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Molecular and serological dynamics of Chlamydia pecorum infection in a longitudinal study of prime lamb production

Citation

Bommana, S and Walker, E and Desclozeaux, M and Jelocnik, M and Timms, P and Polkinghorne, A and Carver, S, Molecular and serological dynamics of Chlamydia pecorum infection in a longitudinal study of prime lamb production, PeerJ, 6 Article e4296. ISSN 2167-8359 (2018) [Refereed Article]


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Copyright Statement

Copyright 2018 Bommana et al. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) https://creativecommons.org/licenses/by/4.0/

DOI: doi:10.7717/peerj.4296

Abstract

Background: Chlamydia 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).

Methods: The study consisted of 76 Border Leicester mixed sex lambs (39 females and 37 males) that were sampled bimonthly from 210 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.

Results: Over 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/l (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 1.72.1 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.

Discussion: This 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.

Item Details

Item Type:Refereed Article
Keywords:Chlamydia, possum
Research Division:Agricultural and Veterinary Sciences
Research Group:Veterinary Sciences
Research Field:Veterinary Microbiology (excl. Virology)
Objective Division:Health
Objective Group:Public Health (excl. Specific Population Health)
Objective Field:Disease Distribution and Transmission (incl. Surveillance and Response)
Author:Carver, S (Dr Scott Carver)
ID Code:124342
Year Published:2018
Funding Support:Australian Research Council (LP140100315)
Deposited By:Zoology
Deposited On:2018-02-19
Last Modified:2018-03-19
Downloads:11 View Download Statistics

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