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Invasions by Eurasian avian influenza virus H6 genes and replacement of the virus' North American clade.

zu Dohna H, Li J, Cardona CJ, Miller J, Carpenter TE - Emerging Infect. Dis. (2009)

Bottom Line: Results suggested that Eurasian H6 subtype has invaded North America several times, with the first invasions occurring 10 years before the first detection of invading isolates.The members of the North American clade decreased from 100% in the 1980s to 20% in the 2000s among H6 isolates from North America.Unraveling the reasons for this large-scale gene movement between hemispheres might identify drivers of global AIV circulation.

View Article: PubMed Central - PubMed

Affiliation: Center for Animal Disease Modeling and Surveillance, University of California School of Veterinary Medicine, Davis, California 95616, USA. hzudohna@ucdavis.edu

ABSTRACT
The spread of highly pathogenic avian influenza virus (AIV) (H5N1) underlines the potential for global AIV movement through birds. The phylogenies of AIV genes from avian hosts usually separate into Eurasian and North American clades, reflecting limited bird migration between the hemispheres. However, mounting evidence that some H6 sequences from North America cluster with Eurasian subtype H6 sequences calls the strict hemispheric divide into question. We conducted a comprehensive phylogenetic analysis of the extent and timing of cross-hemisphere movements by the H6 gene. Results suggested that Eurasian H6 subtype has invaded North America several times, with the first invasions occurring 10 years before the first detection of invading isolates. The members of the North American clade decreased from 100% in the 1980s to 20% in the 2000s among H6 isolates from North America. Unraveling the reasons for this large-scale gene movement between hemispheres might identify drivers of global AIV circulation.

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Related in: MedlinePlus

Proportion of viruses from the North American clade of avian influenza virus among wild bird isolates (blue) or poultry outbreaks (pink) in North America (A) or Eurasia (B). All poultry outbreaks in Eurasia were caused by viruses from the Eurasian clade (results not shown). Wild bird isolates are grouped by decade. Black circles show proportions of all isolates per decade (number of isolates per decade shown next to circles), black lines show fitted logistic regressions, and red circles show individual poultry outbreaks.
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Figure 4: Proportion of viruses from the North American clade of avian influenza virus among wild bird isolates (blue) or poultry outbreaks (pink) in North America (A) or Eurasia (B). All poultry outbreaks in Eurasia were caused by viruses from the Eurasian clade (results not shown). Wild bird isolates are grouped by decade. Black circles show proportions of all isolates per decade (number of isolates per decade shown next to circles), black lines show fitted logistic regressions, and red circles show individual poultry outbreaks.

Mentions: The estimated entry times of these 7 subclades overlapped in part, with the earliest times starting in the late 1970s and the latest around 2005 (Figure 3). The proportion of North American clade members among isolates from North American wild birds decreased from 100% in the 1980s to 20% in the 2000s (Figure 4; p<0.0001, logistic regression, residual deviance = 75, df = 106). Similarly, all H6 introductions into poultry species in North America with sequences submitted to the public databases were caused by viruses from the North American clade before 1998 and by viruses from the Eurasian clade after 1999 (Figure 4). All 38 H6 sequences isolated in North America after 2002 belong to the Eurasian clade. The change in clade composition among North American viruses is visible across the entire North American continent (Technical Appendix Figures 2, 3). One subclade invaded Australia from North America but did not result in a significant impact on the clade composition over time in Eurasia (Figure 4, panel B). The increase of Eurasian H6 among North American H6 isolates did not coincide with an overall increase of H6 prevalence among AIV isolates reported in wild birds in North America (results not shown). All NA genes that were combined with invading H6 genes belonged to North American clades (Technical Appendix Figures 4–7).


Invasions by Eurasian avian influenza virus H6 genes and replacement of the virus' North American clade.

zu Dohna H, Li J, Cardona CJ, Miller J, Carpenter TE - Emerging Infect. Dis. (2009)

Proportion of viruses from the North American clade of avian influenza virus among wild bird isolates (blue) or poultry outbreaks (pink) in North America (A) or Eurasia (B). All poultry outbreaks in Eurasia were caused by viruses from the Eurasian clade (results not shown). Wild bird isolates are grouped by decade. Black circles show proportions of all isolates per decade (number of isolates per decade shown next to circles), black lines show fitted logistic regressions, and red circles show individual poultry outbreaks.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2744232&req=5

Figure 4: Proportion of viruses from the North American clade of avian influenza virus among wild bird isolates (blue) or poultry outbreaks (pink) in North America (A) or Eurasia (B). All poultry outbreaks in Eurasia were caused by viruses from the Eurasian clade (results not shown). Wild bird isolates are grouped by decade. Black circles show proportions of all isolates per decade (number of isolates per decade shown next to circles), black lines show fitted logistic regressions, and red circles show individual poultry outbreaks.
Mentions: The estimated entry times of these 7 subclades overlapped in part, with the earliest times starting in the late 1970s and the latest around 2005 (Figure 3). The proportion of North American clade members among isolates from North American wild birds decreased from 100% in the 1980s to 20% in the 2000s (Figure 4; p<0.0001, logistic regression, residual deviance = 75, df = 106). Similarly, all H6 introductions into poultry species in North America with sequences submitted to the public databases were caused by viruses from the North American clade before 1998 and by viruses from the Eurasian clade after 1999 (Figure 4). All 38 H6 sequences isolated in North America after 2002 belong to the Eurasian clade. The change in clade composition among North American viruses is visible across the entire North American continent (Technical Appendix Figures 2, 3). One subclade invaded Australia from North America but did not result in a significant impact on the clade composition over time in Eurasia (Figure 4, panel B). The increase of Eurasian H6 among North American H6 isolates did not coincide with an overall increase of H6 prevalence among AIV isolates reported in wild birds in North America (results not shown). All NA genes that were combined with invading H6 genes belonged to North American clades (Technical Appendix Figures 4–7).

Bottom Line: Results suggested that Eurasian H6 subtype has invaded North America several times, with the first invasions occurring 10 years before the first detection of invading isolates.The members of the North American clade decreased from 100% in the 1980s to 20% in the 2000s among H6 isolates from North America.Unraveling the reasons for this large-scale gene movement between hemispheres might identify drivers of global AIV circulation.

View Article: PubMed Central - PubMed

Affiliation: Center for Animal Disease Modeling and Surveillance, University of California School of Veterinary Medicine, Davis, California 95616, USA. hzudohna@ucdavis.edu

ABSTRACT
The spread of highly pathogenic avian influenza virus (AIV) (H5N1) underlines the potential for global AIV movement through birds. The phylogenies of AIV genes from avian hosts usually separate into Eurasian and North American clades, reflecting limited bird migration between the hemispheres. However, mounting evidence that some H6 sequences from North America cluster with Eurasian subtype H6 sequences calls the strict hemispheric divide into question. We conducted a comprehensive phylogenetic analysis of the extent and timing of cross-hemisphere movements by the H6 gene. Results suggested that Eurasian H6 subtype has invaded North America several times, with the first invasions occurring 10 years before the first detection of invading isolates. The members of the North American clade decreased from 100% in the 1980s to 20% in the 2000s among H6 isolates from North America. Unraveling the reasons for this large-scale gene movement between hemispheres might identify drivers of global AIV circulation.

Show MeSH
Related in: MedlinePlus