Several serological tests (ELISA, CFT, AGID) are available for the detection of antibodies against M. a. paratuberculosis. The purpose of this study was to estimate the sensitivity and specificity of two methods for serological diagnosis of paratuberculosis.

Materials

The immune responses were investigated on serum samples from 1955 cattle from a contaminated farm and 1923 cattle from a paratuberculosis free area.

Methods

- CFT: at a serum dilution of 1:5 or higher was considerated positive; - Johne's absorbed ELISA for screening and verification: assays were performed with the commercial kits according to the manufacturer's instructions.

Results

Of the 1955 cattle from the contaminated area, 96 (4.9%) samples were positive in ELISA-abs. but in CFT only 22 (1.1%) were positive and 40 (2.0%) samples were doubtful. Concordance of the positive results of the two tests was 2.1% in infected cattle.Of the 1923 cattle from free area in the first year, 35 were positive and 25 doubtful in CFT and in ELISA-abs. only 20 positive samples were detected. At the second control we found in ELISA a smaller number positive samples than in CFT and doubtful samples from first control were negative in the second control. Positive serological results obtained in both lots were confirmed or infirmed by bacteriological and histological analysed.

Conclusions

The comparative investigations of the ability to detect antibodies to M. a. paratuberculosis demonstrated that ELISA was better than CFT, with sensitivity of 90.5 % compared to 83.8% for CFT and a specificity of 99.4% compared to 96.6 % for CFT.ELISA is after numerous authors, the most sensitive method comparative to CFT and AGID. The reading and computerised interpretation of the results allow the utilisation of the method on large scale in the programme of surveillance and eradication of bovine paratuberculosis.