| Abstract: | A total of 15 822 cattle aged 3 years and older, belonging to 378 randomly selected herds, were tested for paratuberculosis using an absorbed enzyme‐linked immunosorbent assay (ELISA); 3.3% tested positive. This percentage was lowest for the group of cattle aged 3–4 years (2.3%) and highest for cattle with the age of 5–6 years (4.5%). The mean Sample to Positive (S/P) ratio of seropositive cattle vaccinated against paratuberculosis was higher (0.75 ± 0.33) than that of seropositive, non‐vaccinated cattle (0.58 ± 0.26). Faecal samples of 422 ELISA‐positive cattle were cultured for the presence of Mycobacterium avium subsp. paratuberculosis, 12% of these were contaminated. The percentage of non‐contaminated samples with positive culture results was 17.3%, with a substantial difference between vaccinated (1.7%) and non‐vaccinated cattle (20.2%). Of the positive cultures, the number of colonies varied from 1–10 (22% of cultures), 11–100 (22%), to more than 100 (55%). The percentage of ELISA‐positive, non‐vaccinated cattle tested culture‐positive was positively correlated with the magnitude of the S/P ratio. This percentage varied from 12% (S/P ratio 0.3–0.5) to 58% (S/P ratio > 1.1), a result that might have implications for interpretation of the test. In this study, the percentage of ELISA‐positive cattle with positive faecal culture results was limited and these individuals were mostly moderate to heavy shedders. |
