Serological analysis ofChlamydophila abortusin Australian sheep and implications for the rejection of breeder sheep for export

Chlamydia abortus Isolation and Identification in Aborted Ovine Fetus in Mari El Republic of Russia

Reproductive disorders, presumably caused by Chlamydia abortus, are common among the ovine population of the Mari El Republic, Russia. C. abortus infection was determined by serologic testing or isolation and detection of the organism by PCR and direct immunofluorescence in tissue samples. Rams, ewes, and lambs (10 individuals each) were randomly chosen for serological testing by the complement fixation test and 7 of 30 (23%) animals tested were positive. Tissue samples were collected from ewes and aborted fetuses for isolation by inoculating chicken embryo yolk sacs (n = 41). The same samples were analyzed by PCR using commercial and in-house PCR kits and by direct immunofluorescence. C. abortus was detected in 58.5% of samples using PCR and in 60.9% of the samples by direct immunofluorescence. Five Chlamydia isolates were cultured in egg yolk sacs and adapted for growth in cell cultures. Phylogenetic analysis showed no substantial difference between Russian isolates and those from other parts of the world. The results of the study further demonstrate the usefulness of PCR for detection of C. abortus as a faster, simpler, and more reliable approach in comparison to culturing the organism and underscoring the necessity of screening for chlamydiosis as a cause of ovine abortion.

Seroprevalence and Risk Factors Associated with Chlamydia abortus Infection in Sheep and Goats in Eastern Saudi Arabia

Chlamydia abortus (C. abortus) is intracellular, Gram-negative bacterium that cause enzootic abortion in sheep and goats. Information on C. abortus seroprevalence and flock management risk factors associated with C. abortus seropositivity in sheep and goats in Saudi Arabia are scarce. The objectives of this study were to (i) estimate the animal, flock, and within-flock seroprevalence of C. abortus among Eastern Province sheep and goat flocks and (ii) identify the flock management and animal risk factors associated with C. abortus seropositivity in Eastern Province, Saudi Arabia. A cross-sectional study with a two-stage sampling process was carried out in the Eastern Province, Saudi Arabia, between 2015 and 2016. A total of 1717 sheep and 1101 goat serum samples were collected from 21 sheep and 14 goat flocks, then were tested for C. abortus antibodies using a commercial ELISA Kit. In addition, vaginal swabs and aborted tissue samples were collected from sheep (n = 48) and goats (n = 15) with recent history of abortion for detection of C. abortuspmp gene using PCR. A questionnaire was constructed to collect information about flock management and animal risk factors possibly associated with C. abortus infection in sheep and goats. The true sheep and goat-level seroprevalences were 11.1% (95% CI: 9.7–12.7) and 10.6% (95% CI: 8.8–12.5), respectively. The true flock-level seroprevalence was 100% for both sheep and goats. However, the average within sheep and goat flocks true seroprevalences were 9.6% (95% CI: 1.8–22.9) and 9.3% (95% CI: 1.8–19.5), respectively. Multivariable logistic regression revealed that introduction of new sheep to the flocks (OR = 2.6; 95% CI: 1.5–4.4), type of breeding system (OR = 1.8; 95% CI: 1.0–3.4), flocks allowing females in (OR = 1.9; 95% CI: 1.1–3.3) or females out (OR = 2.2; 95% CI: 1.1–4.3), and sheep age 1.4–2.8 years (OR = 1.9; 95% CI: 1.3–2.9) were potential risk factors for C. abortus seropositivity in sheep flocks. However, in goat flocks, the introduction of new goats to the flocks (OR: 1.9; 95% CI: 1.2–3.0) was identified as a risk factor, whereas good farm hygiene (OR: 0.3; 95% CI: 0.2–0.7) was identified as a protective factor. C. abortus pmp gene was identified in 45 (93.8%) and 15 (100%) of samples collected from sheep and goats, respectively. These results could be used to implement efficient management measures to prevent and control C. abortus infection in sheep and goats in Eastern Province, Saudi Arabia, but also could be used to reduce the risk of C. abortus infection in sheep and goat flocks with similar management practices in other regions.

A 25-year retrospective study of Chlamydia psittaci in association with equine reproductive loss in Australia

Introduction. Chlamydia psittaci is primarily a pathogen of birds but can also cause disease in other species. Equine reproductive loss caused by C. psittaci has recently been identified in Australia where cases of human disease were also reported in individuals exposed to foetal membranes from an ill neonatal foal in New South Wales.Hypothesis/Gap Statement. The prevalence of C. psittaci in association with equine reproductive over time and in different regions of Australia is not known.Aim. This study was conducted to detect C. psittaci in equine abortion cases in Australia using archived samples spanning 25 years.Methodology. We tested for C. psittaci in 600 equine abortion cases reported in Australia between 1994 to 2019 using a Chlamydiaceae real-time quantitative PCR assay targeting the 16S rRNA gene followed by high-resolution melt curve analysis. Genotyping and phylogenetic analysis was performed on positive samples.Results. The overall prevalence of C. psittaci in material from equine abortion cases was 6.5 %. C. psittaci-positive cases were detected in most years that were represented in this study and occurred in Victoria (prevalence of 7.6 %), New South Wales (prevalence of 3.9 %) and South Australia (prevalence of 15.4 %). Genotyping and phylogenetic analysis showed that the C. psittaci detected in the equine abortion cases clustered with the parrot-associated 6BC clade (genotype A/ST24), indicating that infection of horses may be due to spillover from native Australian parrots.Conclusion. This work suggests that C. psittaci has been a significant agent of equine abortion in Australia for several decades and underscores the importance of taking appropriate protective measures to avoid infection when handling equine aborted material.

Seroepidemiological feature of Chlamydia abortus in sheep and goat population located in northeastern Iran

Chlamydia abortus is a Gram-negative intracellular bacteria responsible for major economic losses due mainly to infection and subsequent induction of abortion in several animal species and poses considerable public health problems in humans. This study was conducted to determine the prevalence of antibody against C. abortus in sheep and goat population of Khorasan Razavi province located in northeastern Iran. Four hundred fifty-two (271 sheep and 181 goats) sera samples from 40 sheep/goat epidemiologic units located in 11 counties were selected. Sera were assayed for antibodies against C. abortus using ELISA assay. Out of 452 sheep and goat sera, 44 [9.70% (95.00%CI: 7.10%-12.40%)] were positive for C. abortus antibodies. 28 out of 40 epidemiologic units (70.00%) and 10 out of 11 counties (91.00%), at least one seropositive sample was found. There was no significant difference between the seropositivity of sheep and goats. Age, sex, and location did not show significant relationship with the test results. The results showed that C. abortus was circulating in wide parts of Khorasan Razavi province. Considering the economic and public health importance of C. abortus, measures should be taken to help prevent its spread and to reduce the zoonotic risk of C. abortus in the studied region.

Chlamydial diversity and predictors of infection in a wild Australian parrot, the Crimson Rosella (Platycercus elegans)

Members of the Chlamydia genus are known to cause disease in both humans and animals. A variety of other species in the order Chlamydiales are increasingly being discovered and emerging as potential pathogens, yet there are scarce data on the diversity, prevalence and impacts of these pathogens in wild birds. To address this gap, we investigated which Chlamydiales species are present in a wild population of a common Australian parrot, the Crimson Rosella (Platycercus elegans). We collected cloacal swabs and serum from 136 individuals in south-eastern Australia, over two years, and tested several predictors of prevalence: age, sex, season and breeding status. We used multiple PCR assays to determine bacterial prevalence in cloacal swabs and a solid-phase ELISA to determine seroprevalence. We found Chlamydiales PCR prevalence of 27.7% (95% CI 20.2, 36.2) and identified at least two families (Chlamydiaceae and Parachlamydiaceae). Regarding known chlamydial avian pathogens, we found C. psittaci at 6.2% (95% CI 2.7, 11.8) and C. gallinacea at 4.6% (95% CI 1.7, 9.8) prevalence. We also identified at least two potentially novel Chlamydiales species, of unknown pathogenicity. Sex and breeding status predicted Chlamydiales PCR prevalence, with females more likely to be infected than males, and non-breeding birds more likely to be infected than breeding birds. Seroprevalence was 16% (95% CI 8.8, 25.9). Season and breeding status were strong predictors of seroprevalence, with highest seroprevalence in autumn and in non-breeding birds. Our results reveal a diversity of Chlamydiales species in this abundant wild host, and indicate that host-specific and temporal factors are associated with infection risk. Our findings suggest that wild parrots are a reservoir of both known and novel Chlamydiales lineages, of zoonotic and pathogenic potential.

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

In Australia, the most researched and perhaps the most successful chlamydial species are the human pathogen Chlamydia trachomatis, animal pathogens Chlamydia pecorum and Chlamydia psittaci. C. trachomatis remains the leading cause of sexually transmitted infections in Australians and trachoma in Australian Indigenous populations. C. pecorum is globally recognised as the infamous koala and widespread livestock pathogen, whilst the avian C. psittaci is emerging as a horse pathogen posing zoonotic risks to humans. Certainly not innocuous, the human infections with Chlamydia pneumoniae seem to be less prevalent that other human chlamydial pathogens (namely C. trachomatis). Interestingly, the complete host range for C. pecorum and C. psittaci remains unknown, and infections by other chlamydial organisms in Australian domesticated and wildlife animals are understudied. Considering that chlamydial organisms can be encountered by either host at the human/animal interface, I review the most recent findings of chlamydial organisms infecting Australians, domesticated animals and native wildlife. Furthermore, I also provide commentary from leading Australian Chlamydia experts on challenges and future directions in the Chlamydia research field.

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

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.

The limitations of commercial serological assays for detection of chlamydial infections in Australian livestock

Chlamydia pecorum and Chlamydia abortus are related ruminant pathogens endemic to different global regions. Potential co-infections combined with the lack of species-specific serological assays challenge accurate diagnosis. Serological screening revealed low C. abortus seropositivity with the peptide-based ELISA (1/84; 1.2%) in Australian sheep yet moderate seropositivity in a Swiss flock with history of C. abortus-associated abortions (17/63; 26.9%). By whole cell antigen complement fixation tests (CFT) and ELISA, chlamydial seropositivity was significantly higher in all groups, suggesting cross-reactivity between these two chlamydial species and non-specificity of the tests. However, only C. pecorum DNA could be detected by qPCR in Chlamydia seropositive Australian animals screened, suggesting chlamydial seropositivity was due to cross-reactivity with endemic C. pecorum infections. These results suggest ascribing Chlamydia seropositivity to chlamydial species in livestock using whole-cell antigen CFT or ELISA should be treated with caution; and that peptide-based ELISA and qPCR provide greater chlamydial species-specificity.

An epizootic of Chlamydia psittaci equine reproductive loss associated with suspected spillover from native Australian parrots

Chlamydia psittaci is an avian pathogen capable of spill-over infections to humans. A parrot C. psittaci strain was recently detected in an equine reproductive loss case associated with a subsequent cluster of human C. psittaci infections. In this study, we screened for C. psittaci in cases of equine reproductive loss reported in regional New South Wales, Australia during the 2016 foaling season. C. psittaci specific-PCR screening of foetal and placental tissue samples from cases of equine abortion (n = 161) and foals with compromised health status (n = 38) revealed C. psittaci positivity of 21.1% and 23.7%, respectively. There was a statistically significant geographical clustering of cases ~170 km inland from the mid-coast of NSW (P < 0.001). Genomic analysis and molecular typing of C. psittaci positive samples from this study and the previous Australian equine index case revealed that the equine strains from different studs in regional NSW were clonal, while the phylogenetic analysis revealed that the C. psittaci strains from both Australian equine disease clusters belong to the parrot-associated 6BC clade, again indicative of spill-over of C. psittaci infections from native Australian parrots. The results of this work suggest that C. psittaci may be a more significant agent of equine reproductive loss than thought. A range of studies are now required to evaluate (a) the exact role that C. psittaci plays in equine reproductive loss; (b) the range of potential avian reservoirs and factors influencing infection spill-over; and (c) the risk that these equine infections pose to human health.

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

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 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.

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/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.

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.

Seroprevalence and Risk Factors of Chlamydia abortus Infection in Goats in Hunan Province, Subtropical China

Chlamydia abortus is an obligate intracellular Gram-negative bacteria, which can infect animals and human, including goats. However, little information on C. abortus infection is available in goats in Hunan province, subtropical China. To investigate the seroprevalence and risk factors of C. abortus infection in goats in Hunan province, China, a total of 911 goat blood samples were collected randomly from 14 herds having number of goats ranging from 1000 to 3000 from March 2014 to December 2015. Seropositive animals were found in 11 out of 14 (78.57%) goat herds with seroprevalence ranging from 0.00% to 29.94% in individual herds. Overall, the seroprevalence of C. abortus infection was different among regions (southern Hunan: 1.78%; northeast Hunan: 5.47%; and west Hunan: 15.29%), gender (male: 4.58% and female: 9.10%), seasons (spring: 5.97%; summer: 2.61%; autumn: 16.88%; and winter: 10.94%), and ages (year ≤1: 2.39%; 1 < year ≤2: 9.58%; 2 < year ≤3: 9.16%; and year >3: 17.57%). Risk factors for C. abortus infection were associated with region, season, and age in this study. To our knowledge, this is the first document to demonstrate the existence of C. abortus infection in goats, and the seroprevalence was 8.45% out of 911 goats in Hunan province.

Longitudinal prevalence and faecal shedding of Chlamydia pecorum in sheep

The prevalence and faecal shedding of Chlamydia spp. in sheep in Australia has not been well described. Two species-specific quantitative PCRs (qPCRs) targeting the chlamydial outer membrane protein cell surface antigen gene (ompA) were validated and used to determine the prevalence and faecal shedding of C. abortus and C. pecorum from faecal samples of lambs at three sampling times (weaning, post-weaning and pre-slaughter) from eight farms in South Australia, New South Wales, Victoria and Western Australia. A total of 3412 faecal samples were collected and screened from approximately 1189 lambs across the four states. C. abortus was not detected in any of the samples screened. The overall prevalence of C. pecorum was 1027/3412 (30.1%) and median bacterial concentrations at weaning, post-weaning and pre-slaughter were 1.8 × 10(7), 1.2 × 10(7) and 9.6 × 10(5)/g faeces, respectively. A subset of C. pecorum positive samples from each farm, (n = 48) was sequenced to confirm their identity. The present study demonstrates that C. pecorum is prevalent in Australian sheep, highlighting a need for further research on the impact of this bacterium on production.