Survey of avian influenza virus distribution in area around Qinghai Lake

Objective To understand the distribution of avian influenza virus in the area around Qinghai Lake in China. Methods Wild bird and poultry related samples were collected from the environments around Qinghai Lake in 2013. Avian influenza viruses were isolated with embryonated chicken eggs and the subtyping of avian influenza virus was conducted then. In order to understand the pathogenicity of avian influenza A (H5N1) viruses, the sequencing of HA genes were conducted. Results A total of 2420 wild bird related samples and 3944 poultry related samples were collected. No avian influenza virus strains were isolated from wild bird related samples, but 49 strains of avian influenza A viruses were isolated from poultry related samples (0.77%), including 27 strains of low pathogenic H9N2 virus, 19 strains of high pathogenic H5N1 virus and 3 strains of mixed H9N2 and H5N1 viruses. The virus isolation rate in poultry related samples was highest in January, followed by September. The virus isolation rates were higher in samples collected from the alive poultry markets in Ledu and Xining. Conclusion No avian influenza viruses were detected from the wild bird related samples collected from core area of Qinghai Lake. All the avian influenza virus strains, including H5N1 strains and H9N2 strains, were isolated from the poultry related samples collected from the area around Qinghai Lake. The co-circulating of two types of avian influenza viruses would facilitate the reassortment of avian influenza viruses, which provides the ecological base for the emerging of pandemic influenza virus.