Abstract:

In the study, using a novel duck reovirus (NDRV) to actively infect commercial ducklings with different maternal antibody levels, and the ducklings' cloacal viral shedding, body weight, spleen index, liver and spleen tissue lesions, and pathological indicators were tested and observed. The goal was to discover the protective effect of maternal antibodies on early NDRV infection in ducklings, laying the foundation for disease prevention and control. A total of 58 one-day-old commercial ducklings were tested for NDRV maternal antibodies. They were grouped according to maternal antibody levels and challenged at 3 days of age. Cloacal swabs were collected on days 3, 5, and 7 post-challenge to test for shedding, and weights were recorded on days 2, 8, and 10. Ducklings were euthanized 7 days post-challenge for necropsy to observe liver and spleen lesions, calculate spleen index, and prepare liver and spleen pathological sections. The results showed that all challenged ducks shed the virus, and high maternal antibody groups were unable to prevent shedding. Weight gain in challenged ducks was significantly lower than the control group (P < 0.01). Necrosis was observed in the spleens, and scattered hemorrhagic foci with necrosis were found in the livers of challenged ducks. The spleen index of challenged ducks was significantly higher than the control group (P< 0.01). There were no significant differences in spleen index and body weight among ducklings with different maternal antibody levels post-challenge (P> 0.05). Liver and spleen cells showed varying degrees of pathological damage. This experiment demonstrates that high maternal antibodies cannot provide effective protection against this NDRV isolate in ducklings. The method of using immune breeder ducks to protect ducklings from infection requires further consideration.

Key words: Novel duck reovirus, duckling, maternal antibody, spleen index, viral shedding, protective effect, pathological indicators