Evaluation of the Standard Vaccination Program Using Razi Institute ND Vaccines Against Circulating Virulent Newcastle Disease Virus

Background: Newcastle disease (ND) remains a significant threat to poultry production worldwide, with genotype VII viruses circulating in Iran since the late ۲۰۰۰s. Despite routine vaccination with heterologous vaccines, questions persist regarding their ability to elicit adequate antibody responses against circulating virulent strains. This study assessed the humoral immune response induced by the national vaccination program using Razi Institute vaccines against genotype VII Newcastle disease virus (NDV). Methods: Seventy one-day-old Hy-Line chicks were divided into five groups. Three vaccinated groups (A, B, C; n=۱۰ each) received the national vaccination program: live B۱+H۱۲۰ (day ۱), inactivated ND+AI and Clone vaccines (day ۸), Lasota (day ۱۸), and IBD (days ۱۶, ۲۳). Two control groups (D, E; n=۱۰, ۲۰ respectively) remained unvaccinated. Serum samples were collected on days ۴, ۲۱, and ۲۸ for hemagglutination inhibition (HI) antibody titers. Results: Maternal antibody titer at day ۴ averaged ۶.۱۴ log₂. Vaccinated groups showed significantly higher HI titers compared to controls at all post-vaccination timepoints (P<۰.۰۵). At days ۲۱and ۲۸, vaccinated groups maintained titers of ۶.۸۶-۸.۸۶ log₂, while control groups exhibited titers of ۱.۷۱-۳.۰۰ log₂. Conclusion: Iran’s standard vaccination program using heterologous Razi Institute vaccines successfully induced robust humoral immunity against genotype VII NDV, demonstrating that genetic mismatch between vaccine and field strains does not preclude effective antibody responses when proper vaccination protocols are implemented.

کلیدواژه ها:

Newcastle disease virus ، Genotype VII ، Antibody titer ، Heterologous vaccine ، Hemagglutination inhibition