The thesis is devoted to the epizootic monitoring of H5 and H7 subtypes of highly pathogenic avian influenza in poultry and wild birds in various regions of Ukraine with isolation of the pathogen, studying of its biological features; retrospective analysis of epizootic status worldwide and in Ukraine, its comparison with modern situation for the detection of main reasons and factors of disease’s occurrence. The major attention in this thesis is paid to the improvement of modern laboratory serological diagnostics of influenza in Ukraine.
It has been found that worldwide epizootic situation concerning highly pathogenic influenza is complex and tense with the increasing of the number (up to 12) of virus antigenic variants which cause the disease. In 2015–2018, 7,122 outbreaks were registered in 68 countries. Starting from 2005, three waves of highly pathogenic avian influenza have been detected in Ukraine: the first (2005–2006) and the second (2008) waves were caused by H5N1 HPAIV, the third one (2016–2017) — by H5N8 HPAIV which was new for Ukraine. In 2016–2017, nine outbreaks of the disease were registered in 5 regions (Kherson, Odesa, Mykolaiv, Ternopil, and Chernivtsi). It has been found that all cases of the introduction of H5N1 and H5N8 HPAIV subtypes to Ukraine and the infection of poultry are connected with wild migratory birds during their migration period and virus transmission from them to household poultry. At the same time, H7 HPAIV and its circulation among poultry has never been registered in Ukraine.
New H5N8 HPAIV virus has been isolated from wild birds А/white-fronted goose/AN/1-15-12/2016, and its biological features have been studied (cultivation ability on chicken embryos, hemagglutinin level) infective (7.19 lg EID50/0.1 cm3) and lethal (8.5 ELD50/0.1 cm3) titers and pathogenicity. It has been proved that it belongs to 2.3.4.4b subclade and related with viruses of the same H5N8 subtype which circulated among poultry and wild birds in various regions of Russia and Western Europe in 2017.
The wide circulation of LPAIV subtypes (Н1, Н3, Н4, Н5, Н6, Н7, Н9, Н11, Н13) among wild birds in 2016–2018 has been confirmed. The simultaneous independent circulation of low and highly pathogenic H5 avian influenza has been proved. The long-term circulation of H7 influenza viruses among wild birds has been confirmed.
The production strain has been cloned from filed epizootic H5N8 HPAIV, which characterized by reduced infectious (6.74 lg EID50/0.1 cm3) and lethal (6.83 lg ELD50/0.1 cm3) activity, as well as by its ability to accumulate in extraembryonic liquid of CE in titers up to 1:256–1:512, the ability to cause the accumulation of specific antibodies in the titer of 7.1 ± 1.1 log2 after vaccination with inactive antigen.
Serological diagnostics has been improved by the addition of new domestic inactivated antigens of H5N8, H5N2, H7N3 subtypes to the test-kit for the detection of antibodies against avian influenza in HI-test, as well as by the selection of optimal lyophilization medium.
