Isolation and Identification of Newcastle Disease Viruses from Naturally Infected Chickens
Isolation and Identification of Newcastle Disease Viruses from Naturally Infected Chickens
Yasser Asaad Hameed Al-Shareef, Firas Hussain Kadim Abawi*
ABSTRACT
Newcastle disease (ND) is one of the most infectious and lethal infections in poultry attributed by severe economic losses and undermining poultry well-being. The ND can cause high mortalities in all types of poultry nevertheless of vaccination status, indicating breakthrough infections. In order to investigate the nature and dynamics of these breakthrough infections, samples were collected from infected flocks with existing clinical signs of the disease. Attempts to isolate, identify and characterize positive samples were made by inoculating chicken embryonated eggs followed by haemagglutination and haemagglutination inhibition assays. Using reverse transcriptase-polymerase chain reaction, the presence of the virus was confirmed and mean death time approach was applied to determine the pathotype of isolates (velogenic). Next, we assessed the most important determinant of ND virus pathogenicity by the analysis of the fusion protein cleavage sites, phylogenetic analysis sand compared genomics of NDV isolates to publish sequences. Isolates characterized here showed 90.37% sequence similarity to the Iranian isolate Asil/IR/AAA158/2019 (MN370894.1) within velogenic clusters. Taken together, clinical, genetics and molecular biological approaches identified velogenic strains of NDV in poultry which breach the immunity induced by the currently applied vaccines, warranting future monitoring to better device control strategies in poultry.
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