Neuropathological Effect of Clade 2.3.2 H5N1 Influenza Virus Isolated from Wild Birds

An outbreak of the Highly Pathogenic Avian Influenza H5N1 (HPAI H5N1) was reported in wild birds in 2010. Three strains (A/black-headed gull/Tyva/8/2010, A/spoonbill/Tyva/1/2010, and A/great crested grebe/Tyva/22/2010) were isolated and studied by the virological and molecularbiological methods. Viruses shown to be highly pathogenic in chicken and mice. We found some disruptions in brain tissues that can be related to the observed neuropathological behavior signs in mice. Close antigenic relationship between the investigated strains and those isolated at the Uvs Nuur Lake in 2009 and in the Russian Far East in 2008 (both clade 2.3.2) were also shown. Phylogenetic analysis of the hemagglutinin gene revealed a close relation to the strains isolated during outbreaks at the same location in 2009, as well as at the Qinghai Lake in 2009, and in Mongolia in 2010; as all of them falling into clade 2.3.2. Early AIV detection in this area can play an important role in terms of outbreak prediction, early warning and isolating new AIV strains when they start spreading from Asia to Russia and Europe. Further investigation of the global distribution of clade 2.3.2 and 2.2 HPAI H5N1 viruses will prove to be invaluable for better understanding of the evolutionary ecology of avian influenza viruses.