Prevalence and Risk Factors of Avian Chlamydiosis Detected by Polymerase Chain Reaction in Psittacine Birds in Thailand

This study surveyed avian chlamydiosis, with the aim to estimate the prevalence and potential risk factors associated with Chlamydia psittaci infection in psittacine birds kept as domestic pets in Thailand. Oropharyngeal swabs were collected from 120 psittacine birds that were randomly selected from hospitals in the central (Bangkok) and northeastern regions (Khon Kaen) of Thailand between 2019 and 2021. The oropharyngeal swabs were subject to polymerase chain reaction testing to detect the C psittaci ompA gene. The prevalence of C psittaci was 2.5% (3/ 120, 95% confidence interval = 0.3-5.3). Of the 3 positive birds, 1 was a Forpus parrot (Forpus species)(CP43TH) and 1 was an African grey parrot (Psittacus erithacus)(CP49TH) from Bangkok; both were juvenile birds with clinical signs of disease. The third positive bird (CP12TH) was a subclinical adult sun conure (Aratinga solstitialis) from Khon Kaen. Two sequences of samples that were previously identified in human psittacosis cases (accession numbers MK032053.1 and HM450409.1) were also examined. Since there was a low number of infected birds, potential associations between C psittaci infection and various environmental variables (eg, cage cleaning, synanthropic birds, quarantine of new birds, and overcrowding) were assessed by Fisher exact tests. This study provides estimates of the prevalence and potential risk factors associated with C psittaci infection in psittacine birds from central (Bangkok) and the northeastern regions (Khon Kaen) of Thailand. The detection of C psittaci in captive psittacine birds demonstrates that there is a possibility for bird-to-bird transmission as well as some zoonotic potential for the human caretakers of these birds. Furthermore, larger-scale studies should be conducted to confirm these findings.

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.

First detection and characterization of Psittaciform bornaviruses in naturally infected and diseased birds in Thailand

In Thailand a proventricular dilation disease (PDD)-like syndrome commonly occurs in captive psittacine birds. The etiology, however, has been unknown to date and studies to detect parrot bornaviruses have never been performed in Southeastern Asia. Therefore, 111 psittacines (22 different species) including birds with suspected PDD based on clinical examination results (n = 65), cage mates of PDD suspected parrots without any clinical signs (n = 39) and dead birds with previous clinic suspicious for PDD (n = 7) were tested for bornaviruses using various reverse transcription polymerase chain reaction (RT-PCR) and realtime RT-PCR protocols, an enzyme-linked immunosorbent assay (ELISA), immunohistochemistry, and genome sequencing. Bornaviral infections, indicated by the presence of RNA or antibody positive reactions were detected in 60 birds (54.1%) belonging to 15 psittaciform species and originating from 41 owners. Occurrence of Psittaciform 1 orthobornavirus was confirmed by sequencing of PCR products in 24 of these birds. Parrot bornavirus (PaBV)-5, belonging to the species Psittaciform 2 orthobornavirus and found only in single birds in the United States of America, Japan and Hungary until now, was identified in a macaw. Full genome sequencing revealed features shared with other strains of this virus. PaBV-4 was the prevalent virus type and the viruses grouped in two of the five genetic PaBV-4 subclusters known so far while PaBV-2 was found in a single patient. Forty-five psittacines of the group of PDD-suspected birds (69.2%), 4 dead birds and 11 clinically healthy cage mates were positive in at least one test the latter suggesting inefficient horizontal transmission in natural infections. Lymphoplasmacytic infiltrations (non-purulent inflammation, ganglioneuritis) and bornavirus antigen were detected in diverse tissues confirming PDD as the disease involved. These results may have a major impact on conservation projects including the five near-threatened parrot species living in the wild in Thailand.