Gamma Interferon
Background
In August 2006, Defra and the Welsh Assembly Government announced proposals for the mandatory use of the gamma interferon (g-IFN) blood test for the diagnosis of bovine tuberculosis (bTB) in certain prescribed circumstances.
Wider Roll Out across England and Wales
From 23 October 2006 Animal Health will extend the deployment in the field of the gamma interferon ( g -I FN) blood test in England and Wales. The g -I FN test will be used in parallel alongside the skin test, to improve the chances of detecting infected cattle and thus speed up the resolution of TB incidents.
The g -I FN test will be used in the following circumstances:-
- On tuberculin test-negative animals in all confirmed new TB incidents in 3 or 4 year testing parishes;
- On tuberculin test-negative animals in severe TB incidents, to inform decisions around whole or partial herd slaughter;
- On tuberculin test-negative animals in herds with persistent, confirmed infection that fail to resolve through repeated short-interval tuberculin tests and have taken basic herd bio-security precautions; and
- On inconclusive reactors that fail to resolve at their first tuberculin retest in herds in 1 and 2 yearly testing parishes.
Additionally, Animal Health may sometimes decide to use the blood test to reduce the probability of a false positive result:
- In chronic, unconfirmed TB incidents in 2, 3 or 4-yearly testing areas, where non-specific cross reactions to tuberculin are suspected; and
- For re-testing of tuberculin test reactors with abnormal skin responses or where interference with the skin test is otherwise suspected.
Use of Gamma Interferon in Scotland 
The Scottish Executive Environment and Rural Affairs Department will, from 23 October 2006, extend the existing use of Gamma Interferon test in Scotland to include:
- On tuberculin test-negative animals in all confirmed new TB incidents in 4 year testing parishes in Scotland;
This will be in addition to the pre-existing ad hoc use of the gamma interferon test in the following circumstances:
- On tuberculin test-negative animals in severe TB incidents, to inform decisions around whole or partial herd slaughter;
- On tuberculin test-negative animals in herds with persistent, confirmed infection that fail to resolve through repeated short-interval tuberculin tests and have taken basic herd bio-security precautions;
- In chronic, unconfirmed TB incidents in 4-yearly testing areas, where non-specific cross reactions to tuberculin are suspected; and
- For re-testing of tuberculin test reactors with abnormal skin responses or where interference with the skin test is otherwise suspected.
The routine use of the test in new confirmed incidents in Scotland will supersede some of the pre-existing uses for the test in the four items above.
Practical Arrangements in England and Wales
Where Animal Health prescribe the use of the g -I FN test, the blood samples will be taken by Animal Health officials and submitted to the Veterinary Laboratories Agency for the results.
All testing costs will be met by the Government and the herd owner will be required to gather cattle in the same way as for a brucellosis blood, TB skin test.
Further Information
To discuss the gamma interferon test further, please contact your local Animal Health Divisional Office .
Additional information on the roll-out of the wider use of the g -IFN test is available on the Defra website at, or available on the following flyer:
Page last modified: 2 April 2007
Page published: 2 April 2007