Evaluation of the gamma-interferon assay for eradication of tuberculosis in a goat herd

Objective To evaluate the usefulness of the gamma-interferon assay in the diagnosis of caprine tuberculosis in comparison with a single intradermal tuberculin test, and to obtain a group of animals free from this infection in a herd with a high prevalence. Design An immunological study involving four serial comparative gamma-interferon and single intradermal tuberculin tests. Animals A herd of 87 goats of Guadarrama breed. Procedure Serial testing and segregation of animals. Results We found that the number of infections detected by the gamma-interferon test was considerably greater than the number detected by the single intradermal tuberculin test. A group of 10 animals was negative to both tests in two consecutive rounds and three kids were negative in the last round of testing. Conclusions Gamma-interferon assay is appropriate for diagnosis and eradication or tuberculosis in goats. This test is able to detect early Mycobacterium bovis infection. Avian reactors with simultaneous increased reaction to bovine PPD in the gamma-interferon assay (designated as avian(B) reactors) should be considered test positive for M bovis. By serial testing with the gamma-interferon and the single intradermal tuberculin tests, and a policy of segregation of kids at birth, it is possible to achieve a group of animals test negative for tuberculosis from a herd of goats with high immunoreactivity to this infection.