Newcastle disease virus (NDV, Avian orthoavulavirus type 1, AOAV-1) is a contagious high-impact poultry pathogen with infections detected worldwide. In the present study, 19,500 clinical samples from wild bird species and poultry collected from 28 regions of Russia between 2017 and 2021 were screened for the presence of the AOAV-1 genome. NDV RNA was detected in 15 samples from wild birds and 63 samples from poultry. All isolates were screened for a partial sequence of the fusion (F) gene that included the cleavage site. Phylogenetic analysis demonstrated that lentogenic AOAV-1 I.1.1, I.1.2.1, and II genotypes were dominant among vaccine-like viruses in the territory of the Russian Federation. A vaccine-like virus with a mutated cleavage site (112-RKQGR^L-117) was detected in turkeys. Among the virulent AOAV-1 strains, viruses of the XXI.1.1, VII.1.1, and VII.2 genotypes were identified. The cleavage site of viruses of the XXI.1.1 genotype had a 112-KRQKR^F-117 amino acid sequence. The cleavage site of viruses with VII.1.1 and VII.2 genotypes had a 112-RRQKR^F-117 amino acid sequence. The data collected by the present study demonstrate the distribution and dominance of the virulent VII.1.1 genotype in the Russian Federation between 2017 and 2021.
Avian infectious bronchitis virus is a cause of major economic losses in poultry industry. However, control of the virus is very complicated due to its high variability. The mutation frequency in the hypervariable region of the S1 gene of the virus isolated from the vaccinated birds annually amounts to 1.5%. Long-term observations of the circulation of IBV isolates detected in a number of poultry farms demonstrated that the virus genetic lineages circulating on the poultry farms could eventually change. This stipulates the need for the continuous monitoring of the virus isolates for the prevention schedule optimization. The paper demonstrates test results of 840 biological samples collected from chickens on the poultry farms in Russia and some CIS countries in 2015–2017. From 311 positive samples 147 IBV isolates were recovered, the majority of which belonged to eight genetic lines of GI genotype: GI-1, GI-12, GI-13, GI-14, GI-16, GI-19, GI-22, GI-23. Moreover, recombinant isolates were detected as well as variant isolates that belonged to none of the known genotypes.
Due to the genetic diversity of low pathogenic avian influenza (LPAI) viruses of subtype H9N2, it deemed appropriate to study the potency of the vaccines based on the antigens of strains А/chicken/Amursky/03/12 and A/chicken/Chelyabinsk/314-1/20 that represent currently circulating in the Russian Federation genetic lineages Y280 and G1, respectively. While low pathogenicity of the agent does not allow demonstrating the vaccine protective properties by the direct methods generally used for potency assessment (e.g. morbidity and mortality), the indirect methods were used: determination of antigenic relatedness of the strains, level of the postvaccinal homologous and heterologous humoral immunity, analysis of the virus genome synthesis inhibition (reduction) in vaccinated birds following their challenge. The strains used in the vaccines were determined to have some antigenic differences, which were demonstrated in the hemagglutination inhibition (HI) assay during control of the postvaccinal immunity in birds. Both vaccines generally induced strong humoral immunity in vaccinated birds (9–10 log2 determined using HI assay) with some difference in the levels of the immune response following the use of homologous or heterologous antigens. It was also reliably determined that homologous immunity facilitated more expressed inhibition of the virus reproduction after the challenge. The level of inhibition (reduction) of the virulent LPAI virus genome synthesis in vaccinated birds following their challenge with H9N2 virus of genetic lineage G1 was higher in birds following homologous vaccination, while the time periods of the genome detection in the biomaterial samples were the same. It was demonstrated that due to antigenic and immunogenic differences between LPAI H9N2 strains, use of both antigenic components in the inactivated vaccines is appropriate.
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