A papova-like virus infection of lovebirds (Agapornis sp)

Pathogenicity of Avian Polyomaviruses and Prospect of Vaccine Development

Polyomaviruses are nonenveloped icosahedral viruses with a double-stranded circular DNA containing approximately 5000 bp and 5–6 open reading frames. In contrast to mammalian polyomaviruses (MPVs), avian polyomaviruses (APVs) exhibit high lethality and multipathogenicity, causing severe infections in birds without oncogenicity. APVs are classified into 10 major species: Adélie penguin polyomavirus, budgerigar fledgling disease virus, butcherbird polyomavirus, canary polyomavirus, cormorant polyomavirus, crow polyomavirus, Erythrura gouldiae polyomavirus, finch polyomavirus, goose hemorrhagic polyomavirus, and Hungarian finch polyomavirus under the genus Gammapolyomavirus. This paper briefly reviews the genomic structure and pathogenicity of the 10 species of APV and some of their differences in terms of virulence from MPVs. Each gene’s genomic size, number of amino acid residues encoding each gene, and key biologic functions are discussed. The rationale for APV classification from the Polyomavirdae family and phylogenetic analyses among the 10 APVs are also discussed. The clinical symptoms in birds caused by APV infection are summarized. Finally, the strategies for developing an effective vaccine containing essential epitopes for preventing virus infection in birds are discussed. We hope that more effective and safe vaccines with diverse protection will be developed in the future to solve or alleviate the problems of viral infection.

Prevalence of Aves Polyomavirus 1 and Beak and Feather Disease Virus From Exotic Captive Psittacine Birds in Chile

Avian polyomavirus disease and psittacine beak and feather disease (PBFD) are both contagious viral diseases in psittacine birds with similar clinical manifestations and characterized by abnormal feathers. To determine the prevalence of Aves polyomavirus 1 (APyV) and beak and feather disease virus (BFDV) in captive, exotic psittacine birds in Chile, feathers from 250 psittacine birds, representing 17 genera, were collected and stored during the period 2013-2016. Polymerase chain reaction testing was used to detect APyV and BFDV were detected in feather bulb samples. The results indicated that 1.6% (4/250) of the samples were positive for APyV, 23.2% (58/250) were positive to BFDV, and 0.8% (2/250) were positive to both APyV and BFDV. This is the first report, to our knowledge, of APyV and BFDV prevalence in captive, exotic psittacine birds in South America. Analysis of 2 Chilean partial sequences of the gene encoding agnoprotein 1a (APyV) and the replication-associated protein (BFDV) extends the knowledge of genomic variability for both APyV and BFDV isolates and their spectrum of hosts. No geographical marker was detected for the local isolates.

Wildlife diseases in New Zealand: recent findings and future challenges

Our knowledge of diseases in New Zealand wildlife has expanded rapidly in the last two decades. Much of this is due to a greater awareness of disease as a cause of mortality in some of our highly threatened species or as a limiting factor to the successful captive rearing of intensely managed species such as hihi (Notiomystis cincta), kiwi (Apteryx spp.) and kakapo (Strigops habroptilus). An important factor contributing to the increase of our knowledge has been the development of new diagnostic techniques in the fields of molecular biology and immunohistochemistry, particularly for the diagnosis and epidemiology of viral and protozoan diseases. Although New Zealand remains free of serious exotic viruses there has been much work on understanding the taxonomy and epidemiology of local strains of avipox virus and circoviruses. Bacterial diseases such as salmonellosis, erysipelas and tuberculosis have also been closely investigated in wildlife and opportunist mycotic infections such as aspergillosis remain a major problem in many species. Nutritional diseases such as hyperplastic goitre due to iodine deficiency and metabolic bone disease due to Ca:P imbalance have made significant impacts on some captive reared birds, while lead poisoning is a problem in some localities. The increasing use of wildlife translocations to avoid the extinction of threatened species has highlighted the need for improved methods to assess the disease risks inherent in these operations and other intensive conservation management strategies such as creching young animals. We have also become more aware of the likelihood of inbreeding suppression as populations of many species decrease or pass through a genetic bottleneck. Climate change and habitat loss, however, remain the greatest threats to biodiversity and wildlife health worldwide. Temperature changes will affect our wildlife habitats, alter the distribution of disease vectors and wildlife predators, or directly harm threatened species in vulnerable localities.

Avian polyomavirus identified in a nestling Gouldian finch (Erythrura gouldiae) in New Zealand

Abstract

CASE HISTORY

Four 4-5-month-old nestlings and one adult in a commercial aviary of 53 Gouldian finches (Erythrura gouldiae) died over a 2-week period in July 2000.

PATHOLOGICAL FINDINGS

One nestling was necropsied and showed bronze-tinged skeletal muscles, a swollen liver with haemorrhagic margins and numerous haemorrhages on serosal surfaces. The histological lesions included multifocal hepatic necrosis and haemorrhage associated with the presence of large clear or basophilic intranuclear inclusions in hepatocytes and Kupffer cells suggestive of avian polyomavirus infection. Similar inclusion bodies were present in splenic histiocytes.

MOLECULAR BIOLOGY

DNA was subsequently extracted from archived portions of liver, spleen, gizzard, heart, lung and kidney. A broad spectrum nested PCR was used to detect polyomavirus which sequence analysis confirmed as finch polyomavirus.

DIAGNOSIS

Avian polyomavirus.

CLINICAL RELEVANCE

Avian virus infections such as polyomavirus should be suspected in cases of sudden death in nestlings, particularly in susceptible species such as psittacine and passerine birds. The archiving of tissues from unconfirmed disease outbreaks provides a valuable resource for retrospective investigations.

A serologic survey for avian polyomavirus and Pacheco's disease virus in Australian cockatoos

Sera collected from wild and captive Australian cockatoos and other psittacine species (n = 411) were tested for antibodies to avian polyomavirus (APV) and Pacheco's disease virus (PDV). Of 144 wild sulphur-crested cockatoos (Cacatua galerita) sampled at three regions in New South Wales (NSW) 96 (64.4%) birds had positive (>/= 1:32) neutralizing antibody titres to avian polyomavirus (range 1:32-1:2048). Two of 17 wild long-billed corellas (Cacatua tenuirostris) were also APV-antibody positive. However, no samples from 107 wild galahs (Eolophus roseicapillus) were positive for neutralizing antibody to APV. Sera were also collected from captive psittacine bird flocks from NSW, Tasmania, Victoria, and Western Australia. In a mixed aviary of cockatoos and lorikeets, APV antibody was detected in sera from sulphur-crested cockatoos, Major Mitchell's cockatoos (Cacatua leadbeateri), a white-tailed black cockatoo (Calyptorhynchus baudinii latirostris), a red-tailed black cockatoo (Calyptorhynchus magnificus) a single galah, a rainbow lorikeet (Trichoglossus haematodus), and a scaley-breasted lorikeet (Trichoglossus chlorolepidotus). All 411 wild and captive birds were negative for the presence of neutralizing antibody to PDV. These results indicate that wild sulphur-crested cockatoos in NSW are enzootically infected with avian polyomavirus and that the sampled populations are free of Pacheco's disease.

A review of DNA viral infections in psittacine birds

To date, several DNA viral infections have been reported in psittacine birds. Psittacine beak and feather disease (PBFD) is characterized by symmetric feather dystrophy and loss and development of beak deformities. PBFD is caused by beak and feather virus, which belongs to the Circoviridae, and is the most important infection in psittacine birds worldwide. Avian polyomavirus infection causes acute death, abdominal distention, and feather abnormalities. Pacheco's disease (PD), which is caused by psittacid herpesvirus type 1, is an acute lethal disease without a prodrome. Psittacine adenovirus infections are described as having a clinical progression similar to PD. The clinical changes in psittacine poxvirus-infected birds include serious ocular discharge, rhinitis, and conjunctivitis, followed by the appearance of ulcerations on the medial canthi of the eyes. Internal papillomatosis of parrots (IPP) is a tumor disease characterized by progressive development of papillomas in the oral and cloacal mucosa. IPP has been suggested to caused by papillomavirus or herpesvirus. However, information about these diseases is limited. Here we review the etiology, clinical features, pathology, epidemiology, and diagnosis of these DNA viruses.

An outbreak of the polyomavirus infection in budgerigars and cockatiels in Slovakia, including a genome analysis of an avian polyomavirus isolate

In winter 2003-04, large numbers of budgerigars (Mellopsitacus undulatus) and cockatiels (Nymphicus hollandicus) fell ill and died in a large parrot-breeding aviary in Slovakia. In budgerigars, the disease outbreak occurred at the age of 2-3 weeks; cockatiels died within their first 7 days of life. In budgerigars, symptoms of the disease included delayed growth, tremor, darkish discoloration of skin, quill bleeding, and feathering defects. cockatiels often died without any symptoms and with a full crop; feathering defects occurred sporadically. Electron microscopy with negative staining of aqueous lysates of the affected skin and of bleeding quills showed isolated or clustered polyomavirus particles 45-50 nm in size. Long filamentous forms of the virus were also found in virion clusters of skin lysates from the budgerigars. In ultrathin sections through the pathologically altered skin tissue of budgerigars, virus particles were present in both nuclei and cytoplasm of epidermal cells, often in crystalline form. In infected cells, enlarged nuclei showed an extensive chromatin margination. On the DNA level, presence of a polyomavirus infection was conclusively proved by the polymerase chain reaction using avian polyomavirus (APV)-specific primers. A sequence analysis of the gene encoding viral protein (VP)1 and of the combined region for VP2 and VP3 proteins revealed a previously undescribed synonymous mutation in this isolate. This report extended the knowledge of the area of APV occurrence and of the spectrum of hosts in the context of genomic and morphologic variability of APV isolates.

Development of a blocking enzyme-linked immunosorbent assay for the detection of avian polyomavirus-specific antibodies

Avian polyomavirus, described originally as budgerigar fledgling disease virus, has been associated with devastating contagious disease outbreaks in budgerigar aviaries. At present, this virus affects a wide range of psittacine and non-psittacine birds worldwide, and the serum neutralisation test is used for the serodiagnosis of avian polyomavirus infections. A blocking enzyme-linked immunosorbent assay was developed for the screening of large numbers of sera collected from various avian species. The assay employs a monoclonal antibody directed against the major structural protein VP1 as a blocking antibody in a sandwich blocking procedure. Either purified avian polyomavirus particles or avian polyomavirus VP1 expressed in recombinant baculovirus-infected Sf9 cells were used as antigen. The specificity of the blocking enzyme-linked immunosorbent assay was evaluated by testing sera directed against mammalian polyomaviruses. Using sera obtained from chicken infected experimentally with avian polyomavirus and a collection of psittacine field-origin sera, a good correlation was observed between the results of the blocking enzyme-linked immunosorbent assay and the serum neutralisation test. However, the blocking enzyme-linked immunosorbent assay is more rapid and more economic. Both, avian polyomavirus particles and VP1 produced by recombinant DNA technology proved to be suitable antigens.

Viremia, virus shedding, and antibody response during natural avian polyomavirus infection in parrots

OBJECTIVE

To determine rapidity of spread and onset and duration of viremia, virus shedding, and antibody production in parrots naturally infected with avian polyomavirus (APV).

DESIGN

Case series.

ANIMALS

92 parrots in 2 aviaries.

PROCEDURE

Blood samples were obtained from parrots naturally exposed to APV during a 3- to 4-month period for determination of serum virus neutralizing antibody and detection of viral DNA. Nestlings from the next year's hatch were monitored for APV infection.

RESULTS

The first indication of inapparent infection was viremia, which developed simultaneously with or was followed within 1 week by cloacal virus shedding and antibody production. Cloacal virus shedding continued after viremia ceased. During viremia, viral DNA was detected continuously in blood samples. Viral DNA was detected in serial cloacal swab specimens in most birds, but it was detected inconsistently in 6 birds and not detected in 3 birds, even though these birds were viremic. Duration of cloacal virus shedding was < or = 4.5 months. In 1 aviary, prevalence of infection was 88% and dissemination of virus through the 3-room building required 4.5 months. In the second aviary, a single-room nursery, prevalence of infection was > or = 90%. For all affected birds, infection could be detected 18 days after the first death.

CONCLUSIONS AND CLINICAL RELEVANCE

If a single sampling is used for polymerase chain reaction detection of viral DNA, blood and cloacal swab specimens are required. In nestling nonbudgerigar parrots, cloacal virus shedding may persist for 4.5 months. Management protocols alone are sufficient to prevent introduction of APV into a nursery.

Disorders of the avian integument

The avian integument consists of highly specialized structures that show extreme variations between species. Feathers are the most obvious part of the integument, and their color and beauty forms an important basis for the attraction of birds to humans. Any disorder in the feathers can be distressing for a client and frustrating for the avian practitioner. The cause of some disorders may be apparent, but others have a complex pathogenesis involving management, human-bird interaction, malnutrition, psychologic factors, disease, or hormone imbalances.

Polymerase chain reaction assay for avian polyomavirus

A polymerase chain reaction assay was developed for detection of budgerigar fledgling disease virus (BFDV). The assay used a single set of primers complementary to sequences located in the putative coding region for the BFDV VP1 gene. The observed amplification product had the expected size of 550 bp and was confirmed to derive from BFDV DNA by its restriction digestion pattern. This assay was specific for BFDV and highly sensitive, being able to detect as few as 20 copies of the virus. By using the polymerase chain reaction, BFDV was detected in adult, nestling, and embryo budgerigar (Melopsitticus undulatus) tissue DNAs and in sera from adult and nestling budgerigars. These results suggest the possibility of persistent infections in adult birds and lend further support to previously described evidence of possible in ovo transmission. BFDV was also detected in chicken embryo fibroblast cell cultures and chicken eggs inoculated with the virus. A 550-bp product with identical restriction enzyme sites was amplified from a suspected polyomavirus isolated from a peach-faced lovebird (Agapornis pesonata) and from tissue DNA from a Hahn's macaw (Ara nobilis) and a sun conure (Aratinga solstitialis) with histological lesions suggestive of polyomavirus infection. These fragments also hybridized with a BFDV-derived probe, proving that they were derived from a polyomavirus very similar, if not identical, to BFDV.