Evidence of vertical transmission of Novel Duck Orthoreovirus in ducks

Since 2017, duck spleen necrosis caused by a new variant duck orthoreovirus (N-DRV) infection had been observed in many provinces in China. This disease causes the growth and development of ducks to be retarded, and the feed return rate is reduced. Because the target organ of the disease is mainly the spleen, the immune suppression of the diseased ducks is easy to secondary infection of other pathogens. In this study, we successfully constructed a breeding duck artificial infection model and found that N-DRV infection can cause pathological changes such as ovarian hemorrhage, follicle atrophy, and fallopian tube bleeding in breeding ducks, resulting in a significant reduction in the fertilization rate and hatching rate of breeding eggs. The qPCR method was used to detect viral RNA in samples of egg vitelline membrane, duck embryo, and duckling’s spleen. It was found that viral RNA was present in the above samples. Although there were no obvious clinical symptoms in the early stage of ducklings, autopsy revealed obvious pathological changes in the spleen and other organs. The sequence distance and phylogenetic analysis of the strain re-isolated from the spleen samples of ducklings (named N-DRV-SD19) confirmed that N-DRV-SD19 was consistent with the strain N-DRV-XT18 used for the infection of the breeding ducks. The findings of the above research confirmed that N-DRV can be vertically transmitted through eggs, which will provide an important reference for the prevention and control of the disease.