Emergence of Influenza A Virus Variants after Prolonged Shedding from Pheasants

[Anne]

[SIZE=-1]Journal of Virology, April 2007, p. 4044-4051, Vol. 81, No. 8
0022-538X/07/$08.00+0 doi:10.1128/JVI.02346-06
Copyright ? 2007, American Society for Microbiology. All Rights Reserved.[/SIZE]
Emergence of Influenza A Virus Variants after Prolonged Shedding from Pheasants<sup>

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Jennifer Humberd,¹^,2 Kelli Boyd,³ and Robert G. Webster¹^* Division of Virology, Department of Infectious Diseases,¹ Animal Resource Center, St. Jude Children's Research Hospital, Memphis, Tennessee 38105,³ Department of Biology, University of Memphis, Memphis, Tennessee 38152²
Received 26 October 2006/ Accepted 19 January 2007
<!-- ABS --> We previously demonstrated the susceptibility of pheasants toinfection with influenza A viruses of 15 hemagglutinin (HA)subtypes: 13/23 viruses tested were isolated for

14 days, allin the presence of serum-neutralizing antibodies; one virus(H10) was shed for 45 days postinfection. Here we confirmedthat 20% of pheasants shed low-pathogenic influenza virusesfor prolonged periods. We aimed to determine why the antibodyresponse did not clear the virus in the usual 3 to 10 days,because pheasants serve as a long-term source of influenza virusesin poultry markets. We found evidence of virus replication andhistological changes in the large intestine, bursa of Fabricius,and cecal tonsil. The virus isolated 41 days postinfection wasantigenically distinct from the parental H10 virus, with correspondingchanges in the HA and neuraminidase. Ten amino acid differenceswere found between the parental H10 and the pheasant H10 virus;four were in potential antigenic sites of the HA molecule. Prolongedshedding of virus by pheasants results from a complex interplaybetween the diversity of virus variants and the host response.It is often argued that vaccination pressure is a mechanismthat contributes to the generation of antigenic-drift variantsin poultry. This study provided evidence that drift variantscan occur naturally in pheasants after prolonged shedding ofvirus, thus strengthening our argument for the removal of pheasantsfrom live-bird retail markets.

 

[gsgs]

Re: Emergence of Influenza A Virus Variants after Prolonged Shedding from Pheasants

10 amino-acids corresponds to about 70 normal mutations,
that's a lot of evolution in one single bird.
Maybe this sort of evolution even plays a considerable role
when compared with b2b2b2..2b - evolution.
Or h2h2..2h.

Also supports the migratory birds vs. poultry-trade sort of spread
over long distances.