Sessions

Intensive agricultural production, the high density of livestock, and the decline of natural habitats together contribute to the accumulation of large numbers of pathogens in the environment. Due to the shrinking of natural habitats, bird species that have adapted to human-made environments may pose a threat to livestock and ornamental birds by carrying and spreading pathogens. For these reasons, the monitoring of pathogens is of fundamental importance for epidemiological control. Molecular methods, particularly PCR-based assays, enable the early and reliable identification of infections, which is indispensable to initiating epidemiological measures in time.

In our study, 588 cloacal swab samples, collected from wild birds, were processed to screen for the immunosuppressive circoviruses (CV). A total of 19 complete and 21 partial genome sequences of circular replication-associated protein encoding single-stranded (CRESS) DNA viruses were determined, 32 of which belonged to circoviruses. As a result of the investigation, two new circovirus species were identified (long-eared owl-associated CV1 and barn owl-associated CV1). In addition, genome sequences of several previously characterized, bird-derived circoviruses (pigeon CV, duck CV, goose CV, gull CV, swan CV, little bittern CV) were also detected. Pathogenic CVs and CVs of unknown etiology occurred in wild birds taxonomically distant from the originally described host species. Examples include the presence of duck CV and pigeon CV in the white stork (Ciconia ciconia), as well as the occurrence of pigeon CV in the peregrine falcon (Falco peregrinus) and the black-headed gull (Chroicocephalus ridibundus). For the viruses characterized here, the infection of birds could not be proven, and it is possible that the viruses only passed through the gastrointestinal tract of the birds without infection and replication. However, since little bittern CV and swan CV have so far been described exclusively in freshwater birds and in their tissue samples, it is conceivable that this group of birds may serve as natural hosts.

Overall, the identified sequences and newly detected virus species contribute to a better understanding of the genetic diversity of CRESS DNA viruses, particularly CVs, and provide an important starting point for future epidemiological and ecological studies. This underscores the importance of monitoring wild birds, which is essential for the timely recognition and management of animal health risks.