A concurrent outbreak of psittacine beak and feather disease virus, and avian polyomavirus infection in budgerigars (Melopsittacus undulatus)

A dual natural infection with psittacine beak and feather disease virus and budgerigar fledgling disease virus in a breeding aviary of budgerigars (Melopsittacus undulatus) is described. One-hundred per cent of newly-hatched birds were affected and mortality was high (85%). Most surviving birds had diarrhoea, feather alterations and 30% mortality after a 5- to 10-week period. Necropsies of 1-week-old and 2-month-old birds demonstrated non-specific lesions, but histologically nuclear inclusions suggestive of viral infection (adenovirus, herpesvirus, polyomavirus) and also cytoplasmic inclusions suggestive of beak and feather disease were seen in integument and internal organs. Staining of tissues with viral specific DNA probes for psittacine beak and feather disease virus and for avian polyomavirus demonstrated simultaneous presence of viral DNA from both viruses in some birds. This is the first description of a concurrent outbreak of psittacine beak and feather disease virus and avian polyomavirus infection in a breeding aviary.

Mortality due to polyomavirus infection in two nightjars (Caprimulgus europaeus)

Two nightjars (Caprimulgus europaeus) from a bird park in the Netherlands died suddenly, with no clinical signs, within 1 month of each other. The main pathologic findings at necropsy were splenomegaly and hepatic necrosis. On histologic examination, intranuclear viral inclusion bodies consistent with avian polyomavirus were observed in the liver, spleen, and kidneys. Polymerase chain reaction testing of samples from the liver, spleen, and kidneys detected avian polyomaviral DNA, and sequence analysis showed that the virus had a sequence homology of 99% to psittacine avian polyomavirus strains. To our knowledge, this is the first report of avian polyomavirus infection in the order Caprimulgiformes. Lovebirds (Agapornis species), which were housed near the nightjars, were considered as the possible source of infection.

Viral proventriculitis in chickens

The objectives of the present study were to examine proventriculi of broiler chicks for lesions, and to classify and record the incidence of these lesions. Deep non-purulent necrotizing proventriculitis (accompanied by adenoepithelial hypertrophy and hyperplasia) was the most common (109/220 = 49.5%) light microscopic diagnosis in the proventriculi examined. Degenerating and necrotic alveolar secretory cells had amorphous, granular or vacuolated cytoplasm. Nuclei usually were either pyknotic, karyorrhectic or karyolytic; however, fewer attached or sloughed cells had swollen nuclei with marginated chromatin and clear centres. Basophilic inclusion bodies were never seen. In five cases examined ultrastructurally, hexagonal virus particles were found in intact nuclei (average size = 68.9 nm, n = 89), associated with unbound condensed chromatin, and within vacuolated spaces in the cytoplasm (average size = 62.3 nm, n = 109). DNA in situ hybridization failed to detect adenovirus or polyomavirus nucleic acids. The presence of intralesional virus suggests that a causal relationship might exist between the virus and the proventricular lesions.

Molecular characterizations of avian polyomavirus isolated from budgerigar in China

Budgerigar fledgling disease is an acute viral infectious disease caused by avian polyomavirus (APV). In this study, 34 liver tissue samples of young, dead budgerigar with typical symptoms were collected in 2004. All the samples had positive polymerase chain reaction (PCR) test based on the VP1 specific primers. VP1 genes of these samples were sequenced and had high similarities to each other (99%-100%). A strain (HBYM02) was isolated and sequenced. As shown in the phylogenetic tree, there are two branches. One branch was composed by strains isolated from Passeriformes, and the other was composed only by one strain isolated from Falconiformes. The genome similarities between our isolate and other reported isolates were very high (> 99%), and the evolution distances in the phylogenetic tree were very short (< 0.005), which suggests that APV in China has the same genotype as those in other regions. The results will be useful for the diagnoses of, and vaccine development for, APV.

Viral diseases of companion birds

Many viruses definitively cause disease in our companion birds, whereas other viruses have been implicated or associated with typical clinical signs. Some families of viruses that have been discovered in mammals have not been associated with disease in birds. It is imperative to perform a necropsy on any birds that die--whether a pet, aviary, or display bird, and despite the fact that other diseases may be present--because viruses can occur concurrently, especially when immunosuppression is present. Also, it is imperative to use available vaccines to decrease and control the incidence of these diseases, as has occurred in the canine and feline pet populations.

Polyomavirus inclusion bodies in chicken caecal epithelium

In this case report we describe the light microscopic and transmission electron microscopic appearance of polyomavirus inclusions in caecal epithelial cells from a chicken with diarrhoea and intestinal parasites. The DNA in situ hybridization technique demonstrated that the polyomavirus reported here is different from polyomaviruses observed in psittaciformes. The chicken polyomavirus described may share some homologous base sequences with psittaciforme polyomavirus; however, the viruses are different. Clinicians and pathologists should be aware that polyomavirus can infect chickens and that polyomavirus inclusion bodies can be found in chicken caecal epithelial cells.

Development and application of an immunohistochemical staining technique to detect avian polyomaviral antigen in tissue sections

An immunohistochemical staining technique was developed to detect polyomaviral antigens of budgerigar fledgling disease in formalin-fixed tissue sections. This technique used an indirect avidin-biotin, alkaline phosphatase labeling system with a mixture of monoclonal antibodies developed against the virus major capsid protein. The staining technique was applied retrospectively to 24 avian accessions which were originally diagnosed as budgerigar fledgling disease or avian polyomavirus infection based on microscopic findings including typical intranuclear inclusions. Immunohistochemical staining resulted in positive reactions in some tissues from 17 of 24 cases. The tissues most frequently containing typical intranuclear inclusions or positive immunohistochemical staining were the spleen, liver, and kidney. Neither of the 2 nonpsittacine cases was positive immunohistochemically. This technique may be used wither as a rapid test on routinely processed diagnostic samples to confirm the presence of avian polyomavirus or for pathogenesis research studies.

Diagnosis of polyomavirus-induced hepatic necrosis in psittacine birds using DNA probes

Liver sections from 32 psittacine birds with multifocal to coalescing hepatocellular necrosis were examined to determine the cause of disease. Avian polyomavirus (APV) infection (19 of 32 birds), bacterial hepatitis (5 of 32 birds), and chlamydiosis (3 of 32 birds) were major causes of hepatic disease. The presence of APV inclusions or nucleic acid was demonstrated using hematoxylin and eosin (HE) staining, DNA in situ hybridization, and DNA amplification with Southern blotting. Amphophilic intranuclear inclusions, suggestive of APV infection, were observed in HE-stained liver sections from 5 of 32 birds. Hepatocellular karyomegaly was present in liver tissues from 10 birds (5 birds with typical APV inclusions and 5 birds without discernable inclusions). DNA in situ hybridization recognized intranuclear APV nucleic acid in liver sections of 18 of 32 birds. DNA amplification with Southern or dot blots also identified APV nucleic acid in processed, paraffin-embedded livers of 18 of 32 birds. This study demonstrates that acute APV infection is a frequent cause of multifocal to coalescing hepatocellular necrosis in psittacine birds. Furthermore, APV infection is best diagnosed using DNA probes, especially when typical intranuclear inclusions are not observed microscopically.