[Diagnosis of Johne's disease]

The authors carried out clinical observations and allergical, bacteriological and serological investigations of 73 dairy cows in a herd affected with paratuberculosis. Durings 18 months, clinical signs of the disease were noted in 2 animals only. It was found that the allergic test with the use of johnin had a limited diagnostic value and made it possible only to suspect the disease in the herd. Avian tuberculin had higher potency than johnin and gave, in most cases, stronger allergic reactions in animals infected with M. johnei that the homologous preparation. Bacterioscopic and cultural examination of the faeces with the use of Stuart's serum-agar medium had a significant diagnostic value because they made it possible to detect the excretion of Johne's bacilli before the clinical signs could be observed. The complement fixation test gave positive results in animals with the clinical symptoms of the disease, or when pathological lesions in the intestines were pronounced. In most of the cows investigated, the pathological changes of the ileocecal valve, characteristic for paratuberculosis, appeared earlier than the positive results of the complement fixation test.