Molecular epidemiology of parrot bornaviruses in Guangdong, China: co-circulation of three genotypes in captive parrots

Proventricular dilatation disease (PDD) is a severe neurological and gastrointestinal disorder of psittacine birds, and parrot bornavirus (PaBV) has been identified as an important virus associated with PDD. Parrots are widely kept as companion animals and are frequently maintained in rescue centers, zoos, breeding farms, and pet trade settings, where close contact among birds and frequent movement of captive parrots may facilitate viral transmission. Despite its recognized importance to psittacine health, the epidemiology of PaBV in captive parrot populations in China, including its prevalence, genetic diversity, and genotype distribution, remains poorly characterized. Therefore, we combined viral metagenomic analysis of selected pooled specimens with individual-level RT-PCR screening to characterize the parrot virome, assess PaBV positivity, and investigate the genetic diversity of the detected PaBV strains in captive parrots in Guangdong Province, China. Among the 1,829,113 viral reads (0.40% of total reads), 25 viral families were identified, including Hepadnaviridae , Microviridae , and Bornaviridae . Assembly yielded 97 filtered viral contigs, with 65 annotated as PaBV. Among 442 individual parrots, 14 were positive for PaBV, giving an overall positivity rate of 3.17%. All PaBV-positive birds were deceased parrots from Jiangmen City, representing 25.0% (14/56) of the deceased parrots examined. Whole-genome amplification identified one PaBV-2, three PaBV-4, and four PaBV-5 strains, with pairwise nucleotide identity among them ranging from 64.6% to 100%. Phylogenetic analysis revealed that the identified PaBV-2, PaBV-4 and PaBV-5 strains clustered with reference strains from Austria, China, Taiwan and Thailand, with nucleotide similarities ranging from 63.4% to 99.6%. The findings provide evidence for farm-level co-circulation of multiple PaBV genotypes within a single captive parrot facility, emphasizing the need for targeted measures to prevent and control PaBV transmission, thereby supporting the health and conservation of captive and endangered parrot populations.