BRIEF REPORT Biological and genetic characterization of a low-pathogenicity avian influenza H6N2 virus originating from a healthy Eurasian coot Songhua Shan • Trevor Ellis • Stan Fenwick • John Edwards • Mark O’Dea • John Parkinson Received: 20 October 2009 / Accepted: 14 December 2009 / Published online: 29 January 2010 Ó Springer-Verlag 2010 Abstract Influenza A virus, A/Eurasian coot/Western Australia/2727/79 (H6N2), from an apparently healthy coot was characterized. This virus was able to grow on MDCK cells and produce a cytopathic effect in the absence of exogenous trypsin and was further characterized as a low- pathogenicity avian influenza virus, with an intravenous pathogenicity index of 0.15 and a 321 PQAETRG 328 motif at the cleavage site of the haemagglutinin gene. It infected domestic chickens, resulting in seroconversion and inter- mittent virus excretion via cloaca and oropharynx under experimental conditions. Phylogenetic analysis showed that the viral genes were closely related to other waterfowl isolates from the same geographic area and time period. Avian influenza (AI) viruses are subdivided into 16 hae- magglutinin (HA) and 9 neuraminidase (NA) subtypes based on the antigenic differences in the HA and NA molecules [1]. Based on virus virulence and clinical signs, AI can be divided into two groups: highly pathogenic avian influenza (HPAI) and low-pathogenicity avian influenza (LPAI). Waterfowl are commonly believed to be a major reservoir of the type A influenza viruses, which are anti- genically and genetically diverse [2]. These waterfowl- origin viruses are occasionally associated with outbreaks of severe avian influenza in domestic poultry [2, 3]. Nevertheless, there have been recent reports of H6 subtype AI outbreaks in commercial poultry [4–6]. The H6 subtype AI viruses had received little attention until the first documented infection of humans with an H5N1 AI virus occurred in Hong Kong in 1997. An H6N1 AI virus, A/teal/HK/W312/97 (H6N1), isolated during this outbreak seemed to be one progenitor of the A/HK/156/97 (H5N1) virus [7]. Although natural human infection with H6 subtype AI virus has not yet been reported, a recent seroprevalence study showed that United States veterinar- ians who have been exposed to birds demonstrated significantly elevated antibody titers against H5, H6, and H7 AI viruses [8]. This raised the possibility that H6 AI viruses could become novel human pathogens [9]. The H6 subtype of AI viruses is one of the most com- monly recognized subtypes in domestic ducks in southern China [10] and in migratory birds in North America and Europe [11]. Surveillance has demonstrated that the con- tinued co-circulation of H5N1, H6N1, and H9N2 AI viru- ses in southern China has led to frequent reassortment in minor poultry species [9, 10]. This, in turn, has greatly increases the genetic diversity of influenza A viruses in this region and highlights the potential for H6 AI viruses and H6 reassortants to cross the species barrier to infect humans. Understanding the epidemiology, ecology, and evolution of H6 AI viruses will be helpful for further understanding of the molecular evolution of H5N1 AI virus and may help in the development of future control measures. A/Eurasian coot/Western Australia/2727/79 (abbrevi- ated A/coot/WA/2727/79) used in this study was isolated from a healthy Eurasian coot (Fulica atra) in Australia [12]. The virus was propagated by inoculation of the allantoic cavity of 9- to 11-day-old specific pathogen-free (SPF) chicken embryonated eggs according to the standard S. Shan Á T. Ellis (&) Á S. Fenwick Á J. Edwards Murdoch University, Perth 6150, Australia e-mail: T.Ellis@murdoch.edu.au M. O’Dea Á J. Parkinson Department of Agriculture and Food Western Australia, Baron-Hay Court, South Perth, WA 6151, Australia 123 Arch Virol (2010) 155:403–409 DOI 10.1007/s00705-010-0588-1