Ocorrência de Chlamydophila psittaci em pombos (Columba livia) na cidade de Salvador, Bahia

A Review of Chlamydial Infections in Wild Birds

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.

Global prevalence of chlamydial infections in birds: A systematic review and meta-analysis

Chamydia species are bacterial pathogens that can infect a wide range of animal hosts including humans. In birds, Chlamydia psittaci is a leading cause of chlamydial infections (avian chlamydiosis) and is a zoonotic pathogen causing human psittacosis. The objectives of this study were to estimate the global prevalence of chlamydial infections in birds, to assess heterogeneity of the prevalence for some particular characteristics (continents, bird orders, specimen types, and diagnostic techniques), and to determine the trend of the prevalence over time. The relevant citations on the prevalence of chlamydial infections in birds were retrieved from PubMed, Scopus, and Web of Science. Titles and abstracts of the retrieved citations were screened for possible eligibility. Then, full-texts of eligible articles were assessed for data extraction. A random effects model was used for estimating the global prevalence of chlamydial infections in birds and for all other meta-analyses. Subgroup meta-analysis was used to assess heterogeneity of the prevalence for the characteristics mentioned above. Meta-regression analysis and cumulative meta-analysis were used to determine the trend of the prevalence over time. The quality of each included study was also evaluated. Of 579 citations, 74 studies (a total of 39,225 bird samples from 26 countries, five continents) were included in meta-analysis. Almost all included studies reported birds with C. psittaci infections. The global prevalence of chlamydial infections in birds was 19.5 % (95 % CI, 16.3 %-23.1 %). No significant differences of the prevalence were observed among continents, the prevalence ranged from 16.5 % (95 % CI, 9.8 %-26.5 %) in South America to 21.7 % (95 % CI, 12.1 %-35.9 %) in North America. No significant differences of the prevalence were observed among bird orders, the prevalence ranged from 13.4 % (95 % CI, 7.0 %-23.9 %) in Passeriformes to 32.0 % (95 % CI, 20.6 %-46.1 %) in Galliformes. No significant differences of the prevalence were observed between specimen types; the prevalence was 18.4 % (95 % CI, 15.2 %-22.2 %) for live specimens and 26.3 % (95 % CI, 17.1 %-38.1 %) for carcass specimens. The prevalence was significantly higher in non-PCR techniques (29.5 %, [95 % CI, 22.4 %-37.8 %]) than in PCR techniques (15.3 %, [95 % CI, 12.1 %-19.1 %]). The cumulative evidence showed that the prevalence of chlamydial infections in birds has been relatively stable around 20 % since 2012. This study indicates that the global prevalence of chlamydial infections in birds is quite high and all bird orders are potential sources for human psittacosis.