Emerging and well-characterized chlamydial infections detected in a wide range of wild Australian birds

Birds can act as successful long-distance vectors and reservoirs for numerous zoonotic bacterial, parasitic and viral pathogens, which can be a concern given the interconnectedness of animal, human and environmental health. Examples of such avian pathogens are members of the genus Chlamydia. Presently, there is a lack of research investigating chlamydial infections in Australian wild and captive birds and the subsequent risks to humans and other animals. In our current study, we investigated the prevalence and genetic diversity of chlamydial organisms infecting wild birds from Queensland and the rate of co-infections with beak and feather disease virus (BFDV). We screened 1114 samples collected from 564 different birds from 16 orders admitted to the Australia Zoo Wildlife Hospital from May 2019 to February 2021 for Chlamydia and BFDV. Utilizing species-specific quantitative polymerase chain reaction (qPCR) assays, we revealed an overall Chlamydiaceae prevalence of 29.26% (165/564; 95% confidence interval (CI) 25.65-33.14), including 3.19% (18/564; 95% CI 2.03-4.99%) prevalence of the zoonotic Chlamydia psittaci. Chlamydiaceae co-infection with BFDV was detected in 9.75% (55/564; 95% CI 7.57-12.48%) of the birds. Molecular characterization of the chlamydial 16S rRNA and ompA genes identified C. psittaci, in addition to novel and other genetically diverse Chlamydia species: avian Chlamydia abortus, Ca. Chlamydia ibidis and Chlamydia pneumoniae, all detected for the first time in Australia within a novel avian host range (crows, figbirds, herons, kookaburras, lapwings and shearwaters). This study shows that C. psittaci and other emerging Chlamydia species are prevalent in a wider range of avian hosts than previously anticipated, potentially increasing the risk of spill-over to Australian wildlife, livestock and humans. Going forward, we need to further characterize C. psittaci and other emerging Chlamydia species to determine their exact genetic identity, potential reservoirs, and factors influencing infection spill-over.

Occurrence of Chlamydiaceae in Raptors and Crows in Switzerland

Bacteria of the family Chlamydiaceae are globally disseminated and able to infect many bird species. So far, 11 species of Chlamydia have been detected in wild birds, and several studies found chlamydial strains classified as genetically intermediate between Chlamydia (C.) psittaci and C.abortus. Recently, a group of these intermediate strains was shown to form a separate species, i.e., C.buteonis. In the present study, 1128 samples from 341 raptors of 16 bird species and 253 corvids representing six species were examined using a stepwise diagnostic approach. Chlamydiaceae DNA was detected in 23.7% of the corvids and 5.9% of the raptors. In corvids, the most frequently detected Chlamydia species was C.psittaci of outer membrane protein A (ompA) genotype 1V, which is known to have a host preference for corvids. The most frequently detected ompA genotype in raptors was M56. Furthermore, one of the raptors harbored C.psittaci 1V, and two others carried genotype A. C.buteonis was not detected in the bird population investigated, so it remains unknown whether this species occurs in Switzerland. The infection rate of Chlamydiaceae in corvids was high compared to rates reported in other wild bird species, but neither Chlamydiaceae-positive corvids nor raptors showed overt signs of disease. Since the Chlamydiaceae of both, raptors and crows were identified as C.psittaci and all C.psittaci genotypes are considered to be zoonotic, it can be suggested that raptors and crows pose a potential hazard to the health of their handlers.

Molecular prevalence and genotyping of Chlamydia spp. in wild birds from South Korea

Wild birds are reservoirs for Chlamydia spp. Of the total 225 samples from wild birds during January to September 2016 in Korea, 4 (1.8%) and 2 (0.9%) showed positive for Chlamydia psittaci and Chlamydia gallinacea, respectively. Phylogenetic analyses and comparisons of sequence identities for outer-membrane protein A (ompA) revealed that Korean C. psittaci fall into three previously known genotypes; genotype E, 1V and 6N, whereas the Korean C. gallinacea were classified as new variants of C. gallinacea. Our study demonstrates that wild birds in South Korea carry at least two Chlamydia species: C. psittaci and C. gallinacea, and provides new information on the epidemiology of avian chlamydiosis in wild birds.

Multi locus sequence typing of Chlamydia reveals an association between Chlamydia psittaci genotypes and host species

Chlamydia comprises a group of obligate intracellular bacterial parasites responsible for a variety of diseases in humans and animals, including several zoonoses. Chlamydia trachomatis causes diseases such as trachoma, urogenital infection and lymphogranuloma venereum with severe morbidity. Chlamydia pneumoniae is a common cause of community-acquired respiratory tract infections. Chlamydia psittaci, causing zoonotic pneumonia in humans, is usually hosted by birds, while Chlamydia abortus, causing abortion and fetal death in mammals, including humans, is mainly hosted by goats and sheep. We used multi-locus sequence typing to asses the population structure of Chlamydia. In total, 132 Chlamydia isolates were analyzed, including 60 C. trachomatis, 18 C. pneumoniae, 16 C. abortus, 34 C. psittaci and one of each of C. pecorum, C. caviae, C. muridarum and C. felis. Cluster analyses utilizing the Neighbour-Joining algorithm with the maximum composite likelihood model of concatenated sequences of 7 housekeeping fragments showed that C. psittaci 84/2334 isolated from a parrot grouped together with the C. abortus isolates from goats and sheep. Cluster analyses of the individual alleles showed that in all instances C. psittaci 84/2334 formed one group with C. abortus. Moving 84/2334 from the C. psittaci group to the C. abortus group resulted in a significant increase in the number of fixed differences and elimination of the number of shared mutations between C. psittaci and C. abortus. C. psittaci M56 from a muskrat branched separately from the main group of C. psittaci isolates. C. psittaci genotypes appeared to be associated with host species. The phylogenetic tree of C. psittaci did not follow that of its host bird species, suggesting host species jumps. In conclusion, we report for the first time an association between C. psittaci genotypes with host species.