Phylogenetic analysis of virulent strains of the Newcastle disease virus isolated from deceased chickens in Tanzania's Morogoro and Iringa regions

Abstract

Background Newcastle disease (ND) is a viral disease afecting a wide range of bird species and has a considerable fnancial impact on the world’s poultry market. The ND virus (NDV) strains currently circulating in poultry throughout Africa, and especially in East Africa, exhibit signifcant genetic variation. Objectives The primary objective of the present investigation was to investigate the NDV genotypes in chickens raised in backyards in Tanzania’s Morogoro and Iringa districts, which were associated with ND outbreaks. Methods Two tissue samples from chickens taken during a suspected ND outbreak in Tanzania’s Morogoro (Eastern zone) and Iringa (Southern highlands zone) were subjected to reverse transcription polymerase chain reaction targeting the fusion (F) and hemagglutinin-neuraminidase (HN) genes, followed by sequencing. Results Based on comprehensive analysis of the entire F and HN gene sequences, the viruses were categorized as genotype VII and displayed signifcant genetic similarity with NDV strains previously identifed in Mozambique, South Africa, Zambia, Zimbabwe, Botswana, Southeast Asia, and China. The uniformity in the amino acid cleavage site motif of the F protein across the examined NDV isolates, characterized by 112R–R–Q/K–K–R–F117, indicates their classifcation as virulent strains. Conclusion Regularly characterizing circulating strains and expanding the study to other parts of Tanzania may help to enhance disease control by giving a more precise picture of the situation regarding ND, especially in light of the issues posed by NDV genotype VII elsewhere