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.

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

Chlamydia psittaci is a zoonotic pathogen with multiple hosts, especially avian, and can be transmitted to humans, causing psittacosis or ornithosis. No effective vaccines have been developed. We therefore isolate and genotype avian C. psittaci strains and investigate the pathogenicity of isolates in the southern Hunan area of China. Among 200 suspicious avian specimens, eight were positive for the C. psittaci outer membrane protein A (ompA) gene (4%), and seven were successfully cultured in human epithelial type 2 and Vero cells (87.5%). Genotyping of the ompA gene of the eight PCR-positive samples revealed that all of the cultured strains, except for the E9 strain, belonged to genotype A. Pathologic changes in the mice infected with C. psittaci via intranasal inoculation showed severe pneumonia and intense infiltration of inflammatory cells in the lung in a dose-dependent manner, and immunohistochemical staining displayed different levels of infiltration of C. psittaci inclusions in the heart, liver, spleen, kidney, and, especially, lung. Our findings demonstrate that genotype A dominates all C. psittaci genotypes in the southern Hunan area and that the C. psittaci avian isolates in this region possess dose-dependent pathogenicity.

Isolation and Characterization of Avian Chlamydia psittaci from Symptomatic Pet Birds in Southern Hunan, China.

The Chlamydia are a globally distributed genus of bacteria that can infect and cause disease in a range of hosts. Birds are the primary host for multiple chlamydial species. The most well-known of these is Chlamydia psittaci, a zoonotic bacterium that has been identified in a range of wild and domesticated birds. Wild birds are often proposed as a reservoir of Chlamydia psittaci and potentially other chlamydial species. The aim of this review is to present the current knowledge of chlamydial infections in wild avian populations. We focus on C. psittaci but also consider other Chlamydiaceae and Chlamydia-related bacteria that have been identified in wild birds. We summarise the diversity, host range, and clinical signs of infection in wild birds and consider the potential implications of these infections for zoonotic transmission and avian conservation. Chlamydial bacteria have been found in more than 70 species of wild birds, with the greatest chlamydial diversity identified in Europe. The Corvidae and Accipitridae families are emerging as significant chlamydial hosts, in addition to established wild hosts such as the Columbidae. Clarifying the effects of these bacteria on avian host fitness and the zoonotic potential of emerging Chlamydiales will help us to understand the implications of these infections for avian and human health.

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A Review of Chlamydial Infections in Wild Birds.

Cross-sectional study on Chlamydiaceae prevalence and associated risk factors on commercial and backyard poultry farms in Mexico.

AIM: To describe the Chlamydia psittaci genotypes in samples from native and introduced birds from New Zealand by analysis of the sequence variation of the ompA gene.METHODS: DNA was extracted from...

A preliminary survey of Chlamydia psittaci genotypes from native and introduced birds in New Zealand.

A mortality episode of endemic and endangered psittacine birds from the genera Ara and Amazona occurred during January 2015. The birds were housed in a management unit for wildlife conservation that receives wild-caught birds from illegal trade. In total, 11 (57%) adult birds of different origins that shared these accommodations died. Only four of them were sent for diagnosis. The main lesions found at necropsy were consistent with those described previously for avian chlamydiosis; the presence of Chlamydiaceae was confirmed through immunofluorescence and amplification with further sequencing of the 16S ribosomal RNA gene by using hepatic tissue. Due to the lack of specific diagnostic tools on primary psittacine diseases, the pathogenic effects of systemic, respiratory, or enteric infections with high mortality rates remain unknown in Mexico. In this study, specific molecular identification of avian chlamydiosis was performed using a nested PCR on liver tissues, as well as choanal and cloacal swab samples, confirming the presence of Chlamydia psittaci in all of them. In addition, it was possible to obtain the ompA gene sequence from processed clinical samples, thereby allowing us to determine that the A genotype was affecting these birds. Although this genotype is the most commonly found worldwide in psittacine birds, this case report describes the first avian chlamydiosis outbreak affecting critically endangered and endemic psittacines subjected to reintegration programs in Mexico. Consequently, this study demonstrates the necessity of more exhaustive biosecurity strategies because other pathogens may be present and should be assessed, especially in highly threatened birds, before releasing them into their habitats.

J. A. De la Garza-García

Papers

First Identification of Chlamydia psittaci in the Acute Illness and Death of Endemic and Endangered Psittacine Birds in Mexico