Isolation, genotyping, and sub-genotyping of Newcastle disease virus from commercial broiler chickens in Northern Egypt

In poultry, viral diseases, including the Newcastle virus (NDV), are considered among the causes of profitable losses in poultry, which directly affect livestock and the general health of birds. NDV is a ssRNA paramyxovirus causing a contagious disease in chickens ranging from subclinical infections to 100% death. Therefore, this research was conducted to follow up on the Newcastle disease virus recently circulating in commercial poultry farms in northern Egypt and compare the master amino acids that determine the velogeneity of the ND virus. In addition, this research compared their relationship to the vaccines currently in use. A specific-pathogen-free chicken (EE-SPF) egg was used to isolate NDV from chicken farms. Then the inoculated allantoic fluids were tested for NDV using the Hemagglutination Test and Hyper-Immune Serum against LaSota NDV. Furthermore, the F gene was molecularly characterized and sequenced. The results showed that 15 allantoic fluids were positive for NDV. From 9 isolates that were sequenced, seven isolates (ON497007, ON497008, ON497010, ON497011, ON497012, and ON497013, and ON532692) clustered into sub-genotype VII.1.1 and the other 2 (ON497006 and ON497009) into sub-genotype XXI.1.1. In addition, all the isolates in this investigation carry the velogenic strain's characteristic velogenic motif 112RKQKR*F117. In conclusion, the circulating ND in vaccinated chicken flocks in Egypt genotype VII.1.1 and XXI.1.1. Moreover, there was a residual substitution between most isolates, and genotype VII vaccine's strain (R/K), and autogenous vaccine strain (E/R) at position 78. These results are expected to help provide the latest characteristic information on NDV in northern Egypt.