Paratuberculosis in Danish dairy herds: development and testing of improved methods for the diagnosis of paratuberculosis

摘要

Two hundred and fifty-two cattle selected from dairy herds infected with Mycobacterium avium subsp. paratuberculosis (M. a. paratuberculosis) and 119 cattle selected from dairy herds presumably free of paratuberuclosis were tested in a prospective cohort study. Preliminary results from the evaluation of a test for cellular immunity (IFN-#gamma# test) to infection with M. a. paratuberculosis showed a marked difference in the frequency of test-positives in the 2 cohorts. 113 (45 percent) animals tested positive from the infected herds and 3 (3 percent) animals tested positive from the presumably free herds. Consistently test-positive animals were from 9-12 months of age and older, indicating a possibility of unveiling Infected animals at an early stage of infection when other tests for paratuberculosis are negative. Four culture-positive cows developing clinical paratuberculosis changed from test-positive to test-negative in the IFN-#gamma# test. We assume that a change from test-positive to test-negative in IFN-#gamma# test may predict onset of clinical paratuberculosis. However, further results from the prospective study are necessary to strengthen these assumptions.