Paratuberculosis in a cattle herd: comparison of allergic, serologic and faecal microscopic tests

In a beef herd of 230 cows kept on pasture and infected with Mycobacterium paratuberculosis, faecal samples were tested microscopically and the blood serum by the complement fixation and the immunodiffusion test. Intradermal tests were carried out simultaneously with bovine and avian tuberculin as well as with two dilutions (0.86 mg/ml and 0.50 mg/ml tuberculoprotein) of paratuberculin. In the tested herd 35.2% of the cows gave positive faecal tests while 10 and 9.1% were positive in the agar gel immunodiffusion (AGID) and complement fixation test (CFT), respectively. The allergens showed wide variations, but as a whole they were positive in 58.1% of the faecal positive, and in 60.9 and 76.2% of the AGID and CFT positive ones, respectively. The allergic tests were positive in 54.4, 53.7 and 52.2% of the faecal, AGID and CFT negative cows, respectively. The prognosis of such herds is disadvantageous. Elimination of infection can only be expected if after improvement of hygienic circumstances the diseased animals are continuously culled and a new breeding stock reared in isolation.