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To determine whether avian bornaviruses (ABVs) were a factor in proventricular dilatation disease (PDD), we used immunohistochemistry, reverse transcription-PCR, and nucleotide sequence analysis to examine paraffin wax-embedded or frozen tissue samples of 31 psittacine birds with this disease. PDD is a fatal disease of psittacine birds associated with nonsuppurative encephalitis and ganglioneuritis of the upper intestinal tract. Tissue samples had been collected from 1999 through 2008 in Austria, Switzerland, Hungary, and Australia. Immunohistochemical demonstration of viral antigen within the brain and vegetative nerve system of the gastrointestinal tract provides strong evidence for a causative role of ABVs in this condition. Partial sequences of nucleoprotein (p40) and matrix protein (gp18) genes showed that virus in most of our cases belonged to the ABV-2 and ABV-4 groups among the 5 genogroups described so far. Viral sequences of 2 birds did not match any of the described sequences and clustered together in a new branch termed ABV-6. [ABSTRACT FROM AUTHOR]

A canary bird (Serinus canaria) died with nonsuppurative ganglioneuritis of the proventriculus and gizzard and encephalitis, lesions comparable to proventricular dilatation disease (PDD) of psittacine birds. Recently, several genotypes of a novel avian bornavirus have been linked to PDD. In the canary, bornaviral antigen was detected by immunohistochemistry in both neural and extraneural tissues. The widespread viral dissemination was confirmed by reverse transcription-PCR. Sequence analysis revealed a unique genotype of avian bornavirus. This observation suggests that bornaviruses are natural pathogens of several avian species and that the family Bornaviridae comprises more viral genotypes (or viral species) than previously assumed.