Characterization of low-pathogenicity H5N1 avian influenza viruses from North America.
Wild-bird surveillance in North America for avian influenza (AI) viruses with a goal of early identification of the Asian H5N1 highly pathogenic AI virus has identified at least six low-pathogenicity H5N1 AI viruses between 2004 and 2006. The hemagglutinin (HA) and neuraminidase (NA) genes from all 6 H5N1 viruses and an additional 38 North American wild-bird-origin H5 subtype and 28 N1 subtype viruses were sequenced and compared with sequences available in GenBank by phylogenetic analysis. Both HA and NA were phylogenetically distinct from those for viruses from outside of North America and from those for viruses recovered from mammals. Four of the H5N1 AI viruses were characterized as low pathogenicity by standard in vivo pathotyping tests. One of the H5N1 viruses, A/MuteSwan/MI/451072-2/06, was shown to replicate to low titers in chickens, turkeys, and ducks. However, transmission of A/MuteSwan/MI/451072-2/06 was more efficient among ducks than among chickens or turkeys based on virus shed. The 50% chicken infectious dose for A/MuteSwan/MI/451072-2/06 and three other wild-waterfowl-origin H5 viruses were also determined and were between 10(5.3) and 10(7.5) 50% egg infective doses. Finally, seven H5 viruses representing different phylogenetic clades were evaluated for their antigenic relatedness by hemagglutination inhibition assay, showing that the antigenic relatedness was largely associated with geographic origin. Overall, the data support the conclusion that North American H5 wild-bird-origin AI viruses are low-pathogenicity wild-bird-adapted viruses and are antigenically and genetically distinct from the highly pathogenic Asian H5N1 virus lineage.
Spackman
Erica
E
Southeast Poultry Research Laboratory, U.S. Department of Agriculture-Agricultural Research Service, 934 College Station Road, Athens, GA 30605, USA. Erica.Spackman@ars.usda.gov
Swayne
David E
DE
Suarez
David L
DL
Senne
Dennis A
DA
Pedersen
Janice C
JC
Killian
Mary Lea
ML
Pasick
John
J
Handel
Katherine
K
Pillai
Smitha P Somanathan
SP
Lee
Chang-Won
CW
Stallknecht
David
D
Slemons
Richard
R
Ip
Hon S
HS
Deliberto
Tom
T
D000818:Animals; D000941:Antigens / Q000737:chemistry; D001717:Birds; D002645:Chickens; D004372:Ducks; D005814:Genes, Viral; D016679:Genome, Viral; D053124:Influenza A Virus, H5N1 Subtype / Q000737:chemistry* / Q000235:genetics* / Q000472:pathogenicity; D005585:Influenza in Birds / Q000821:virology*; D020128:Inhibitory Concentration 50; D009656:North America; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013997:Time Factors; D014422:Turkeys
D000941:Antigens