Efficacy Evaluation of an Inactivated Duck Tembusu Virus Vaccine

To evaluate the potential use of an inactivated virus-based vaccine for the control and prevention of the newly emerged duck Tembusu virus infection in China, a duck Tembusu virus isolate, Tembusu-HB, was propagated in 12-day-old duck embryos and inactivated by treatment with formaldehyde. The inactivated viral antigen was emulsified with mineral oil, and five batches of the vaccine were manufactured. The immunogenicity and protection efficacy of the vaccine were evaluated in Beijing ducks and Beijing white geese. Results showed that more than 80% of immunized ducks were protected against virulent virus challenge after two intramuscular or subcutaneous injections of the inactivated vaccine, as evidenced by the negative virus isolation results. The protection is also correlated with a positive virus-specific antibody response as detected by ELISA. In contrast, none of the control ducks and geese had any detectable antibody response. Virus was isolated from all control ducks and geese after virulent virus challenge. Interestingly, a variable level of protection (20%-80%) was observed in Beijing white geese immunized twice with the same batches of vaccine, suggesting a species-specific effect of the vaccine. Overall, the results clearly suggest that the inactivated duck Tembusu virus vaccine is immunogenic and provides protection against virulent virus challenge.