Characterization of recent North American low- pathogencity avian influenza H7 isolates in SPF leghorns, turkeys and pekin ducks

Abstract

The pathogenicity of twelve recent low-pathogenicity H7 avian influenza isolates was evaluated through clinical signs, relative oral/pharyngeal (O/P) and cloacal viral shed, serology, histopathology and immunohistochemistry in SPF leghorns, Pekin ducks, and turkeys. Gene constellation and phylogenetic analysis revealed that seven of the isolates (CK/MD/MinMah/04, TK/VA/67/02, GH/MA/1408081-11/02, CK/PA/9801289/98, CK/NY/3112-1/95, TK/NY/4550-5/94, and CK/NY/30749-3/00) were typical of the low-pathogenicity H7N2 lineage viruses circulating in live bird markets while five isolates (Pintail/MN/423/99, Mallard/OH/421/87, Ruddy Turnstone/DE/1538/00, CK/NJ/15086-3/94, and CK/NY/12273-11/99) were found to be of wild-bird origin. Four pathogenicity trials were conducted to evaluate these twelve isolates that had been characterized (Southeast Poultry Research Laboratory) as low-pathogenicity avian influenza. Phylogenetic analysis of the HA1 sequence revealed multiple sublineages in the H7 subtype, four of the sublineages are represented in this study to determine differences in pathogenesis.