Characterization of a new genotype of avian bornavirus from wild ducks

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.

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.

Experimental infection of aquatic bird bornavirus in Muscovy ducks

Aquatic bird bornavirus (ABBV-1), an avian bornavirus, has been reported in wild waterfowl from North America and Europe that presented with neurological signs and inflammation of the central and peripheral nervous systems. The potential of ABBV-1to infect and cause lesions in commercial waterfowl species is unknown. The aim of this study was to determine the ability of ABBV-1 to infect and cause disease in day-old Muscovy ducks (n = 174), selected as a representative domestic waterfowl. Ducklings became infected with ABBV-1 through both intracranial and intramuscular, but not oral, infection routes. Upon intramuscular infection, the virus spread centripetally to the central nervous system (brain and spinal cord), while intracranial infection led to virus spread to the spinal cord, kidneys, proventriculus, and gonads (centrifugal spread). Infected birds developed both encephalitis and myelitis by 4 weeks post infection (wpi), which progressively subsided by 8 and 12 wpi. Despite development of microscopic lesions, clinical signs were not observed. Only five birds had choanal and/or cloacal swabs positive for ABBV-1, suggesting a low potential of Muscovy ducks to shed the virus. This is the first study to document the pathogenesis of ABBV-1 in poultry species, and confirms the ability of ABBV-1 to infect commercial waterfowl.

Avian Bornavirus Research—A Comprehensive Review

Avian bornaviruses constitute a genetically diverse group of at least 15 viruses belonging to the genus Orthobornavirus within the family Bornaviridae. After the discovery of the first avian bornaviruses in diseased psittacines in 2008, further viruses have been detected in passerines and aquatic birds. Parrot bornaviruses (PaBVs) possess the highest veterinary relevance amongst the avian bornaviruses as the causative agents of proventricular dilatation disease (PDD). PDD is a chronic and often fatal disease that may engulf a broad range of clinical presentations, typically including neurologic signs as well as impaired gastrointestinal motility, leading to proventricular dilatation. It occurs worldwide in captive psittacine populations and threatens private bird collections, zoological gardens and rehabilitation projects of endangered species. In contrast, only little is known about the pathogenic roles of passerine and waterbird bornaviruses. This comprehensive review summarizes the current knowledge on avian bornavirus infections, including their taxonomy, pathogenesis of associated diseases, epidemiology, diagnostic strategies and recent developments on prophylactic and therapeutic countermeasures.

Avian Bornaviruses in Wild Aquatic Birds of the Anseriformes Order in Poland

Bornaviruses are a diverse family of viruses infecting various hosts, including birds. Aquatic bird bornavirus 1 (ABBV-1) and aquatic bird bornavirus 2 (ABBV-2) have been found in wild waterfowl but data on their prevalence are scarce. To gain knowledge on the occurrence of ABBVs in Poland, samples originating from dead birds of the Anseriformes order collected in 2016–2021 were tested with a real time RT-PCR method targeting the ABBVs genome. A total of 514 birds were examined, including 401 swans, 96 ducks and 17 geese. The presence of ABBV-1 RNA was detected in 52 swans (10.1% of all tested birds) from 40 different locations. No positive results were obtained for ducks and geese. Sequences of about 2300 bases were generated for 18 viruses and phylogenetic analysis was performed. A relatively low genetic diversity of the examined ABBV-1 strains was observed as all were gathered in a single cluster in the phylogenetic tree and the minimum nucleotide identity was 99.14%. The Polish strains were closely related to ABBV-1 identified previously in Denmark and Germany, but a limited number of sequences from Europe hinders the drawing of conclusions about interconnections between Polish and other European ABBVs. The results of the present study provide new insights into the distribution and genetic characteristics of ABBVs in wild birds in Europe.

A New Multiplex Real-Time RT-PCR for Simultaneous Detection and Differentiation of Avian Bornaviruses

Avian bornaviruses were first described in 2008 as the causative agents of proventricular dilatation disease (PDD) in parrots and their relatives (Psittaciformes). To date, 15 genetically highly diverse avian bornaviruses covering at least five viral species have been discovered in different bird orders. Currently, the primary diagnostic tool is the detection of viral RNA by conventional or real-time RT-PCR (rRT-PCR). One of the drawbacks of this is the usage of either specific assays, allowing the detection of one particular virus, or of assays with a broad detection spectrum, which, however, do not allow for the simultaneous specification of the detected virus. To facilitate the simultaneous detection and specification of avian bornaviruses, a multiplex real-time RT-PCR assay was developed. Whole-genome sequences of various bornaviruses were aligned. Primers were designed to recognize conserved regions within the overlapping X/P gene and probes were selected to detect virus species-specific regions within the target region. The optimization of the assay resulted in the sensitive and specific detection of bornaviruses of Psittaciformes, Passeriformes, and aquatic birds. Finally, the new rRT-PCR was successfully employed to detect avian bornaviruses in field samples from various avian species. This assay will serve as powerful tool in epidemiological studies and will improve avian bornavirus detection.

Isolation of Ontario aquatic bird bornavirus 1 and characterization of its replication in immortalized avian cell lines

BACKGROUND

Aquatic bird bornavirus 1 (ABBV-1) has been associated with neurological diseases in wild waterfowls. In Canada, presence of ABBV-1 was demonstrated by RT-qPCR and immunohistochemistry in tissues of waterfowls with history of neurological disease and inflammation of the central and peripheral nervous tissue, although causation has not been proven by pathogenesis experiments, yet. To date, in vitro characterization of ABBV-1 is limited to isolation in primary duck embryo fibroblasts. The objectives of this study were to describe isolation of ABBV-1 in primary duck embryonic fibroblasts (DEF), and characterize replication in DEF and three immortalized avian fibroblast cell lines (duck CCL-141, quail QT-35, chicken DF-1) in order to evaluate cellular permissivity and identify suitable cell lines for routine virus propagation.

METHODS

The virus was sequenced, and phylogenetic analysis performed on a segment of the N gene coding region. Virus spread in cell cultures, viral RNA and protein production, and titres were evaluated at different passages using immunofluorescence, RT-qPCR, western blotting, and tissue culture dose 50% (TCID₅₀) assay, respectively.

RESULTS

The isolated ABBV-1 showed 97 and 99% identity to European ABBV-1 isolate AF-168 and North American ABBV-1 isolates 062-CQ and CG-N1489, and could infect and replicate in DEF, CCL-141, QT-35 and DF-1 cultures. Viral RNA was detected in all four cultures with highest levels observed in DEF and CCL-141, moderate in QT-35, and lowest in DF-1. N protein was detected in western blots from infected DEF, CCL-141 and QT-35 at moderate to high levels, but minimally in infected DF-1. Infectious titre was highest in DEF (between approximately 10⁵ to 10⁶ FFU / 10⁶ cells). Regarding immortalized cell lines, CCL-141 showed the highest titre between approximately 10⁴ to 10⁵ FFU / 10⁶ cells. DF-1 produced minimal infectious titre.

CONCLUSIONS

This study confirms the presence of ABBV-1 among waterfowl in Canada and reported additional in vitro characterization of this virus in different avian cell lines. ABBV-1 replicated to highest titre in DEF, followed by CCL-141 and QT-35, and poorly in DF-1. Our results showed that CCL-141 can be used instead of DEF for routine ABBV-1 production, if a lower titre is an acceptable trade-off for the simplicity of using immortalized cell line over primary culture.

Bornaviruses in naturally infected Psittacus erithacus in Portugal: insights of molecular epidemiology and ecology

Background: The genus Orthobornavirus comprises non-segmented, negative-stranded RNA viruses able to infect humans, mammals, reptiles and various birds. Parrot bornavirus 1 to 8 (PaBV-1 to 8) causes neurological and/or gastrointestinal syndromes and death on psittacines. We aimed to identify and to produce epidemiologic knowledge about the etiologic agent associated with a death of two female Psittacus erithacus (grey parrot). Methods and Results: Both parrots were submitted for a complete standardised necropsy. Tissue samples were analysed by PCR. The findings in necropsy were compatible with bornavirus infection. Analysis revealed PaBV-4 related with genotypes detected in captive and in wild birds. The N and X proteins of PaBV-4 were more related to avian bornaviruses, while phosphoprotein was more related to variegated squirrel bornavirus 1 (VSBV-1). Within the P gene/phosphoprotein a highly conserved region between and within bornavirus species was found. Conclusions: Portugal is on the routes of the intensive world trade of psittacines. Broad screening studies are required to help understanding the role of wild birds in the emergence and spread of pathogenic bornaviruses. PaBV-4 phosphoprotein is closer to VSBV-1 associated with lethal encephalitis in humans than with some of the avian bornaviruses. The highly conserved P gene/phosphoprotein region is a good target for molecular diagnostics screenings.

Apparent resolution of parrot bornavirus infection in cockatiels (Nymphicus hollandicus)

Parrot bornavirus (PaBV), the etiologic agent of proventricular dilatation disease (PDD), is a major cause of concern in the avian health community. Within an infected flock, some birds will develop PDD and succumb to disease, while others remain healthy. Until now, there has been no study describing the results of long-term infection in apparently healthy carriers. For the last 5 years, the Schubot Exotic Bird Health Center at Texas A&M University has monitored individual PaBV shedding data in a flock of 66 naturally infected cockatiels. Of these birds, 53 were detected shedding PaBV4 in their droppings by reverse transcriptase polymerase chain reaction on at least one occasion. However, the prevalence of shedding declined over time, with the last positive cloacal swab being in October 2013. To determine whether the decline and eventual lack of shedding was an indication of virus elimination, seven previously shedding birds were euthanized and necropsied in 2016. Neither any gross lesion of PDD was observed nor was there any evidence of PDD or bornaviral encephalitis detected by histopathology. All tissues tested were negative for the presence of PaBV by reverse transcriptase polymerase chain reaction and immunohistochemistry. Thus, there was no evidence of an ongoing, productive infection in these birds. There are two possible explanations for these results. One possibility is that the birds were previously infected and have subsequently eliminated the virus. Alternatively, there may have been as few as three truly infected birds in the flock and the transient detection of PaBV in the droppings of other birds may simply be a "pass-through" phenomenon.

Divergent bornaviruses from Australian carpet pythons with neurological disease date the origin of extant Bornaviridae prior to the end-Cretaceous extinction

Tissue samples from Australian carpet pythons (Morelia spilota) with neurological disease were screened for viruses using next-generation sequencing. Coding complete genomes of two bornaviruses were identified with the gene order 3'-N-X-P-G-M-L, representing a transposition of the G and M genes compared to other bornaviruses and most mononegaviruses. Use of these viruses to search available vertebrate genomes enabled recognition of further endogenous bornavirus-like elements (EBLs) in diverse placental mammals, including humans. Codivergence patterns and shared integration sites revealed an ancestral laurasiatherian EBLG integration (77 million years ago [MYA]) and a previously identified afrotherian EBLG integration (83 MYA). The novel python bornaviruses clustered more closely with these EBLs than with other exogenous bornaviruses, suggesting that these viruses diverged from previously known bornaviruses prior to the end-Cretaceous (K-Pg) extinction, 66 MYA. It is possible that EBLs protected mammals from ancient bornaviral disease, providing a selective advantage in the recovery from the K-Pg extinction. A degenerate PCR primer set was developed to detect a highly conserved region of the bornaviral polymerase gene. It was used to detect 15 more genetically distinct bornaviruses from Australian pythons that represent a group that is likely to contain a number of novel species.

From nerves to brain to gastrointestinal tract: A time-based study of parrot bornavirus 2 (PaBV-2) pathogenesis in cockatiels (Nymphicus hollandicus)

Parrot bornaviruses (PaBVs) are the causative agents of proventricular dilatation disease, however key aspects of its pathogenesis, such as route of infection, viral spread and distribution, and target cells remain unclear. Our study aimed to track the viral spread and lesion development at 5, 10, 20, 25, 35, 40, 60, 80, 95 and 114 dpi using histopathology, immunohistochemistry, and RT-PCR. After intramuscular inoculation of parrot bornavirus 2 (PaBV-2) in the pectoral muscle of cockatiels, this virus was first detected in macrophages and lymphocytes in the inoculation site and adjacent nerves, then reached the brachial plexus, centripetally spread to the thoracic segment of the spinal cord, and subsequently invaded the other spinal segments and brain. After reaching the central nervous system (CNS), PaBV-2 centrifugally spread out the CNS to the ganglia in the gastrointestinal (GI) system, adrenal gland, heart, and kidneys. At late points of infection, PaBV-2 was not only detected in nerves and ganglia but widespread in the smooth muscle and/or scattered epithelial cells of tissues such as crop, intestines, proventriculus, kidneys, skin, and vessels. Despite the hallmark lesion of PaBVs infection being the dilation of the proventriculus, our results demonstrate PaBV-2 first targets the CNS, before migrating to peripheral tissues such as the GI system.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): Borna disease

Borna disease has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of Borna disease to be listed, Article 9 for the categorisation of Borna disease according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to Borna disease. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, Borna disease cannot be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL because there was no compliance on criterion 5 A(v). Consequently, the assessment on compliance of Borna disease with the criteria as in Annex IV of the AHL, for the application of the disease prevention and control rules referred to in Article 9(1) is not applicable, as well as which animal species can be considered to be listed for Borna disease according to Article 8(3) of the AHL.

The pathogenesis of proventricular dilatation disease

Bornaviruses cause neurologic diseases in several species of birds, especially parrots, waterfowl and finches. The characteristic lesions observed in these birds include encephalitis and gross dilatation of the anterior stomach — the proventriculus. The disease is thus known as proventricular dilatation disease (PDD). PDD is characterized by extreme proventricular dilatation, blockage of the passage of digesta and consequent death by starvation. There are few clinical resemblances between this and the bornaviral encephalitides observed in mammals. Nevertheless, there are common virus-induced pathogenic pathways shared across this disease spectrum that are explored in this review. Additionally, a review of the literature relating to gastroparesis in humans and the control of gastric mobility in mammals and birds points to several plausible mechanisms by which bornaviral infection may result in extreme proventricular dilatation.

Of Ducks and Men: Ecology and Evolution of a Zoonotic Pathogen in a Wild Reservoir Host

A hallmark of disease is that most pathogens are able to infect more than one host species. However, for most pathogens, we still have a limited understanding of how this affects epidemiology, persistence and virulence of infections—including several zoonotic pathogens that reside in wild animal reservoirs and spillover into humans. In this chapter, we review the current knowledge of mallard (Anas platyrhynchos) as host for pathogens. This species is widely distributed, often occupying habitats close to humans and livestock, and is an important game bird species and the ancestor to domestic ducks—thereby being an excellent model species to highlight aspects of the wildlife, domestic animal interface and the relevance for human health. We discuss mallard as host for a range of pathogens but focus more in depth of it as a reservoir host for influenza A virus (IAV). Over the last decades, IAV research has surged, prompted in part to the genesis and spread of highly pathogenic virus variants that have been devastating to domestic poultry and caused a number of human spillover infections. The aim of this chapter is to synthesise and review the intricate interactions of virus, host and environmental factors governing IAV epidemiology and evolution.

Viral vector vaccines expressing nucleoprotein and phosphoprotein genes of avian bornaviruses ameliorate homologous challenge infections in cockatiels and common canaries

Avian bornaviruses are causative agents of proventricular dilatation disease (PDD), an often fatal disease of parrots and related species (order Psittaciformes) which is widely distributed in captive psittacine populations and may affect endangered species. Here, we established a vaccination strategy employing two different well described viral vectors, namely recombinant Newcastle disease virus (NDV) and modified vaccinia virus Ankara (MVA) that were engineered to express the phosphoprotein and nucleoprotein genes of two avian bornaviruses, parrot bornavirus 4 (PaBV-4) and canary bornavirus 2 (CnBV-2). When combined in a heterologous prime/boost vaccination regime, NDV and MVA vaccine viruses established self-limiting infections and induced a bornavirus-specific humoral immune response in cockatiels (Nymphicus hollandicus) and common canaries (Serinus canaria forma domestica). After challenge infection with a homologous bornavirus, shedding of bornavirus RNA and viral loads in tissue samples were significantly reduced in immunized birds, indicating that vaccination markedly delayed the course of infection. However, cockatiels still developed signs of PDD if the vaccine failed to prevent viral persistence. Our work demonstrates that avian bornavirus infections can be repressed by vaccine-induced immunity. It represents a first crucial step towards a protective vaccination strategy to combat PDD in psittacine birds.

Phylogenetic Analysis Supports Horizontal Transmission as a Driving Force of the Spread of Avian Bornaviruses

BACKGROUND

Avian bornaviruses are a genetically diverse group of viruses initially discovered in 2008. They are known to infect several avian orders. Bornaviruses of parrots and related species (Psittaciformes) are causative agents of proventricular dilatation disease, a chronic and often fatal neurologic disease widely distributed in captive psittacine populations. Although knowledge has considerably increased in the past years, many aspects of the biology of avian bornaviruses are still undiscovered. In particular, the precise way of transmission remains unknown.

AIMS AND METHODS

In order to collect further information on the epidemiology of bornavirus infections in birds we collected samples from captive and free-ranging aquatic birds (n = 738) and Passeriformes (n = 145) in Germany and tested them for the presence of bornaviruses by PCR assays covering a broad range of known bornaviruses. We detected aquatic bird bornavirus 1 (ABBV-1) in three out of 73 sampled free-ranging mute swans (Cygnus olor) and one out of 282 free-ranging Eurasian oystercatchers (Haematopus ostralegus). Canary bornavirus 1 (CnBV-1), CnBV-2 and CnBV-3 were detected in four, six and one out of 48 captive common canaries (Serinus canaria forma domestica), respectively. In addition, samples originating from 49 bornavirus-positive captive Psittaciformes were used for determination of parrot bornavirus 2 (PaBV-2) and PaBV-4 sequences. Bornavirus sequences compiled during this study were used for phylogenetic analysis together with all related sequences available in GenBank.

RESULTS OF THE STUDY

Within ABBV-1, PaBV-2 and PaBV-4, identical or genetically closely related bornavirus sequences were found in parallel in various different avian species, suggesting that inter-species transmission is frequent relative to the overall transmission of these viruses. Our results argue for an important role of horizontal transmission, but do not exclude the additional possibility of vertical transmission. Furthermore we defined clearly separated sequence clusters within several avian bornaviruses, providing a basis for an improved interpretation of transmission events within and between wild bird populations and captive bird collections.

Aquatic Bird Bornavirus 1 in Wild Geese, Denmark

To investigate aquatic bird bornavirus 1 in Europe, we examined 333 brains from hunter-killed geese in Denmark in 2014. Seven samples were positive by reverse transcription PCR and were 98.2%-99.8% identical; they were also 97.4%-98.1% identical to reference strains of aquatic bird bornavirus 1 from geese in North America.

The genome sequence of parrot bornavirus 5

Although several new avian bornaviruses have recently been described, information on their evolution, virulence, and sequence are often limited. Here we report the complete genome sequence of parrot bornavirus 5 (PaBV-5) isolated from a case of proventricular dilatation disease in a Palm cockatoo (Probosciger aterrimus). The complete genome consists of 8842 nucleotides with distinct 5' and 3' end sequences. This virus shares nucleotide sequence identities of 69-74 % with other bornaviruses in the genomic regions excluding the 5' and 3' terminal sequences. Phylogenetic analysis based on the genomic regions demonstrated this new isolate is an isolated branch within the clade that includes the aquatic bird bornaviruses and the passerine bornaviruses. Based on phylogenetic analyses and its low nucleotide sequence identities with other bornavirus, we support the proposal that PaBV-5 be assigned to a new bornavirus species:- Psittaciform 2 bornavirus.

Parrot bornavirus-2 and -4 RNA detected in wild bird samples in Japan are phylogenetically adjacent to those found in pet birds in Japan

Bornaviruses (family Bornaviridae) are non-segmented negative-strand RNA viruses. Avian bornaviruses (ABVs), which are causative agents of proventricular dilatation disease, are a genetically diverse group with at least 15 genotypes, including parrot bornaviruses (PaBVs) and aquatic bird bornavirus 1(ABBV-1). Borna disease virus 1(BoDV-1), which infects mammals and causes neurological diseases, has also been reported to infect avian species, although the numbers of the cases have been markedly fewer than those of ABVs. In this study, we conducted genetic surveillance to detect ABVs (PaBV-1 to -5 and ABBV-1) and BoDV-1 in wild birds in Japan. A total of 2078 fecal or cloacal swab samples were collected from wild birds in 2006, 2007, 2008, and 2011, in two regions of Japan. The results demonstrated the presence of PaBV-2 and -4 RNA, while no positive results for other PaBVs, ABBV-1, and BoDV-1 were obtained. PaBV-2 and -4 RNA were detected in 18 samples (0.9 %) of the genera Anas, Grus, Larus, Calidris, Haliaeetus, and Emberiza, in which either PaBV-2 RNA or PaBV-4 RNA, or both PaBV-2 and -4 RNA were detected in 15 (0.7 %), 5 (0.2 %), and 2 (0.1 %) samples, respectively. The nucleotide sequences of PaBV-2 and -4 detected in these samples from wild birds are phylogenetically close to those found in samples from pet birds in Japan, with identities ranging from 99.8 to 100 % and from 98.2 to 99.4 %, respectively. To the best of our knowledge, this is the first report on the detection of PaBV-2 and -4 RNA detected in samples from wild birds.