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

Cross-European laboratory evaluation of commercial and in-house real-time PCR assays for the detection of Chlamydia abortus in small ruminants

Chlamydia abortus is a bacterial pathogen that causes enzootic abortion of ewes (EAE), a disease of sheep and goats with potential risks to human health. Accurate detection is essential for disease management and prevention. While serological tests have been widely used for herd screening, they are lacking in terms of sensitivity and specificity. PCR methods, particularly real-time PCR, are now preferred due to their improved sensitivity and accuracy for confirmation of clinical cases and for use in routine surveillance. This study aimed to compare and evaluate the analytical parameters and diagnostic performance of two commercial PCR tests and four in-house PCR methods for their suitability for diagnosing EAE. Two of the in-house methods are based on the ompA gene, which is specifically used to detect C. abortus in ruminants. The other two tests target different genetic markers, that also allow the detection of avian C. abortus strains. The study found that all PCR tests had a similar analytical sensitivity and were effective in identifying C. abortus in clinical samples, such as placentas, vaginal swabs and fetal organs especially in animals showing symptoms. However, detection in asymptomatic carriers was more difficult. One of the ompA-based assays showed superior diagnostic accuracy, particularly compared to the commercial kits, with a diagnostic sensitivity of 98.0 % and a diagnostic specificity of 96.6 % and is thus the one recommended for routine testing. The study also concluded that the interpretation criteria of the commercial kits should be reviewed to improve their reliability.

Clinical diagnosis and treatment of seven patients diagnosed pneumonia caused by Chlamydia abortus: a case series report

Background

Chlamydia abortus pneumonia is very rare in normal people. At present, there is a lack of clinical data on the clinical characteristics and diagnosis and treatment experience of patients with this type of infection. Our team had recently treated 7 cases of these patients. This study aims to comprehensively summarize and analyze the clinical characteristics and treatment methods of Chlamydia abortus pneumonia, and to provide clinical evidence for the diagnosis and treatment of Chlamydia abortus pneumonia.

Methods

Clinical data were retrospectively collected from patients diagnosed with Chlamydia abortus pneumonia through metagenomic next-generation sequencing (mNGS) at the Department of Pulmonary and Critical Care Medicine, Meizhou People's Hospital.

Results

Seven patients with Chlamydia abortus pneumonia reported a history of poultry exposure, experiencing fever alongside respiratory or digestive symptoms. Marked elevation of blood inflammation markers, accompanied by hypoproteinemia and liver damage, was observed. Chest CT scans revealed pneumonia and pleural effusion. Chlamydia abortus was detected in blood or bronchoalveolar lavage fluid (BALF) through mNGS, often co-occurring with Chlamydia psittaci or other bacteria infections. Notably, Doxycycline demonstrated efficacy in treating Chlamydia abortus.

Conclusion

Chlamydia abortus infection is a zoonotic disease, particularly among individuals with a history of poultry exposure, and mNGS emerges as a reliable diagnostic tool for its detection. Chlamydia abortus infection manifests with systemic and lung inflammation, effectively addressed through Doxycycline therapy.

Molecular characterisation of the Australian and New Zealand livestock Chlamydia pecorum strains confirms novel but clonal ST23 in association with ovine foetal loss

Chlamydia pecorum is a veterinary pathogen associated with abortions and perinatal mortality in sheep. Recent studies investigating foetal and perinatal lamb mortality in sheep from Australia and New Zealand identified C. pecorum clonal sequence type (ST)23 strains in aborted and stillborn lambs. Presently, there is limited genotypic information on C. pecorum strains associated with reproductive disease, although whole genome sequencing (WGS) of one abortigenic ST23 C. pecorum strain identified unique features, including a deletion in the CDS1 locus of the chlamydial plasmid. We applied WGS on two ST23 strains detected in aborted and stillborn lambs from Australia and used phylogenetic and comparative analyses to compare these to the other available C. pecorum genomes. To re-evaluate the genetic diversity of contemporary strains, we applied C. pecorum genotyping, and chlamydial plasmid sequencing to a range of C. pecorum positive samples and isolates from ewes, aborted foetuses and stillborn lambs, cattle and a goat from diverse geographical regions across Australia and New Zealand.The two new C. pecorum genomes are nearly identical to the genome of the Australian abortigenic strain including the unique deletion in the chlamydial plasmid. Genotyping revealed that these novel C. pecorum ST23 strains are widespread and associated with sheep abortions on Australian and New Zealand farms. In addition, a goat C. pecorum strain (denoted ST 304) from New Zealand was also characterised. This study expands the C. pecorum genome catalogue and describes a comprehensive molecular characterisation of the novel livestock ST23 strains associated with foetal and lamb mortality.

Detection of viral antibodies in camel sera using magnetic particle spectroscopy

Pandemics like SARS-Cov-2 very frequently have their origin in different animals and in particular herds of camels could be a source of zoonotic diseases. This study took advantage on a highly sensitive and adaptable method for the fast and reliable detection of viral antibodies in camels using low-cost equipment. Magnetic nanoparticles (MNP) have high variability in their functionalization with different peptides and proteins. We confirm that 3-aminopropyl triethoxysilane (APTES)-coated MNP could be functionalized with viral proteins. The protein loading could be confirmed by simple loading controls using FACS-analysis (p < 0.05). Complementary combination of antigen and antibody yields in a significant signal increase could be proven by both FACS and COMPASS. However, COMPASS needs only a few seconds for the measurement. In COMPASS, the phase φ_n on selected critical point of the fifth higher harmonic (n = 5th). Here, positive sera display highly significant signal increase over the control or negative sera. Furthermore, a clear distinction could be made in antibody detection as an immune response to closely related viruses (SARS-CoV2 and MERS). Using modified MNPs along with COMPASS offers a fast and reliable method that is less cost intensive than current technologies and offers the possibility to be quickly adapted in case of new occurring viral infections. KEY POINTS: • COMPASS (critical offset magnetic particle spectroscopy) allows the fast detection of antibodies. • Magnetic nanoparticles can be adapted by exchange of the linked bait molecule. • Antibodies could be detected in camel sera without washing steps within seconds.

The Seroprevalence of Chlamydia Infection in Sheep in Shanxi Province, China

Chlamydia, an obligate intracellular bacterium, can cause chlamydiosis in humans and animals worldwide and also leads to serious economic losses to the sheep industry. However, the information on Chlamydia infection in sheep was limited in Shanxi Province, northern China. In the present study, a total of 984 serum samples of sheep were collected from 11 regions in Shanxi Province, northern China in the autumn of 2020. The antibodies against Chlamydia and Chlamydia abortus were examined by the indirect hemagglutination assay (IHA) and indirect enzyme-linked immunosorbent assay (ELISA), respectively. The result showed that 351 (35.67%, 95% CI 32.68-38.66) of 984 serum samples were positive for Chlamydia, and the seroprevalence ranged from 6.67% to 70.79% among the different regions. In addition, antibodies to C. abortus infection were detected in 78 (7.93%, 95% CI 6.24-9.61) of 984 serum samples, and the seroprevalence ranged from 6.24% to 14.81% among the different regions. This is the first report on the seroprevalence of Chlamydia and C. abortus in sheep in Shanxi province, northern China. The findings provide baseline information for preventing and controlling Chlamydia infection in sheep in Shanxi Province, China.

Zambrano-Rodríguez P. The Use of Peptides in Veterinary Serodiagnosis of Infectious Diseases: A Review

Peptides constitute an alternative and interesting option to develop treatments, vaccines, and diagnostic tools as they demonstrate their scope in several health aspects; as proof of this, commercial peptides for humans and animals are available on the market and used daily. This review aimed to know the role of peptides in the field of veterinary diagnosis, and include peptide-based enzyme-linked immunosorbent assay (pELISA), lateral flow devices, and peptide latex agglutination tests that have been developed to detect several pathogens including viruses and bacteria of health and production relevance in domestic animals. Studies in cattle, small ruminants, dogs, cats, poultry, horses, and even aquatic organisms were reviewed. Different studies showed good levels of sensitivity and specificity against their target, moreover, comparisons with commercial kits and official tests were performed which allowed appraising their performance. Chemical synthesis, recombinant DNA technology, and enzymatic synthesis were reviewed as well as their advantages and drawbacks. In addition, we discussed the intrinsic limitations such as the small size or affinity to polystyrene membrane and mention several strategies to overcome these problems. The use of peptides will increase in the coming years and their utility for diagnostic purposes in animals must be evaluated.

Species, sex and geographic variation in chlamydial prevalence in abundant wild Australian parrots

Chlamydia psittaci (order: Chlamydiales) is a globally distributed zoonotic bacterium that can cause potentially fatal disease in birds and humans. Parrots are a major host, yet prevalence and risk factors for infection in wild parrots are largely unknown. Additionally, recent research suggests there is a diverse range of novel Chlamydiales circulating in wildlife. We therefore sampled seven abundant parrot species in south-eastern Australia, taking cloacal swabs and serum from n = 132 wild adults. We determined C. psittaci and Chlamydiales prevalence and seroprevalence, and tested for host species, sex, geographical and seasonal differences, and temporal changes in individual infection status. Across all species, Chlamydiales prevalence was 39.8% (95% CI 31.6, 48.7), C. psittaci prevalence was 9.8% (95% CI 5.7, 16.3) and C. gallinacea prevalence was 0.8% (95% CI 0.1, 4.5). Other Chlamydiales species were not identified to species level. We identified two C. psittaci strains within the 6BC clade, which is highly virulent in humans. Seroprevalence was 37.0% (95% CI 28.5, 46.4). Host species (including crimson rosellas, galahs, sulphur-crested cockatoos and blue-winged parrots) differed in seroprevalence and Chlamydiales prevalence. Galahs had both highest Chlamydiales prevalence (54.8%) and seroprevalence (74.1%). Seroprevalence differed between sites, with a larger difference in males (range 20–63%) than females (29–44%). We reveal a higher chlamydial prevalence than previously reported in many wild parrots, with implications for potential reservoirs, and transmission risks to humans and other avian hosts.

First report of Chlamydophila abortus infection in the dromedary camel (Camelus dromedarius) population in eastern Algeria

Chlamydiosis is caused by an obligate intracellular gram-negative bacterium of the genus Chlamydophila which is a zoonotic pathogen. The objectives of the study were to identify the seroprevalence of antibodies against Chlamydophila abortus in dromedary camel herds from four districts in eastern Algeria, as well as to estimate the association between seroprevalence and certain factors present at the animal and herd levels. Blood samples were collected from a random sample of animals within each of 82 camel herds. Serum samples were subjected to a C. abortus ELISA test, and association between the presence of antibodies and potential risk factors was estimated. Animal and herd seroprevalence were 2.5 % and 15.8 %, respectively, indicating substantial exposure of camels to C. abortus in the four districts studied. Age, breed, and sex did not influence seroprevalence in tested animals. Based on the univariate analysis, contact with sheep and goats, contact with other camel herds, and histories of abortion were major risk factors for infection. By using multivariate analysis, contact of camels with sheep and goats and with others camel herds, through shared grazing or watering points, were important factors for transmission of chlamydiosis with an odds ratio of 3.3 and 9.4, respectively. At the herd level the introduction of purchased animals was the major risk factor. This baseline information will be highly useful for launching C. abortus control programs in the region and potentially elsewhere.

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.