Herd prevalence studies of Mycobacterium avium ssp paratuberculosis (MAP) in cattle using serological tests: opportunities, limitations and costs

Infection status of cattle herds concerning Mycobacterium avium spp. paratuberculosis (MAP) is based on direct MAP detection or detection of MAP specific antibodies. This study aimed to calculate laboratory costs for a representative herd prevalence survey of MAP infections in Thuringian cattle herds. Therefore, sensitivity and specificity of ELISA-tests for detection of MAP antibodies which are licensed in Germany had to be evaluated using the target population to calculate the sample size which allows to classify a herd as MAP positive or MAP negative at a 95 % probability level. A total of 460 fecal culture positive cattle from 16 MAP positive herds and 344 fecal culture negative individuals from seven MAP negative herds were tested in each of the four ELISA's. In relation to fecal culture, diagnostic sensitivity ranged between 23.3% and 32.2%, and diagnostic specificity between 96.8% and 98.6%. A minimum sample size of 610 individuals per herd and 1.69 Mio Euro laboratory costs were calculated for the best performing ELISA test. Using the fecal culture based approach a maximum sample size of 41 cattle and 0.47 Mio Euro were necessary. Costs of serological testing exceeded costs for a culture based testing for all ELISA-tests. Considering limitations of required sample size and difficult assessment of positive test results, serological testing is suitable to evaluate MAP infection status in large cattle herds, but not in small herds.