Molecular detection and characterization of Parrot Bornavirus 4 (PaBV-4) in captive psittacine birds in India

Avian bornaviruses are a recently described genetically diverse group consisting of 15 separate viruses within five different viral species belonging to the genus Orthobornavirus within the family Bornaviridae. Amongst the avian bornaviruses discovered, the parrot bornaviruses (PaBV) belonging to species Orthobornavirus alphapsittaciforme possess the highest veterinary relevance and is considered to be a major threat to psittacine aviculture. Since the discovery of PaBV in psittacine birds suffering from proventricular dilatation disease (PDD) in 2008, PaBV infections have been reported worldwide. In India, to assess whether avian bornaviruses circulates in parrots, 83 psittacines from 13 different species including birds with suspected PDD based on clinical examination results (n = 33), cage mates of PDD-suspected birds without any clinical signs (n = 26) and dead birds with previous clinic suspicious for PDD (n = 24) were tested for PaBV. Cloacal swabs were collected from live birds and tissues were collected from dead birds and investigated for the presence of PaBV-RNA using reverse transcription polymerase chain reaction (RT-PCR). PaBV infection was detected in 44 birds (53.01%) belonging to 9 psittaciform species. Eighteen of the group of PDD-suspected birds (54.54%), 21 dead birds (87.50%), and 5 clinically healthy cage mates (19.23%) were positive for PaBV-RNA. Sequence analysis of the matrix (M) gene revealed infection by PaBV-4, belonging to the species Orthobornavirus alphapsittaciforme. To the best of our knowledge, there is no publication describing the circulation of Orthobornavirus alphapsittaciforme, PaBV-4 in captive psittacines in India. This study highlights the major impact on conservation projects including endangered/ vulnerable/ near threatened species as these birds rely on captive breeding for their survival. Therefore, there is an urgent need to recognize and understand the factors that might play a critical role in recent expansion of emergent avian pathogens and how they continue to spread and thrive.