Efficacy and economic evaluation of a novel genotype VII marker vaccine for Newcastle disease in layers.

Newcastle disease (ND) poses a serious threat to poultry, with vaccination remaining the most effective control strategy. However, the widely used ND vaccine strain exhibits significant antigenic mismatch with prevalent genotype VII Newcastle disease virus (NDV), necessitating increased vaccination dosages and frequencies. This study evaluated optimization of immunization schedules for the ND marker vaccine based on genotype VII MG7 strain. Three groups were tested: Group A (4 vaccinations with inactivated ND marker vaccine), Group B (5 vaccinations with combined inactivated and live ND marker vaccines), and Group C (7 vaccinations with LaSota genotype II vaccine). Results showed that Groups A and B maintained hemagglutination inhibition antibody titers above 9 log₂ before laying and ≥ 8 log₂ during the four-month laying period, providing superior immune persistence compared to Group C. The study has confirmed that the specific ELISA test successfully distinguished between chickens that received the marked vaccine and those that did not. Furthermore, the marker vaccine strategy did not interfere with immune response to H5 and H7 subtype avian influenza vaccines. Notably, Group B achieved the highest production efficiency, with 3.01 CNY higher benefit per chicken versus Group C, while reducing vaccination stress and improving flock welfare. These findings demonstrate that the genotype VII marker vaccine is effective and provides a key tool for future ND eradication.