Introduction.

Available tests for diagnosing paratuberculosis are based on detection of either the pathogen or of the host's immune response to this. Detection by bacteriological culture of faeces samples requires minimum 8 weeks of incubation; thus, detection of antibody response by ELISA would be advantageous for diagnosis of paratuberculosis. Here a milk ELISA and a serum ELISA for detection of antibodies against Mycobacterium avium ssp. paratuberculosis were evaluated.

Materials and methods.

Milk and serum were obtained concurrently from 6 dairy herds infected with Mycobacterium avium ssp. paratuberculosis and from 2 non-infected dairy herds. The two ELISAs were compared with CF test and culture.

Results and discussion.

At a cut-off value of 7 OD%, all 6 culture positive herds were found positive in the serum ELISA, whereas one of the 6 herds was found negative in the milk ELISA. All 6 culture positive herds were found positive in the CFT. In the 2 culture negative herds, the serum and the milk ELISA deemed all serum samples negative at this cut-off value, whereas 4 serum samples from one of these herds were found positive in the CFT. The highest cut-off value enabling the milk ELISA to record all 6 culture positive herds as positive was 4 OD%. The highest cut-off value enabling the serum ELISA to record all 6 culture positive herds as positive was 17 OD%. Individual sample sensitivity and specificity of the ELISAs at the cut-off values of 4, 7 and 17 OD%, respectively, were estimated. At 17 OD%, both ELISAs were almost equally effective in detecting infected herds. In a control programme, an ELISA would be a good first step for identifying the affected herds. The use of milk samples instead of the serum samples would be more convenient, as milk samples are easier to collect.