In Thuringia, a federal stateof Germany, paratuberculosis is being monitored by a voluntary control programme. Within the framework of this programme, a dairy herd of about 400 cattle with clinical problems of untreatable chronic diarrhea was tested for the first time to detect paratuberculosis. The objective of the present investigation was to determine the status of paratuberculosis in this herd, to analyse the diagnostic significance of an absorbed ELISA and the faecal culture, and compare it with age and lactation. Cattle older than 24 months (n=279) were included in the study. The ELISA included a preabsorption step with Mycobacteria phlei to detect specific antibodies to Mycobacterium avium ssp.paratuberculosis in serum. Faecal culture was carried out on HEYM supplemented with mycobactin J.

In faecal culture (gold standard), 93 cows (33 %) were detected as shedders and in ELISA, 39 cows (14 %) were positive or doubtful. Of the 93 shedders, only 31 cows (33 %) were classified as positive or doubtful by the ELISA. Almost half of the shedders were in the first or second lactation period. No obvious differences in age of cows between serological negative and positive shedders were observed. The average milk production of shedders was reduced by approximately 1000 kg per lactation period, which corresponds to 10 % of the milk production.

There was a high prevalence of paratuberculosis in the herd. Faecal culture is still the most suitable method to determine the individual status of paratuberculosis in a herd as most of the shedders were not detected by ELISA. In view of the economic losses through reduced milk production, a herd management based on testing of the individual animals by faecal culture was found necessary to institute an effective control programme for paratuberculosis in infected herds.