Detection and heterogeneity of herpesviruses causing Pacheco's disease in parrots

A Survey of Diseases in Different Species of Wild, Captive, and Illegally Traded Birds in Brazil

Native and exotic avian species can act as reservoirs of pathogens, including bacteria and viruses, with conservation and public health implications. A retrospective study on the diagnosis and frequency of diseases in wild and exotic avian species was conducted. The occurrence of particular diseases was associated with the type of captivity or the bird's origin. The investigation included macroscopic and microscopic descriptions and the molecular determination of the causative agent(s). Additional immunohistochemical (IHC) analysis, PCR, and genetic sequencing were conducted. A total of 243 cases were compiled for the study, mainly consisting of native wild species (39.1%) obtained from illegal trade. Primary infectious diseases, mainly parasitic (18.1%) and viral (17.7%), were the most common, although coinfections were substantial (18.1%) in birds rescued from trafficking. Fractures and neoplasms accounted for 3.7% and 3.3% of the cases, respectively. Parasitic and viral diseases were the most common in both exotic and wild birds. Chlamydia psittaci, a lethal and zoonotic bacterium, was an important cause of death, especially in native Psittaciformes. The recent detection of Psittacid alphaherpesvirus 5 (PsAHV 5) in exotic psittacines and the diagnosis of coinfections in trafficked birds highlight the importance of monitoring avian health to control potential pathogens that may endanger conservation efforts.

Naturally occurring psittacid alphaherpesvirus 3 and probable adenovirus coinfection in an Indian ringneck parakeet in the United States

Psittacid alphaherpesvirus 3 (PsAHV-3) is a rarely reported virus that has been associated with pneumonia in psittacine birds. A 5-mo-old Indian ringneck parakeet (syn. rose-ringed parakeet; Psittacula krameri) was euthanized after developing torticollis and lethargy. Postmortem examination of the parakeet revealed severe pneumonia with syncytial cells containing eosinophilic intranuclear inclusion bodies (INIBs) in the respiratory epithelium. Gene sequencing of total DNA extraction detected PsAHV-3 in the frozen lung. The pancreas had severe lytic necrosis, with the remaining parenchymal cells expanded by large basophilic INIBs. Electron microscopy of the pancreas revealed intranuclear paracrystalline arrays of viral particles morphologically resembling adenovirus. Although we found 3 PsAHV-3 cases in birds in a literature search, we found no cases with adenoviral coinfection.

Unexpected Pathogen Diversity Detected in Australian Avifauna Highlights Potential Biosecurity Challenges

Birds may act as hosts for numerous pathogens, including members of the family Chlamydiaceae, beak and feather disease virus (BFDV), avipoxviruses, Columbid alphaherpesvirus 1 (CoAHV1) and Psittacid alphaherpesvirus 1 (PsAHV1), all of which are a significant biosecurity concern in Australia. While Chlamydiaceae and BFDV have previously been detected in Australian avian taxa, the prevalence and host range of avipoxviruses, CoAHV1 and PsAHV1 in Australian birds remain undetermined. To better understand the occurrence of these pathogens, we screened 486 wild birds (kingfisher, parrot, pigeon and raptor species) presented to two wildlife hospitals between May 2019 and December 2021. Utilising various qPCR assays, we detected PsAHV1 for the first time in wild Australian birds (37/486; 7.61%), in addition to BFDV (163/468; 33.54%), Chlamydiaceae (98/468; 20.16%), avipoxviruses (46/486; 9.47%) and CoAHV1 (43/486; 8.85%). Phylogenetic analysis revealed that BFDV sequences detected from birds in this study cluster within two predominant superclades, infecting both psittacine and non-psittacine species. However, BFDV disease manifestation was only observed in psittacine species. All Avipoxvirus sequences clustered together and were identical to other global reference strains. Similarly, PsAHV1 sequences from this study were detected from a series of novel hosts (apart from psittacine species) and identical to sequences detected from Brazilian psittacine species, raising significant biosecurity concerns, particularly for endangered parrot recovery programs. Overall, these results highlight the high pathogen diversity in wild Australian birds, the ecology of these pathogens in potential natural reservoirs, and the spillover potential of these pathogens into novel host species in which these agents cause disease.

Detection and Phylogenetic Characterization of a Novel Herpesvirus in Sooty Terns Onychoprion fuscatus

Since 2005, we have recorded annual episodes of alphaherpesvirus outbreaks in chicks of magnificent frigatebird Fregata magnificens on the Ile du Grand Connétable Nature Reserve in French Guiana. In 2009, we found sooty terns, Onychoprion fuscatus, that live sympatrically with frigatebirds, with visible clinical signs of a potential viral infection. To determine if the symptoms observed in sooty terns could be associated with an alphaherpesvirus previously identified in frigatebirds, we carried out molecular screening of samples collected from seven individuals. We identified and characterized a novel viral sequence from five birds. BLAST searches, pairwise nucleotide, and amino acid sequence comparisons, as well as phylogenetic analyses confirmed that the sequence belonged to the Herpesviridae family, of the Alphaherpesvirinae subfamily. We observed that it clustered with strains isolated from Podargidae (Caprimulgiformes), Columbiformes, and Falconiformes, but was distinct from the frigatebird herpesvirus. We have tentatively named it Onychoprion fuscatus alphaherpesvirus 1, (OfusAHV1). These two sequences, although found syntopic on the Ile du Grand Connétable, belong to two distinct alphaherpesvirus strains. Thus, the clinical symptoms showed by sooty terns do not likely result from a cross-species transmission event. Future work is needed to better characterize the virus and to investigate herpesvirus prevalence in healthy, free-ranging sooty terns, and to assess the impact of the virus on population viability.

Avian Papilloma and Squamous Cell Carcinoma: a Histopathological, Immunohistochemical and Virological study

In this retrospective study, we describe the histopathological findings in seven papillomas and 45 squamous cell carcinomas (SCCs) from psittacine birds, raptors and domestic fowl. The age of affected birds ranged from 3 to 40 years, with median age significantly higher in psittacines (P = 0.014). The majority of tumours were located in the skin (24/52, 46.2%) or uropygial gland (10/52, 19.2%). Thirty of the SCCs (66.7%) were well differentiated and 15 (33.3%) were poorly-differentiated. SCCs exhibited a significantly higher degree of nuclear pleomorphism (P = 0.005) and a greater proportion were ulcerated (P = 0.001) compared with papillomas; however, there was no significant difference in mitotic count (MC) or inflammation score. The expression of cyclo-oxygenase (COX)-2 and E-cadherin was investigated by immunohistochemistry. The COX-2 total score (TS) was significantly higher in SCCs compared with papillomas (P = 0.002), but the difference between COX-2 TS of well- and poorly-differentiated SCCs was not significant. COX-2 labelling was predominantly cytoplasmic, but some tumours had concurrent membranous and/or perinuclear labelling. SCCs with membranous labelling had a significantly higher MC (P = 0.028). A significantly higher proportion of SCCs were negative for E-cadherin compared with papillomas (P = 0.042), but there was no significant difference between well- and poorly-differentiated SCCs. Fourteen papillomas and SCCs from psittacines were also tested by polymerase chain reaction for the presence of Psittacus erithacus papillomavirus 1 and Psittacid herpesvirus 1, but all samples tested negative. We demonstrate for the first time the expression of COX-2 and E-cadherin in avian tissues, and suggest that these markers may be useful in differentiating papillomas from SCCs, particularly when sample size is small.

Phylogenetic characterization of a novel herpesvirus found in the liver and lungs of a Chilean flamingo (Phoenicopterus chilensis)

A novel herpesvirus was detected in a 17-day-old Chilean flamingo (Phoenicopterus chilensis) with pneumonia, hepatopathy, and severe anemia that was housed in California. Postmortem examination identified a pale, enlarged liver, mildly increased fluid in the lungs, and red foci in the spleen. Histologic examination revealed marked hepatic necrosis with syncytia, splenic necrosis, and interstitial pneumonia with eosinophilic intranuclear inclusions within hepatocytes and in unidentified cells of the lung. Transmission electron microscopy identified virions consistent with a herpesvirus in the nucleus and cytoplasm of degenerative hepatocytes. Nested consensus PCR, sequencing, and phylogenetic analysis identified a novel herpesvirus within the genus Iltovirus in the subfamily Alphaherpesvirinae.

Neck Kaposiform haemangioendothelioma in a Fischer's lovebird (Agapornis fischeri)

A six-year-old female Fischer's lovebird (Agapornis fischeri) presented at necropsy with a cutaneous mass on the neck, 3.5cm in diameter, yielding and with blood content. Histopathological findings showed a neoplasm characterized by proliferation of vascular endothelial cells. The histology of the mass revealed a multinodular, focally infiltrating tumor. Deeper dermal nodules were made of spindle cells forming vascular slits reminiscent of the histology seen in Kaposi's sarcoma (KS). More superficially located dermal nodules consisted of small blood vessels, with histology resembling capillary hemangioma. The spindle cells and capillaries were strongly positive for Vimentin, endothelial cell marker CD31, and negative for sarcomeric α-smooth muscle actin (α-SMA). Intravascular platelet trapping and Periodic acid-Schiff (PAS)-positive hyaline globules were also observed. Differential diagnosis included Kaposi's sarcoma, capillary haemangioma, spindle cell haemangioendothelioma, and epithelioid haemangioendothelioma. Based on morphological and immunohistochemical findings, the tumor was diagnosed as a cutaneous Kaposiform haemangioendothelioma (KHE), a rare, low-grade malignant vascular neoplasm. Other organs showed no abnormalities. PCR amplifications, conducted using Kaposi's sarcoma-associated herpesvirus (KSHV)-specific primers and degenerate sets of primers designed to detect and characterize members of the Herpesviridae, on DNA extracted from tumor tissue and from whole blood failed to amplify any KSHV-related sequence. Moreover, no specific signal was obtained using primers for detection of psittacine herpesvirus, known to be linked to Pacheco's disease in parrots. To the best of our knowledge, this unusual case is the third report of KHE in a non-human animal species, the first described in a bird.

Genotypic characterization of psittacid herpesvirus isolates from Brazil

Thirty-six isolates of psittacid herpesvirus (PsHV), obtained from 12 different species of psittacids in Brazil, were genotypically characterized by restriction fragment length polymorphism (RFLP) analysis and PCR amplification. RFLP analysis with the PstI enzyme revealed four distinct restriction patterns (A1, X, W and Y), of which only A1 (corresponding to PsHV-1) had previously been described. To study PCR amplification patterns, six pairs of primers were used. Using this method, six variants were identified, of which, variants 10, 8, and 9 (in this order) were most prevalent, followed by variants 1, 4, and 5. It was not possible to correlate the PCR and RFLP patterns. Twenty-nine of the 36 isolates were shown to contain a 419 bp fragment of the UL16 gene, displaying high similarity to the PsHV-1 sequences available in GenBank. Comparison of the results with the literature data suggests that the 36 Brazilian isolates from this study belong to genotype 1 and serotype 1.

Identification and isolation of psittacid herpesvirus from psittacids in Brazil

Psittacid herpesvirus (PsHV) was isolated from 41 birds kept in captivity in Belo Horizonte, Minas Gerais/Brazil using chicken embryo fibroblasts (CEF) cell cultures. For this study, leukocytes or cloacal swabs of live birds were used. Also, portions of liver, spleen or kidney from birds collected at necropsy were utilized for these tests. PCR tests confirmed the presence of PsHV in 100% of samples. Thirty-three of the PCR products were sequenced and the results disclosed a 99% and 100% identity when compared with other sequences PsHV-1 (AY372243.1 and AF261756.1), previously deposited in GenBank. In addition, histopathology was performed and 19 of the 29 birds contained random multifocal lymphoplasmacytic hepatitis with necrotic foci, suggestive of viral infection. Three samples were examined by electron microscopy to visualize the viral particles obtained from cell culture. The viral structures measured 269 nm in average, had envelopes with an icosahedral capsid and tegument, consistent with herpesvirus. Thus, a total of 41 isolates were obtained from PsHV cell cultivation in CEF, confirming the circulation of the virus between parrots kept in captivity in Belo Horizonte, and affirming the importance of further studies in this area.

Molecular genetic and pathogenic characterization of psittacid herpesvirus type 1 isolated from a captive galah (Eolophus roseicapillus) in Japan

Psittacid herpesvirus type 1 (PsHV-1) was isolated from a captive galah (Eolophus roseicapillus) in Japan that was suspected of having Pacheco's disease (PD), an acute fatal disease in psittacine birds. PsHV-1 has been classified into four genotypes based on the UL16 gene sequence. In the present study, we investigated the genetic and pathogenic characteristics of the isolated virus, FOY-1, compared with a reference strain, RSL-1. The FOY-1 strain was classified into PsHV-1 genotype 2. The FOY-1 strain was found to be less pathogenic to budgerigars than RSL-1, which was classified as genotype 4 in an in vivo study. This is the first report regarding the classification of originally isolated PsHV-1 in Japan and its characterization by animal infection experiment.

Respiratory herpesvirus infection in two Indian Ringneck parakeets

A flock of Indian Ringneck parakeets ( Psittacula krameri manillensis) was imported to the United States from Australia. Soon after, 1 parakeet suddenly died, and a second parakeet died after a 2-day course of illness, which consisted of anorexia, lethargy, emaciation, and dyspnea. At necropsy, the affected birds had diffuse consolidation and red discoloration of the lungs, as well as thickened, congested air sacs. The microscopic examination revealed multifocal, necrotizing bronchitis, parabronchitis, and interstitial pneumonia. The lumen of the affected airways contained numerous, large syncytial cells with up to 15 nuclei. The nuclei of these syncytial cells often contained large, eosinophilic inclusion bodies, consistent with herpesvirus. The epithelium of the trachea and air sacs was hypertrophied and contained syncytial cells with intranuclear inclusion bodies similar to the bronchi. In addition, a few intranuclear inclusion bodies were also present in the epithelial cells that line the air capillaries. On ultrastructural examination, the nuclei of degenerating epithelial cells contained clusters of viral nucleocapsid proteins and unenveloped, icosahedral, viral particles that were approximately 90 nm in diameter. In addition, some epithelial cells contained clusters of enveloped viral particles approximately 105 nm in diameter, within the cytocavitary network. These lesions are characteristic of those caused by respiratory herpesvirus of parakeets.

Pacheco's disease in a Hungarian zoo bird population: a case report

An epizootic of Pacheco's disease is reported from a zoo bird population. The infection was introduced by wild-captured Patagonian conures (Cyanoliseus patagonus) despite 61 days of quarantine. The disease affected several parrot species and, interestingly, three out of seven bearded barbets (Lybius dubius). The mortality rate was 30.93%. Autopsy revealed abdominal hyperaemia with liver haemorrhages and, in less rapid cases, yellowish discoloration and fragility of the liver. Death was caused by the collapse of circulation. Histopathology demonstrated liver cell necrosis, disintegration of the lobular structure, and a few intranuclear inclusion bodies. Icosahedral virions were detected by electron microscopy. The virus was isolated in the allantoic cavity of embryonated chicken eggs as well as in chicken embryo fibroblast cell culture. A 281-bp-long fragment of psittacid herpesvirus DNA was detected by PCR in cell culture material and liver samples of the affected birds. To our knowledge this is the first report of Pacheco's disease in bearded barbets as well as the first occurrence of Pacheco's disease in Hungary.

Psittacid herpesvirus 1 and infectious laryngotracheitis virus: Comparative genome sequence analysis of two avian alphaherpesviruses

Psittacid herpesvirus 1 (PsHV-1) is the causative agent of Pacheco's disease, an acute, highly contagious, and potentially lethal respiratory herpesvirus infection in psittacine birds, while infectious laryngotracheitis virus (ILTV) is a highly contagious and economically significant avian herpesvirus which is responsible for an acute respiratory disease limited to galliform birds. The complete genome sequence of PsHV-1 has been determined and compared to the ILTV sequence, assembled from published data. The PsHV-1 and ILTV genomes exhibit similar structural characteristics and are 163,025 bp and 148,665 bp in length, respectively. The PsHV-1 genome contains 73 predicted open reading frames (ORFs), while the ILTV genome contains 77 predicted ORFs. Both genomes contain an inversion in the unique long region similar to that observed in pseudorabies virus. PsHV-1 is closely related to ILTV, and it is proposed that it be assigned to the Iltovirus genus. These two avian herpesviruses represent a phylogenetically unique clade of alphaherpesviruses that are distinct from the Marek's disease-like viruses (Mardivirus). The determination of the complete genomic nucleotide sequences of PsHV-1 and ILTV provides a tool for further comparative and functional analysis of this unique class of avian alphaherpesviruses.

A novel psittacid herpesvirus found in African grey parrots (Psittacus erithacus erithacus)

DNA from a novel alphaherpesvirus was amplified from a cloacal papilloma, a cutaneous papilloma, and the normal cloacal mucosa of African grey parrots (Psittacus erithacus erithacus). Phylogenetically, the virus was most closely related to the psittacid herpesvirus, but demonstrated sufficient nucleotide and amino acid diversity to be considered a new alphaherpesvirus. It is proposed that the previously described psittacid herpesvirus be designated as psittacid herpesvirus 1 (PsHV-1), and this new species be classified as psittacid herpesvirus 2 (PsHV-2). It is speculated that PsHV-2 co-evolved with the African grey parrot and should therefore be present in these birds in the wild.

Phylogenetic analysis of the DNA polymerase gene of a novel alphaherpesvirus isolated from an Indian Gyps vulture

The DNA polymerase gene of a novel herpesvirus, vulture herpesvirus (VHV), isolated from an Indian Gyps vulture was completely sequenced using primer walking and transposon insertion strategies. DNA sequencing analysis revealed a single open reading frame (ORF) of 3660 nucleotides (53% G-C content) able to encode 1219 amino acids. Identification was based on a nucleotide sequence identity of approximately 50% to other herpesvirus sequences found in Genbank. Nine motifs were identified that are conserved amongst all known herpesviruses and are found within the 3'-5' exonuclease and DNA binding functional domains of the DNA polymerase enzyme. Phylogenetic analysis using Clustal W with neighbour-joining revealed VHV to group within the subfamily Alphaherpesvirinae, more closely related to the avian herpesviruses than to those of other species. Partial sequence data also revealed VHV to contain other genes fundamental to the structure and replication of all herpesvirus genomes. A Real Time PCR Taqman assay specific for the VHV DNA polymerase gene was designed to detect the presence of VHV genomic material in post mortem tissue samples from diseased birds. Positive tissues included the spleen, rectum, thymus, kidney and brain. A herpesvirus specific to vultures may pose a threat to the management of captive breeding programs being established to assist the survival of wild populations of Gyps vultures.

Psittacid herpesviruses associated with mucosal papillomas in neotropical parrots

Mucosal papillomas are relatively common lesions in several species of captive neotropical parrots. They cause considerable morbidity and in some cases, result in mortality. Previous efforts to identify papillomavirus DNA and proteins in these lesions have been largely unsuccessful. In contrast, increasing evidence suggests that mucosal papillomas may contain psittacid herpesviruses (PsHVs). In this study, 41 papillomas from 30 neotropical parrots were examined by PCR with PsHV-specific primers. All 41 papillomas were found to contain PsHV DNA. This 100% prevalence of PsHV infection in the papilloma population was found to be significantly higher than PsHV infection prevalence observed in other surveys of captive parrots. PsHV genotypes 1, 2, and 3, but not 4 were found in these lesions. Psittacus erithacus papillomavirus DNA and finch papillomavirus DNA were not found in the papillomas. A papilloma from a hyacinth macaw (Anodorhynchus hyacinthinus) was found to contain cells that had immunoreactivity to antiserum made to the common antigenic region of human papillomavirus (HPV) L1 major capsid protein. However, four other mucosal papillomas were negative for this immunoreactivity, and negative control tissues from a parrot embryo showed a similar staining pattern to that seen in the cloaca papilloma of the hyacinth macaw, strongly suggesting that the staining seen in hyacinth macaw papilloma was nonspecific. Based on these findings, it was concluded that specific genotypes of PsHV play a direct role in the development of mucosal papillomas of neotropical parrots and there is no evidence to suggest the concurrent presence of a papillomavirus in these lesions.

Molecular phylogeny of the psittacid herpesviruses causing Pacheco's disease: correlation of genotype with phenotypic expression

Fragments of 419 bp of the UL16 open reading frame from 73 psittacid herpesviruses (PsHVs) from the United States and Europe were sequenced. All viruses caused Pacheco's disease, and serotypes of the European isolates were known. A phylogenetic tree derived from these sequences demonstrated that the PsHVs that cause Pacheco's disease comprised four major genotypes, with each genotype including between two and four variants. With the exception of two viruses, the serotypes of the virus isolates could be predicted by the genotypes. Genotypes 1 and 4 corresponded to serotype 1 isolates, genotype 2 corresponded to serotype 2 isolates, and genotype 3 corresponded to serotype 3 isolates. The single serotype 4 virus mapped to genotype 4. DNA from a virus with a unique serotype could not be amplified with primers that amplified DNA from all other PsHVs, and its classification remains unknown. Viruses representing all four genotypes were found in both the United States and Europe, and it was therefore predicted that serotypes 1, 2, and 3 were present in the United States. Serotype 4 was represented by a single European isolate that could not be genetically distinguished from serotype 1 viruses; therefore, the presence of serotype 4 in the United States could not be predicted. Viruses of genotype 4 were found to be the most commonly associated with Pacheco's disease in macaws and conures and were least likely to be isolated in chicken embryo fibroblasts in the United States. All four genotypes caused deaths in Amazon parrots, but genotype 4 was associated with Pacheco's disease only in Amazons in Europe. Genotypes 2, 3, and 4, but not 1, were found in African grey parrots. Although parrots from the Pacific distribution represent a relatively small percentage of the total number of birds with Pacheco's disease, all four genotypes were found to cause disease in these species.

Phylogenetic analysis identifies the 'megabacterium' of birds as a novel anamorphic ascomycetous yeast, Macrorhabdus ornithogaster gen. nov., sp. nov

An organism commonly referred to as 'megabacterium' colonizes the gastric isthmus of many species of birds. It is weakly gram-positive and periodic acid-Schiff-positive and stains with silver stains. Previous studies have shown that it has a nucleus and a cell wall similar to those seen in fungi. Calcofluor white M2R staining suggests that the cell wall contains chitin, a eukaryote-specific substance, and rRNA in situ hybridization demonstrates that it is a eukaryote. To characterize this organism phylogenetically, DNA was extracted from purified cells. rDNA was readily amplified by PCR with pan-fungal DNA primer sets and primer sets derived from the newly determined sequence, but not with bacteria-specific primer sets. Specific primer sets amplified rDNA from isthmus scrapings from an infected bird, but not from a non-infected bird or other control DNA. The sequence was confirmed to derive from the purified organism by in situ rRNA hybridization using a specific probe. Phylogenetic analysis of sequences of the 18S rDNA and domain D1/D2 of 26S rDNA showed the organism to be a previously undescribed anamorphic ascomycetous yeast representing a new genus. The name Macrorhabdus ornithogaster gen. nov., sp. nov. is proposed for this organism. The type material is CBS 9251T (= NRRL Y-27487T).