Characterization of Newcastle Disease Virus Circulating in Vaccinated Poultry Farms in Egypt During 2020

Abstract

Newcastle disease virus (NDV) is responsible for huge economic losses in birds worldwide. This study aims to isolate, identify, pathotype, and genetically characterize field isolates of NDV from various governorates in Egypt in 2020 (Giza, Gharbya, Kalyobiya, Cairo, and Menofiya). After the third passage, 23 of 50 infected samples (46%) showed positive hemagglutination activity in the collected allantoic fluid. The results revealed that all isolates from the governorates of Menoufia, Cairo, and Giza were velogenic, with a Mean death time (MDT) of 48 hours and an Intracerebral pathogenicity index (ICPI) ranging from 1.55-1.65. Sequencing the 766-bp segment, including the 3' end of the matrix gene and the 5' end of the fusion gene from three different isolates, indicated that they all possessed the 112RRQKRF117 motif typical of the virulent isolates. The sequenced isolates were grouped with class II genotype VIIb and had a high genetic distance to the LaSota reference strain. It is concluded that NDV strains circulating among vaccinated poultry farms in Egypt are virulent genotype VII and had a high genetic distance to the LaSota reference strain, resulting in significant economic losses.