Avian bornavirus genotype 4 recovered from naturally infected psittacine birds with proventricular dilatation disease in South Africa

Abstract

The occurrence of proventricular dilatation disease caused by avian bornavirus (ABV) in
captive psittacine birds has long been suspected in South Africa. This report documents the first
detection by polymerase chain reaction and gene sequence analyses of ABV from three clinical
cases of proventricular dilatation disease (PDD) in captive bred blue and gold macaws (Araara
rauna) resident in this country. Lymphoplasmacytic encephalitis, gastrointestinal myenteric
gangioneuritis and leiomyositis were the most prominent histopathological changes and ABV
genotype 4 was detected in tissues from all three birds. Immunohistochemical stains for ABV
antigen revealed positive labelling of neurons and glial cells of the brain, myenteric ganglia
and nerve fibres as well as smooth muscle cells of the gastrointestinal tract of all three birds.
In one bird, positive labelling of the peripheral nerves was observed. The identical sequence
of the analaysed genome fragment of all three samples, history that all of these birds had
originated from the same breeding facility, and young age at presentation raise the question
of possible vertical transmission.