Methods of detection of Chlamydia psittaci in domesticated and wild birds

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.

A new species of Chlamydia isolated from Siamese crocodiles (Crocodylus siamensis)

Chlamydia is a known pathogen in both saltwater and freshwater crocodiles. However, the exact species/strain has not been clearly identified. In this study, we successfully cultivated Siamese crocodile Chlamydia in McCoy cells at a temperature of 30°C. Electron microscopy; phylogeny based on nine conserved taxonomically informative markers, on ompA, or on seven housekeeping genes; and whole-genome sequencing and analysis of the isolate confirmed the identity of the isolate as a new member of the genus Chlamydia, a new species that we name Chlamydia crocodili.

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

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.

Chlamydia psittaci in fulmars on the Faroe Islands: a causative link to South American psittacines eight decades after a severe epidemic

A psittacosis epidemic linked to fulmar hunting occurred on the Faroe Islands in the 1930s. This study investigates a plausible explanation to the 20% human mortality in this outbreak. Phylogenetic analysis showed that Chlamydia psittaci isolated from fulmars were closely related to the highly virulent 6BC strains from psittacines and are compatible with an acquisition by fulmars of an ancestor of the 6BC clade in the 1930s. This supports the hypothesis that the outbreak on the Faroe Islands started after naïve fulmars acquired C. psittaci from infected dead parrots thrown overboard when shipped to Europe in the 1930s.

Detection of Chlamydia psittaci Genotypes Among Birds in Northeast Iran

We determined the prevalence of Chlamydia psittaci genotypes in asymptomatic and symptomatic birds in northeast Iran. Samples were collected from 11 species of Psittaciformes and 1 species of Columbiformes from 2015 to 2016. Choanal cleft and cloacal swab samples, fresh fecal samples, and/or tissue samples of 70 symptomatic and 130 asymptomatic birds were collected and tested by molecular detection (nested polymerase chain reaction [PCR] testing specific for C psittaci). Results showed C psittaci was detected in 37 (18.5%) of 200 birds (18/37 symptomatic and 19/37 asymptomatic birds) by nested PCR assay. Of the PCR-positive samples, 14 products were positive for oligonucleotide sets CTU/CTL by a second PCR assay and genotyped by outer membrane protein A (ompA) gene sequencing. Of the 10 samples positive for genotype A (cockatiels [Nymphicus hollandicus, n = 5], ring-necked parakeet [Psittacula krameri, n = 2], African gray parrot [Psittacus erithacus, n = 3]), 6 samples were from asymptomatic and 4 from symptomatic birds. Genotype B was observed in 3 samples from symptomatic birds (P krameri [n = 2], pigeon [Columba livia, n = 1]), and provisional genotype I was detected in one symptomatic cockatiel. These findings revealed the importance of monitoring imported asymptomatic birds in developing countries, especially the Middle East, where there is no systematic monitoring. To the best of our knowledge, this is the first report regarding the detection of C psittaci provisional genotype I in cockatiels.

Risk factors associated with Chlamydia psittaci infection in psittacine birds

Chlamydia psittaci is the aetiological agent of chlamydiosis in birds, especially Psittaciformes. The objective of the present study was to detect C. psittaci by means of semi-nested PCR among psittacine birds sold at pet markets and kept as pet birds in Salvador, Bahia, Brazil. Questionnaires were used to identify risk factors involved in the epidemiology of the disease. In addition, the management of birds and cages was observed at each location studied. The frequency of C. psittaci infection was 10.6 % (33/311) in the psittacine birds studied. Birds kept in households were less frequently positive (3.4 %; 5/148) than those at pet markets (17.2 %; 28/163). Among the several factors analysed in the epidemiology of the disease, only population density (P = 0.001) and cage hygiene (P = 0.041) in birds at pet markets were significantly associated with C. psittaci infection. These results demonstrate the presence of C. psittaci infection in Psittaciformes kept as pets and held at pet markets in Salvador, Bahia, showing that this micro-organism is a public health concern. Control measures should be encouraged to prevent the spread of the agent among birds, as well as among employees and customers.

Antimicrobial susceptibility and molecular typing of multiple Chlamydiaceae species isolated from genital infection of women in Egypt

This study investigated the existence of vaginal Chlamydia infection and the prevalence of the disease in symptomatic gynecologically diseased women in Egypt. In addition, the antibiotics penicillin, tetracycline, and erythromycin were evaluated for their in vitro antichlamydial activity of the isolated strains. Vaginal swabs (n=160) were collected from females gynecologically diseased using cotton swabs. Samples were tested for Chlamydia by Vero cells tissue culture, chicken embryo, Gimenez staining, direct fluorescein-conjugated monoclonal antibody staining, and immunoperoxidase. Polymerase chain reaction (PCR) analyses conducted for the presence of chlamydial DNA was used to detect its specific DNA by the omp2 gene. PCR analyses conducted for the presence of chlamydial DNA revealed that 112/160 (70%) were positive for Chlamydiaceae. The specific DNA defined by the omp2 gene identified them as Chlamydia trachomatis (17/112, 15.2%), Chlamydophila psittaci (56/112, 50.0%), and Chlamydophila abortus (40/112, 35.7%). The antibiotics penicillin, tetracycline, and erythromycin at different concentrations were effective in inactivating the viability of Chlamydiaceae isolates.

Development of PCR/dot blot assay for specific detection and differentiation of taeniid cestode eggs in canids

We report the development of a colourimetric PCR/dot blot assay targeting the mitochondrial gene NADH dehydrogenase subunit 1 (nad1) for differential diagnosis of taeniid eggs. Partial sequences of the cestode nad1 gene were aligned and new primers were designed based on conserved regions. Species-specific oligonucleotide probes (S-SONP) for canine taeniid cestodes were then designed manually based on the variable region between the conserved primers. Specifically, S-SONP were designed for the Taenia crassiceps, T. hydatigena, T. multiceps, T. ovis, T. taeniaeformis, Echinococcus granulosus (genotype 1), E. multilocularis and E. vogeli. Each probe showed high specificity as no cross-hybridisation with any amplified nad1 fragment was observed. We evaluated the assay using 49 taeniid egg-positive samples collected from dogs in Zambia. DNA from 5 to 10 eggs was extracted in each sample. Using the PCR/dot blot assay, the probes successfully detected PCR products from T. hydatigena in 42 samples, T. multiceps in 3 samples, and both species (mixed infection) in the remaining 4 samples. The results indicate that the PCR/dot blot assay is a reliable alternative for differential diagnosis of taeniid eggs in faecal samples.

A novel Chlamydiaceae-like bacterium found in faecal specimens from sea birds from the Bering Sea

The family Chlamydiaceae contains several bacterial pathogens of important human and veterinary medical concern, such as Chlamydia trachomatis and Chlamydophila psittaci. Within the order Chlamydiales there are also an increasing number of chlamydia-like bacteria whose biodiversity, host range and environmental spread seem to have been largely underestimated, and which are currently being investigated for their potential medical relevance. In this study we present 16S rRNA, rnpB and ompA gene sequence data congruently indicating a novel chlamydia-like bacterium found in faecal specimens from opportunistic fish-eating sea birds, belonging to the Laridae and Alcidae families, from the Bering Sea. This novel bacterium appears to be closer to the Chlamydiaceae than other chlamydia-like bacteria and is most likely a novel genus within the Chlamydiaceae family.

Chlamydophila psittaci DNA Detection in the Faeces of Cage Birds

In this study, we investigated the shedding of Chlamydophila psittaci in faecal samples from cage birds using PCR testing. A total of 47 faeces samples were collected from four different aviaries. Main symptoms determined after clinical investigation and owner histories of the birds showed that the birds had respiratory system problems changing from mild to severe. They also showed conjunctivitis, diarrhoea or no symptoms at all. DNA extractions from faeces were performed with the QIAamp DNA Stool Mini Kit. Following PCR with Cp. psittaci specific primers, 43 (91.5%) samples were determined to harbour-specific DNA. Only one bird from each aviary was found to be negative by PCR. As all the samples from birds showing clinical signs were PCR positive, these signs could be correlated to psittacosis in these birds. Cp. psittaci shedding in faeces was detected in all the aviaries. After restriction analysis of PCR amplicons with AluI enzyme, all the isolates showed the same RFLP (Restriction Fragment Length Polymorphism) patterns with the control Cp. psittaci DNA. PCR following QIAamp DNA stool mini kit extraction of faecal samples was found to be a rapid, specific, sensitive, reproducible test, which did not need additional nested PCR of samples.

A Comparative Study of Detecting Chlamydophila psittaci in Pet Birds Using Isolation in Embryonated Egg and Polymerase Chain Reaction

This study, for the first time in Turkey, investigated the existence of Chlamydophila psittaci and determined the prevalence of its disease, chlamydiosis, in pet birds. Polymerase chain reaction (PCR) was compared with other testing methods that have been typically used in the diagnosis of C. psittaci. Fecal specimens (n =96) of avian origin were tested by PCR and two identification methods, modified Gimenez staining (mGS) and direct fluorescein-conjugated monoclonal antibody staining (FA). The identification methods were implemented by staining the yolk sacs of embryonated chicken eggs inoculated at 6 days of age and harvested between 3 and 10 days after inoculation. Fecal specimens from pet birds were randomly collected from pet shops and homes. These specimens were then used to isolate C. psittaci and to detect its specific DNA. The inocula that were prepared from fecal specimens were then inoculated into yolks of 6-day-old embryonated chicken eggs. The preparations from egg yolk sacs were examined with mGS and direct FA after three blind passages. The PCR method was used to detect specific DNA in feces. In 96 fecal specimens, 33 (34.4%) were positive with PCR, 21 (21.9%) were positive with mGS, and 29 (30.2%) were positive with FA. Among 33 positive specimens with PCR, 28 specimens were positive with FA, and 20 specimens were positive with mGS. The sensitivity and specificity were 59% and 94% between FA and mGS, and 97% and 93% between FA and PCR, respectively.

Chlamydophila psittaci in free-living Blue-fronted Amazon parrots (Amazona aestiva) and Hyacinth macaws (Anodorhynchus hyacinthinus) in the Pantanal of Mato Grosso do Sul, Brazil

Chlamydophila psittaci (C. psittaci) infection was evaluated in 77 free-living nestlings of Blue-fronted Amazon parrots (Amazona aestiva) and Hyacinth macaws (Anodorhynchus hyacinthinus) in the Pantanal of Mato Grosso do Sul, Brazil. Tracheal and cloacal swab samples from 32 wild parrot and 45 macaw nestlings were submitted to semi-nested PCR, while serum samples were submitted to complement fixation test (CFT). Although all 32 Amazon parrot serum samples were negative by CFT, cloacal swabs from two birds were positive for Chlamydophila DNA by semi-nested PCR (6.3%); these positive birds were 32 and 45 days old. In macaws, tracheal and cloacal swabs were positive in 8.9% and 26.7% of the samples, respectively. Complement-fixing antibodies were detected in 4.8% of the macaw nestlings; macaw nestlings with positive findings were between 33 and 88 days old. These results indicate widespread dissemination of this pathogen in the two evaluated psittacine populations. No birds had clinical signs suggestive of chlamydiosis. To the best of our knowledge, this is the first report on C. psittaci in free-living Blue-fronted Amazon parrots and Hyacinth macaws in Brazil.

Prevalence of Chlamydophila psittaci in fecal droppings from feral pigeons in Amsterdam, The Netherlands

In many cities, the feral rock dove is an abundant bird species that can harbor Chlamydophila psittaci. We determined the prevalence and genotype of C. psittaci in fresh fecal samples from feral pigeons in Amsterdam, The Netherlands. The prevalence was 7.9% overall (26/331; 95% confidence interval, 5 to 11). Ten genotyped PCR-positive samples were all genotype B.

Chlamydophila psittaci in Fulmars, the Faroe Islands

Chlamydophila psittaci was detected in 10% of 431 fulmars examined from the Faroe Islands. Analysis of ompA showed a sequence almost identical to that of the type strain. The origin of C. psittaci outbreaks in fulmars is discussed. Despite a high level of exposure, the risk for transmission of C. psittaci to humans is low.

Methodology in diagnostic virology

Selection of proper assays and appropriate interpretation of results can be a challenge to the veterinary clinician. Assays vary in methodology, sensitivity, and specificity. These assays can be invaluable in attaining the correct diagnosis, but a clear understanding of the assay and the results is essential. To this end, communication with the laboratory personnel is crucial. Optimal sample selection, shipping recommendations, assay selection, and interpretation should be discussed with the laboratory staff.

Bacterial sinusitis as a cause of beak deformity in an Antipodes Island parakeet(Cyanoramphus unicolor)

CASE HISTORY

From 26 days of age, an Antipodes Island parakeet (Cyanoramphus unicolor) was noted to have a severe beak deformity and reduced bodyweight gain compared to its nest mate. The bird was euthanised at 43 days of age.

CLINICAL AND PATHOLOGICAL FINDINGS

The beak abnormality consisted of distortion of the right nares and severe shortening resulting in deviation of the upper maxilla to the right and cranially. On sectioning the head, copious mucoid material was found in the infraorbital sinus and the bony sinus architecture was disrupted. Histopathological examination of the infraorbital sinuses revealed a large focus of chronic but active inflammation, bony lysis on the right side and pockets of a mixed population of bacteria.

DIAGNOSIS

Severe beak deformity, likely secondary to bacterial sinusitis.

CLINICAL RELEVANCE

The case illustrates the need to look for underlying aetiologies to beak malformation, particularly in young parrots.

KEYWORDS

Sinusitis, beak malformation, Antipodes Island parakeet, parrot, beak growth.

Detection of Chlamydia suis from clinical specimens: comparison of PCR, antigen ELISA, and culture

Cell culture is still widely regarded as the gold standard in chlamydial diagnosis despite its well-known limitations in terms of sensitivity. On the other hand, the polymerase chain reaction (PCR) has emerged as a promising alternative because of rapidity and high sensitivity. However, validation of methodologies is required before the issue of standardization can be addressed. In the present study, 109 clinical samples (organ tissue, nasal, and faecal swabs) from pigs experimentally infected with Chlamydia suis were examined by cell culture, nested PCR in the ompA gene region, and two different antigen enzyme-linked immunosorbent assays (ELISAs) in order to compare the diagnostic performance of these methods. Culture and PCR produced the highest proportion of concordant results (kappa coefficient 0.712). Among 99 samples, 34 were positive in both assays, 51 were negative in both assays, 12 culture-negatives were positive in PCR, and only 2 culture-positives were negative in PCR. Thus, the sensitivity and specificity of PCR vs. culture as standard were 94.4% and 81.0%, respectively, whereas the corresponding values for culture vs. PCR as standard were 73.9% and 96.2%, respectively. Both ELISA tests performed considerably weaker. The data underline the potential of PCR as a powerful detection method for chlamydiae.

Psittacosis/avian chlamydiosis

Considerable progress continues to be made in understanding chlamydial organisms, their host species, diagnosis, and treatment. (1-3) Thus, national guidelines are updated annually to provide a standardized approach to handling infections in humans and birds. (2-3) Prior to development of these guidelines, considerable variation in approach by state agencies has been documented. (39) A more recent national assessment of state regulations and procedures has not been conducted. Decreasing imports of birds and increasing education may contribute to a reduction in human risk from avian infections. Keeping new birds separate from old birds in aviaries and poultry production facilities may reduce the incidence of avian chlamydiosis. Although wide-scale testing of birds may not be cost effective, (28) focal testing and treatment may help reduce human risk. The recent loss of a major source for pelleted feed for small birds, such as budgerigars, was a severe setback for veterinarians and local agencies in managing this disease. However, new medication formulas under development may help to address this problem. (2-3)