Interspecies transmission of an H7N3 influenza virus from wild birds to intensively reared domestic poultry in Italy.
Since the "bird flu" incident in Hong Kong SAR in 1997, several studies have highlighted the substantial role of domestic birds, such as turkeys and chickens, in the ecology of influenza A viruses. Even if recent evidence suggests that chickens can maintain several influenza serotypes, avian influenza viruses (AIVs) circulating in domestic species are believed to be introduced each time from the wild bird reservoir. However, so far the direct precursor of influenza viruses from domestic birds has never been identified. In this report, we describe the antigenic and genetic characterization of the surface proteins of H7N3 viruses isolated from wild ducks in Italy in 2001 in comparison to H7N3 strains that circulated in Italian turkeys in 2002-2003. The wild and domestic avian strains appeared strictly related at both phenotypic and genetic level: homology percentages in seven of their genes were comprised between 99.8% (for PB2) and 99.1% (for M), and their NA genes differed mainly because of a 23-aminoacid deletion in the NA stalk. Outside this region of the molecule, the NAs of the two virus groups showed 99% similarity. These findings indicate that turkey H7N3 viruses were derived "in toto" from avian influenza strains circulating in wild waterfowl 1 year earlier, and represent an important step towards the comprehension of the mechanisms leading to interspecies transmission and emergence of potentially pandemic influenza viruses.
Campitelli
Laura
L
Department of Virology, Istituto Superiore Sanita', Rome, Italy. campitel@iss.it
Mogavero
Elvira
E
De Marco
Maria Alessandra
MA
Delogu
Mauro
M
Puzelli
Simona
S
Frezza
Fabiola
F
Facchini
Marzia
M
Chiapponi
Chiara
C
Foni
Emanuela
E
Cordioli
Paolo
P
Webby
Richard
R
Barigazzi
Giuseppe
G
Webster
Robert G
RG
Donatelli
Isabella
I
D000595:Amino Acid Sequence; D000818:Animals; D000835:Animals, Wild / Q000821:virology; D001715:Bird Diseases / Q000635:transmission* / Q000821:virology; D004372:Ducks / Q000821:virology*; D019143:Evolution, Molecular; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D009980:Influenza A virus / Q000235:genetics / Q000302:isolation & purification*; D005585:Influenza in Birds / Q000635:transmission* / Q000821:virology; D007558:Italy; D008969:Molecular Sequence Data; D009439:Neuraminidase; D010802:Phylogeny; D011201:Poultry Diseases / Q000635:transmission* / Q000821:virology; D014422:Turkeys / Q000821:virology*; D014764:Viral Proteins
D019267:Hemagglutinin Glycoproteins, Influenza Virus; D014764:Viral Proteins; C487630:NA protein, influenza A virus; D009439:Neuraminidase