Characterization of duck H5N1 influenza viruses with differing pathogenicity in mallard (Anas platyrhynchos) ducks

Abstract

A number of H5N1 influenza outbreaks have occurred in aquatic birds in Asia. As aquatic birds are the natural reservoir of influenza A viruses and do not usually show clinical disease upon infection, the repeated H5N1 outbreaks have highlighted the importance of continuous surveillance on H5N1 viruses in aquatic birds. In the present study we characterized the biological properties of four H5N1 avian influenza viruses, which had been isolated from ducks, in different animal models. In specific pathogen free (SPF) chickens, all four isolates were highly pathogenic. In SPF mice, the S and Y isolates were moderately pathogenic. However, in mallard ducks, two isolates had low pathogenicity, while the other two were highly pathogenic and caused lethal infection. A representative isolate with high pathogenicity in ducks caused systemic infection and replicated effectively in all 10 organs tested in challenged ducks, whereas a representative isolate with low pathogenicity in ducks was only detected in some organs in a few challenged ducks. Comparison of complete genomic sequences from the four isolates showed that the same amino acid residues that have been reported to be associated with virulence and host adaption/restriction of influenza viruses were present in the PB2, HA, NA, M and NS genes, while the amino acid residues at the HA cleavage site were diverse. From these results it appeared that the virulence of H5N1 avian influenza viruses was increased for ducks and that amino acid substitutions at the HA cleavage site might have contributed to the differing pathogenicity of these isolates in mallards. A procedure for the intravenous pathogenicity index test in a mallard model for assessing the virulence of H5/H7 subtype avian influenza viruses in waterfowl is described.

Pathogenesis of highly pathogenic avian influenza A virus (H7N1) infection in chickens inoculated with three different doses

“…2006; Pálmai et al, 2007;Teifke et al, 2007;Yamada et al, 2007;Nakamura et al, 2008;Brown et al, 2009;Pantin-Jackwood & Swayne, 2009;Tang et al, 2009;Goletic et al, 2010). However, our study shows that, not only the encephalus, but also the spinal cord is consistently affected early in the infection with this H7 subtype HPAIV, which has been previously reported in chickens and mice infected with different HPAIV subtypes (Kobayashi et al, 1996a;Lipatov et al, 2003;Park et al, 2000;Pasick et al, 2010).…”

Shedding and serologic responses following primary and secondary inoculation of house sparrows (Passer domesticus) and European starlings (Sturnus vulgaris) with low-pathogenicity avian influenza virus

“…Serologic responses following LPAIV infection vary by host species and depend upon the origin, dose and subtype of the infecting virus (Kida et al, 1980;Lu & Castro, 2004;Mundt et al, 2009); also, detection of antibodies varies by assay (Spackman et al, 2009;Sullivan et al, 2009). Antibody detection following AIV experimental inoculation of chickens, ducks, and passerines has been variable, sometimes with a transitory or lack of detectable humoral immune response (van der Goot et al, 2003;Al-Attar et al, 2008;Fereidouni et al, 2010). For example, seroprevalence among mallards (Anas platyrhynchos) that had been experimentally inoculated with LPAIV decreased from approximately 90 to 65% between 14 and 21 d.p.i., as determined by a commercially available ELISA (Spackman et al 2009).…”

“…In past studies, virus was recovered from respiratory and gastrointestinal tissues of LPAIV experimentally inoculated passerines (including sparrows) and mallards from 2 to 7 d.p.i. (Roy et al, 1983;Tang et al, 2009), and infectious HPAIV (H7N7) was detected in both respiratory and gastrointestinal tissues of experimentally inoculated starlings and sparrows from 2 to 3 d.p.i. (Nestorowicz et al, 1987).…”

Differences in highly pathogenic avian influenza viral pathogenesis and associated early inflammatory response in chickens and ducks

“…However, certain HPAI H5N1 may run a fatal course in ducks (Kishida et al, 2005;Tang et al, 2009), which is dependent on the age and the genetic background of the ducks (Pantin-Jackwood et al, 2007aLö ndt et al, 2010;Cagle et al, 2011;Wasilenko et al, 2011). It was suggested that high pathogenicity of H5N1 in ducks was due to viral replication in heart and brain, instead of ''conventional'' gastrointestinal tract replication (Kim et al, 2008;Lö ndt et al, 2008Lö ndt et al, , 2010Bingham et al, 2009).…”