Isolation and Molecular Characterization of Class II novel genotype of Newcastle disease virus from field outbreaks in Mizoram, NER, India

Newcastle disease in its most virulent form affects the poultry population of all ages. Such an infection causes a huge economic loss to the poultry industry. A study was conducted in the Selesih, Melthum, and Zemabawk districts in Mizoram this year in which phylogenetic analysis was carried out to determine the circulating strains in Mizoram. Detailed necropsy was conducted on the poultry carcasses collected from the above farms. Gross and histopathological changes were observed in all vital organs which were suggestive of Newcastle disease, and suspensions from the suspected tissue samples were inoculated in 9-10-day-old embryonated eggs for isolation of the Newcastle disease virus. The isolates were tested by targeting and amplification of the full-length fusion glycoprotein of the Newcastle disease virus of 1662 bp in length by using reverse transcriptase-polymerase chain reaction. The full-length amplicons were sequenced and phylogenetic analysis was carried out using phylogenetic analysis tools like MEGA7. The analysis of the amino acid sequences present at the fusion cleavage site and phylogenetic tree suggested that the virus circulating in the remote districts of Mizoram belonged to a velogenic strain with sequences at the fusion cleavage site from positions 113-117 as RRQKR’F and belonged to a new genotype XXII as per the updated phylogenetic nomenclature system. The new genotype XXII was further classified into two subgenotypes under the updated classified nomenclature system as XXII.1 and XXII.2.