Abstract
BackgroundAlthough extensive data demonstrates that the majority of H6 duck isolates belonged to a single H6N2 virus lineage with a single gene constellation in southern China from 2000 to 2005, the prevalence of H6N2 virus in poultry in Eastern China is largely unknown.ResultsEpidemiology revealed that H6N2 viruses were the most frequently detected influenza subtypes in live bird markets from 2002 to 2008 in Eastern China, but from 2009 onwards, they were replaced with novel H6N6 viruses. We phylogenetically and antigenically analyzed 42 H6 viruses isolated mainly in domestic ducks from 2002 to 2010 in Eastern China. Surprisingly, none of these isolates grouped with the previously described H6N2 viruses which belonged to a single H6N2 virus lineage with a single gene constellation in domestic ducks in southern China from 2000 to 2005. Two distinct hemagglutinin lineages were identified and they all underwent frequent reassortment with multiple virus subtypes from the natural gene pool, but few reassortants were persistent or prevalent.ConclusionsFive subtypes of H6 influenza viruses (H6N1, H6N2, H6N5, H6N6 and H6N8) cocirculated in Eastern China, which form a significant part of the natural influenza virus reservoir in domestic ducks, and significant viral reassortment is still ongoing in this species.
Highlights
Extensive data demonstrates that the majority of H6 duck isolates belonged to a single H6N2 virus lineage with a single gene constellation in southern China from 2000 to 2005, the prevalence of H6N2 virus in poultry in Eastern China is largely unknown
In California, the H6N2 viruses were nonpathogenic in experimentally infected chickens [9], but pathogenicity tests showed that all the H6N1 viruses isolated in Taiwan were of low pathogenicity and might lead to economic loss when associated with other diseases [6]
H6 influenza viruses from poultry in Eastern China Influenza virus surveillance of apparently healthy poultry species, including duck, goose and chicken, in live bird markets (LBM) from July 2002 to December 2010 revealed that multiple influenza A virus subtypes were cocirculating in these birds, and H6 influenza viruses were present in aquatic and terrestrial poultry
Summary
Extensive data demonstrates that the majority of H6 duck isolates belonged to a single H6N2 virus lineage with a single gene constellation in southern China from 2000 to 2005, the prevalence of H6N2 virus in poultry in Eastern China is largely unknown. During the H5N1 outbreak in Hong Kong in 1997, A/Teal/Hong Kong/W312/97 (W312-like), an H6N1 avian influenza virus was isolated from a live bird markets (LBM). Subsequent characterisation of the virus revealed that seven gene segments were closely related to the A/Hong Kong/156/97 (156-like) influenza viruses, which infected 18 humans in 1997 [1,2]. A/Quail/ Hong Kong/G1/97 (G1-like), an H9N2 virus, shared the same six internal gene segments with the 156-like influenza viruses. The incident highlights the potential for avian influenza viruses to cross the species barrier and infect humans without reassort [7,8,9], gene exchanges between viruses from domestic ducks and aquatic birds occur frequently [7]. In California, the H6N2 viruses were nonpathogenic in experimentally infected chickens [9], but pathogenicity tests showed that all the H6N1 viruses isolated in Taiwan were of low pathogenicity and might lead to economic loss when associated with other diseases [6]
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