Proventricular Dilatation Disease Research Articles

Parrot bornavirus infection: correlation with neurological signs and feather picking?

Borna disease virus is the causative agent of Borna disease, which is characterised by nonsuppurative meningoencephalomyelitis caused by cellular immune responses against the viral antigens.1 This virus has been extensively...

Detection of Avian Bornavirus in Wild and Captive Passeriformes in Brazil.

Avian bornaviruses (ABVs) are the causative agents of proventricular dilatation disease (PDD), a fatal neurologic disease considered to be a major threat to psittacine bird populations. We performed a reverse transcription PCR survey to detect the presence of canary avian bornavirus (CnBV) in birds of order Passeriformes related to different clinical manifestations, such as sudden death, neurologic signs, apathy, anorexia, excessive beak growth, and PDD. A total of 227 samples from captive and wild canaries were included, of which 80 samples were captive birds, comprising saffron finches (n = 71) and common canary (n = 9), and 147 samples were wild birds distributed among a variety of several species. Two samples from captive birds (2/80) were positive for ABV, and in wild birds, only one sample was positive for ABV. The positive samples were subjected to DNA sequencing, and only the CnBV-1 serotype was found, which was the first time it was detected outside of Germany (Austria/Hungary), where it was first detected in 2009. Phylogenetic analysis confirmed that avian bornavirus serotype CnBV-1 is present in order Passeriformes in Brazil.

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

In Thailand a proventricular dilation disease (PDD)-like syndrome commonly occurs in captive psittacine birds. The etiology, however, has been unknown to date and studies to detect parrot bornaviruses have never been performed in Southeastern Asia. Therefore, 111 psittacines (22 different species) including birds with suspected PDD based on clinical examination results (n = 65), cage mates of PDD suspected parrots without any clinical signs (n = 39) and dead birds with previous clinic suspicious for PDD (n = 7) were tested for bornaviruses using various reverse transcription polymerase chain reaction (RT-PCR) and realtime RT-PCR protocols, an enzyme-linked immunosorbent assay (ELISA), immunohistochemistry, and genome sequencing. Bornaviral infections, indicated by the presence of RNA or antibody positive reactions were detected in 60 birds (54.1%) belonging to 15 psittaciform species and originating from 41 owners. Occurrence of Psittaciform 1 orthobornavirus was confirmed by sequencing of PCR products in 24 of these birds. Parrot bornavirus (PaBV)-5, belonging to the species Psittaciform 2 orthobornavirus and found only in single birds in the United States of America, Japan and Hungary until now, was identified in a macaw. Full genome sequencing revealed features shared with other strains of this virus. PaBV-4 was the prevalent virus type and the viruses grouped in two of the five genetic PaBV-4 subclusters known so far while PaBV-2 was found in a single patient. Forty-five psittacines of the group of PDD-suspected birds (69.2%), 4 dead birds and 11 clinically healthy cage mates were positive in at least one test the latter suggesting inefficient horizontal transmission in natural infections. Lymphoplasmacytic infiltrations (non-purulent inflammation, ganglioneuritis) and bornavirus antigen were detected in diverse tissues confirming PDD as the disease involved. These results may have a major impact on conservation projects including the five near-threatened parrot species living in the wild in Thailand.

Studies on immunity and immunopathogenesis of parrot bornaviral disease in cockatiels

We have demonstrated that vaccination of cockatiels (Nymphicus hollandicus) with killed parrot bornavirus (PaBV) plus recombinant PaBV-4 nucleoprotein (N) in alum was protective against disease in birds challenged with a virulent bornavirus isolate (PaBV-2). Unvaccinated birds, as well as birds vaccinated after challenge, developed gross and histologic lesions typical of proventricular dilatation disease (PDD). There was no evidence that vaccination either before or after challenge made the infection more severe. Birds vaccinated prior to challenge largely remained free of disease, despite the persistence of the virus in many organs. Similar results were obtained when recombinant N, in alum, was used for vaccination. In some rodent models, Borna disease is immune mediated thus we did an additional study whereby cyclosporine A was administered to unvaccinated birds starting 1day prior to challenge. This treatment also conferred complete protection from disease, but not infection.

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.

Proventricular dilatation disease (PDD) outbreak in blue-and-gold macaws (Ara ararauna) in the State of Santa Catarina, southern Brazil

ABSTRACT: Proventricular dilatation disease (PDD) is a lethal and important disease of captive psittacine birds, and affects a wide range of species, including endangered ones, and lacks an effective treatment. This report describes PDD in three blue-and-gold macaws (Ara ararauna) in southern Brazil. All three macaws originated from the same aviary and presented similar clinical signs including anorexia, apathy, emaciation and prostration. At necropsy, one of the macaws presented an enlarged proventriculus. Histologically, lymphoplasmacytic infiltrates was observed in the ganglia and nerves of the esophagus, crop, proventriculus, ventriculus, heart, adrenal glands, and adrenal medulla of all three cases. Two macaws had meningoencephalomyelitis and one had myocarditis. Immunohistochemistry identified PaBV antigen in the brain, proventricular, ventricular ganglia, and epicardial ganglia, and cardiomyocytes of all three macaws.

Could introducing confiscated parrots to zoological collections jeopardise conservation breeding programmes?

SummaryConfiscated parrots are frequently introduced to captive populations in zoological institutions, regularly with insufficient health screening. This short communication describes a case where 25 confiscated parrots, from four different locations, were brought to the same zoological institution within two years, where they were kept under quarantine conditions. A year after the last birds arrived, several birds died due to either proventricular dilatation disease or herpesvirus infection. As all individuals belonged to rare species, the surviving birds were transferred to the Justus-Liebig-University in Giessen, Germany, for thorough diagnostics including parrot bornavirus, psittacine herpesvirus 1, adenovirus, polyomavirus, circovirus, Chlamydia psittaci, and mycobacteria. Birds that tested negative for all pathogens were transferred to captive breeding programmes, whereas pathogen carriers were paired up in collections of a similar pathogen status. This case report highlights the dangers of latent infections with different pathogens and the importance of managed screening programmes if such populations are to be considered for conservation.

Campylobacter colonization is not associated with proventricular dilatation disease in psittacines.

Psittacine proventricular dilatation disease (PDD) is a neurological disease caused by parrot bornaviruses. A competing theory suggests that intestinal colonization by Campylobacter species may also be a potential cause of PDD or that their presence may be required for disease development. This theory proposes that PDD results from the activities of antiganglioside antibodies on enteric neurons in a manner similar to the pathogenesis of Guillain–Barré syndrome in humans. We therefore cultured feces from domestic chickens as well as from multiple parrot species to determine whether Campylobacter spp. could be detected in the latter. We failed to detect Campylobacter in a flock of cockatiels known to be highly susceptible to experimental parrot bornavirus-induced PDD. Even in naturally infected psittacines suffering from clinical PDD, no Campylobacter species were detected. Conversely, Campylobacter was readily cultured from domestic poultry samples and confirmed by using matrix-associated laser desorption ionization mass spectroscopy/real-time polymerase chain reaction. We conclude that not only are Campylobacter infections of psittacines uncommon, but also that infection by Campylobacter species is not related to the etiology of PDD.

Plasma protein, haematologic and blood chemistry changes in African grey parrots (Psittacus erithacus) experimentally infected with bornavirus

ABSTRACTBornaviruses are considered to be the causative agent of proventricular dilatation disease (PDD) in psittacine birds. In order to detect haematological and blood chemistry changes during the development of PDD and a possible correlation with clinical signs and the virological status, six African grey parrots (Psittacus erithacus) were experimentally infected with parrot bornavirus 4 (PaBV-4) by subcutaneous route. All six parrots developed clinical signs of varying extent and successful infection was confirmed in all the birds by seroconversion or detection of RNA of the PaBV-4 infection strain. Based on population-based and intra-individual reference ranges established during 12 months prior to experimental infection, only minor haematological changes were detected in individual birds after infection. Changes in blood chemistry were restricted to aspartate aminotransferase, creatine kinase, total protein, glucose and uric acid. Plasma protein electrophoresis revealed marked changes starting 10 weeks post infection characterized by an increase in the γ-globulin fraction and a gradual decrease to normal values during weeks 22–34. Indications of an acute-phase reaction at the initial stages of infection were not detected. While three birds suffered from clinical signs of PDD, which included weight loss and neurological disorders and died before development of haematological and plasma protein changes, recovery of clinical disease was paralleled in the remaining birds by an increase in γ-globulins and bornavirus-specific antibody titres.

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.

Are anti-ganglioside antibodies associated with proventricular dilatation disease in birds?

The identification of Parrot bornaviruses (PaBV) in psittacine birds with proventricular dilatation disease (PDD) has not been sufficient to explain the pathogenesis of this fatal disease, since not all infected birds develop clinical signs. Although the most accepted theory indicates that PaBV directly triggers an inflammatory response in this disease, another hypothesis suggests the disease is triggered by autoantibodies targeting neuronal gangliosides, and PDD might therefore resemble Guillain-Barré Syndrome (GBS) in its pathogenesis. Experimental inoculation of pure gangliosides and brain-derived ganglioside extracts were used in two different immunization studies. The first study was performed on 17 healthy chickens (Gallus gallus domesticus): 11 chickens were inoculated with a brain ganglioside extract in Freund’s complete adjuvant (FCA) and six chickens inoculated with phosphate-buffered saline. A second study was performed five healthy quaker parrots (Myiopsitta monachus) that were divided into three groups: Two quaker parrots received purified gangliosides in FCA, two received a crude brain extract in FCA, and one control quaker parrot received FCA alone. One chicken developed difficult in walking. Histologically, only a mild perivascular and perineural lymphocytic infiltrate in the proventriculus. Two quaker parrots (one from each treatment group) had mild lymphoplasmacytic encephalitis and myelitis. However, none of the quaker parrots developed myenteric ganglioneuritis, suggesting that autoantibodies against gangliosides in birds are not associated with a condition resembling PDD.

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 protect cockatiels from inflammatory lesions after heterologous parrot bornavirus 2 challenge infection

Avian bornaviruses are causative agents of proventricular dilatation disease (PDD), a chronic neurologic and often fatal disorder of psittacines including endangered species. To date no causative therapy or immunoprophylaxis is available. Our previous work has shown that viral vector vaccines can delay the course of homologous bornavirus challenge infections but failed to protect against PDD when persistent infection was not prevented.The goal of this study was to refine our avian bornavirus vaccination and infection model to better represent natural bornavirus infections in order to achieve full protection against a heterologous challenge infection.We observed that parrot bornavirus 2 (PaBV-2) readily infected cockatiels (Nymphicus hollandicus) by combined intramuscular and subcutaneous injection with as little as 102.7foci-forming units (ffu) per bird, whereas a 500-fold higher dose of the same virus administered via peroral and oculonasal route did not result in persistent infection. These results indicated that experimental bornavirus challenge infections with this virus should be performed via the parenteral route.Prime-boost vaccination of cockatiels with Newcastle disease virus (NDV) and modified vaccinia virus Ankara (MVA) vectors expressing the nucleoprotein and phosphoprotein genes of PaBV-4 substantially blocked bornavirus replication following parenteral challenge infection with 103.5ffu of heterologous PaBV-2. Only two out of six vaccinated birds had very low viral levels detectable in a few organs. As a consequence, only one vaccinated bird developed mild PDD-associated microscopic lesions, while mock-vaccinated controls were not protected against PaBV-2 infection and inflammation.Our results demonstrate that NDV and MVA vector vaccines can protect against invasive heterologous bornavirus challenge infections and subsequent PDD. These vector vaccines represent a promising tool to combat avian bornaviruses in psittacine populations.

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.

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.

BackgroundAvian 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 MethodsIn 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 StudyWithin 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.

Synergistic antiviral activity of ribavirin and interferon-α against parrot bornaviruses in avian cells.

Avian bornaviruses are the causative agents of proventricular dilatation disease (PDD), a widely distributed and often fatal disease in captive psittacines. Because neither specific prevention measures nor therapies against PDD and bornavirus infections are currently available, new antiviral strategies are required to improve animal health. We show here that the nucleoside analogue ribavirin inhibited bornavirus activity in a polymerase reconstitution assay and reduced viral load in avian cell lines infected with two different parrot bornaviruses. Furthermore, we observed that ribavirin enhanced type I IFN signalling in avian cells. Combined treatment of avian bornavirus-infected cells with ribavirin and recombinant IFN-α strongly enhanced the antiviral efficiency compared to either drug alone. The combined use of ribavirin and type I IFN might represent a promising new strategy for therapeutic treatment of captive parrots persistently infected with avian bornaviruses.

Occurrence of Bacterial and Viral Pathogens in Common and Noninvasive Diagnostic Sampling from Parrots and Racing Pigeons in Slovenia.

Airborne pathogens can cause infections within parrot (Psittaciformes) and pigeon (Columbiformes) holdings and, in the case of zoonoses, can even spread to humans. Air sampling is a useful, noninvasive method which can enhance the common sampling methods for detection of microorganisms in bird flocks. In this study, fecal and air samples were taken from four parrot holdings. Additionally, cloacal and oropharyngeal swabs as well as air samples were taken from 15 racing pigeon holdings. Parrots were examined for psittacine beak and feather disease virus (PBFDV), proventricular dilatation disease virus (PDDV), adenoviruses (AdVs), avian paramyxovirus type-1 (APMV-1), avian influenza virus (AIV), Chlamydia psittaci (CP), and Mycobacterium avium complex (MAC). MAC and AdVs were detected in three parrot holdings, CP was detected in two parrot holdings, and PBFDV and PDDV were each detected in one parrot holding. Pigeons were examined for the pigeon circovirus (PiCV), AdVs, and CP; PiCV and AdVs were detected in all investigated pigeon holdings and CP was detected in five pigeon holdings.

Parrot Bornavirus (PaBV)-2 isolate causes different disease patterns in cockatiels than PaBV-4

ABSTRACTPsittaciform 1 bornavirus (PaBV) has already been shown to be the aetiologic agent of proventricular dilatation disease, a significant disease of birds. However, the pathogenesis of PaBV infection has not yet been resolved and valid data regarding the pathogenicity of different PaBV species are lacking. Thus, the present study was aimed to characterize the influence of two different PaBV species on the course of disease. Eighteen cockatiels were inoculated intracerebrally (i.c.) or intravenously (i.v.) with a PaBV-2 isolate under the same conditions as in a previous study using PaBV-4. Birds were surveyed and sampled for 33 weeks to analyse the course of infection and disease in comparison to that of PaBV-4. Similar to PaBV-4, PaBV-2 induced a persistent infection with seroconversion (from day 6 p.i. onwards) and shedding of viral RNA (from day 27 p.i. onwards). However, in contrast to PaBV-4, more birds displayed clinical signs and disease progression was more severe. After PaBV-2 infection, 12 birds exhibited clinical signs and 10 birds revealed a dilated proventriculus in necropsy. After PaBV-4 infection only four birds revealed clinical signs and seven birds showed a dilatation of the proventriculus. Clinically, different courses of disease were observed after PaBV-2 infection, mainly affecting the gastrointestinal tract. This had not been detected after PaBV-4 infection where more neurological signs were noted. The results provide evidence for different disease patterns according to different PaBV species, allowing the comparison between the infection with two PaBV species, and thus underlining the role of viral and individual host factors for disease outcome.

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.