Serological surveillance and associated risk factor analysis of parrot bornavirus infection in parrots in Taiwan

Authors: Jing-Yuan Chen, Meng-Chi Wu, Zhi-Syun Fang, Hui-Wen Chen

The bornaviruses of Psittacifomes, parrot bornavirus 1 to 8 (PaBV-1 to -8), belong to Orthobornavirus within the family Bornaviridae, are the major etiology of proventricular dilation disease (PDD), for psittacine species. PDD is a contagious and lethal disorder for infected birds leading to chronic neuroinflammation and gastrointestinal disorders. Up to date, it is still a lack of surveillance reports of PaBV infection in the captive parrot population, nor information about the well-established methodology for serologic diagnosis in Taiwan. To clarify the prevalence of PaBV infection in Taiwan, two PaBV strains, PaBV-4 NTUCL7 strain (GenBank: OM939725) and PaBV-5 NTUCL54 strain (GenBank: OM777141), were isolated from naturally infected parrots and propagated by serial passage on QM7 cell lines. To generate viral stock for the following studies, PaBV was purified from virus persistently-infected QM7 cells with a sucrose cushion centrifuge. Serological diagnosis procedures of immunocytochemistry (ICC) assay and western blot (WB) assay were established using Taiwan PaBV-4 and PaBV-5 isolates. Then, a serological surveillance program was conducted to understand the prevalence of PaBV infection in the captive parrot population by analyzing serum samples collected from vet clinics or hospitals in Taiwan. The surveillance results profiled a positive rate at 25.68% (95/370) in the analyzed serum from 16 genera of parrots. Besides, based on the recorded information of clinical cases, the parrot over 1-year-old has a higher possibility of being PaBV antibody-positive than the juvenile population, with an odds ratio of 2.10. Moreover, since variable symptoms, including asymptomatic, neurological symptoms and gastrointestinal symptoms, may be noted in PaBV-infected birds, the symptoms recorded in clinical diagnosis were also analyzed with the result of serological diagnosis to elucidate several risk factors as symbols of PaBV infection. The analyzed results suggested that parrots with any of the clinical signs (odds ratio: 2.81), neurological signs (odds ratio: 2.25), gastrointestinal signs (odds ratio: 3.24) or PDD (OR: 3.00) may have a significantly higher chance of being PaBV antibody-positive in serological diagnosis result. Overall, two serological diagnosis measures were demonstrated to be applied in serological diagnosis in this study and accordingly evaluated the prevalence of PaBV infection in Taiwan’s captive parrot population. Moreover, several associated factors were analyzed to provide useful clinical observation indicators and revealed the coordination with serological diagnosis results.