In two psittacines infected iv, the gastrointestinal signs were apparent on day 116 or 126 post infection. In two birds given ABV iv, the neurological signs started on days 159 or 199 dpi . Avian bornaviruses have been reported, yet not proven, as the cause of proventricular dilatation disease (PDD), a disease of pet parrots. While a report of research using a 'positive' brain cell culture (confirmed to contain an avian bornavirus) from a psittacine (parrot) that died with confirmed histopathological diagnosis of PDD (mononuclear infiltrative ganglioneuritis). In this study this 'positive' inoculant was used to infect another parrot. This resulted in the inoculated bird's death and the subsequent histopathological diagnosis of PDD. This research does not fulfil the four criteria points known as Koch's postulate to establish a causal relationship between a causative microbe and a disease. Other research with an inoculant derived from birds with ABV-only infections (with no PDD histopathological changes) did not develop any signs of PDD. These birds were carefully monitored over extended periods, well exceeding the documented 90-day inoculation period for PDD, yet failed to show any signs of PDD. However, the differences in responses to the experimental infections may be associated to ABV strain variation in pathogenicity, the chronic nature of the infection and the difficulty in standardizing the experimental hosts.