Guidance

Testing for TB in your herd: what this means to you (Scotland)

Updated 14 February 2024

Section 1: Why we test

Bovine TB

Bovine tuberculosis (TB) is a chronic, infectious disease of bovine animals (cattle, buffalo and bison) that mainly affects the respiratory system. It is caused by the bacterium Mycobacterium bovis (M. bovis), which can also infect and cause TB in badgers, deer, goats, pigs and many other mammals, including people.

Bovine TB can spread to cattle in a number of ways, including contact with:

• an infected domestic animal (usually other cattle)
• infected wild animals (including badgers)
• contaminated equipment, feedstuffs, slurry

Scotland’s Officially Tuberculosis Free (OTF) status

Scotland has been Officially Tuberculosis Free (OTF) since 2009. This means that Scotland has maintained a low and stable incidence of TB. Maintaining this status is a priority.

The OTF status has significant economic benefits for the Scottish cattle industry:

• fewer and more targeted risk-based TB tests (some herds are exempt from testing if they meet the low risk criteria)
• greater export opportunities
• reduced risk of TB infecting wildlife

If the number of TB breakdowns in any year exceeds certain levels, OTF status may be lost.

The risks to people from bovine TB

While people can be infected with M. bovis, most cases of TB in humans in Great Britain arise from infection with the human tubercle bacillus (M. tuberculosis). This bacillus is closely related to M. bovis but it is transmitted through close contact between people rather than from cattle. The risk of people contracting bovine TB from cattle in Great Britain is currently considered very low, but cases have been recorded in the last few years. The risk is increased where unpasteurised milk or milk products are consumed.

Get further information on managing the public health consequences of bovine TB.

Testing cattle for bovine TB

The Scottish Government has testing programmes in place for:

• surveillance (screening cattle for the presence of infection)
• breakdown management (where a herd is known to have infection present)
• where there is suspicion of infection

These testing programmes determine the TB status of the herd and facilitate trade in cattle and products, both domestic and international. Testing is carried out to:

• protect public health
• identify TB infected cattle and prevent it spreading
• make sure that cattle do not suffer because of TB

Anyone who keeps cattle is required by law to have their cattle tested for bovine TB, unless your herd is exempt from testing.

Cattle in Scotland are tested at a default interval of 48 months (4-yearly routine herd testing), but in certain circumstances a herd may need testing more often. APHA notifies the keepers of these herds individually.

Some Scottish herds which are ‘low risk’ will be exempt from the 4-yearly routine herd testing. They will also be notified separately.

Effective surveillance is essential to identify TB infection early. This reduces the spread of disease and maintains Scotland’s OTF status.

Surveillance does not rely on testing alone. There are also requirements for:

• reporting of suspicious clinical cases
• reporting of suspicious lesions at routine inspection in the slaughterhouse and at private post-mortem examinations

Reports will result in investigation, restrictions where necessary and additional testing.

Once infection has been identified in a herd, testing is then increased, in order to identify other infected animals within the herd and to return the herd to TB free status as quickly and effectively as possible. This will reduce the opportunity for further spread of the disease both within and around a herd.

Additional testing is carried out where there is suspicion of infection, either in an individual animal or a herd due to:

• a report from the slaughterhouse of lesions that are suspected to be due to infection with M bovis
• an animal that has been identified as moving from a farm on which TB is present
• infection in another herd which may have spread to animals in your herd, either due to location or due to management, such as sharing equipment

A report from the slaughterhouse

Sometimes lesions suggestive of TB are found in animals at routine slaughter inspection. These are known as slaughterhouse cases. If such lesions are found, your herd will be placed under movement restrictions pending further investigation and your local APHA office will discuss your testing requirements with you.

Inconclusive Reactors (IRs)

Finding only Inconclusive Reactors (IRs), with no reactors in your routine herd or other surveillance test may be an early indication that you have infection in your herd. Depending on your TB history, the whole herd or only the IRs will be restricted.

The IRs must be isolated.

In Scotland, ‘isolation’ means:

• the animals must be kept on land or in accommodation where they do not share space with other animals. No other animals must access manure, slurry or drainage from the accommodation
• there must be no nose-to-nose contact between isolated animals and other animals
• when kept in a building, there must be an airtight barrier to separate isolated animals from other animals

APHA will send you a letter explaining the restrictions and the testing necessary.

IRs will receive additional tests. If they get negative results, APHA will lift restrictions.

Pre-movement and post-movement testing

All cattle over 42 days old from areas of England or Wales on annual (or more frequent) testing intervals must be pre-movement tested within 30 days before they enter a Scottish herd.

From 18 May 2023, a short interval test or other skin test carried out during a TB breakdown before the officially TB free status of a herd has been reinstated (the clearing test), will not meet pre-movement testing requirements.

Cattle must also be post-movement tested between 60 and 120 days of their arrival in a Scottish herd. This is to reduce the risk of spreading TB from one herd to another.

Cattle 42 days old and over moving from 4-yearly testing areas in England must be pre-movement tested. This is unless they have resided in a low incidence area for the duration of their lives.

Cattle imported from Northern Ireland and non-OTF countries, including the Republic of Ireland, must be post-movement tested. This is between 60 and 120 days of their arrival in a Scottish herd.

Get information on pre-movement and post-movement testing and a list of exemptions

Requirement to test

APHA will send you a notice to tell you when your herd or a specific animal requires testing and you must arrange a bovine TB test before the date that this test is due. Your herd will be placed under movement restrictions (TB2) immediately if testing becomes overdue as the TB status of your herd will be unknown. The restrictions prevent movements of cattle on or off your premises and will remain in force until your testing has been completed and there is no evidence of TB. Where testing is overdue, licences authorising low risk moves will not be issued (zero tolerance).

The compensation payable for any reactors identified in tests which are overdue may be reduced.

The TB status of your herd

Herds giving negative results at routine surveillance testing are classed as Officially TB Free (OTF).

Where animals are removed from your herd after a skin test finding of reactors (or inconclusive reactors at consecutive tests), the OTF status of your herd will be suspended (OTFS).

OTF status will be withdrawn (OTFW) if either:

• lesions typical of bovine TB are found at post-mortem examination
• the M. bovis organism is detected by a polymerase chain reaction (PCR) test or on culture

This is important as it means your herd will require additional testing before restrictions can be lifted.

Suspension: Officially TB Free status Suspended (OTFS)

The OTF status of your herd will be suspended when either:

• at least one animal has failed the TB skin test (this is a ‘reactor’ animal)
• at least one animal has had 2 inconclusive skin test results consecutively
• a tuberculin skin test is completed and IRs are identified with no skin test reactors
• at least one animal has had an inconclusive skin test result and your herd had its OTF status withdrawn at any time in the last 3 years
• suspect lesions of TB are detected in animals at routine slaughter inspection
• one of your live animals shows possible signs of TB and tests positive to a skin test
• one of your animals is slaughtered or dies before testing and lesions typical of TB are found in the carcass
• the TB status of the herd is unknown because a routine tuberculin skin test is overdue

In all cases, your herd will be placed under movement restrictions (TB2) and further testing done.

Withdrawal: Officially TB Free status Withdrawn (OTFW)

The OTF status of your herd will be withdrawn when either:

• lesions typical of TB are found at the post-mortem examination of tuberculin skin or TB blood test reactors or IRs
• M. bovis is detected by a PCR test or cultured from tissue samples from any animal in the herd
• your herd’s status is suspended and a high risk of TB infection is identified

OTFW breakdown herds need further testing before TB herd restrictions can be lifted.

Enforcement of TB policy

When your herd is put under movement restrictions either as a result of suspicion or confirmation of TB or as a result of a TB test being overdue, APHA may inform your local authority.

Any non-compliance with the conditions of notices, pre-movement testing, licences or TB testing requirements is a breach of the legislation and the local authority or Scottish Government may consider taking appropriate enforcement action.

Your local authority will follow its enforcement policy and take action as appropriate. This ranges from verbal advice and written warnings to prosecution.

Offences are covered under the Animal Health Act 1981 and penalties include the following:

• compulsory TB testing at the expense of the owner
• written warning
• fine not exceeding £5,000 per offence
• a custodial sentence

A failure to comply with the TB legislation may also be considered an intentional breach of cross compliance and could result in a reduction in payment on a number of schemes, including the Basic Payment Scheme (BPS) for your farm.

Read more about the Basic Payment Scheme on the Scottish Government website.

Section 2: How we carry out the TB test

The Single Intradermal Comparative Cervical Tuberculin (SICCT) test, commonly known as the tuberculin skin test, is the primary bovine TB test used throughout Europe.

The gamma interferon TB blood test is used alongside the skin test in certain circumstances to help identify animals at an earlier stage of infection.

The IDEXX Antibody blood test is also used in herds where after repeat skin and interferon gamma testing the herd fails to regain its OTF status. But, this is not commonly used in Scotland.

The tuberculin skin test

The tuberculin skin test is the internationally accepted standard for detection of infection with M. bovis. It is considered the best test currently available.

It is designed to test the animal’s immune response and involves injecting a small amount of tuberculin (a harmless protein extract of M. bovis) into the skin of the animal. In most cattle infected with M. bovis, this will cause the animal’s immune system to react to the tuberculin and result in a localised allergic reaction (swelling) of the skin a few days after the injection.

Cattle are sometimes infected with other types of mycobacteria which may also cause the animal to react to the test. To distinguish between animals infected with M. bovis and those infected by other mycobacteria, each animal is also injected with an extract from the organism that can cause TB in birds (avian TB) at the same time.

The test is read 72 hours after the injections have been carried out. The size and nature of the reaction to both types of tuberculin (‘avian’ and ‘bovine’) are compared to determine whether the test result is considered positive, negative or inconclusive.

The person carrying out your test will be an approved tester trained to carry out the tuberculin skin test. This will either be a vet from your nominated veterinary practice, an APHA vet or an APHA Animal Health Officer.

Preparation for the test

APHA will send you a test notification letter giving details of the test that is required.

You are required by law to provide appropriate facilities and assistance to enable the tester to carry out the test.

A properly planned test, using well designed and constructed handling facilities, will avoid unnecessary stress for you and your cattle, save time and, most importantly, be safer for all involved.

If you have any questions about the test, please contact your local APHA office or your vet for advice.

What animals to test

The test notification letter from APHA will specify which animals need testing. You must ensure that all eligible animals are presented for testing.

Identification

Make sure your cattle are correctly identified. This is a legal requirement but will also make it easier and quicker to identify individuals and record skin measurements or blood samples against the correct animal.

Gathering

To avoid delays, your cattle should be gathered in readiness for the test. If it is not possible to test all your eligible cattle on a single day, you must be able to keep them in the same, separate groups until all cattle have been tested.

Records

You should make sure that the record of the cattle present in your herd is correct and up-to-date on ScotEID. This record is often used by the tester to download a list of the cattle that are eligible for testing and all animals on this list must be accounted for.

You may be asked to provide your herd register/cattle movement records and veterinary medicines records, so please have these available for inspection.

Veterinary treatment and other tasks

While you have the cattle gathered you may wish to undertake other management tasks but these should not interfere with the test. Routine veterinary medicines, such as wormers or vaccines, should only be given to animals once they have tested with negative results.

Previously tested animals

Animals that have recently moved onto your premises may have been skin tested for TB in the previous 60 days. If you can provide evidence of this test you will need to notify the person doing the test and these animals will not be tested. If you are unable to provide evidence, they will need to be tested at a date that is at least 60 days after the movement on to your herd. If in doubt, ask your vet.

Facilities

Handling facilities will be needed for both days of the test to allow safe movement of, access to and good restraint of the animal being tested. The tester must have safe and well-lit access to:

• read and record the animal’s identification tag
• clip the test areas on the neck
• measure the skin thickness of the clipped areas and
• inject the tuberculin

You will need to provide suitable handling facilities for the cattle to be tested, such as a crush and penning system, ideally linked by a securely constructed race.

The facilities should be in good working order and appropriate for the size and breed of cattle to be tested, for example specially adapted if handling Highland or Longhorn cattle. If you do not own a crush or penning system, you should arrange to borrow or hire one. To make sure you do not compromise the biosecurity of your herd, or anyone else’s, all equipment should be cleansed and disinfected before and after use.

Get advice on suitable handling, restraint and housing of cattle on the Health and Safety Executive website.

Assistance

By providing sufficient and appropriately experienced help to move groups of cattle into and through the handling facilities, the test will go more quickly with less stress to your animals and less risk of injury to all involved. APHA staff will not routinely be able to help gather or move animals.

If you fail to present your cattle for testing safely and the tester considers the facilities and assistance provided to be inadequate, the test will not proceed until the issues are resolved. This could mean your test will become overdue and, if this is the case, movement restrictions will be applied.

Procedures for the test

For each test:

• the animal is identified (by its official ear tag) and its identification recorded
• the hair is clipped to mark two injection sites in the middle of the side of the neck, one above the other
• the thickness of a fold of skin at each site is measured with callipers and recorded in mm
• tuberculin is injected into the skin; avian tuberculin into the upper site, bovine tuberculin in the lower site
• after 72 hours, the tester returns, re-checks each animal’s identity, palpates the skin at the injection sites and re-measures and records any reactions, and records the results of the test against each animal

You must record the use of the tuberculin in your medicines records. The tester will give you the details that you need, such as batch number and quantity. But it is still your responsibility to ensure that this is added to your medicines records.

The gamma interferon blood test for TB

In specific circumstances, the gamma interferon test is used in combination with the skin test to help with early identification and removal of TB infected animals and reduce the risk of further spread of disease.

The tuberculin skin test is the primary test used across the world for the mass screening of cattle. The gamma interferon test is an additional approved test and is used based on veterinary advice in herds with severe breakdowns, persistent or recurrent TB problems, or breakdowns in areas where TB incidence is low. Some of these tests have to be completed before the movement restrictions can be removed from the herd.

Gamma interferon tests can only be carried out by APHA staff. Usually it will be an Animal Health Officer who will take blood samples from your cattle.

Cattle testing positive to the gamma interferon test will be classed as reactors and will be valued and slaughtered in the same way as skin test reactors.

The IDEXX Antibody test

In certain situations the IDEXX Antibody test can be used alongside the skin test and the gamma interferon test to identify TB infected animals, but it is not widely used in Scotland.

An animal’s immune response to infection with M. bovis, the organism responsible for bovine TB, is a very complex one and not all TB infected animals respond positively to the skin test or the gamma interferon test.

The IDEXX test aims to detect antibodies, proteins that the immune system makes to help fight infection. Before the blood sample is taken, the animal must have had a skin test 10-30 days earlier to stimulate release of these specific antibodies to M. bovis.

Further information

Read about Bovine TB on the Scottish Government website.

Contact your local APHA office in Scotland for further practical advice and guidance.

Devolution of animal health and welfare power has resulted in a number of significant differences in the policies regarding bovine TB in Wales, England and Scotland. GOV.UK, the Scottish Government, and Welsh Government websites provide up to date detail on these policies.

If you farm on the border of England and Scotland, you should be aware that the location of your animals at the time of the test will influence which protocols are relevant to you.