Isolation and characterization of a duck reovirus strain from mature ducks in China.

In 2018, a disease characterized by splenic hemorrhage and necrosis killed ducks in a duck farm in Guangxi province, China. A duck reovirus strain was isolated from the tissues of the dead ducks by inoculating duck embryos and BHK-21 cells. Electron microscopy of the cultured the isolate showed that the viral particles were nearly round in shape and approximately 70 nm in diameter, and they were designated DRV-GL18. Sequence analysis showed that the GL18 strain viral genome was 23,419 nt in length and had 10 dsRNA segments. Phylogenetic analysis of cDNA amplicons of segments encoding the protein σC which are outer capsid proteins showed that the isolate belongs to the branch of the epidemic strains of duck reovirus. The Recombination Detection Program (RDP) and SimPlot program analyses suggested potential genetic recombination events in the M2 segments. Pathogenicity experiments revealed that GL18 produced severe hemorrhaging in livers and necrosis in the spleen of infected SPF ducklings. A death rate of 50% in the experimental ducklings was calculated during the first 7 d, and the rest of the ducklings were observed to undergo spleen necrosis. These data suggested that GL18 is a duck reovirus isolate with severer pathogenicity, and it could be a candidate for development of vaccine. This is the first reported isolation of duck reovirus from mature ducks.