Highly pathogenic and low pathogenic avian influenza H5 subtype viruses in wild birds in Ukraine

There have been three waves of highly pathogenic avian influenza (HPAI) outbreaks in commercial, backyard poultry and wild birds in Ukraine. The first (2005-2006) and the second (2008) waves were caused by H5N1 HPAI virus, with 45 outbreaks among commercial poultry (chickens) and backyard fowl (chickens, ducks, and geese) in four regions of Ukraine (AR Crimea, Kherson, Odesa, Sumy Oblast). H5N1 HPAI viruses were isolated from dead wild birds: Cormorants (Phalacrocorax carbo) and Great Crested Grebes (Podiceps cristatus) in 2006, 2008. The third HPAI wave consisted of nine outbreaks of H5N8 HPAI in wild and domestic birds, beginning in November 2016 in the Central and South Regions (Kherson, Odesa, Chernivtsi, Ternopil, Mykolaiv Oblast). H5N8 HPAI virus was detected in dead Mute Swan (Cygnus olor), Peacocks (Pavo cristatus) (in zoo), Ruddy Shelduck (Tadorna ferruginea), White-fronted Goose (Anser albifrons) and from environmental samples in 2016, 2017. Wide wild bird surveillance for avian influenza (AI) virus was conducted from 2006 to 2016 in Ukraine regions suspected of being intercontinental (North-South and East-West) flyways. A total of 21,511 samples were collected from 105 species of wild birds representing 27 families and 11 orders. Eighty-two low pathogenic avian influenza (LPAI) viruses were isolated (including one H5N2 LPAI virus in 2010) from wild birds with a total of 23 antigenic hemagglutinin (HA) and neuraminidase (NA) combinations. Fifteen of 16 known avian HA subtypes were isolated. Two H5N8 HPAI viruses and two H5N2 LPAI viruses were isolated from live wild birds and environmental samples (fresh bird feces) during surveillance before the outbreak in poultry. The Ukrainian H5N1, H5N8 HPAI and H5N2 LPAI viruses belong to different H5 phylogenetic groups. Our results demonstrate the great diversity of AI viruses in wild birds in Ukraine, as well as the importance of this region for studying the ecology of avian influenza.