Estimation of the prevalence of Mycobacterium avium subsp. paratuberculosis by PCR in sheep blood

The prevalence of Mycobacterium avium subsp. paratuberculosis (Map) infection in sheep was estimated by blood PCR. One thousand and five hundred sheep belonging to 150 sheep flocks of Trás-os-Montes e Alto Douro (TMAD, Portugal) were studied. Animals were divided into two groups of five sheep each according their health status: “apparently healthy animals” and “paratuberculosis suspect animals”. Samples were pooled in groups of five. PCR detected Map DNA in 56 (18.7%) pool samples. The overall individual prevalence of Map in this study ranged from 6.4% to 15.4%. Map was found in 20.7% pooled samples from apparently healthy and in 16.7% pooled samples from suspect animals. The aim of the present study was to estimate the prevalence of ovine paratuberculosis using a PCR pool screen approach. The results showed that a simple blood PCR method could be reliably performed on pools of five samples in order to estimate the prevalence of Map infection in the ovine population.