Avian bornavirus in the urine of infected birds

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.

Wounds as the Portal of Entrance for Parrot Bornavirus 4 (PaBV-4) and Retrograde Axonal Transport in Experimentally Infected Cockatiels (Nymphicus hollandicus)

In this study, we investigated the natural route of infection of psittacine bornavirus (PaBV), which is the causative agent of proventricular dilatation disease (PDD) in psittacines. We inoculated two infection groups through wounds with a PaBV-4 isolate. In nine cockatiels (Nymphicus hollandicus) we applied a virus suspension with a titer of 103 50% tissue culture infection dose (TCID50) via palatal lesions (Group P, P1-9). In a second group of three cockatiels, we applied a virus suspension with a titer of 104 TCID50 to footpad lesions (Group F, F1-3). In two cockatiels, the control (or "mock") group, we applied a virus-free cell suspension (Group M, M1-2) via palatal lesions. The observation period was 6 mo (Groups P and M) or 7 mo (Group F). We monitored PaBV-4 RNA shedding and seroconversion. At the end of the study, we examined the birds for the presence of inflammatory lesions, PaBV-4 RNA, and antigen in tissues, as well as virus reisolation of brain and crop material. We did not observe any clinical signs typical of PDD during this study. We also did not see seroconversion or PaBV RNA shedding in any bird during the entire investigation period, and virus reisolation was not successful. We only found PaBV-4 RNA in sciatic nerves, footpad tissue, skin, and in one sample from the intestine of Group F. In this group, the histopathology revealed mononuclear infiltrations mainly in skin and footpad tissue; immunohistochemistry showed positive reactions in spinal ganglia and in the spinal cord, and slightly in skin, footpad tissues, and sciatic nerves. In Groups P and M we found no viral antigen or specific inflammations. In summary, only the virus application on the footpad lesion led to detectable PaBV RNA, mononuclear infiltrations, and positive immunohistochemical reactions in tissues of the experimental birds. This could suggest that PaBV spreads via nervous tissue, with skin wounds as the primary entry route.

Treatment With Nonsteroidal Anti-Inflammatory Drugs Fails To Ameliorate Pathology In Cockatiels Experimentally Infected With Parrot Bornavirus-2

Purpose

Parrot bornavirus is the etiological agent of Parrot bornavirus syndrome, also referred to and comprising proventricular dilatation disease or PDD, macaw wasting disease, enteric ganglioneuritis and encephalitis, and avian ganglioneuritis. It has been suggested that nonsteroidal anti-inflammatory drugs may be able to ameliorate this disease. Therefore, this study investigated the effects of two commonly used nonsteroidal anti-inflammatory drugs, celecoxib and meloxicam, on cockatiels experimentally inoculated with Parrot bornavirus-2 (PaBV-2).

Materials and methods

Twenty-seven cockatiels were randomized into 3 groups of 9 birds, matched with respect to historical PaBV shedding, weight, and sex. The cockatiels were inoculated with cell culture-derived PaBV-2 by the intranasal and intramuscular routes. Beginning at 23 days post-inoculation, birds in each group received oral treatment once daily with placebo, meloxicam (1.0 mg/kg), or celecoxib (10.0 mg/kg).

Results

Within 33–79 days post-inoculation, 2 birds died and 6 birds were euthanized based on neurological or gastrointestinal signs consistent with Parrot bornavirus syndrome: 2 birds were euthanized in the placebo group, 1 bird died and 1 bird was euthanized in the meloxicam-treated group, and 1 bird died and 3 birds were euthanized in the celecoxib-treated group. Of these 8 birds, black intestinal contents were found upon necropsy in 2 birds of the meloxicam-treated group and 2 birds of the celecoxib-treated group. At day 173 (±2) post-inoculation, the remaining 19 birds were euthanized. Necropsy and histopathology showed lesions characteristic of Parrot bornavirus syndrome in 23 cockatiels. Histopathologic lesions were present in birds of all 3 groups. There was no statistical difference between the groups nor was there a statistical difference among the 3 treatment groups in the detection of PaBV RNA and PaBV nucleoprotein using RT-PCR and immunohistochemistry, respectively.

Conclusion

Meloxicam and celecoxib treatments do not appear to alter the clinical presentation, viral shedding, gross lesions, histopathology, or viral distribution. Treatment with NSAIDs may cause gastrointestinal toxicity in cockatiels experimentally inoculated with PaBV-2.

Comparison Of Four Anti-Avian IgY Secondary Antibodies Used In Western Blot And Dot-Blot ELISA To Detect Avian Bornavirus Antibodies In Four Different Bird Species

Purpose

This study evaluated the specificity of different avian secondary antibodies used in Western blot and dot-blot ELISA to detect avian bornavirus antibodies in bird plasma.

Methods

Plasma samples were collected from: two Blue and gold macaws, one positive and one negative for avian bornavirus by RT-PCR; a Cockatiel and a Monk parakeet prior to and following experimental infection; and, two Mallards, one positive and one negative for avian bornavirus by RT-PCR Samples were analyzed by Western blot and dot-blot ELISA that incorporated recombinant avian bornavirus nucleoprotein as the target analyte. Four species-specific anti-IgY secondary antibodies were used in the assays: goat anti-macaw IgY, goat anti-bird IgY, goat anti-duck IgY, and rabbit anti-chicken IgY.

Results

In the Western blot, anti-macaw IgY secondary antibody produced strong signals with Blue and gold macaw and Cockatiel positive plasma, but no signal with Mallard positive plasma. Anti-bird IgY secondary antibody produced strong signals with Blue and gold macaw, Cockatiel, and Mallard positive plasma. Anti-duck and anti-chicken IgY secondary antibody produced a strong and moderate signal, respectively, only with Mallard positive plasma. In the dot-blot ELISA, there was a distinct and significant difference (P<0.05) in the signal intensity between the different secondary antibodies within a bird species. Anti-macaw IgY secondary antibody produced significantly (P<0.05) stronger signals than the other secondary antibodies in Blue and gold macaw, Cockatiel, and Monk parakeet positive plasma, while anti-duck IgY secondary antibody produced significantly (P<0.05) stronger signals than the other secondary antibodies in Mallard positive plasma.

Conclusion

In testing psittacines with immunoassays, and especially in assays that incorporate short incubation reaction times such as a dot-blot ELISA, species-specific anti-IgY secondary antibodies provided more accurate results.

Avian Ganglioneuritis in Clinical Practice

Avian ganglioneuritis (AG) comprises one of the most intricate pathologies in avian medicine and is researched worldwide. Avian bornavirus (ABV) has been shown to be a causative agent of proventricular dilatation disease in birds. The avian Bornaviridae represent a genetically diverse group of viruses that are widely distributed in captive and wild populations around the world. ABV and other infective agents are implicated as a cause of the autoimmune pathology that leads to AG, similar to human Guillain Barrè syndrome. Management of affected birds is beneficial and currently centered at reducing neurologic inflammation, managing secondary complications, and providing nutritional support.

Aquatic bird bornavirus 1 infection in a captive Emu (Dromaius novaehollandiae): presumed natural transmission from free-ranging wild waterfowl

An adult female emu (Dromaius novaehollandiae) presented with anorexia, maldigestion, weight loss, and various subtle nervous deficits. After four months of unrewarding diagnostics, treatments, and supportive care, the emu was euthanized due to lack of clinical improvement and progressive weight loss. Gross pathology revealed a very narrow pylorus and multiple flaccid diverticula of the small intestines. Histopathological findings included severe lymphoplasmacytic encephalomyelitis and multifocal lymphocytic neuritis associated with the gastrointestinal tract. Immunohistochemistry and polymerase chain reaction on the brain were positive for an avian bornavirus (ABV), and partial sequencing of the matrix gene identified aquatic bird bornavirus-1 (ABBV-1), 100% identical to viruses circulating in wild Canada geese (Branta canadensis). As wild geese frequently grazed and defaecated in the emu's outdoor exhibit, natural transmission of ABBV-1 from free-ranging waterfowl to the emu was presumed to have occurred.

Investigation of Different Infection Routes of Parrot Bornavirus in Cockatiels

The aim of this study was to determine the natural infection route of parrot bornavirus (PaBV), the causative agent of proventricular dilatation disease (PDD) in psittacines. For this purpose, nine cockatiels ( Nymphicus hollandicus ) were inoculated orally, and nine cockatiels were inoculated intranasally, with a PaBV-4 isolate. To compare the results of the trials, the same isolate and the same experimental design were used as in a previous study where infection was successful by intravenous as well as intracerebral inoculation. After inoculation, the birds were observed for a period of 6 mo and tested for PaBV RNA shedding, virus replication, presence of inflammatory lesions, and PaBV-4 antigen in tissues, as well as specific antibody production. In contrast to the previous study involving intravenous and intracerebral infections, clinical signs typical for PDD were not observed in this study. Additionally, anti-PaBV antibodies and infectious virus were not detected in any investigated bird during the study. Parrot bornavirus RNA was detected in only four birds early after infection (1-34 days postinfection). Furthermore, histopathologic examination did not reveal lesions typical for PDD, and PaBV antigen was not detected in any organ investigated by immunohistochemistry. In summary, oral or nasal inoculation did not lead to a valid infection with PaBV in these cockatiels. Therefore it seems to be questionable that the formerly proposed fecal-oral transmission is the natural route of infection in immunocompetent adult or subadult cockatiels.

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.

Occurrence of a mosquito vector in bird houses: Developmental consequences and potential epidemiological implications

Even with continuous vector control, dengue is still a growing threat to public health in Southeast Asia. Main causes comprise difficulties in identifying productive breeding sites and inappropriate targeted chemical interventions. In this region, rural families keep live birds in backyards and dengue mosquitoes have been reported in containers in the cages. To focus on this particular breeding site, we examined the capacity of bird fecal matter (BFM) from the spotted dove, to support Aedes albopictus larval growth. The impact of BFM larval uptake on some adult fitness traits influencing vectorial capacity was also investigated. In serial bioassays involving a high and low larval density (HD and LD), BFM and larval standard food (LSF) affected differently larval development. At HD, development was longer in the BFM environment. There were no appreciable mortality differences between the two treatments, which resulted in similar pupation and adult emergence successes. BFM treatment produced a better gender balance. There were comparable levels of blood uptake and egg production in BFM and LSF females at LD; that was not the case for the HD one, which resulted in bigger adults. BFM and LSF females displayed equivalent lifespans; in males, this parameter was shorter in those derived from the BFM/LD treatment. Taken together these results suggest that bird defecations successfully support the development of Ae. albopictus. Due to their cryptic aspects, containers used to supply water to encaged birds may not have been targeted by chemical interventions.

Investigation into the possibility of vertical transmission of avian bornavirus in free-ranging Canada geese (Branta canadensis)

To investigate the possibility of in ovo infection with avian bornavirus (ABV) in wild Canada geese (Branta canadensis), 53 eggs were opportunistically collected at various stages of embryonic development from 16 free-ranging goose nests at a large urban zoo site where ABV infection is known to be present in this species. ABV RNA was detected in the yolk of one of three unembryonated eggs using real-time reverse transcription polymerase chain reaction. ABV RNA was not identified in the brains from 23 newly hatched goslings or 19 embryos, nor from three early whole embryos. Antibodies against ABV were not detected in the plasma of any of the hatched goslings using an enzyme-linked immunosorbent assay. Possible reasons for the failure to detect ABV RNA in hatchlings or embryos include low sample size, eggs deriving from parents not actively infected with ABV, the testing of only brain tissue, and failure of the virus to replicate in Canada goose embryos. In conclusion, this preliminary investigation demonstrating the presence of ABV RNA in the yolk of a Canada goose egg provides the first evidence for the potential for vertical transmission of ABV in waterfowl.

Avian bornavirus in free-ranging waterfowl: prevalence of antibodies and cloacal shedding of viral RNA

We surveyed free-ranging Canada Geese (Branta canadensis), Trumpeter Swans (Cygnus buccinator), Mute Swans (Cygnus olor), and Mallards (Anas platyrhynchos) to estimate the prevalence of antibodies to avian bornavirus (ABV) and of cloacal shedding of ABV RNA in southern Ontario, Canada. Blood samples and cloacal swabs were collected from 206 free-ranging Canada Geese, 135 Trumpeter Swans, 75 Mute Swans, and 208 Mallards at 10 main capture sites between October 2010 and May 2012. Sera were assessed for antibodies against ABV by enzyme-linked immunosorbent assay and swabs were evaluated for ABV RNA using real-time reverse-transcription PCR. Serum antibodies were detected in birds from all four species and at each sampling site. Thirteen percent of the geese caught on the Toronto Zoo site shed ABV RNA in feces compared with 0% in geese sampled at three other locations. The proportions of shedders among Mute Swans, Trumpeter Swans, and Mallards were 9%, 0%, and 0%, respectively. Birds that were shedding viral RNA were more likely to have antibodies against ABV and to have higher antibody levels than those that were not, although many birds with antibodies were not shedding. We confirmed that exposure to, or infection with, ABV is widespread in asymptomatic free-ranging waterfowl in Canada; however, the correlation between cloacal shedding, presence of antibodies, and presence of disease is not fully understood.

Detection of Avian bornavirus in multiple tissues of infected psittacine birds using real-time reverse transcription polymerase chain reaction

Avian bornavirus (ABV), the cause of proventricular dilation disease in psittacine birds, has been detected in multiple tissues of infected birds using immunohistochemical staining (IHC) and reverse transcription polymerase chain reaction (RT-PCR). In the current study, real-time RT-PCR, using primers targeting the ABV matrix gene, was used to detect ABV in 146 tissues from 7 ABV-infected psittacine birds. Eighty-six percent of the samples tested positive, with crossing point values ranging from 13.82 to 37.82 and a mean of 22.3. These results were compared to the findings of a previous study using gel-based RT-PCR and IHC on the same samples. The agreement between the 2 RT-PCR techniques was 91%; when tests disagreed it was because samples were negative using gel-based RT-PCR but positive on real-time RT-PCR. Agreement with IHC was 77%; 16 out of 74 samples were negative using IHC but positive on real-time RT-PCR. The results suggest that real-time RT-PCR is a more sensitive technique than gel-based RT-PCR and IHC to detect ABV in tissues. The tissues that were ranked most frequently as having a high amount of viral RNA were proventriculus, kidney, colon, cerebrum, and cerebellum. Skeletal muscle, on the other hand, was found to have a consistently low amount of viral RNA.

Avian bornavirus and proventricular dilatation disease: diagnostics, pathology, prevalence, and control

Avian bornavirus (ABV) has been shown the cause of proventricular dilatation disease (PDD) in psittacines. Many healthy birds are infected with ABV, and the development of PDD in such cases is unpredictable. As a result, the detection of ABV in a sick bird is not confirmation that it is suffering from PDD. Treatment studies are in their infancy. ABV is not restricted to psittacines. It has been found to cause PDD-like disease in canaries. It is also present at a high prevalence in North American geese, swans, and ducks. It is not believed that these waterfowl genotypes can cause disease in psittacines.