Highly pathogenic avian influenza virus A (H7N3) in domestic poultry, Saskatchewan, Canada, 2007

Abstract

Epidemiologic, serologic, and molecular phylogenetic methods were used to investigate an outbreak of highly pathogenic avian influenza on a broiler breeding farm in Saskatchewan, Canada. Results, coupled with data from influenza A virus surveillance of migratory waterfowl in Canada, implicated wild birds as the most probable source of the low pathogenicity precursor virus.

Figure 1

Avian influenza virus H7-specific antibody titers of serum samples from 55-week-old breeder chickens (A), 24-week-old roosters (B), and 32-week-old breeder chickens (C), Saskatchewan, Canada, September 26, 2007. Titers of individual birds were determined by the ability of 2-fold serial serum dilutions to inhibit agglutination 0.5% (vol/vol) chicken erythrocyte suspensions by 4 hemagglutination inhibition units of avian influenza virus (H7N3) A/chicken/British Columbia/2004.

Figure 2

Phyogenetic analysis of avian influenza virus H7 (A) and N3 (B) genes. Trees were generated with MEGA software (8) by using the neighbor-joining method (9). Evolutionary distances were computed by using the method of Nei and Gojobori (10). Percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (1,000 replicates) is shown next to the branches. Scale bars indicate substitutions per site.