewhat in recent years. There is no clear explanation for this pattern, because bTB is a chronic disease with a complex epidemiology and reservoirs of infection in cattle and, in some areas of GB, wildlife. There has been no stable time series because of surveillance and testing changes. For example, there have been different herd testing frequencies in each parish over time, ranging from annual to four-yearly and changing every year until those frequencies were unified in Wales in 2010 (annual) and in England in 2013 (annual and four-yearly). There has since been the introduction of 6-monthly testing.

There are several possible explanations:

The smoothed trend represents true seasonal changes in the transmission risk and prevalence of infection in wildlife and cattle populations. However, there is no strong evidence to support this.
After FMD, higher risk herds were tested every 3 to 4 years and could have contributed to a cyclically higher incidence rate. However, breakdowns in the 4-yearly (and formerly 3-yearly) testing areas represent a small and decreasing proportion of the breakdowns in any given year.
When testing resumed in 2002 following the 2001 FMD outbreak, high-risk herds may have been identified and put under restrictions if a reactor was identified, then control tested for a period (when they cannot generate a new incident). Once the bTB incident has been resolved and OTF herd status is restored, the herd becomes susceptible to a new incident as it undergoes post-breakdown surveillance tests at 6 and 18 months after regaining OTF status.
The incidence rate reflects changes to testing policy unrelated to the FMD outbreak, in particular increases in testing in 2005 and 2008.

In terms of prevalence (the percentage of herds with an open TB incident), figure 2 shows an increase in England and Wales at the beginning of 2002. This may have been the result of the suspension of TB testing during the FMD outbreak in February-October 2001 (including the 60-day tests of TB-infected herds to regain OTF status) along with the detection of new breakdowns through routine slaughterhouse surveillance. Although TB herd testing gradually resumed from the end of 2001, a proportion of higher-risk herds were put under TB restrictions pending completion of their overdue tests. Prevalence continued to increase steadily from 2002. In Wales there were peaks in 2009 and 2012, following which there has been a decline and stabilisation of the trend. After a peak in England in early 2013 the trend appears to have stabilised. However, for both England and Wales it is too early to conclude that this is part of a new longer term trend.

5.4 bTB Surveillance policy in GB

Bovine TB surveillance and control policy – including how frequently animals are tested for bTB – varies between England, Wales and Scotland and has changed over time.

Timeline

1990s: most herds in GB tested every four years and background testing intervals determined on a parish basis. Herds in parishes with a high incidence of bTB breakdowns (in the South West of England and in parts of Wales) are tested on an annual or biennial basis, with a smaller number of three-yearly testing herds.

2004 to 2010: the proportion of parishes and herds in England and Wales with annual testing increases gradually as the disease spread, with a corresponding decrease in the proportion of parishes with four-yearly testing.

2005 to 2006: mandatory pre-movement skin testing of cattle in annually tested herds was introduced. First in Scotland in September 2005 followed by England in June 2006 and Wales in May 2006.

October 2009: the European Commission designates Scotland as an officially bTB free region of the UK.

January 2010: In England, a core annual testing area is established, spanning entire counties in the South West and West Midlands (the ‘high risk area’) and surrounded by a ‘buffer’ of two-yearly testing parishes. Most of the rest of England remains on background four-year testing. The Welsh Government puts all cattle herds in Wales on annual bTB testing (with herds in the small Intensive Action Area of West Wales put on 6-monthly bTB testing).

2011 and 2012: further expansion of the annual testing area in England to the east and north.

January 2013: herd testing intervals are determined on a county basis and England is split into annual testing and four-yearly testing counties. Annual testing of herds is extended to all the counties at the edge of the high risk area. Three- and two-yearly testing is abolished.

January 2015: all cattle herds in the edge area of Cheshire are put on six-monthly testing.

April 2016: mandatory post-movement skin testing of cattle was introduced in the Low risk area of England

October 2017: regionalised approach to TB eradication applied in Wales with the introduction of Low, Intermediate and High TB Areas.

January 2018: annual testing of cattle herds replaced with six-monthly herd testing in the higher incidence regions of the expanded Edge Area and annual herd testing supplemented with targeted (‘radial’) testing of herds located within a 3km radius of new OTFW incidents detected in the rest of the Edge Area.

2020 The IDEXX antibody test was approved as a “relevant test” under Part 2 of the Tuberculosis (Wales) Order 2010 (as amended). Any animal giving rise to a positive reaction to the to the antibody test will be considered a reactor and removed, with compensation being provided to the owner. These statistics do not yet capture all antibody test positive animals slaughtered and will be updated during 2021 reporting year.

January 2021: 6-monthly testing introduced in Staffordshire and Shropshire in the High Risk Area of England, with plans to extend this to the entirety of the High Risk Area in July 2021. 2021 testing intervals and a map of GB TB areas are published online.

November 2021 – Wales TB Areas changed on epidemiology advice so that 3 spatial units that were part of the Low TB Area, will temporarily be part of the Intermediate North TB Area. See frequently asked questions

5.5 Current differences in surveillance policy in GB

The regional and county-level statistics published as part of this statistical notice show that there are considerable differences in the distribution and frequency of bovine TB across GB.

Since 2011, the trends for the herd incidence rate showing incidents with officially TB-free status withdrawn (OTFW) per 100 herd years at risk of infection during the year are not directly comparable for Wales and the other countries of GB. In Wales the number of incidents includes those where there is no confirmation of TB via post mortem examination or bacteriological culture, but where the herd’s OTF status is withdrawn for epidemiological reasons. The overall herd incidence rate (figure 1 and table 1.1) should be used to compare countries.

Scotland

Scotland has had officially TB-free (OTF) status since 2009 and has relatively few herd breakdowns. The herd incidence is very low and stable and is largely driven by sporadic introductions of infected cattle into Scotland. Scotland has in place a risk-based routine herd testing policy. This targets testing at higher risk herds. Around 59 per cent of herds are considered low risk herds and are exempt from routine testing. These are herds which have 50 or fewer animals, minimal import of animals from high risk areas and send a high proportion of animals to slaughter. Herds that are not exempt are tested every four years.

Wales

In Wales, TB incidence and prevalence varies across regions. From 1 October 2017, a regionalised approach to TB eradication applies in Wales with the introduction of Low, Intermediate and High TB Areas. This means that measures can be tailored to address the varying risks and disease. The TB areas in Wales are established on the basis of epidemiological evidence and risks in each area. See a map of TB Areas. This regionalisation brought some changes to Pre- and Post- movement testing rules. From 1 October 2017 pre-movement testing is not required for movements within the Low TB Area and from the Low TB Area to other parts of Wales. Cattle moved into the Low TB Area from other areas (not including the English LRA) require a post-movement test. All herds in Wales are tested for the disease at least annually. The strategically-located Intensive Action Area (north Pembrokeshire and small parts of Ceredigion and Carmarthenshire) has one of the highest incidence rates of bovine TB in Wales. Here there are extra measures in place to control the disease, such as stricter cattle controls, 6-monthly testing and improved biosecurity.

England

In England, there are wide geographical variations in the incidence and prevalence of bTB. This is reflected in the division of the country into three different epidemiological areas, with different disease control strategies and herd testing regimes applied in each of them:

In the Low Risk Area of the North, East and South East of England, the incidence of bTB is very low and stable and most cattle herds are routinely tested every four years. Similar to Scotland, the majority of breakdowns in the Low Risk Area can be linked to movements of undetected infected cattle from other areas of GB.
In the Edge Area, the herd incidence is higher than in the Low Risk Area, although this varies from county to county. After a relatively stable period, prevalence has been increasing in more recent years. On 1 January 2018 the five part Edge, part HRA counties: Cheshire, Derbyshire, East Sussex, Oxfordshire and Warwickshire, moved to all Edge. Testing intervals have been published.
In the High Risk Area of the West Midlands and South West of England, the incidence and prevalence of infected cattle have increased steadily to relatively high levels. This is partly a result of a reservoir of endemic M. bovis infection in the local wildlife. There is evidence of a slowing down in both the incidence and prevalence rates since around 2012.

5.6 Link to Methodology Documentation

For a description of the data sources and methodology used in the calculation of the TB statistics, together with notes on data revisions policy etc., please refer to the Background and Methodology document.

5.7 Trends in herd tests

From October 2015 to November 2016 there were steady decreases in the number of TB tests completed on herds. The decrease is mainly as a result of changes in APHA testing procedures made in November 2015, and more specifically to testing of cattle that have moved out of TB-infected herds before detection of the disease (“TB forward tracings”). Changes to these “tracing” tests include:

Bespoke tracing tests of individual animals are no longer performed in England if a whole-herd (or similar) test is already due in the herd of destination within 60 days of the tracing test date, and in Wales if the tracing test is due within the existing herd test window.
Combining multiple tracing tests for a herd where the traced cattle originate from more than one holding and where test deadlines are within a one month period. Such tests were previously counted separately.

TB tracing tests are included in the “Herd tests” and the “Total cattle tests” measures and these changes are thought to account for much of the decrease in the herd test measures.

Question 7

6.  Glossary

Accepted Answer

Bovine tuberculosis (bTB)

Bovine tuberculosis is caused by the bacterium Mycobacterium bovis (M. bovis). Cattle are the natural host of the bacterium. Many other species, including wildlife such as badgers and less commonly deer, are also susceptible to M. bovis and can develop TB and transmit the infection to other species.

Breakdown

A breakdown is the term used to describe the occurrence in a herd of at least one animal with a positive reaction to the skin test, or the identification of M. bovis in an animal with TB lesions detected at routine slaughter. The affected herd is then placed under restrictions and loses its Officially TB Free (OTF) status.

Direct Contact (DC)

An animal in an OTFW incident that, although not a test reactor, was considered to have been exposed to Mycobacterium bovis and compulsorily slaughtered.

Inconclusive reactor (IR)

An animal showing a positive reaction to bovine tuberculin that was not strong enough for it to be deemed a reactor. Such animals are usually isolated and subjected to a second skin test after 60 days, unless removed earlier as DCs or IFN-γ test reactors or voluntarily slaughtered by their owner.

Headline herd incidence

The incidence of a disease is the disease occurrence in new cases in a defined population over a designated time period. The National Statistics use new herd incidents per 100 herd years at risk of infection during the year as herd incidence definition. Herds which were previously OTF but either had cattle that reacted to a tuberculin test or had a tuberculous animal disclosed by routine meat inspection at slaughter, during the 12 months ending the date shown, divided by the amount of time herds tested during that period were unrestricted and at risk of infection. Figures for Wales include incidents where OTF status has been withdrawn for epidemiological reasons only.

Herd-years at risk

The sum of the time (days, months or years) herds in the population are unrestricted and are therefore at risk of a new incident, among the group of herds that have had a herd-level test during the period of interest.

Time at risk

Time spent not under restriction and at risk of having bTB during the observation period.

Herd prevalence

Herds which were not officially TB-free (i.e. herds under movement restrictions with OTF status suspended or withdrawn) due to a TB incident, at the end of the period as percentage of the number of herds registered on the APHA’s Sam (computer) system.

High Risk Area (HRA) of England

In the West Midlands and the South West of England, the incidence and prevalence of infected cattle have increased steadily to relatively high levels. This is partly a result of a reservoir of endemic M. bovis infection in the local wildlife. Herds are tested for bTB annually. 2021 intervals and a map of GB TB areas are published.

Edge Area of England

In the Edge Area herd incidence is higher than in the Low Risk Area, although this varies from county to county. Herds are tested for bTB annually or every six months. The Edge boundary was updated in January 2018 to include the parts of the counties of Derbyshire, Warwickshire, Oxfordshire, East Sussex and Cheshire that had been designated HRA. It also spans Nottinghamshire, Leicestershire, Northamptonshire, Buckinghamshire and Hampshire. 2021 intervals and a map of GB TB areas are published.

Low Risk Area (LRA) of England

North, East and parts of South East of England, the incidence of bTB is very low and stable and most cattle herds are routinely tested every four years. Similar to Scotland, the majority of breakdowns in the Low Risk Area can be linked to movements of undetected infected cattle from other areas of GB. 2021 intervals and a map of GB TB areas are published.

Officially bovine tuberculosis free herd status suspended (OTFS)

Incidents where OTF status was suspended because of reactors in the herds, but post-mortem evidence of TB is not detected. The status remains suspended until further herd tests confirm no infection remains on the farm. Figures for Wales include incidents where OTF status has been withdrawn for epidemiological reasons only.

Officially bovine tuberculosis free herd status withdrawn (OTFW)

Incidents where OTF status was withdrawn from the herd due to the detection of lesions typical of TB during post-mortem examination of one or more test reactors or inconclusive reactors, or where samples from one or more reactor, inconclusive reactor or a slaughterhouse case produce positive culture results for Mycobacterium bovis. Figures for Wales do not include incidents where OTF status has been withdrawn for epidemiological reasons only. These are currently included within the OTFS figures.

Officially TB Free (OTF) status of a country or region

“OTF Status” takes its meaning from European law: for a region or Member State of the EU to be considered to be OTF the annual incidence of herds with confirmed M. bovis infection must not have exceeded 0.1% and at least 99.9% of the herds within it must have been free from bTB at the end of the year for at least six consecutive years.

Single intradermal comparative cervical test (SICCT)

The tuberculin skin test: if tuberculin (a purified sterile cocktail of proteins derived from M. bovis cultures) is injected into the skin of an animal infected with M. bovis, this will cause a localised allergic reaction characterised by temporary swelling of the skin, which is measured 72 hours after the injection. The principle is very similar to the skin tests for TB in humans.

Gamma interferon test (IFN-γ or gIFN)

Laboratory-based blood test approved as an ancillary diagnostic tool that measures the release of γ-IFN in whole blood cultures stimulated with tuberculin.

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Applies to England, Scotland and Wales