Integrated diagnostic approach for Leptospira spp. detection in SMEDI associated reproductive disease of swine.

Leptospirosis is a notifiable disease in human and all mammals in Germany. Besides late term abortions, leptospiral infection of sows is also mentioned as a differential in terms of SMEDI. The objective of the present study was to apply an integrated diagnostic approach in such cases under field conditions and to evaluate best suited specimen for molecular detection of Leptospira spp. in affected fetuses. Therefore, MAT of fetal and sow sera and LipL32 and 16S RNA gene qPCR for fetal specimens (kidney, liver, stomach content, meconium) was used for Leptospira spp. diagnostic to detect pathogenic serovars and to distinguish between pathogenic groups I and II of Leptospira spp. in SMEDI associated cases, respectively. In total, 36 litters with 142 fetuses from 16 farms were enrolled in this examination. In total 44.4 % of the sow sera were positive by MAT. Six out of sixteen (37.5 %) serum samples were positive for only one serovar, whereas 62.5 % (10/16) showed multiple positive results. MAT positivity for serovars Bratislava, Pomona, Australis and Autumnalis in sows was significantly associated with positive qPCR results from the corresponding offspring. All PCR positive samples (n = 20) revealed that leptospires belonged to subclade P1 or pathogenic group I identified by 16S RNA gene PCR. Highest detection rates and DNA loads were present in kidney samples whereas stomach and meconium samples revealed the lowest rates of detection and DNA loads.