Improved vaccination against Newcastle disease by an in ovo recombinant HVT-ND combined with an adjuvanted live vaccine at day-old.

The continuous outbreaks of fatal Newcastle disease (ND) in commercial poultry flocks demonstrate that current vaccination strategies are not fully efficacious and should be improved by new generation of vaccines. In this context, maternally immune conventional layer chickens were vaccinated in ovo with a turkey herpesvirus recombinant expressing the fusion (F) gene of NDV (rHVT-ND) and/or at day-old with an apathogenic enterotropic live ND vaccine co-administrated or not with chitosan by oculo-nasal route. The induced vaccinal immune responses and conferred protection against a challenge with a circulating NDV velogenic viscerotropic strain were evaluated. The innovative rHVT-ND/live ND-chitosan vaccination regimen provided the best protection against mortality and morbidity as well as the strongest reduction of virus shedding that could be related to the higher measured cellular immune response and digestive antibody-mediated immunity.