DEFRA has set out the circumstances under which the gamma interferon test will be used to detect cattle with bovine tuberculosis.

The government announced last week (10 Aug) that the gamma interferon will be used as an adjunct to the tuberculin skin test from October.

Under the new policy the gamma interferon test will be applied mainly in three and four yearly testing parishes in an attempt to ensure that infection in such areas does not become established in cattle or wildlife.

The test will also continue to be available to use as a disease control tool in TB hotspot areas. 

DEFRA estimates that about 50,000 tests per year will be performed using the gamma interferon.

From October 2006 the use of gamma interferon test will be mandatory in the following prescribed circumstances:

• All confirmed new incidents in three or four-year parish testing intervals, including those that fail to resolve through repeated skin tests or where complete or partial de-population is contemplated.

• Confirmed incidents failing to resolve (with visible lesions), despite taking biosecurity precautions in one and two-year testing parishes, including those herds where a complete or partial de-population is contemplated.
• Used at the first inconclusive reactor retest in unresolved herds in one and two year testing parishes. 

Additionally, the test will be used occasionally to enhance specificity in the following limited circumstances:

• Non-specific reactor procedure for unconfirmed breakdowns in two, three, or four-year testing parishes and cases of suspected fraudulent reactors.