Epidemiology and Molecular Characterization of Genotype XIII.2.2 of Class II Newcastle Disease Virus from Vaccinated Flocks in Kerala, India

Aims: To investigate the epidemiology and phylogenetic characteristics of Newcastle Disease Virus (NDV) outbreaks in poultry flocks in Kerala, India, during 2023-2024, focusing on the emergence of new virulent genotypes. The emergence of these genotypes can increase disease severity in poultry, reduce the effectiveness of existing vaccines, and necessitate the development of updated vaccination strategies to control outbreaks effectively. Study Design: This study was a field-based epidemiological and phylogenetic analysis of NDV in poultry flocks across various regions of Kerala. Place and Duration of Study: The study was conducted in Kerala from January f2023 to May 2024 in both layer and broiler farms. Methodology: Forty samples from Forty poultry flocks were surveyed for NDV infection. RT-PCR was employed to target the fusion protein gene, revealing the prevalence of NDV. Epidemiological data, including seasonal patterns of NDV occurrence, were collected. Phylogenetic analysis of the isolated NDV strains was performed to compare them with known vaccine strains. Results: NDV was detected in 5 out of 40 of the sampled poultry flocks (12.5%), predominantly during the dry season from December to May. Phylogenetic analysis indicated that the prevalent genotype XIII.2.2, identified in the samples, differed significantly from the existing vaccine strains and emerged predominantly from vaccinated flocks. Conclusion: The emergence of genotype XIII.2.2 in vaccinated flocks indicates that existing vaccines may not effectively control NDV outbreaks in Kerala. Future research should aim to characterize the genetic diversity of NDV strains and assess the efficacy of novel vaccine candidates. Practical recommendations include updating vaccine formulations to address emerging genotypes, strengthening surveillance systems, and reinforcing biosecurity measures to enhance NDV prevention and control in the region.