The prevalence and genetic characterization of Chlamydia psittaci from domestic and feral pigeons in Poland and the correlation between infection rate and incidence of pigeon circovirus

Chlamydia psittaci in Faecal Samples of Feral Pigeons (Columba livia forma urbana) in Urban Areas of Lublin city, Poland

Pigeons are a typical host and natural reservoir of Chlamydia psittaci, the etiological agent of avian chlamydiosis, considered as a neglected zoonotic diseases. The aim of the study was to determine the prevalence of C. psittaci in faecal samples of feral pigeons (Columba livia forma urbana) as a potential source of infection related to the presence of synanthropic birds in urban areas. A total of 143 samples of dry and fresh faeces of feral pigeons, were collected in the city of Lublin (Poland), from April to September 2021. Molecular detection of C. psittaci was performed by nested-PCR and real-time PCR, confirmed by sequencing. Among the collected samples, 5 positive results were obtained in nested-PCR (3.5%), while in real-time PCR, the number of positive samples increased to 11 (7.7%). The positive samples showed 100% identity to the C. psittaci strain AMK (CP047319.1). C. psittaci was found in 7 out of 111 (6.3%) faecal samples collected in public places, and in 4 out of 32 (12.5%) samples from the nesting site (4.9% and 2.8% among a total of 143 samples, respectively). The infection was detected in both dry and fresh faeces (9.1% and 4.5%, respectively). The highest number of positive results was obtained in June—5 (3.5%). Feral pigeons occurring in urban areas are a natural reservoir of C. psittaci posing a potential risk of zoonotic infections. However, further studies on exposure to contaminated pigeon faeces in terms of occupational and non-occupational risk of chlamydiosis are needed.

Pigeon Circovirus over Three Decades of Research: Bibliometrics, Scoping Review, and Perspectives

The pigeon circovirus (PiCV), first described in the literature in the early 1990s, is considered one of the most important infectious agents affecting pigeon health. Thirty years after its discovery, the current review has employed bibliometric strategies to map the entire accessible PiCV-related research corpus with the aim of understanding its present research landscape, particularly in consideration of its historical context. Subsequently, developments, current knowledge, and important updates were provided. Additionally, this review also provides a textual analysis examining the relationship between PiCV and the young pigeon disease syndrome (YPDS), as described and propagated in the literature. Our examination revealed that usages of the term 'YPDS' in the literature are characterizations that are diverse in range, and neither standard nor equivalent. Guided by our understanding of the PiCV research corpus, a conceptualization of PiCV diseases was also presented in this review. Proposed definitions and diagnostic criteria for PiCV subclinical infection (PiCV-SI) and PiCV systemic disease (PiCV-SD) were also provided. Lastly, knowledge gaps and open research questions relevant to future PiCV-related studies were identified and discussed.

Global prevalence of zoonotic pathogens from pigeon birds: A systematic review and meta-analysis

Pigeons have been considered the most preferred companion for human civilizations since prehistoric times. Despite the fact that pigeons offer the most palatable and nutritious food and provide pleasure to humans, they can pose a health risk because of carrying infectious and zoonotic organisms. Moreover, the scanty of systematic reports on the occurrence of zoonotic pathogens in pigeon makes the situations worst. Hence, the current study conducted a systematic review and meta-analysis to evaluate the global prevalence of zoonotic pathogens among the pigeon population from existing segregated literatures. Four internationally recognized databases including Google Scholar, Scopus, PubMed, and Science Direct were used to search the published studies from January 2000 to October 2021. Analyzing the total 18,589 samples, mean prevalence estimates of pigeon pathogens worldwide were found to be 17% (95% CI:13-21) whereas serological and molecular prevalence were reported as 18% (95% CI:12-23) and 17% (95% CI:10-23). Meanwhile, virus, bacteria, and protozoal pathogens were found to be 21% (10-32%), 17% (12-23%), and 14% (10-19%), respectively. Moreover, continent wise analysis of all zoonotic pigeon pathogens has revealed the highest prevalence rate in Asia 20% (95% CI: 14-26%), followed by Europe 16% (95% CI: 08-24%), Africa 16% (95% CI: 07-24%), and America (North and South) 10% (95% CI: 03-17%). Furthermore, the highest number of studies were reported from Iran showed the prevalence rate of 20%, China 13%, Bangladesh 37%, and Poland 15%. Therefore, this prevalence of data would be helpful to the policymakers to develop appropriate intervention strategies to prevent and control diseases in their respective locations.

Molecular detection and phylogenetic analysis of pigeon circovirus from racing pigeons in Northern China

Background

Pigeon circovirus (PiCV) infections in pigeons (Columba livia) have been reported worldwide. Currently, pigeon racing is becoming increasingly popular and considered to be a national sport in China, and even, the greatest competitions of racing pigeons are taking place in China. However, there are still no epidemiologic data regarding PiCV infections among racing pigeons in China. The purpose of our study was to provide information of prevalence, genetic variation and evolution of PiCV from racing pigeons in China.

Results

To trace the prevalence, genetic variation and evolution of PiCV in sick and healthy racing pigeons, 622 samples were collected from 11 provinces or municipalities in China from 2016 to 2019. The results showed that the positive rate of PiCV was 19.3% (120/622) at the sample level and 59.0% (23/39) at the club level, thus suggesting that the virus was prevalent in Chinese racing pigeons. A sequence analysis revealed that the cap genes of the PiCV strains identified in our study displayed a high genetic diversity and shared nucleotide homologies of 71.9%–100% and amino acid homologies of 71.7%–100%. 28 and 36 unique amino acid substitutions were observed in the Cap and Rep proteins derived from our PiCV strains, respectively. A cladogram representation of PiCV strains phylogeny based on 90 cap gene sequences showed that the strains in this study could be further divided into seven clades (A, B, C, E, G, H, and I) and some of them were closely related to worldwide strains from different types of pigeons. A large number of recombination events (31 events) were also detected in the PiCV genomes from Chinese racing pigeons.

Conclusions

These findings indicate that PiCV strains circulating in China exhibit a high genetic diversity and also contribute to information of prevalence, genetic variation and evolution of PiCV from racing pigeons in China.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08425-8.

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.

Investigation of Lethal Concurrent Outbreak of Chlamydiosis and Pigeon Circovirus in a Zoo

Simple Summary

The present study aimed to investigate a lethal outbreak of chlamydiosis and pigeon circovirus (PiCV) infection in a zoo. A retrospective follow-up indicates that the lethal outbreak might be an independent episode. The high prevalence of PiCV positivity in the aviaries suggests that PiCV infection might play a key role in augmenting the lethality of chlamydiosis in birds. Persistently monitoring both pathogens and identifying potential PiCV carriers or transmitters might also help prevent lethal disease outbreaks.

Abstract

During the spring, an outbreak of sudden death involving 58 birds occurred in a zoo. Histopathological examinations revealed variable numbers of intracytoplasmic basophilic microorganisms in the macrophages, hepatocytes, and renal epithelium of most birds, along with occasional botryoid intracytoplasmic inclusion bodies within histiocytes in the bursa of Fabricius. Based on the results of histopathological examinations, immunohistochemical staining, transmission electron microscopy, and polymerase chain reactions, genotype B Chlamydia psittaci infection concurrent with pigeon circovirus (PiCV) was diagnosed. A retrospective survey, including two years before the outbreak and the outbreak year, of C. psittaci and PiCV infections of dead birds in the aviaries, revealed that the outbreak was an independent episode. The findings of this study indicate that concurrent infection with C. psittaci and PiCV might lead to lethal outbreaks of chlamydiosis, particularly Streptopelia orientalis. In addition, persistently monitoring both pathogens and identifying potential PiCV carriers or transmitters might also help prevent lethal disease outbreaks.

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.

HEALTH SCREENING OF THE EUROPEAN ENDANGERED SPECIES PROGRAM CAPTIVE POPULATION OF THE PINK PIGEON (NESOENAS MAYERI)

The population of the Mauritian pink pigeon (Nesoenas mayeri) fell to fewer than 20 individuals in the 1970s. Following intensive conservation efforts, the free-living population is now estimated to be 470 individuals. However, because of the population bottleneck the species remains at risk of extinction because of genetic loss and inbreeding depression. A European captive population was established in 1977 and a European Endangered Species Program (EEP) was formalized in 1992. As birds in the EEP captive population possess unique alleles not observed in the surviving free-living birds, the EEP management plan recommends transferring EEP birds to Mauritius to improve genetic diversity. Health screening of the current EEP population to identify circulating pathogens was performed. Forty-two birds from three collections in the United Kingdom and one in Jersey were screened for a wide range of pathogens, present clinically or subclinically, including important viruses, bacteria, protozoa, and helminths. Eleven birds tested positive for at least one pathogen: Trichomonas spp. (5), Yersinia kristensenii (2), Yersinia aleksiciae (1), coccidial oocysts (3), and strongyle ova (3). None of the positive birds showed overt signs of clinical disease, although two birds with Trichomonas spp. had suboptimal body condition. Genotyping of one Trichomonas gallinae sample revealed a type-C strain (low pathogenicity). The results from this screening will contribute towards a disease risk assessment, to create a pre-export protocol for translocation of captive EEP birds to Mauritius.

The Clinical Infection with Pigeon Circovirus (PiCV) Leads to Lymphocyte B Apoptosis But Has No Effect on Lymphocyte T Subpopulation

The pathology of pigeon circovirus (PiCV) is still unknown, but it is regarded as an immunosuppressant. This study aimed to find a correlation between PiCV natural infection and immunosuppression. The study was conducted with 56 pigeons divided into the following groups: PiCV-positive but showing (group S) or not (group I) non-specific clinical symptoms and asymptomatic pigeons negative for PiCV (group H). The percentage and apoptosis of T CD3⁺ and B IgM⁺ splenocytes; the expression of CD4, CD8, and IFN-γ genes in splenic mononuclear cells; the number of PiCV viral loads in the bursa of Fabricius; and the level of anti-PiCV antibodies were analyzed. The results showed that the percentage of B IgM⁺ cells was almost two-fold lower in group S than in group H, and that ca. 20% of the lymphocytes were apoptotic. No increased apoptosis was detected in TCD3⁺ subpopulation. The PiCV viral loads were approximately one thousand and ten thousand times higher in group S than in groups I and H, respectively. Our results indicate a possible correlation between the number of PiCV viral loads and severity of PiCV infection and confirm that PiCV infection leads to the suppression of humoral immunity by inducing B lymphocyte apoptosis.

Common bacterial, viral, and parasitic diseases in pigeons (Columba livia): A review of diagnostic and treatment strategies

Pigeons (Columba livia) have been associated with humans for a long time now. They are raised for sport (pigeon race), exhibition (display of fancy breeds), food, and research. Most of the pigeons kept are Racing Homers, trained to compete in the pigeon race. Other breeds, such as Rollers, Nose Divers, Doneks are bred for their aerial abilities. Incorporation of a good preventive medicine program is one of the most critical factors in averting infectious diseases in pigeon flocks. This review summarizes the common bacterial, viral, and parasitic infections in pigeons. The different clinical signs, symptoms, diagnostic strategies, prevention, and treatments were described in this review. Current researches, molecular diagnostic assays, and treatment strategies such as vaccines and drug candidates were included. The information found in this review can provide insights for veterinarians and researchers studying pigeons to develop effective and efficient immunoprophylactic and diagnostic tools for pigeon diagnosis and therapeutics.

Infectious Causation of Abnormal Host Behavior: Toxoplasma gondii and Its Potential Association With Dopey Fox Syndrome

The apicomplexan parasite Toxoplasma gondii, the causative agent of toxoplasmosis, can infect all warm-blooded animals. T. gondii can subtly alter host behaviors-either through manipulation to enhance transmission to the feline definitive host or as a side-effect, or "constraint," of infection. In humans, T. gondii infection, either alone or in association with other co-infecting neurotropic agents, has been reliably associated with both subtle behavioral changes and, in some cases, severe neuropsychiatric disorders, including schizophrenia. Research on the potential impact of T. gondii on the behavior of other long-lived naturally infected hosts is lacking. Recent studies reported a large number of wild red foxes exhibiting a range of aberrant behavioral traits, subsequently classified as Dopey Fox Syndrome (DFS). Here we assessed the potential association between T. gondii and/or other neurotropic agents with DFS. Live, captive foxes within welfare centers were serologically tested for T. gondii and, if they died naturally, PCR-tested for vulpine circovirus (FoxCV). Post-mortem pseudo-control wild foxes, obtained from pest management companies, were PCR-tested for T. gondii, FoxCV, canine distemper virus (CDV), canine adenovirus type (CAV)-1 and CAV-2. We also assessed, using non-invasive assays, whether T. gondii-infected foxes showed subtle behavioral alterations as observed among infected rodent (and other) hosts, including altered activity, risk, and stress levels. All foxes tested negative for CAV, CDV, CHV, and DogCV. DFS was found to be associated with singular T. gondii infection (captives vs. pseudo-controls, 33.3% (3/9) vs. 6.8% (5/74)) and singular FoxCV infection (66.7% (6/9) vs. 11.1% (1/9)) and with T. gondii/FoxCV co-infection (33.3% (3/9) vs. 11.1% (1/9)). Overall, a higher proportion of captive foxes had signs of neuroinflammation compared to pseudo-controls (66.7% (4/6) vs. 11.1% (1/9)). Consistent with behavioral changes seen in infected rodents, T. gondii-infected foxes displayed increased attraction toward feline odor (n=6 foxes). These preliminary results suggest that wild foxes with DFS are infected with T. gondii and likely co-infected with FoxCV and/or another co-infecting neurotropic agent. Our findings using this novel system have important implications for our understanding of both the impact of parasites on mammalian host behavior in general and, potentially, of the infectious causation of certain neuropsychiatric disorders.

Comparison of the immune response to vaccination with pigeon circovirus recombinant capsid protein (PiCV rCP) in pigeons uninfected and subclinically infected with PiCV

Infections with immunosuppressive pigeon circovirus (PiCV) pose the most severe health problem to the global pigeon breeding. The vaccination with immunogenic PiCV recombinant capsid protein (PiCV rCP) is a potential tool for disease control. Because of the high prevalence of PiCV asymptomatic infections, the subclinically infected pigeons will be vaccinated in practice. The aim of this study was to answer a question if vaccination of asymptomatic, infected with PiCV pigeons induces a similar immune response to PiCV rCP as in uninfected birds. One hundred and twenty 6-week-old carrier pigeons were divided into 4 groups (2 groups of naturally infected and uninfected with PiCV individuals). Birds from groups V and V1 were vaccinated twice with PiCV rCP mixed with an adjuvant, whereas pigeons from groups C and C1 were immunized with an adjuvant only. The expression of genes encoding IFN-γ, CD4, and CD8 T lymphocyte receptors; the number of anti-PiCV rCP IgY-secreting B cells (SBC) and anti-PiCV rCP IgY were evaluated 2, 21, 39 and 46 days post vaccination (dpv). Study results showed that the expression of CD8 and IFN-γ genes was higher in both groups of infected pigeons than in the uninfected birds, irrespective of vaccination. In the uninfected birds, the expression of these genes was insignificantly higher in the vaccinated pigeons. The anti-PiCV rCP IgY-SBC were detected on 2 and 23 dpv and seroconversion was noted on 23 and 39 dpv in V and V1 groups, respectively. In the light of the results obtained, it could be concluded that pigeon circovirus recombinant capsid protein elicits the immune response in both naturally infected and uninfected pigeons, but its rate varies depending on PiCV infectious status. The infection with PiCV masks the potential cellular immune response to the vaccination with PiCV rCP and leads to the suppression of humoral immunity.

Chlamydiaceae: Diseases in Primary Hosts and Zoonosis

Bacteria of the Chlamydiaceae family are a type of Gram-negative microorganism typified by their obligate intracellular lifestyle. The majority of the members in the Chlamydiaceae family are known pathogenic organisms that primarily infect the host mucosal surfaces in both humans and animals. For instance, Chlamydia trachomatis is a well-known etiological agent for ocular and genital sexually transmitted diseases, while C. pneumoniae has been implicated in community-acquired pneumonia in humans. Other chlamydial species such as C. abortus, C. caviae, C. felis, C. muridarum, C. pecorum, and C. psittaci are important pathogens that are associated with high morbidities in animals. Importantly, some of these animal pathogens have been recognized as zoonotic agents that pose a significant infectious threat to human health through cross-over transmission. The current review provides a succinct recapitulation of the characteristics as well as transmission for the previously established members of the Chlamydiaceae family and a number of other recently described chlamydial organisms.

Prevalence and Genotyping of Chlamydia psittaci from Domestic Waterfowl, Companion Birds, and Wild Birds in Taiwan

Chlamydia psittaci, the causative agent of avian chlamydiosis, an important zoonotic disease, infects a wide range of birds. Infected birds, whether symptomatic or asymptomatic, intermittently shed the agent through respiratory and intestinal routes. Therefore, it is essential to investigate the epizootiology of C. psittaci in poultry, pet birds, and wild birds. In this study, cloacal or fecal swabs collected from domestic waterfowl, psittacine birds, Columbidae, and wild birds were used to determine the prevalence of C. psittaci in Taiwan between 2014 and 2017. The C. psittaci infection rate was as high as 34.2% among domestic waterfowl farms. The waterfowl isolates clustered into two groups based on ompA phylogeny: one group (G1-like) clustered with the Polish G1 strains; the other group (waterfowl-TW) clustered near, but independently from, the classical ABE genotype cluster. Separately, 3.1% of parrot samples tested positive for C. psittaci belonging to genotype A. C. psittaci isolates of genotype B were detected in 10.1% of racing pigeons and other Columbidae. Wild bird samples from a wildlife refuge had a 2.2% prevalence rate; among these, two atypical C. psittaci genotypes were detected in samples from a Malayan night heron (Gorsachius melanolophus) and a Taiwan barbet (Megalaima nuchalis). Taken together, our results revealed that the risk of C. psittaci transmission from domestic waterfowl and Columbidae birds to humans could be underestimated, given the high prevalence rates in these birds. Furthermore, the free-range rearing system of waterfowl in Taiwan may promote C. psittaci transmission between poultry and wild birds. Pet birds and racing pigeons, which are in close contact with people, are also possible sources for cross-species transmission. Further studies are necessary to elucidate the virulence, biological and genetic characteristics, and modes of transmission of Taiwanese C. psittaci isolates to facilitate the prevention and control of C. psittaci infection.

The JAK/STAT3 signaling pathway mediates inhibition of host cell apoptosis by Chlamydia psittaci infection

The JAK-STAT3 signaling pathway is a key regulator of cell growth, motility, migration, invasion and apoptosis in mammalian cells. Infection with intracellular pathogens of the genus Chlamydia can inhibit host cell apoptosis, and here we asked whether the JAK-STAT3 pathway participates in chlamydial anti-apoptotic activity. We found that, compared with uninfected cells, levels of JAK1 and STAT3 mRNA as well as total and phosphorylated JAK1 and STAT3 protein, were significantly increased in C. psittaci-infected HeLa cells. Moreover, the apoptosis rate of infected cells was higher after treatment with the tyrosine kinase inhibitor AG-490 (2-cyano-3-(3, 4-dihydroxyphenyl)-N-(phenylmethyl)-2-propenamide). Immunoblotting of apoptosis-related proteins showed that C. psittaci infection reduces Bax, but increases Bcl-2, protein levels, resulting in reduced activation of caspase-3, caspase-7, caspase-9 and PARP; AG490 attenuates these effects. Together, our data suggest that the JAK/STAT3 signaling pathway facilitates the anti-apoptotic effect of C. psittaci infection by reducing the Bax/Bcl-2 apoptotic switch ratio, and by inhibiting the intracellular activation of key pro-apoptotic enzymes.

Immunogenicity of Pigeon Circovirus Recombinant Capsid Protein in Pigeons

Pigeon circovirus (PiCV) is the most frequently diagnosed virus in pigeons and is thought to be one of the causative factors of a complex disease called the young pigeon disease syndrome (YPDS). The development of a vaccine against this virus could be a strategy for YPDS control. Since laboratory culture of PiCV is impossible, its recombinant capsid protein (rCP) can be considered as a potential antigen candidate in sub-unit vaccines. The aim of this basic research was to evaluate the immune response of pigeons to PiCV rCP. Sixty six-week-old carrier pigeons were divided into two groups (experimental immunized with PiCV rCP mixed with an adjuvant, and control immunized with an adjuvant only), and immunized twice in a 21-day interval. On the day of immunization and on two, 23, 39, and 46 days post first immunization (dpv), samples of blood, spleen, and bursa of Fabricius were collected from six birds from each group to examine anti-PiCV rCP IgY, anti-PiCV rCP IgY-secreting B cells (SBC), IFN-γ gene expression, and percentage of T CD3⁺, CD4⁺, CD8⁺, and B IgM⁺ lymphocytes. The results indicated a correct immune response to PiCV rCP both in humoral and cell-mediated immunity, which was manifested by seroconversion since 23 dpv, by a significantly higher anti-PiCV rCP IgY-SBC number on two and 23 dpv, and significantly higher IFN-γ gene expression since two dpv. There were no significant differences or trends noted between particular T and B lymphocyte subpopulations. To conclude, PiCV rCP may be deemed immunogenic and could be considered as an antigen candidate in sub-unit vaccines against PiCV infections in pigeons.

A novel group A rotavirus associated with acute illness and hepatic necrosis in pigeons (Columba livia), in Australia

Cases of vomiting and diarrhoea were reported in racing pigeons in Western Australia in May, 2016. Morbidity and mortality rates were high. Similar clinical disease was seen in Victoria in December and by early 2017 had been reported in all states except the Northern Territory, in different classes of domestic pigeon–racing, fancy and meat bird–and in a flock of feral pigeons. Autopsy findings were frequently unremarkable; histological examination demonstrated significant hepatic necrosis as the major and consistent lesion, often with minimal inflammatory infiltration. Negative contrast tissue suspension and thin section transmission electron microscopy of liver demonstrated virus particles consistent with a member of the Reoviridae. Inoculation of trypsin-treated Vero, MDBK and MA-104 cell lines resulted in cytopathic changes at two days after infection. Next generation sequencing was undertaken using fresh liver samples and a previously undescribed group A rotavirus (genotype G18P[17]) of avian origin was identified and the virus was isolated in several cell lines. A q-RT-PCR assay was developed and used to screen a wider range of samples, including recovered birds. Episodes of disease have continued to occur and to reoccur in previously recovered lofts, with variable virulence reported. This is the first report of a rotavirus associated with hepatic necrosis in any avian species.

Recombinant Goose Circoviruses Circulating in Domesticated and Wild Geese in Poland

Circoviruses are circular single-stranded DNA (ssDNA) viruses that infect a variety of animals, both domestic and wild. Circovirus infection in birds is associated with immunosuppression and this in turn predisposes the infected animals to secondary infections that can lead to mortality. Farmed geese (Anser anser) in many parts of the world are infected with circoviruses. The majority of the current genomic information for goose circoviruses (GoCVs) (n = 40) are from birds sampled in China and Taiwan, and only two genome sequences are available from Europe (Germany and Poland). In this study, we sampled 23 wild and 19 domestic geese from the Gopło Lake area in Poland. We determined the genomes of GoCV from 21 geese; 14 domestic Greylag geese (Anser anser), three wild Greylag geese (A. anser), three bean geese (A. fabalis), and one white fronted goose (A. albifrons). These genomes share 83–95% nucleotide pairwise identities with previously identified GoCV genomes, most are recombinants with exchanged fragment sizes up to 50% of the genome. Higher diversity levels can be seen within the genomes from domestic geese compared with those from wild geese. In the GoCV capsid protein (cp) and replication associated protein (rep) gene sequences we found that episodic positive selection appears to largely mirror those of beak and feather disease virus and pigeon circovirus. Analysis of the secondary structure of the ssDNA genome revealed a conserved stem-loop structure with the G-C rich stem having a high degree of negative selection on these nucleotides.

The epidemiology, molecular characterization and clinical pathology of circovirus infections in pigeons - current knowledge

The first cases of circovirus infections in pigeons were documented less than 25 years ago. Since then, circovirus infections have been reported on nearly all continents. The specificity of pigeon breeding defies biosecurity principles, which could be the reason for the high prevalence of PiCV infections. PiCV infections in pigeons lead to atrophy of immune system organs and lymphocyte apoptosis. Infected birds could be more susceptible to infections of the respiratory and digestive tract. PiCV has been associated with the young pigeon disease syndrome (YPDS). PiCVs are characterized by high levels of genetic diversity due to frequent point mutations, recombination processes in the PiCV genome and positive selection. Genetic recombinations and positive selection play the key role in the evolution of PiCV. A protocol for culturing PiCV under laboratory conditions has not yet been developed, and traditional vaccines against the infection are not available. Recombinant capsid proteins for detecting anti-PiCV antibodies have been obtained, and these antigens can be used in the production of diagnostic tests and subunit vaccines against PiCV infections. However, YPDS has complex etiology, and it remains unknown whether immunization against PiCV alone will contribute to effective control of YPDS.

Persistence of Chlamydia psittaci in Various Temperatures and Times

Chlamydia psittaci, an obligate intracellular gram-negative bacteria, causes an important zoonotic disease in humans, namely, psittacosis. The objective of this study was to determine the persistent viability of C. psittaci at various temperature conditions. The cloacal swab samples were collected from feral and racing pigeons to find a C. psittaci field strain. The bacterial isolation showed that 1.3% of feral pigeons were PCR positive, while all samples of racing pigeons were PCR negative. Also, bacterial characterization suggested that it belonged to genotype B, which had bacterial titers 3.2 and 3.89 log 50% lethal dose/ml, respectively. A bacterial persistence test was performed, and the results showed that C. psittaci could survive at 56 C for up to 72 hr. In conclusion, C. psittaci could be found in feral pigeons in central Thailand. The bacteria can survive in equatorial temperature areas. This study was the first to report that C. psittaci could survive and has infectivity at 56 C for 72 hr. Therefore, awareness of C. psittaci infection in humans is necessary and should be a public health concern.

Deficiency of LIGHT signaling pathway exacerbates Chlamydia psittaci respiratory tract infection in mice

LIGHT, a costimulatory member of the immunoglobulin superfamily (Ig SF), can greatly impact T cell activation. The role of the LIGHT signaling pathway in chlamydial infection was evaluated in mice following respiratory tract infection with Chlamydia psittaci. Compared with wild type (WT) mice, LIGHT knockout (KO) mice showed significant reduction of body weight, much lower survival rate, higher bacterial burden, prolonged infection time courses and more severe pathological changes in lung tissue. The mRNA levels of IFN-γ, TNF-α, IL-17 and IL-12 in the lung tissue of LIGHT KO mice were significantly lower than those in WT mice. While there was no obvious difference in the percentages of CD4⁺ and CD8⁺ T cells in the spleens of the two groups of mice, there was a markedly elevated percentage of CD4⁺ CD25⁺ FoxP3⁺ Treg cells in LIGHT KO mice. Together, these results demonstrate that the LIGHT signaling pathway is not only required for inflammatory cytokine production as part of the host response to chlamydial infection, but also influences the differentiation of CD4⁺ CD25⁺ FoxP3⁺ Treg cells, both of which may be essential for control of C. psittaci respiratory tract infection.

Application of pigeon circovirus recombinant capsid protein for detecting anti-PiCV antibodies in the sera of asymptomatic domestic pigeons and the potential use of a combination of serological and molecular tests for controlling circovirus infections in pigeon breeding flocks

The aim of this study was to evaluate the serologic status of domestic pigeons not infected and asymptomatically infected with the pigeon circovirus (PiCV) with the use of an enzyme-linked assay based on PiCV recombinant capsid protein as a plate antigen. Recombinant PiCV capsid protein was produced by transforming E. coli BL21 (DE3) Rosetta colonies with expression plasmids.Blood samples and cloacal swabs were collected from 171 asymptomatic pigeons. The birds were divided into two groups (infected and not infected with PiCV) based on the results of Sybr Green real time PCR screening for the presence of PiCV genetic material. Approximately 70% of the pigeons tested positive for anti-PiCV antibodies regardless of their infection status. Antibody levels, the coefficient of variation and standard deviation were significantly higher in the group of infected pigeons.The results indicate that ELISA is a highly useful test that complements molecular methods in evaluations of PiCV infection status in domestic pigeons. The spread of pigeon circovirus infections can be controlled by keeping breeding flocks free of PiCV, which can only be achieved by subjecting birds to real time PCR and serological tests.

Oral Uptake of Chlamydia psittaci by Ducklings Results in Systemic Dissemination

Enteric infections caused by Chlamydia (C.) psittaci are frequent in ducks, but mostly remain subclinical under field conditions. To emulate natural infection, we investigated the pathogenic potential of a C. psittaci field strain in orally inoculated 4-day-old ducklings. Three different challenge doses were tested and seven contact animals were also mock-inoculated with buffer in each group. Over the course of ten days, the birds were monitored for clinical symptoms and chlamydial dissemination before final examination of tissues using histopathology and immunohistochemistry. While the challenge strain disseminated systemically to all internal organs, mild signs of diarrhea were confined to ducklings inoculated with the highest dose (4.3 x 10⁸ IFU/mL, Group 1). No other clinical symptoms or histopathological lesions were seen. The chlamydial load in internal organs as measured by PCR depended on the challenge dose and was unevenly distributed, i.e. high loads in spleen, liver, and distal small and large intestinal tract (ileum, cecum and rectum) vs. ten times lower values in lungs and proximal small intestinal tract (duodenum and jejunum). Notably, the C. psittaci infection of contact birds became evident on day 10 post-infection, with bacterial loads comparable to those of experimentally-infected animals, thus suggesting rapid bird-to-bird transmission of the challenge strain.

Avian Chlamydiosis Zoonotic Disease

This review presents recent data about avian chlamydiosis. Chlamydia psittaci has been considered to be the main causative agent of chlamydiosis in birds; however, two new Chlamydia species have been detected recently-C. gallinacea in breeding birds and C. avium in wild birds. We discuss the zoonotic potential of avian Chlamydia species.

A new duck circovirus sequence, detected in velvet scoter (Melanitta fusca) supports great diversity among this species of virus

BACKGROUND

The aim of this study was to investigate the presence of circoviruses in wild bird populations, in Poland. Circoviruses possess immuno-suppressive properties and might interfere with the health of wild birds.

METHOD

83 birds, which belonged to 23 species, were tested with broad-range, nested PCR. The obtained PCR products were sequenced and new primers designed, to analyse the full-length, viral genome. A phylogenetic analysis was conducted, to find any relationship to known circoviruses.

RESULTS

The circovirus DNA sequence was found in 4 birds. All samples originated from the velvet scoter (Melanitta fusca) a marine duck from the Merginae sub-family. Birds which tested positive for the circovirus were found dead in fishing nets, off the Baltic coast. During post-mortem examination, carcasses of two of the scoters showed only light emaciation, while the two other birds appeared healthy. The obtained, full-length, circovirus sequence revealed 1,988 nucleotides and the presence of typical features (i.e. Cap, Rep and ORF3). Nucleotide similarity to other duck circoviruses was 84 to 86 %. Phylogenetic analysis of the complete genome and cap gene, indicated that the new circovirus is related to known duck circoviruses, especially to sub-types sometimes referred to as duck circovirus genotype 1, but not genotype 2.

CONCLUSIONS

In this study, we have reported a new duck circovirus sequence detected in the velvet scoter, a species of marine duck. Sequence comparison and phylogenetic analysis of the new virus sequence support previous reports that duck circovirus (DuCV) is a species with a high degree of diversity. The viral sequence obtained from the velvet scoter suggests that DuCV may infect birds from the Anatinae sub-family. More studies are needed to prove if the velvet scoter and other marine ducks act as a reservoir for DuCV.

Seroprevalence and Risk Factors of Chlamydia Infection in Domestic Rabbits (Oryctolagus cuniculus) in China

Chlamydia spp. are obligate intracellular bacteria distributed all over the world, known to cause various forms of diseases in animals and humans. In the present study, a serological survey was conducted to detect the seroprevalence and risk factors associated with rabbit chlamydiosis in northeast China, including Liaoning province, Jilin province, Heilongjiang province, and Inner Mongolia Autonomous Region. Antibodies to Chlamydia were determined by indirect hemagglutination assay (IHA). The overall seroprevalence was estimated at 17.88% in total of 800 blood samples. The Chlamydia seroprevalence varied in domestic rabbits from different factors, and genders of domestic rabbits were considered as major risk factors associated with Chlamydia infection. Our study revealed a widespread and high prevalence of Chlamydia infection in domestic rabbits in northeast China, with higher exposure risk in female domestic rabbits. These findings suggested the potential importance of domestic rabbits in the transmission of zoonotic Chlamydia infection, and thus Chlamydia should be taken into consideration in diagnosing rabbit diseases. To our knowledge, there is no report of Chlamydia infection in domestic rabbits in China and the results extend the host range for Chlamydia, which has important implications for public health and the local economy.