# Occurrence of diverse circoviruses in wild birds in Hungary

## TL;DR

This study found diverse circoviruses in wild birds in Hungary, suggesting they may spread widely and affect bird health and conservation.

## Contribution

The study identifies new circovirus species and expands the host range of known circoviruses in wild birds.

## Key findings

- Circoviruses were detected in 32 out of 588 wild bird samples.
- New circovirus species were identified, including long-eared owl-associated CV1 and barn owl-associated CV1.
- Known circoviruses were found in bird species previously not associated with them, such as white storks and peregrine falcons.

## Abstract

Circoviruses (CVs) infect a wide range of avian hosts, including domestic, ornamental and wild birds. The immunosuppressive effect of these viruses could make the host more susceptible to other pathogens. This study aimed to assess the potential hosts and genetic features of CVs or other related viruses in wild birds. Cloacal swab samples of 588 birds were processed for screening of circoviral sequences using nested PCR. Altogether, 19 complete genome and 21 partial sequences of small, circular, rep-encoding DNA viruses were determined, 32 of which belonged to CVs. Along with some newly established CV species (virus name long-eared owl-associated CV1 and barn owl-associated CV1), genomic sequences of previously characterized avian CVs (pigeon CV, duck CV, goose CV, gull CV, swan CV and little bittern CV) were identified. Pathogenic CVs and CVs of unknown aetiology occur in wild birds taxonomically distant from the originally described host species, such as the duck CV and pigeon CV in white stork (Ciconia ciconia), as well as pigeon CV in peregrine falcon (Falco peregrinus) and black-headed gull (Chroicocephalus ridibundus). The results draw attention to the widespread distribution of these viruses among wild birds which, by hiding in the host and reducing defensibility, could pose a threat to both poultry farming and efforts to wild bird conservation.

The online version contains supplementary material available at 10.1186/s13567-025-01696-5.