A study of risk factors associated with Newcastle disease and molecular characterization of genotype XIII Newcastle disease virus in backyard and commercial poultry in Assam, India

The continuous emergence of Newcastle disease virus (NDV) poses a persistent threat to the poultry industry. Recent increasing outbreaks of NDV in the North East region of India have highlighted the need to closely monitor and analyze the potential risk factors for Newcastle disease (ND) outbreaks. In the present study, an attempt was made to genotype the circulating Newcastle disease virus (NDV) in the backyard and commercial poultry flocks in Assam, India. Sera samples from unvaccinated backyard poultry flocks and tissue samples of ND suspected cases were collected and tested for the presence of NDV antibodies using the Haemagglutination inhibition (HI) test. A total of seven NDV isolates were analyzed from different districts of Assam, India, both genotypically and pathotypically. All isolates were characterized as virulent, carrying 112RRKQRF117 amino acid residues at the cleavage site. As determined by phylogenetic analysis, the isolates clustered with members of genotype XIII of class II NDV. Further analysis of risk factors of ND occurrence was conducted through a questionnaire survey. All the results indicated an occurrence of genotype XIII of NDV in the farms with inadequate biosecurity and farming practices. •Seroprevalence of ND in Assam, India is 23.89%.•The MDT and ICPI of circulating NDV strains were found to be 76.0 ± 2.69 to 87.6 ± 1.00 h and 1.05 ± 0.02 to 1.37 ± 0.02 respectively.•A phylogenetic analysis based on partial F gene sequences showed that the NDV isolates clustered with members of genotype XIII of class II NDV.•Studies revealed that the risk factors related to biosecurity and farm practices appear to have a significant role in the severity of Newcastle disease in poultry.