Duck Orbivirus and Egg Production: A Newly Identified Duck Orbivirus Is the Etiological Agent of Egg Production Decline in Chinese Breeder Ducks

ABSTRACT The genus Orbivirus comprises double‐stranded RNA viruses, many of which are arthropod‐borne and are associated with febrile, hemorrhagic, or reproductive diseases in animals. In recent years, unexplained outbreaks, characterized by a marked decline in egg production, have occurred in breeder duck flocks in China. To identify the causative agent, samples were collected from affected farms in multiple regions between 2022 and 2025 and analyzed using high‐throughput sequencing, phylogenetic analysis, transmission electron microscopy, cell infection assays, and animal challenge experiments. A previously unreported Orbivirus —designated duck orbivirus (DORV)—was identified. An epidemiological investigation indicated that the outbreaks mainly affected breeder ducks during the peak laying period (21–55 weeks of age), with a 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 Parry's Lagoon virus (PLV) and Corriparta virus (CORV). Electron microscopy revealed icosahedral particles of 30–40 nm in diameter. DORV replicated efficiently in duck‐derived and mosquito‐derived cells, but not in canine‐derived and chicken‐derived 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 ovaries, 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 the virus. These results provide a foundation for future surveillance and prevention of emerging waterfowl diseases.