Isolation of Newcastle Disease Virus Genotype VII from Native Chicken in Republic Democratic of Timor-Leste

Abstract

Newcastle disease (ND) is a contagious disease and still a threat to the development of chicken farms in several countries including the Republic Democratic of Timor-Leste. There were reported local outbreaks every year in the country. The causative agent of ND is Avian orthoavulavirus-1 (AOAV-1) common name Newcastle disease virus (NDV). The objective of this study was to isolate the NDV currently circulating in Timor-Leste and to determine its genotype based on phylogenetic tree analysis and its virulence based on molecular analysis of the Fusion (F) gene cleavage site. In this study samples of dead chickens suspected due to ND were taken from two different sites in Timor-Leste namely Kilotons and Atabae district. Tissue samples were collected for histopathological examination and viral isolation. Allantoic fluids were harvested and confirmation of NDV was carried out by standard methods hemagglutination test (HA) and the hemagglutination inhibition test (HI). Partial fragments of the F and HN proteins gene were amplified using NDV-specific primers in a one-step RT-PCR reaction. The PCR product was then sequenced, and the nucleotide sequences were then used for building a phylogenetic tree with other NDV strains representative of genotype I-VII that are available in the GenBank. Based on phylogenetic analysis it was found that the new isolates belonging to genotype VII with the amino acid sequence of the F gene cleavage site were a virulent type and possibly viscerotropic velogenic NDV.