DETECTION OF MYCOBACTERIUM-BOVIS INFECTION IN SKIN TEST-NEGATIVE CATTLE WITH AN ASSAY FOR BOVINE INTERFERON-GAMMA

Mycobacterium bovis was isolated from respiratory secretions and lymph nodes from 15 skin test-negative cattle which exhibited interferon-ga mma responses. These field cases, identified by blood testing, constit uted a significant proportion of skin test-negative cattle which had b een subjected to extensive post mortem examinations. Typical tuberculo us lesions were found in seven of them. The consequences of cattle wit h early tuberculosis infection not being detected by traditional tuber culin testing are considered.