Molecular detection of Chlamydophila abortus in post-abortion sheep at oestrus and subsequent lambing

Enzootic abortion of ewes (EAE), resulting from infection with the bacterium Chlamydophila abortus (C. abortus), is a major cause of lamb loss in Europe. The purpose of this study was to assess the potential impact of the shedding of organisms in post-abortion ewes at oestrus and subsequent lambing on the epidemiology of EAE. Using a newly developed C. abortus specific real-time PCR assay, few chlamydial genomes could be detected in vaginal swabs taken from post-abortion ewes at oestrus. At subsequent parturition, all ewes lambed normally with no macroscopic or microbiological evidence of infection. Real-time PCR analysis of placental samples identified very few or no chlamydial genomes, which contrasted significantly with samples taken at the time of abortion, where an average of 2.7 × 107 chlamydial genomes per microgram of total tissue DNA was detected. Few genomes could also be detected from vaginal and cervical tissue samples and lymph nodes taken post-mortem. The results, although not discounting the possibility of a chronic low level persistent infection in post-abortion ewes, suggest that the low levels of chlamydial DNA detected during the periovulation period and at lambing do not significantly impact on the epidemiology of EAE. In terms of flock management, the products of abortion should be considered the major and principal source of infection for transmission to naïve ewes.