Isolation, identification, and pathogenicity of Novel Duck Reovirus strain from ducklings in China.

Novel duck reovirus (NDRV) is a prevalent pathogen that seriously threatens China's waterfowl industry. It primarily induces hemorrhage and necrosis in the liver and spleen of ducklings, leading to immunosuppression and even causes high mortality in severe cases. In this study, a total of 150 tissue samples were collected from diseased ducks in Jiangxi Province, China. Among these samples, 40 were confirmed to be NDRV-positive. To further characterize the prevalent NDRV strains, virus isolation and identification were carried out using these positive samples, and four strains (NDRV-JX01, NDRV-JX02, NDRV-JX11, NDRV-JX12) were successfully isolated. Phylogenetic analysis based on the σC gene showed that the four strains clustered with the same evolutionary branch as prevalent NDRV strains in China, with the amino acid identity ranging from 94.1% to 99.1%. Pathogenicity revealed that the NDRV-JX01 strain was pathogenic to one‑day‑old mule ducklings, triggering depression, anorexia, and even death, with a mortality rate of 33.3%. Histopathological analysis revealed that lesions were mainly concentrated in the spleen, liver, and bursa of Fabricius, with lesion severity positively correlated with the clinical symptoms and gross lesions. Tissue tropism analysis further indicated that the NDRV-JX01 strain exhibited a broad tissue infection spectrum in ducklings, with the highest viral loads detected in the spleen, liver, and bursa of Fabricius. Moreover, NDRV-JX01 infection was found to trigger hepatic dysfunction and significantly alter the expression profiles of immune-related genes in ducklings. In summary, these findings expand our knowledge of the genetic diversity and pathogenic characteristics of NDRV, and provide reliable theoretical support for the prevention and control of this pathogen in waterfowl.