Abstract
BackgroundNewcastle disease (ND) causes severe economic losses in poultry industry worldwide. Egyptian poultry industry suffered from severe economic losses since the isolation of Velogenic Newcastle disease virus (vNDV) genotype VIId in 2011 and up till now despite the use of different vaccination programs. So, this study aimed to isolate and characterize the vNDV from a total of 120 poultry flocks from ten provinces in the Egyptian Delta region with a history of respiratory manifestation, high mortalities or a decrease in egg production between 2015 and 2019. Seventy-three samples’ allantoic fluid (73/120, 60.8%) were positive for hemagglutination with chicken RBCs. These samples were submitted to molecular examination using qRT-PCR specific primers for AOAV-1, highly pathogenic avian influenza (HPAI-H5), low pathogenic avian influenza (LPAI-H9) and infectious bronchitis virus (IBV).ResultsFifty samples (50/120: 41.6%) were confirmed positive for AOAV-1, based on genetic analysis of matrix and fusion protein. The co-infection rate of other respiratory viral diseases examined was 1.6, 14.1, and 4.1%, for HPAI-H5, LPAI-H9, and IBV, respectively. Biologically, the intracerebral pathogenicity index of ten selected AOAV-1 isolates ranged from 1.70 to 1.98, which indicated the velogenic nature of these isolates. All the sixteen sequenced isolates were AOAV-1 genotype VII.1.1. The full F gene sequence of six examined AOAV-1 VII.1.1 isolates contained the seven neutralizing epitopes, and the glycosylation motif of six-potential sites for N linked glycosylation at residues 85, 191, 366, 447, 471, and 541.ConclusionIt could be concluded that the high prevalence of AOAV-1 genotype VII.1.1 in the Egyptian chicken flocks despite the intensive vaccination with live and killed ND vaccines, as all the 16 isolates tested were belonged to this genotype. Homologous vaccination is badly needed to control and reduce the spread of AOAV-1 genotype VII.1.1infection in Egyptian poultry flocks.
Highlights
Newcastle disease (ND) causes severe economic losses in poultry industry worldwide
Newcastle disease virus (NDV) or Avian paramyxoviruses 1 (APMV-1) was recently classified to Genus Avian Orthoavulavirus, family Paramyxoviridae and common NDV is recently known as Avian Orthoavulavirus-1 (AOAV-1) [3, 4]
Isolation of AOAV-1 in Specific Pathogen Free Embryonated Chicken Eggs (SPF-ECE) and slide HA testing The embryos of inoculated eggs were died between the 2nd and the 4th days post-inoculation in many samples
Summary
Newcastle disease (ND) causes severe economic losses in poultry industry worldwide. Egyptian poultry industry suffered from severe economic losses since the isolation of Velogenic Newcastle disease virus (vNDV) genotype VIId in 2011 and up till despite the use of different vaccination programs. This study aimed to isolate and characterize the vNDV from a total of 120 poultry flocks from ten provinces in the Egyptian Delta region with a history of respiratory manifestation, high mortalities or a decrease in egg production between 2015 and 2019. Newcastle disease (ND) encompasses a critical impact amongst the most economically viral poultry diseases leading to high mortality and morbidity rates in the susceptible poultry. It still causing a drop in egg production even in vaccinated layers [1]. Updated classification criteria of AOAV-1 genotype VII viruses merged all the subgenotypes into only 3, VII.1.1 including previous subgenotypes (b, d, e, j, l), VII.1.2 included previous subgenotypes (f), and VII. included the previous subgenotypes (h, i, k) [5]
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