TDK conference 2019

Proventricular dilatation disease (PDD), a chronic wasting disease of mainly large parrots, is well-known for its miscellaneous and fatal nature since the 1970s. The clinical signs are mostly related to the impairment of the gastrointestinal motility. However, seizures, behavioural changes, and ataxia can be detected if the disease involves the central nervous system. The aetiology has long been unknown, but recently pyrosequencing of organ samples originated from diseased birds, revealed a novel bornavirus. The pathomechanism of the diseases caused by parrot bornaviruses (PaBV) is unclear and the diagnostics are still yet to be refined. Previous studies prove that avian bornaviruses are present in Hungary and they may cause significant losses in parrot collections. In this study, we gained further data on the occurrence of the virus, using new diagnostic methods. The sensitivity of reverse transcription polymerase chain reaction (RT-PCR) on RNA yielded from the feather calami samples (FC) was compared to the RT-PCR on cloacal swab or faeces samples (GI), which are widely used in routine diagnostic applications. Furthermore, we performed a serological exam using an ELISA test validated to detect anti-ganglioside antibodies produced during the pathogenesis of PDD. The results of this test can inform us about the neuropathy before the appearance of the major clinical signs. Our samples originated from the Budapest Zoo and Botanical Garden (20), the Clinic of Exotic Animal and Wildlife Medicine, UVMB (19) and from macaw owners (15). Out of the total number of 14 positive birds, resulted from the simultaneous diagnostics, only 7 avian bornavirus positive parrots were proven by the gastrointestinal (GI) sample exclusively, whereas feather calami verified the positivity of 10 birds. Thus the diagnostics done separately would have resulted in 50% (GI) and 29% (FC) false-negative birds. PaBV has now been detected in Hungary for the first time in Kea (Nestor notabilis - feather calami). According to studies conducted with a significant number of samples from western and southern European aviaries, the prevalence of ABV infection can be as high as 18.6 % in asymptomatic collections. The results of the present study indicate that the infection rates in Hungary are comparable to those in the references. We tested serum samples from 7 PaBV positive and a PaBV negative parrot with ELISA test to check the presence of anti-ganglioside autoantibodies. Two of 8 parrots were found positive for the presence of antibodies directed to brain gangliosides. One of them, a red-and-green macaw (Ara chloropterus) was the only bird of the 8 that showed clinical signs of PDD.

Feather calamus sample proved as a reliable source of parrot bornavirus RNA in our assessment. Therefore we recommend it to be involved in the molecular diagnostic tests of parrot bornavirus infection. Demonstration of anti-ganglioside autoantibodies can support the early diagnosis of PDD.