The specificity and sensitivity of the fluorescent antibody test in cattle experimentally infected with Mycobacterium avium and Mycobacterium johnei.

In five calves experimentally infected with Mycobacterium avium and in 10 with M johnei it was shown that the serological response by the fluorescent antibody (FA) test was specific. The serological response in the M avium infected calves was transitory and lasted up to five months. The first evidence of a serological response with the FA test in the M johnei dosed calves occurred at four months, and all calves had reacted by nine months after dosing. At the 23 tests carried out between four and 32 months after dosing, when the experiment was terminated, an average of 5-8 animals was positive at any one test. Johne's disease was confirmed bacteriologically and histologically in six of the 10 calves though none had shown clinical signs.