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

Abstract

Infectious Ovine Keratoconjunctivitis (IOK) is a contagious ocular disease of sheep. A range of organisms have been observed as the aetiological agents of IOK. In this study, the presence of chlamydial pathogens (C. pecorum, C. abortus, C. psittaci) in conjunctival swabs was tested for. The swabs were collected from sheep with varying grades of IOK in an Australian pre‐export feedlot. The sheep had been rejected from a shipment because of the eye disease. The relative contribution of chlamydial pathogens to IOK and the rejection of animals was evaluated. In total, 149 conjunctival swabs were taken from rejected sheep (IOK Grades 1 to 6; n = 126) as well as those with healthy eyes (Grade 0; n = 23). Screening for chlamydial pathogens was done using species–specific qPCR assays. Chlamydial DNA was detected in 35.6% (53/149) of conjunctival samples. C. pecorum was the most predominant species with an overall prevalence of 28.9% (43/149). C. psittaci prevalence was 6.7% (10/149). Both organisms were detected in healthy as well as IOK‐affected eyes. All swabs tested negative for C. abortus. The results from this study demonstrate that Chlamydia spp can be readily detected in sheep presenting with IOK. The zoonotic C. abortus was not detected in any of the samples in this study, providing further evidence to the suggestion that this pathogen remains absent from Australia. Although the exact contribution of Chlamydia spp in the IOK pathogenesis is unclear, such studies are anticipated to be of benefit to Australian domestic and live export production systems.

Chlamydia pecorum detection in aborted and stillborn lambs from Western Australia

“…Prior to genotyping, the C. pecorum positive DNA samples from six liver and two cotyledon samples taken from eight aborted and/or stillborn lambs from four different farms (Additional file 2 ) were quantified for C. pecorum genome copy number (tested in duplicate) using standard curve calibrated and High Resolution Melt (HRM) C. pecorum qPCR assay [ 43 ]. The genome copy number/µL in samples ranged from 3.41 × 10 2 –2.47 × 10 5 copies/µL DNA template, with geometric mean of 7.26 × 10 3 copies/µL (Table 2 ).…”

Chlamydial infection and on‐farm risk factors in dairy cattle herds in South East Queensland

“…Each amplification assay was performed as recently described and calibrated using serially diluted known standards. A positive (cultured isolates C. pecorum E58, C. psittaci CR009 and C. abortus B577 DNA) and negative (MilliQ water) control was included in each run, with all samples tested in duplicate . Bovine mitochondrial DNA ( Cytochrome B) was used as an internal standard to assess the integrity of the sample and the presence and/or absence of PCR inhibitors .…”

Chlamydiae from Down Under: The Curious Cases of Chlamydial Infections in Australia

“…As such, the use of these assays may be contributing to unnecessary rejection of animals in various international markets that require Cab testing, consequently reducing profitability and incurring losses to the industry. A recent study screening for chlamydial pathogens in conjunctival swabs collected from rejected sheep with varying grades of infectious ovine keratoconjunctivitis (IOK) from an Australian pre-export feedlot also demonstrated that Cpec ocular infections are common in both sheep presenting with IOK, as well as healthy animals [89]. These findings further support a role for Cpec infections in economic losses to the Australian sheep industry.…”

“…In contrast, until recently the reports in Australia were anecdotal, inconclusive and rare. Since the description of Cps infections in horses, Cps has been detected in a limited number of domesticated cattle and sheep [88,89], however wider surveys are warranted to truly elucidate whether the livestock animals are indeed commonly infected with this pathogen and represent "new" reservoirs, or if Cps detection is a result of "spill-over" from birds and/or environmental exposure ( Figure 1A).…”

“…While the exact economic and production losses incurred due to these infections remains unquantified, Cpec infections pose a problem in the thriving Australian live export industry [131,132]. Chlamydia abortus (Cab) is considered an exotic pathogen in Australia and New Zealand, with many recent surveillance studies supporting this observation [89,129,131]. In a recent pilot study, it was shown that commercially available Cab-specific assays demonstrate low specificity, yet high rates of Cab seropositivity in laboratory confirmed Cpec infected Australian sheep and in the absence of any detectable Cab infection [131].…”