The immunological response of llamas (Lama glama) following experimental infection with Mycobacterium bovis.

Llamas were experimentally infected with Mycobacterium bovis in order to evaluate the axillary skin test and the ELISA as diagnostic procedures for tuberculosis in llamas (Lama glama). Six llamas were given a single intratracheal challenge with 1 of 2 doses of a recent field isolate of M. bovis and 2 llamas were left as noninfected controls. This resulted in a progressive disease in some animals with 1 mortality as early as 68 d post-infection (PI). The tuberculin skin test, at the axillary site, was positive in 4 of 5 infected llamas at 80 d PI. At 143 d PI, all 3 surviving lamas were positive, including the one which had not responded at 80 d PI. The application of skin and serological tests throughout the course of this experiment adds support for the need to further evaluate the skin test and its anamnestic effect on serodiagnosis since serological responses were generally not observed in the absence of skin testing or antibiotic treatment. The wide variation in M. bovis antigens recognized by the serological response would indicate that a diagnostic panel should include multiple antigens such as MPB70 and lipoarabinomannan (LAM). While skin testing or serology alone may be of limited value to diagnose tuberculosis in llamas, together they may offer an enhanced potential for immunodiagnosis of tuberculosis.