Contribution to the diagnosis of Johne's disease in cattle. Comparative studies on the validity of Ziehl-Neelsen staining, faecal culture and a commercially available DNA-Probe (R) test in detecting Mycobacterium paratuberculosis in faeces from cattle

In the present study, 132 selected faecal samples from clinically affected and subclinically infected cattle from dairy herds known to be affected by Johne's disease were investigated for the presence of Mycobacterium paratub erculosis using Ziehl-Neelsen staining, faecal culture and a commercially a vailable DNA-Probe(R) test. The sensitivity was 36.4% for Ziehl-Neelsen sta ining, 85.6% for faccal culture and 47.7% for the DNA-Probe(R) test. Provin g the presence of acid-fast bacteria in 49.3% of the samples from clinicall y affected cattle and 19.3% of those from subclinically infected cattle, Zi ehl-Neelsen staining had the lowest detection rate of the three tests under investigation. Faecal culture showed the highest detection rare of M. para tuberculosis in samples from both clinically affected (84.0%) and subclinic ally infected (87.7%) animals, The DNA-Probe(R) test showed a positive resu lt in 68.0% of the samples from clinically affected cattle and 21.1% of tho se from subclinically infected cattle. Ziehl-Neelsen staining: proved unrel iable in diagnosing Johne's disease. Faecal culture was the most sensitive method for detecting M. paratuberculosis both in clinically affected and su bclinically infected cattle. The sensitivity of a commercially available DN A-Probe(R) test has to be enhanced to enable a quick and reliable diagnosis of Johne's disease.