A newly identified Duck orbivirus as the etiological agent of egg-production decline in Chinese breeder ducks

The genus Orbivirus comprises double-stranded RNA viruses, many of which are transmitted by arthropods and cause febrile, hemorrhagic, or reproductive diseases in animals. In recent years, unexplained outbreaks characterized by marked egg-production decline have occurred in breeder duck flocks in China. To identify the causative agent, samples were collected from affected farms in multiple regions across China between 2022 and 2025. Representative samples were analyzed by high-throughput sequencing, followed by phylogenetic analysis, transmission electron microscopy, host cell infection assays, and animal challenge experiments. A previously unreported Orbivirus, designated Duck orbivirus (DORV), was identified. Epidemiological investigation indicated that outbreaks mainly affected breeder ducks during the peak laying period (21-55 weeks of age), with higher incidence in summer and autumn. The DORV genome contains ten double-stranded RNA segments encoding seven structural and five nonstructural proteins. Phylogenetic analysis showed that DORV is closely related to Parrys Lagoon virus (PLV) and Corriparta virus (CORV). Electron microscopy revealed icosahedral particles 30-40 nm in diameter. DORV replicated efficiently in DEF, DEL and C6/36 cells but not in MDCK and LMH cells, suggesting a restricted host range with potential arthropod-borne features. Infection of breeder ducks with DORV-SD01 reduced egg production by 30-40% and caused lesions in the ovary, liver, and spleen. This study describes a novel duck-origin Orbivirus linked to egg-production decline, offering new etiological insights and extending the host spectrum of Orbivirus. The results provide a foundation for future surveillance and prevention of emerging waterfowl diseases.