Metagenomic next-generation sequencing in the family outbreak of psittacosis: the first reported family outbreak of psittacosis in China under COVID-19.

Chlamydia psittaci infection in humans, also known as psittacosis, is usually believed to be an uncommon disease which mainly presents as community-acquired pneumonia (CAP). It is usually sporadic, but outbreaks of infection may occasionally occur. In outbreaks, diagnosis and investigations were usually hampered by the non-specificity of laboratory testing methods to identify C. psittaci. In this study, we use metagenomic next-generation sequencing (mNGS) in the diagnosis of a family outbreak of psittacosis under COVID-19. Three members of an extended family of 6 persons developed psittacosis with pneumonia and hepatic involvement with common symptoms of fever and weakness. Two newly purchased pet parrots, which had died successively, were probably the primary source of infection. Imagings show lung consolidations and infiltrates, which are difficult to be differentiated from CAP caused by other common pathogens. mNGS rapidly identified the infecting agent as C. psittaci within 48 h. The results of this work suggest that there are not characteristic clinical manifestations and imagings of psittacosis pneumonia which can differentiate from CAP caused by other pathogens. The use of mNGS can improve accuracy and reduce the delay in the diagnosis of psittacosis especially during the outbreak, which can shorten the course of the disease control. Family outbreak under COVID-19 may be related to the familial aggregation due to the epidemic. To our knowledge, this is the first reported family outbreak of psittacosis in China, and the first reported psittacosis outbreak identified by the method of mNGS in the world.

Recent history of psittacosis in Australia: expanding our understanding of the epidemiology of this important globally distributed zoonotic disease.

Psittacosis is a human systemic disease caused by infection with Chlamydia psittaci. Shortly after reports emerged of a global pandemic associated with contact with imported parrots, Australian researchers including Macfarlane Burnet and others demonstrated that C. psittaci was widespread in Australian parrots. Australian cases over the last two decades have revealed that environmental exposure and contact with infected horses are also risk factors in an increasingly complicated epidemiological picture for this zoonotic disease.

Laboratory methods for case finding in human psittacosis outbreaks: a systematic review.

BACKGROUND: Psittacosis outbreak investigations require rapid identification of cases in order to trace possible sources and perform public health risk assessments. In recent outbreaks in the Netherlands, such investigations were hampered by the non-specificity of laboratory testing methods to identify human Chlamydia psittaci infections. METHOD: A systematic search of PubMed and Scopus databases of literature published between 01 January, 1986 and 03 July, 2017 was done to find best practices of laboratory-testing methods used in psittacosis outbreaks of two or more human cases. Reference lists of included articles were hand searched to identify additional articles. RESULTS: Thirty-seven eligible articles were identified, describing 44 human psittacosis outbreaks in 12 countries. Laboratory tests performed were PCR (with various targets), serologic tests (complement binding reactions, ELISA's, immunofluorescence tests and immuno-peroxidase tests) and culture, in various combinations. The literature provided no 'gold standard' laboratory testing strategy to identify recent human C. psittaci infections. In most psittacosis outbreaks, for a considerable number of cases (or tested individuals in an exposed cohort), C. psittaci infection could not be confirmed, nor excluded as causative pathogen. None of the testing strategies was found to be suitable for (nearly) full case finding. CONCLUSION: PCR enables rapid identification of human psittacosis patients and helps source finding by genotyping but has the disadvantage that sensitivity is high only in the acute phase. In outbreak situations, there is often a time delay and therefore, there is a need for new serologic testing methods next to PCR, with good specificity and sensitivity. Moreover, serum is easier to collect than the preferred diagnostic materials for PCR. A serologic test that can reliably confirm infection status without the necessity of convalescent serum sampling would enhance case finding, source tracing, identification of risk factors and assessment of burden of disease in various settings.

Wild and domestic bird faeces likely source of psittacosis transmission-A case-control study in Sweden, 2014-2016.

Psittacosis is a zoonotic disease transmitted by birds. In Sweden, where psittacosis is notifiable, an average of eight cases per year were reported between 2002 and 2012. In 2013, an unusual increase in cases in southern Sweden was associated with exposure to wild birds. To further explore specific risk factors connected to wild birds and identify other risk factors for sporadic psittacosis, we conducted a case-control study including all domestically acquired psittacosis cases reported between December 2014 and April 2016 in Sweden. Cases were age-, sex- and geo-matched to controls randomly selected from a population register. Cases and controls completed a questionnaire investigating detailed exposures to wild and domestic birds. We compared cases to controls, calculating adjusted matched odds ratios (amOR) using conditional logistic regression. Thirty-one cases were notified: all cases lived in southern Sweden and 26 were ill during winter season. Two risk factors were independently associated with psittacosis infection: cleaning a wild bird feeder (amOR = 18.95; 95% CI: 2.11-170.03) and owning domestic birds (amOR = 5.55, 95% CI: 1.16-26.61). Our results suggest that exposure to bird faeces, for example when cleaning a wild bird feeder, was the main route of transmission. Following this study, the Public Health Agency of Sweden published recommendations on good practices when cleaning surfaces contaminated with bird faeces and recommended use of bird feeders with a design limiting faeces accumulation.

Chlamydiosis in farmed chickens in Slovakia and zoonotic risk for humans.

INTRODUCTION: Chlamydia psittaci is an obligate intracellular Gram-negative bacterium causing respiratory disease (chlamydiosis) or asymptomatic carriage in poultry. In humans, it is a zoonotic agent of ornithosis/psittacosis. Due to low awareness of the disease and variable clinical presentation, psittacosis is often remains unrecognised as such by general practitioners. Zoonotic transfer occurs through inhalation of contaminated aerosols, and originates from feathers, faecal material and respiratory tract exudates. OBJECTIVE: The aim of this study was to investigate chickens for the presence of Chlamydia sp. from pharyngeal and cloacal swabs and review the zoonotic risk for humans. MATERIAL AND METHODS: 138 clinically healthy chickens from farms in Slovakia were examined for the presence of Chlamydia sp. The age of the chickens was 6 months. Two different samples were used - pharyngeal swabs and cloacal swabs. Each sample was examined by the molecular PCR method, and in the case of a positive result the identity of the obtained sequences was examined by a BLAST search. RESULTS: Of the total number of 276 examined samples from 138 chickens, 19 (6.9%) showed positivity for C. psittaci infection, 12 (8.7%) which were positive from pharyngeal swabs and 7 (5.1%) from cloacal swabs. None of the chickens were positive in both samples. Phylogenetic examination of the 19 isolates identified in the study, based on the 23S rRNA gene sequence, revealed that the isolates obtained were identical with C. psittaci, and genetically very close to genotypes B and genotype E. CONCLUSIONS: C. psittaci infections are apparently emerging in chickens. Chicken-processing plant employees should be considered a risk group for human psittacosis. There is a need for higher awareness and for efficient risk assessment and management.

Compendium of Measures to Control Chlamydia psittaci Infection Among Humans (Psittacosis) and Pet Birds (Avian Chlamydiosis), 2017.

Psittacosis, also known as parrot fever and ornithosis, is a bacterial infection that can cause severe pneumonia and other serious health problems in humans. It is caused by Chlamydia psittaci. Reclassification of the order Chlamydiales in 1999 into 2 genera (Chlamydia and Chlamydophila) was not wholly accepted or adopted. This resulted in a reversion to the single, original genus Chlamydia, which now encompasses all 9 species including Chlamydia psittaci. During 2003-2014, 112 human cases of psittacosis were reported to the Centers for Disease Control and Prevention through the Nationally Notifiable Diseases Surveillance System. While many types of birds can be infected by C psittaci, in general, the literature suggests that human cases can most often occur after exposure to infected parrot-type birds kept as pets, especially cockatiels, parakeets, and conures. In birds, C psittaci infection is referred to as avian chlamydiosis. Infected birds shed the bacteria through feces and nasal discharges, and humans become infected from exposure to these materials. This compendium provides information about psittacosis and avian chlamydiosis to public health officials, physicians, veterinarians, the pet bird industry, and others concerned with controlling these diseases and protecting public health. The recommendations in this compendium provide standardized procedures to control C psittaci infections. This document will be reviewed and revised as necessary, and the most current version replaces all previous versions. This document was last revised in 2010. Major changes in this version include a recommendation for a shorter treatment time for birds with avian chlamydiosis, additional information about diagnostic testing, including genotyping, clearer language associated with personal protective equipment recommended for those caring for confirmed or exposed birds, and incorporating a grading scale with recommendations generally based on the United States Preventive Services Task Force's methods.

First Experimental Evidence for the Transmission of Chlamydia psittaci in Poultry through Eggshell Penetration.

Eggshell penetration by pathogens is considered a potential route for their transmission in poultry flocks. Additionally, in case of zoonotic pathogens, contact with infected eggs or their consumption can result in human infection. Chlamydia psittaci is a zoonotic bacterium that causes a respiratory disease in poultry and humans. In this study, we provide an experimental evidence for eggshell penetration by C. psittaci. Additionally, we show that after eggshell penetration, C. psittaci could eventually infect the growing embryo. Our findings portend the potential of horizontal trans-shell transmission as a possible route for the spread of C. psittaci infection in poultry flocks. Considering that horizontal transmission of pathogens via eggs mainly occurs in hatcheries and hatching cabinets, we suggest the latter as critical control points in the transmission of C. psittaci to hatching chicks and broilers, as well as to the hatchery workers and consumers of table eggs.

Australian human and parrot Chlamydia psittaci strains cluster within the highly virulent 6BC clade of this important zoonotic pathogen.

Chlamydia psittaci is an avian pathogen and zoonotic agent of atypical pneumonia. The most pathogenic C. psittaci strains cluster into the 6BC clade, predicted to have recently emerged globally. Exposure to infected parrots is a risk factor with limited evidence also of an indirect exposure risk. Genome sequencing was performed on six Australian human and a single avian C. psittaci strain isolated over a 9 year period. Only one of the five human patients had explicit psittacine contact. Genomics analyses revealed that the Australian C. psittaci strains are remarkably similar, clustering tightly within the C. psittaci 6BC clade suggested to have been disseminated by South America parrot importation. Molecular clock analysis using the newly sequenced C. psittaci genomes predicted the emergence of the 6BC clade occurring approximately 2,000 years ago. These findings reveal the potential for an Australian natural reservoir of C. psittaci 6BC strains. These strains can also be isolated from seriously ill patients without explicit psittacine contact. The apparent recent and global spread of C. psittaci 6BC strains raises important questions over how this happened. Further studies may reveal whether the dissemination of this important zoonotic pathogen is linked to Australian parrot importation rather than parrots from elsewhere.

Chlamydia-host cell interaction not only from a bird's eye view: some lessons from Chlamydia psittaci.

Chlamydia psittaci causes psittacosis/ornithosis in birds and is an economically important pathogen for poultry farming. It also infects nonavian domestic animals as well as rodents, and is a zoonotic human pathogen responsible for atypical pneumonia. The bacterium efficiently disseminates in host organisms causing pulmonary and systemic disease. Its rapid entry, fast replication cycle, and tight control of intracellular transport routes contribute to the host-to-host transmission and efficient growth observed with C. psittaci. Recent studies have revealed that the pathogen copes better than other chlamydial strains with proinflammatory effectors produced during the early immune reaction of infected hosts. These features likely contribute to successful infections and might explain the potent adaptation and evasion characteristics of the agent. Current findings on cell-autonomous, innate, and adaptive defenses against C. psittaci provide novel insights into the concerted immune mechanisms involved in the clearance of the pathogen. Further in-depth studies on C. psittaci and other related agents in cellular as well as animal models are needed to develop more efficient antichlamydial therapies and vaccination strategies.

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.

Multiple human-to-human transmission from a severe case of psittacosis, Sweden, January-February 2013.

Proven transmission of Chlamydia psittaci between humans has been described on only one occasion previously. We describe an outbreak which occurred in Sweden in early 2013, where the epidemiological and serological investigation suggests that one patient, severely ill with psittacosis after exposure to wild bird droppings, transmitted the disease to ten others: Two family members, one hospital roommate and seven hospital caregivers. Three cases also provided respiratory samples that could be analysed by PCR. All the obtained C. psittaci sequences were indistinguishable and clustered within genotype A. The finding has implications for the management of severely ill patients with atypical pneumonia, because these patients may be more contagious than was previously thought. In order to prevent nosocomial person-to-person transmission of C. psittaci, stricter hygiene measures may need to be applied.

Atypical pneumonia.

PURPOSE OF REVIEW: We present the key advances in the infections that clinicians conventionally associate with atypical pneumonia: legionellosis, Mycoplasma pneumonia, Chlamydophila species pneumonia and Q fever. RECENT FINDINGS: There have been significant developments in molecular diagnosis to include Mycoplasma pneumoniae and Chlamydophila pneumoniae in multiplex PCR of respiratory specimens. There are diagnostic challenges in distinguishing carriage from infection, which is recognized in C. pneumoniae and now also evident in M. pneumoniae. Macrolide-resistant M. pneumoniae has emerged in Asia. There are new antimicrobials on the horizon in the ketolide class with activity against typical and atypical pathogens and useful empirical agents. SUMMARY: There are few advances in our knowledge of the epidemiology of atypical pathogens or the effectiveness of antimicrobial therapy--empirical or pathogen specific. However, if molecular testing becomes widely implemented, there will be an increased understanding of the epidemiology and presentation of atypical pneumonia and a shift to more targeted antimicrobial therapy.

Emerging Chlamydia psittaci infections in chickens and examination of transmission to humans.

Chlamydia psittaci and atypical Chlamydiaceae infections are (re)-emerging in chickens. We therefore examined the prevalence of C. psittaci, atypical Chlamydiaceae and their zoonotic transmission on 19 Belgian chicken farms. Atypical Chlamydiaceae were not detected in chickens but 18 out of 19 farms were positive for C. psittaci by culture and PCR. C. psittaci ompA genotypes A and D were discovered. None of the examined humans (n = 31) was infected with atypical Chlamydiaceae, but 29 (93.5%) of them were positive for C. psittaci by culture and PCR. Genotypes A, D and a mixed infection with genotypes C and D were found. Humans (n = 2) working at the C. psittaci-negative farm never had respiratory complaints, while 25 out of 29 positive farmers (86.2%) reported yearly medical complaints potentially related to psittacosis. Four of them currently experienced respiratory disease and one of them was being treated with antibiotics. Four farmers (12.5%) mentioned that they had pneumonia after starting to keep chickens. Occupational physicians should be aware of emerging Chlamydiaceae infections in chickens.

Zoonotic infection with Chlamydia psittaci at an avian refuge centre.

This paper reports the zoonotic transmission of Chlamydia psittaci at a wild bird refuge centre resulting in the infection of members of the staff. Pharyngeal swabs were culture positive in 26% (11/42) of the sampled birds, and molecular characterisation of isolates revealed genotypes A, B, D, and E/B. The finding reflects multiple distinct infections and highlights the endemic nature of this pathogen in avian wildlife. Two clinically normal birds being prepared for release were found to be excreting C. psittaci genotype B or E/B and viable genotype B was detected in pharyngeal swabs from 30% (3/10) of the human workers tested. The findings suggest there should be enhanced surveillance and control measures in place in bird rehabilitation centres in order to minimise the risk of both zoonoses and of re-introduction of infection back into wildlife populations.

Epidemiological investigations on the possible risk of distribution of zoonotic bacteria through apparently healthy homing pigeons.

Clinically healthy homing pigeons may serve as an unnoticed reservoir for zoonotic bacteria. Hence, healthy pigeons from 172 different racing pigeon lofts were examined for Salmonella serovars, Campylobacter spp. and Chlamydophila (Chlamydia) psittaci. Two samplings were performed during the racing season in summer (1242 adult and 1164 juvenile pigeons) and two during winter (1074 adult pigeons). Each sampling was accompanied by a questionnaire to identify risk factors for positive lofts. Between 0.9 and 3.7%, 13.1 and 23.7%, and 12.8 and 42.6% of lofts were tested positive by cultural methods or polymerase chain reaction for Salmonella Typhimurium var. Copenhagen, Campylobacter jejuni and C. psittaci, respectively. The detection rate of C. psittaci was twice as high in samples from juvenile pigeons (29.1%) compared with samples from adult pigeons (15.0%, P <0.001). No other influence of age or season was detected. For the first time, pigeon-derived C. jejuni isolates (n=15) were characterized for their ability to invade human enterocytes in vitro. All isolates were invasive with an invasion index between 0.4 and 34.1 (human reference strain: average 11.3). Of 50 C. jejuni isolates tested for antimicrobial susceptibility, 46.0% were resistant to ciprofloxacin. All isolates were sensitive to erythromycin and tetracycline. The analysis of risk factors in association with the infection status of lofts for C. jejuni and C. psittaci suggested that biosecurity measures reduce the risk of infection. This study indicated a zoonotic potential of pigeon-derived C. jejuni. However, clinically healthy homing pigeons pose only a low risk for transmission of the investigated pathogens to humans.

Unusual increase of psittacosis in southern Sweden linked to wild bird exposure, January to April 2013.

Free-living wild birds worldwide act as reservoir for Chlamydia psittaci, but the risk of transmission to humans through contact with wild birds has not been widely documented. From 12 January to April 9 2013, a total of 25 cases of psittacosis were detected in southern Sweden, about a threefold increase compared with the mean of the previous 10 years. A matched case-control study investigating both domestic and wild bird exposure showed that cases were more likely than controls to have cleaned wild bird feeders or been exposed to wild bird droppings in other ways (OR: 10.1; 95% CI: 2.1-47.9). We recommend precautionary measures such as wetting bird feeders before cleaning them, to reduce the risk of transmission of C. psittaci when in contact with bird droppings. Furthermore, C. psittaci should be considered for inclusion in laboratory diagnostic routines when analysing samples from patients with atypical pneumonia, since our findings suggest that psittacosis is underdiagnosed.

Infection, disease, and transmission dynamics in calves after experimental and natural challenge with a Bovine Chlamydia psittaci isolate.

Chlamydia (C.) psittaci is the causative agent of psittacosis, a zoonotic disease in birds and man. In addition, C. psittaci has been repeatedly found in domestic animals and is, at least in calves, also able to induce respiratory disease. Knowledge about transmission routes in cattle herds is still deficient, and nothing is known about differences in host response after either experimental or natural exposure to C. psittaci. Therefore, our recently developed respiratory infection model was exploited to evaluate (i) the presence of the pathogen in blood, excretions and air, (ii) the possibility of transmission and (iii) clinical symptoms, acute phase and immune response until 5 weeks after exposure. In this prospective study, intrabronchial inoculation of 10(8) inclusion-forming units of C. psittaci (n = 21 calves) led to reproducible acute respiratory illness (of approximately one week), accompanied by a systemic inflammatory reaction with an innate immune response dominated by neutrophils. Excretion and/or exhalation of the pathogen was sufficient to transmit the infection to naïve sentinel calves (n = 3) co-housed with the infected animals. Sentinel calves developed mild to subclinical infections only. Notably, excretion of the pathogen, predominantly via feces, occurred more frequently in animals naturally exposed to C. psittaci (i.e. sentinels) as compared to experimentally-inoculated calves. The humoral immune response was generally weak, and did not emerge regularly following experimental infection; however, it was largely absent after naturally acquired infection.