Genetic Analysis of F protein Gene of Recently Isolated Newcastle Disease Virus

Abstract

Newcastle disease is an infectious mild to lethal virus disease of birds specifically the domestic chicken. The NDV caused by paramyxovirus of the genus Rubulavirus (species Newcastle diseases virus). The disease has different signs marked by highly inconstant respiratory, digestive, tremors, diarrhea, incoordination, coughing and twitching of head. The disease attack all ages of chickens especially it's destructive to young birds. NDV is an enveloped virus with two membrane proteins: the haemagglutinin–neuraminidase (HN) protein involved in cell attachment and release, and the fusion (F) protein involved in mediating fusion of the viral envelope with cellular membranes. Newcastle disease virus (NDV) still considered as a huge concern in Egyptian poultry industry, in spite of massive vaccination programs implemented from along years ago. The main object of the current study is to do a molecular identification of both surface glycoproteins genes of NDv virions of a recently isolated field strain during 2019. Tracheas were collected from 10 chicken - NDv vaccinated - broilers flocks suffered from mild to moderate respiratory manifestations with Mortalities varied from 10 to 25 % at Giza governorate during October 2019. Only 5 samples showed HA activity after blind Propagation at SPF eggs and only one sample (S4) was +Ve APMV-1 by rtRT-PCR. Sequence of the cleavage site of the F protein gene showed typical known sequence of velogenic NDv strains (112RRQKRF117). Molecular and phylogenetic analysis of both F and HN proteins genes of S4 new isolate showed high similarity and close relation with Chinese strains of Genotype VII sub type D reached 97.28 % for F protein gene and 98.72% suggesting a role of migratory or wild birds in NDV evolution in Egypt. Further epidemiological and surveillance work is strongly recommended to define the exact role of migratory and wild birds role in NDV evolution in last years.