Estimation of the prevalence at animal level of paratuberculosis in female cattle of Saxony-Anhalt (Germany)

Johne’s disease (paratuberculosis) is a chronic, untreatable disease of ruminants caused by Mycobacterium avium subspecies paratuberculosis. It leads to economic losses in livestock production but is also suspected to be involved in the pathogenesis of Crohn’s disease in humans. In 2007/2008 a study was conducted to estimate the prevalence at animal level of paratuberculosis among the female cattle of Saxony-Anhalt (Germany). In order to keep study costs low and participating farms confidential, no farms were visited to actively draw samples. Instead, animals were pre-selected in a formal random sampling process and additionally tested by ELISA for paratuberculosis when samples suitable for serology were routinely submitted to the State Office of Consumer Protection Saxony-Anhalt for any diagnostics. Out of 896 samples, 38 tested positive, giving an apparent prevalence of 4.2%. Based on the test quality traits of the ELISA employed in the study (POURQUIER ELISA Paratuberculosis) the true prevalence was estimated to 6.7% (95% CI, 3.0-10.4%). No spatial clustering of positive results was detected by a scan statistic. Prevalence estimates for age strata tended to show an incline to a maximum at age class of 5 years and a subsequent decline with higher age classes. Estimates tended to show an incline with herd size.