Bovine TB Tests

SICTT - Tuberculin skin test 

What is it? An injection of Avian & Bovine tuberculin administered by a Veterinarian, who measures the skin fold and conducts a second measurement test within 72 hours.

How it works - It involves injecting a small amount of both Avian and Bovine tuberculin into the skin of an animal. If an animal is infected, the animal will display a localised allergic reaction (in the form of swelling) a few days after the injection. All skin swellings with an increase of more than 2mm in the thickness of the skin fold must be recorded as positive reactions, as should any swelling irrespective of size, showing oedema.

Efficacy - The sensitivity of the test remains moderate with estimates typically in the range of 50 - ­60% using the standard test interpretation.

Status - The tuberculin skin test is the primary screening test for TB in cattle in Great Britain. It has been in use in Great Britain since 1942.

Gamma Interferon Test 

What is it? A Laboratory-based blood test

How it works - A single blood test that exploits the immune response.

Efficacy - The g-IFN has a good sensitivity and appears to detect infected animals earlier than the skin test. Unlike the tuberculin skin test, it can be carried out as often as necessary, and there is no need to wait 60 days between tests.

Status - The Gamma Interferon test (g-IFN) has been introduced to improve testing of cattle alongside the tuberculin skin test. European legislation stipulates that the Member States must use the skin test for routine herd testing.

 

Phage

What is it? A bacteriophage-based method. An isothermal DNA amplification protocol using Recombinase Polymerase Amplification (RPA). 

How it works - Blood Sampling. 2 ml from a Single Comparative Cervical Intradermal Tuberculin (SCCIT).

Efficacy - Viable MTC bacteria were detected in 66% (27/41) of samples. Of these 41 animals sampled, 32% (13) had visible lesions. In the visible lesion (VL) group, 85% (11/13) had detectable levels of MTC whereas only 57% (16/28) of animals which had no visible lesions (NVL) were found to have detectable mycobacteremia.

Status - 2016 Peer Review.

 

The Polymerase Chain Reaction (PCR) Test 

What is it? The Polymerase Chain Reaction (PCR) assay or test detects small amounts of DNA from mixed samples, and this method is often combined with immunomagnetic separation (IMS), which increases the concentration of the samples resulting in increased test sensitivity.

How it works - Test is carried out on faecal and environmental samples.

Efficacy - While PCR has been demonstrated to identify M.bovis in spiked samples in the laboratory with 100% specificity (100% reliable that a positive test result means disease is present) and 97% sensitivity (97% successful at correctly identifying diseased samples), it has been found to be less sensitive for samples in the field.

Status - Still under research development.

 

Elisa Test 

What is it? Antibody testing in cattle serum and plasma samples. 

How it works - The measurement of antibody responses to M.bovis antigens MPB70 and MPB83 in milk samples from Dairy Cows. Results within 2 hours.

Efficacy - Antibody tests are generally regarded as having a low sensitivity, of around 52%, although they have high specificities >97.5% depending upon the antigenic targets used. 

Status - Validated and certified by the OIE as fit for the purposes defined in the kit. Registration number 20120107.

 

Abattoir Inspections

What is it? A visual test carried out after slaughter in the Abattoir.

How it works - Human observation.

Efficacy - Around 28% of infected cattle are identified after slaughter by human observation.

Status - Operative.

 

The Badger and Cattle Vaccination Initiative