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

PARROT BORNAVIRUSES IN PSITTACINES KEPT IN CAPTIVITY IN THE STATE OF SANTA CATARINA, BRAZIL

Parrot bornaviruses are responsible for proventricular dilatation disease (PDD) in psittacines. This study aimed to determine the occurrence and factors associated with Parrot bornaviruses infection in psittacines kept in captivity in a state in the southern region of Brazil. A cross-sectional study was carried out with 192 birds from two facilities (A and B) in 2019, using choanal, esophageal, and cloacal swabs and feathers, totaling 768 samples subjected to reverse-transcription polymerase chain reaction (RT-PCR), for the matrix (M) protein gene with a final product of 350 base pairs (bp). Genetic sequencing of three positive samples was performed by the Sanger method. In the study, the overall virus occurrence was 35.9% (69/192), with 40.4% (42/104) in Facility A and 30.7% (27/88) in Facility B. Sequencing analysis of the samples revealed the presence of Parrot bornavirus 2 (PaBV-2) in both facilities. Swab samples from the choanal (40/69), esophageal (30/69), cloacal (35/69), and feather (15/69) tested positive, facilitating the molecular diagnosis of Parrot bornaviruses. The results indicated that there is no single ideal sample type for antemortem molecular diagnosis of this virus. Simultaneously testing all four samples at the same time point yielded more diagnoses than testing any single sample among the four. Most of the 29 sampled psittacine species were native, and 46.9% of the birds (90/192) consisted of endangered species. Among the psittacines that tested positive, 88.4% (61/69) were clinically healthy, and 8.7% (6/69) exhibited clinical or behavioral signs, including behavioral changes, alterations in feathering, and changes in body score at the time of collection. This study showcases the application of minimally invasive sampling for diagnosing Parrot bornaviruses, enabling sample collection when the birds are restrained for clinical evaluation. This approach facilitates a prompt and effective antemortem diagnosis, thereby serving as an efficient screening method for parrots kept in captivity.

Surveillance of Parrot Bornavirus in Taiwan Captive Psittaciformes

Parrot bornavirus (PaBV) is an infectious disease linked with proventricular dilatation disease (PDD) with severe digestive and neurological symptoms affecting psittacine birds. Despite its detection in 2008, PaBV prevalence in Taiwan remains unexplored. Taiwan is one of the leading psittacine bird breeders; hence, understanding the distribution of PaBV aids preventive measures in controlling spread, early disease recognition, epidemiology, and transmission dynamics. Here, we aimed to detect the prevalence rate of PaBV and assess its genetic variation in Taiwan. Among 124 psittacine birds tested, fifty-seven were PaBV-positive, a prevalence rate of 45.97%. Most of the PaBV infections were adult psittacine birds, with five birds surviving the infection, resulting in a low survival rate (8.77%). A year of parrot bornavirus surveillance presented a seasonal pattern, with peak PaBV infection rates occurring in the spring season (68%) and the least in the summer season (25%), indicating the occurrence of PaBV infections linked to seasonal factors. Histopathology reveals severe meningoencephalitis in the cerebellum and dilated cardiomyopathy of the heart in psittacine birds who suffered from PDD. Three brain samples underwent X/P gene sequencing, revealing PaBV-2 and PaBV-4 viral genotypes through phylogenetic analyses. This underscores the necessity for ongoing PaBV surveillance and further investigation into its pathophysiology and transmission routes.

Detection of a new avian bornavirus in barn owl (Tyto alba) by pan-viral microarray

A barn owl (Tyto alba) died with neurological signs compatible with a viral infection. After discarding other possible infections caused by circulating viruses in the area, analysis of the central nervous system using a pan-viral microarray revealed hybridization to canary bornavirus 2 (CnBV-2). Subsequent sequence analysis confirmed the presence of a virus sharing more than 83% identity with CnBV-2. Surprisingly, the new sequence corresponds to a new virus, here named Barn owl Bornavirus 1 (BoBV-1), within the Orthobornavirus serini species. Moreover, it is the first member of this species that has been detected in a non-passerine bird, indicating that Orthobornavirus serini species comprises viruses with a wider range of hosts than previously presumed. The use of this microarray has proven to be an excellent tool for viral detection in clinical samples, with capacity to detect new viral variants. This allows the diagnosis of a great range of viruses, which can cause similar disease symptoms and which identification by PCR methods might be tedious, probably unsuccessful and, in the long run, expensive. This platform is highly useful for a fast and precise viral detection, contributing to the improvement of diagnostic methods.

Evolutionary Analysis of a Parrot Bornavirus 2 Detected in a Sulphur-Crested Cockatoo (Cacatua galerita) Suggests a South American Ancestor

Parrot bornavirus (PaBV) is an RNA virus that causes Proventricular Dilatation Disease (PDD), neurological disorders, and death in Psittaciformes. Its diversity in South America is poorly known. We examined a Cacatua galerita presenting neuropathies, PDD, and oculopathies as the main signs. We detected PaBV through reverse transcription polymerase chain reaction (RT-PCR) and partial sequencing of the nucleoprotein (N) and matrix (M) genes. Maximum likelihood and Bayesian phylogenetic inferences classified it as PaBV-2. The nucleotide identity of the sequenced strain ranged from 88.3% to 90.3% against genotype PaBV-2 and from 80.2% to 84.4% against other genotypes. Selective pressure analysis detected signs of episodic diversifying selection in both the N and M genes. No recombination events were detected. Phylodynamic analysis estimated the time to the most recent common ancestor (TMRCA) as the year 1758 for genotype PaBV-2 and the year 1049 for the Orthobornavirus alphapsittaciforme species. Substitution rates were estimated at 2.73 × 10-4 and 4.08 × 10-4 substitutions per year per site for N and M, respectively. The analysis of population dynamics showed a progressive decline in the effective population size during the last century. Timescale phylogeographic analysis revealed a potential South American ancestor as the origin of genotypes 1, 2, and 8. These results contribute to our knowledge of the evolutionary origin, diversity, and dynamics of PaBVs in South America and the world. Additionally, it highlights the importance of further studies in captive Psittaciformes and the potential impact on endangered wild birds.

Molecular detection of bornavirus in parrots imported to China in 2022

BACKGROUND

Avian bornavirus (ABV) is a neurotropic virus, it has been established as the primary causative agent of proventricular dilatation disease (PDD). However, substantial international trade and transnational trafficking of wild birds occur, potentially enabling these birds to harbor and transmit pathogens to domestic poultry, adversely affecting their well-being. Real-time RT-PCR was employed to detect the presence of PaBV-4 in parrots imported to China in 2022.

RESULTS

In 2022, a total of 47 cloacal swabs from 9 distinct species of parrots were collected at the Wildlife Rescue Monitoring Center in Guangdong, China. The purpose of this collection was to detect the presence of PaBV-4. Using real-time PCR techniques, it was determined that the positive rate of PaBV-4 was 2.12% (1 out of 47) in parrots. The PaBV-4 virus was detected in a Amazona aestiva that had been adopted for one month. Conversely, all other species tested negative for the virus. Subsequently, the whole genome of the PaBV-4 GD2207 strains was sequenced, and the homology and genetic evolution between these strains and previously published PaBV-4 strains on GenBank were analyzed using DNAStar and MEGA7.0 software. The findings revealed that the full-length genome of PaBV-4 consisted of 8915 nucleotides and encoded six proteins. Additionally, it exhibited the highest nucleotide similarity (99.9%) to the GZ2019 strain, which causes death and severe clinical symptoms in Aratinga solstitialis. Furthermore, when compared to other strains of PaBV-4, the GD2207 strain demonstrated the highest amino acid homology with GZ2019. The phylogenetic analysis demonstrated that the GD2207 strain clustered with various strains found in Japanese, American, and German parrots, indicating a close genetic relationship with PaBV-4, but it revealed a distant relationship with PaBV-5 Cockg5 from America. Notably, the GD2207 was closely associated with the GZ2019 strain from Aratinga solstitialis in China.

CONCLUSION

This study presents the preliminary identification of PaBV-4 in Amazona aestiva parrots, emphasizing its importance as the predominant viral genotype linked to parrot infections resulting from trade into China. Through genetic evolution analysis, it was determined that the GD2207 strain of PaBV-4 exhibits the closest genetic relationship with GZ 2019 (Aratinga solstitialis, China), M14 (Ara macao, USA), AG5 (Psittacus erithacus, USA) and 6758 (Ara ararauna, Germany) suggesting a shared ancestry.

Translating conventional wisdom on chicken comb color into automated monitoring of disease-infected chicken using chromaticity-based machine learning models

Bacteria- or virus-infected chicken is conventionally detected by manual observation and confirmed by a laboratory test, which may lead to late detection, significant economic loss, and threaten human health. This paper reports on the development of an innovative technique to detect bacteria- or virus-infected chickens based on the optical chromaticity of the chicken comb. The chromaticity of the infected and healthy chicken comb was extracted and analyzed with International Commission on Illumination (CIE) XYZ color space. Logistic Regression, Support Vector Machines (SVMs), K-Nearest Neighbors (KNN), and Decision Trees have been developed to detect infected chickens using the chromaticity data. Based on the X and Z chromaticity data from the chromaticity analysis, the color of the infected chicken's comb converged from red to green and yellow to blue. The development of the algorithms shows that Logistic Regression, SVM with Linear and Polynomial kernels performed the best with 95% accuracy, followed by SVM-RBF kernel, and KNN with 93% accuracy, Decision Tree with 90% accuracy, and lastly, SVM-Sigmoidal kernel with 83% accuracy. The iteration of the probability threshold parameter for Logistic Regression models has shown that the model can detect all infected chickens with 100% sensitivity and 95% accuracy at the probability threshold of 0.54. These works have shown that, despite using only the optical chromaticity of the chicken comb as the input data, the developed models (95% accuracy) have performed exceptionally well, compared to other reported results (99.469% accuracy) which utilize more sophisticated input data such as morphological and mobility features. This work has demonstrated a new feature for bacteria- or virus-infected chicken detection and contributes to the development of modern technology in agriculture applications.

Molecular Detection, Risk Factors and Public Awareness of Avian Bornavirus among Captive and Non-captive Birds in Peninsular Malaysia

Introduction

Proventricular dilatation disease (PDD) is caused by avian bornavirus (ABV) has been identified in psittacine, non-psittacine birds and waterfowl. Birds may show signs of gastrointestinal tract deficit or neurological dysfunction or even both. The objectives of this study were to determine the molecular prevalence, risk factors and public awareness of ABV and PDD among captive and non-captive birds in Peninsular Malaysia.

Material and Methods

A total of 344 cloacal swabs or faeces were collected and subjected to detection using the RT-PCR assay. Meanwhile, KAP questionnaires were distributed by using the Google forms platform.

Results

Molecular prevalence studies revealed that 4.5% (9/201) of the pet birds were ABV-positive, whereas 0% (0/143) in waterfowl. Nine positive pet birds were identified to be PaBV-2, which is closest to ABV isolates EU781967 (USA). Among the risk factors analysed, category, age and, location, were found to show an association with the ABV positivity. The KAP survey result showed: the respondents have low knowledge (32.9%), however, they showed positive attitude (60.8%) and good practice (94.9%). The association between knowledge, attitude and practice showed that there was a significant association between knowledge-attitude and also attitude-practice (P<0.05).

Conclusion

This study proved that avian bornavirus (ABV) causes proventricular dilatation disease (PDD) among a group of pet birds of Psittaciformes, but it is present in Peninsular Malaysia with a low prevalence rate. Furthermore, in addition to the useful databases obtained from this study, the level of public awareness on the importance of avian bornavirus that causes fatal disorders among a wide range of bird species is satisfactorily raised.

Seeing beyond a Dilated Proventriculus: Diagnostic Tools for Proventricular Dilatation Disease in Psittacine Birds

Proventricular dilatation disease (PDD) is a life-threatening neurological disease caused by parrot bornaviruses (PaBVs) that affects several species worldwide. PDD can be clinically manifested as either a central nervous system condition or a gastrointestinal condition if the nerves and ganglia of the gastrointestinal tract are compromised. We intend to provide a concise review for veterinary clinicians and diagnosticians with focus on the main tools available for PDD diagnosis, including gross and histopathology, immunohistochemistry, molecular techniques and serology. We suggest that a combination of different strategies can increase the success of diagnostic outcomes, as tools such as reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) can be implemented for identification of bornaviral infections in live patients, and gross pathology, histopathology, immunohistochemistry and RT-PCR can provide reliable results for postmortem diagnosis of PDD.

Update on immunopathology of bornavirus infections in humans and animals

Knowledge on bornaviruses has expanded tremendously during the last decade through detection of novel bornaviruses and endogenous bornavirus-like elements in many eukaryote genomes, as well as by confirmation of insectivores as reservoir species for classical Borna disease virus 1 (BoDV-1). The most intriguing finding was the demonstration of the zoonotic potential of lethal human bornavirus infections caused by a novel bornavirus of different squirrel species (variegated squirrel 1 bornavirus, VSBV-1) and by BoDV-1 known as the causative agent for the classical Borna disease in horses and sheep. Whereas a T cell-mediated immunopathology has already been confirmed as key disease mechanism for infection with BoDV-1 by experimental studies in rodents, the underlying pathomechanisms remain less clear for human bornavirus infections, infection with other bornaviruses or infection of reservoir species. Thus, an overview of current knowledge on the pathogenesis of bornavirus infections focusing on immunopathology is given.