Immunogenicity and efficacy of NewFluRazi vaccine against Newcastle disease in SPF chickens.

Abstract

Newcastle Disease (ND) is a major poultry disease worldwide causing substantial economic losses in the poultry production system. This research aimed to assess efficacy of the NewFluRazi vaccine to in protecting against Newcastle disease. In the study, 90 specific pathogen-free (SPF) chickens, 21 days old, were randomly divided into five groups-four groups were vaccinated while one group remained unvaccinated. At 42 days of age, all birds in the four vaccinated groups and the control group were exposed to a highly virulent genotype VII strain of the virus circulating locally. Hem-agglutination inhibition test was performed against the antigen on day 42 to assess immunogenicity. For pathological analysis, tissue samples were collected on days 3, 5 and 7 post-challenge. Lung, trachea, cecal-tonsil and spleen tissues were collected and analysed using real-time PCR on days 3, 5 and 7 post-challenge to detect the presence of the virus. The findings revealed that antibody titers increased in all groups 21 days' post-vaccination. Antibody levels in the NewFluRazi and the international bivalent groups were higher than in the national bivalent vaccine group with mean titers of 5.2, 5.2, and 5, respectively. Pathological assessment following the challenge showed no significant difference in the mean lesion scores between the groups. Viral gene expression in the tissues was significantly lower in the NewFluRazi vaccine group compared to the international bivalent vaccine group. For instance, on day 5 post-challenge, the mean CT value for the tissues in the NewFluRazi group was 34.12, whereas it was 22.08 in the international bivalent vaccine group. Overall, our results indicate that the NewFluRazi vaccine was more effective than the international bivalent vaccine in reducing viral presence in the target tissues following challenge.