Molecular and serological dynamics ofChlamydia pecoruminfection in a longitudinal study of prime lamb production

Abstract

BackgroundChlamydia pecorum is a globally significant livestock pathogen causing pathology and production losses. The on-farm infection and serological dynamics and the relevance of existing diagnostic tools for diagnosing C. pecorum in livestock remains poorly characterized. In this study, we characterized the antigen and antibody dynamics of this pathogen in a longitudinal study of prime lamb production, utilizing the infection focused C. pecorum-specific 16S rRNA qPCR assay and serology based chlamydial Complement fixation Test (CFT).MethodsThe study consisted of 76 Border Leicester mixed sex lambs (39 females and 37 males) that were sampled bimonthly from 2–10 months of age in a commercial farm operating in Central NSW, Australia. Blood/plasma was analysed for CFT antibodies, and swabs from conjunctival, rectal and vaginal sites were analysed for C. pecorum shedding using qPCR. We assessed the temporal and overall dynamics of C. pecorum in lambs, including detailed description and comparison of qPCR and CFT, the timing of first detection by either diagnostic method, the lag between infection and antibody response; and the distribution of qPCR load and CFT antibody titre over time.ResultsOver the study period, C. pecorum was highly prevalent (71.0% by qPCR, 92.1% by CFT, 96.0% by both), with 21.1% (16/76) lambs shedding ≥1, 000 qPCR copies/µl (denoted as high shedders). C. pecorum shedding (as evidence of infection) were first observed at two months of age (14.4%) with a significant peak of infection occurring at six months of age (34.2%), whereas seroconversions peaked at eight months of age (81.5%). 52.6% of C. pecorum qPCR and CFT positive lambs became qPCR negative by 10 months of age, indicating clearance of chlamydial infection. Although CFT is utilised for on-farm detection of active infection, we confirm that it lagged behind qPCR detection (average lag 1.7 ± 2.1 months) and that the proportion of qPCR positives simultaneously identified by CFT was low with 2/11 (18.1%), 0/13, 17/25 (68.0%), 5/7 (71.4%) and 1/10 (10.0%) concurrent seroconversions occurring at two, four, six, eight and 10 months of age, respectively.DiscussionThis work reveals rapid rates of C. pecorum infection and widespread exposure during lamb production. The comparison of molecular and serological diagnostic agreement longitudinally, supports the use of qPCR as an important ancillary tool for the detection of active infections in conjunction with chlamydial CFT for routine veterinary diagnostics. Development of rapid Point-of-Care (POC) tools for diagnosing active infection would be valuable for producers and veterinarians.

Molecular Detection and Identification of Chlamydiaceae in the Eyes of Wild and Domestic Ruminant Hosts from Northern Spain

“…Methodological differences with previous studies prevent a direct comparison of prevalences, since in Australian lambs both serological and different molecular analyses were performed. These methodological differences, such as using flocked vs. non flocked swabs or using different molecular methods, can affect analytical sensitivity for Chlamydiaceae detection [ 23 ], further complicating prevalence comparison. Apart from the methodological aspects, possible differences in sample prevalence may respond to different epidemiological situations.…”

Detection of Chlamydiaceae in ocular swabs from Australian pre‐export feedlot sheep

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Mini Review: Antimicrobial Control of Chlamydial Infections in Animals: Current Practices and Issues

“…The intestinal site appears to be a natural habitat for infection of chlamydiae infecting mammalian and avian hosts, wherein studies have reported long-term GIT infections with continual shedding of the pathogen in the feces (Meyer and Eddie, 1933; York and Baker, 1951; Yang et al, 2014). This is particularly important because GIT infections associated with fecal shedding in flocks and herds appear to be the precursor to abortion, encephalitis, polyarthritis, conjunctivitis, and pneumonia in ruminants (Campos-Hernández et al, 2014; Hoffmann et al, 2015; Walker et al, 2016; Bommana et al, 2018). Ruminal and small animal models also suggest that neither the host immune system nor the use of antimicrobials is successful in clearing chlamydiae from the gut (Yeruva et al, 2013; Rank and Yeruva, 2014), due to the establishment of an antibiotic-protected reservoir in the GIT and down regulatory mechanisms further inhibiting the adaptive immune response from resolving GIT infections (Igietseme et al, 2001).…”