cells around the infected nerve fibres. Easy at PME on the dead bird, but more difficult in the live patient! A biopsy from the crop has been recommended as a diagnostic test, and is relatively easy to perform, but in this University’s studies, only 76% of positively infected birds showed lesions in the crop. Biopsies from proventriculus and gizzard showed 86% and 93% positive ganglioneuritis respectively, but these samples are far more invasive and difficult to perform in the live bird. Swabs taken from the crop and cloaca

(vent), and blood samples are far easier to obtain. These are then tested in a laboratory for virus RNA, or anti-viral antibodies. However, not all samples will show the presence of the virus. In 276 known positive birds tested, virus material was detected in just 35 of the swabs, 45 of the blood samples, and only 25 in both. So many ‘negative’ test results would be unreliable. Having discovered Bornavirus, further

work was needed to prove that this apparently ubiquitous virus was indeed the cause of clinical PDD. Julia described experiments in which Avian Bornavirus obtained from macaws (ABV4) and cockatiels (ABV2) were injected into virus- free laboratory cockatiels. 100% of the infected birds developed ABV antibodies in their blood, and viral RNA was recovered from crop and cloacal swabs, but not all developed clinical signs, even by this


injection of active virus. In those that did become ill, ABV4 produced milder, mostly neurological signs, while ABV2 resulted in more severe, gastro-intestinal signs. Follow-up tests attempted to demonstrate

the natural route of infection between birds. Trials included dosing live virus via the nose, mouth and open wounds, but none produced clinical disease in any of the tested birds. This may be because virus taken from macaws was given to cockatiels, or that the dose of virus was too low, but either way to date there is no confirmation of the natural route of this infection between birds. So what does all this mean for the parrot

enthusiast? Julia summarised these findings as follows. Avian (Parrot) Bornavirus causes PDD and

neurological signs. 18% of clinically healthy parrots are

infected with ABV, and many birds will remain ABV positive for years with no clinical signs. Often one partner of a pair will be ABV+, while its mate remains ABV- Thus in a parrot collection, there may be

three groups of birds – • ABV+ birds, with clinical signs of PDD • ABV+ birds, but clinically healthy • ABV- birds, also clinically healthy Control therefore involves –

• Confirm PDD diagnosis by ruling out other conditions such as yeast infections etc.

• Test for ABV with crop and cloacal swabs

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