Protective efficacy of newcastle disease vaccines against prevalent strains in recent years.

[Objective] To investigate the protective efficacy of currently available Newcastle disease vaccines against currently prevalent strains and thus provide guidance for the application of vaccines and the prevention and control of Newcastle disease. [Method] The 6-week-old SPF chickens were respectively inoculated with five live attenuated Newcastle disease vaccines (A, B, C, D, and E) at the dose of 1-fold or 0.01-fold usage via intranasal, intraocular or oral route. After 14 d post immunization, the titers of HI antibody were detected. And all the chickens were challenged by Newcastle disease virus (NDV) F48E9 standard strain or the isolated wild strains, NDV-2007-HB and NDV-2008-YB. The clinical symptoms of chickens were continuously observed, and the morbidity and mortality were determined. [Result] After 14 d post immunization, antibodies were induced at a protective level in chickens immunized with the five vaccines. As shown by the animal experiment, the five vaccines at the dose of 1-fold or 0.01-fold usage protected all vaccinated chickens from the death caused by NDV F48E9 strain, and more than 90% of vaccinated chickens from the death caused by NDV-2007-HB strain, while the vaccines, A, B, and C, at the dose of 0.01-fold usage protected more than 90% of vaccinated chickens from the death caused by NDV-2008-YB strain. [Conclusion] Under laboratory conditions, the currently available Newcastle disease vaccines have better protective efficacy against the two currently prevalent NDV strains and prevent the occurrence of Newcastle disease.