Globally, infections of the obligate intracellular pathogen, Chlamydia pecorum, in sheep are poorly understood, despite a growing evidence that these infections are almost ubiquitous.
To further understanding the diagnosis and impact of C. pecorum infection on prime lamb production, in this study, a species-specific quantitative polymerase chain reaction (qPCR) targeting the C. pecorum 16S ribosomal RNA region and an anti-Chlamydia serological complement fixation test (CFT) were used to determine the prevalence and shedding of C. pecorum from a commercial sheep flock (n=105) in Central Western NSW, over a period of 10 months.
83% of the lambs sampled at all five time points tested positive for C. pecorum by both CFT and qPCR, with 13.3%, 22.2% and 17.14% qPCR positivity detected at rectal, vaginal and ocular sites, respectively. Based on our preliminary statistical analysis on the dynamics of the natural infection, we found that, at the age of six months, most lambs sero-convert to C. pecorum- specific antibodies but remain PCR negative, although a subset of lambs sero-converted as early as two months and had detectable PCR loads. 41% of qPCR and CFT positive lambs cleared their infection by 10 months of age. This study indicates a high prevalence of C. pecorum infection in Australian sheep, and provides a glimpse of the infection dynamics and the importance of both CFT and qPCR methods in the diagnosis of these infections.