Objective Disease symptoms and reproduction of the attenuated strain S C30(NDRV-S-C30) of novel duck reovirus on inoculated Muscovy ducklings were studied.
Method Specific primers were designed to establish a RT-qPCR method for detecting the NDRV nucleic acid in two-day-old Muscovy ducklings intramuscularly injected with NDRV-S-C30. Symptoms of viremia in the blood and viral shedding in the throat and cloaca were observed on the infected ducklings. Viral replication in the birds was monitored on samples of sera, liver, and spleen as well as cloaca and throat swabs collected in 1, 2, 3, 4, 6, 8, 10, 12, and 14 d after the vaccination (dpv) for NDRV nucleic acid detection by RT-qPCR.
Result A specific RT-qPCR assay developed for the NDRV detection showed the viral shedding in the throat appeared in 2–8 dpv and in the cloaca in 2–10 dpv and peaked in 4–6 dpv, the viremia in 1–4 dpv and peaked in 1–2 dpv, and the NDRV-S in the liver within 3–6 dpv and in the spleen 1–8 dpv.
Conclusion NDRV-S-C30, a attenuated strain, showed virus shedding through the oral cavity and cloaca after immunization of young ducks. It only caused a weak viral bloodstream response and had weak replication ability in the liver. It had lost the ability to cause pathological damage to susceptible target organs. The occurrences and time durations of the viral shedding and viremia in the Muscovy ducklings caused by NDRV-S-C30 were determined. The information would aid the evaluation of immunization efficacy in combating the disease caused by the attenuated virus strain.
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