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J. Virol. doi:10.1128/JVI.01368-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Characterization of Low Pathogenicity H5N1 Avian Influenza Viruses from North America

Southeast Poultry Research Laboratory, USDA-ARS, Athens, Georgia, USA; National Veterinary Services Laboratories, USDA-APHIS, Ames, Iowa, USA; National Centre for Foreign Animal Disease, CFIA, Winnipeg, Manitoba, Canada; The Ohio State University, Food Animal Health Research Program, Ohio Agricultural Research and Development Center, Wooster, Ohio, USA; The Ohio State University, Department of Veterinary Preventive Medicine, College of Veterinary Medicine, Columbus, Ohio, USA; Southeastern Cooperative Wildlife Disease Study, College of Veterinary Medicine, University of Georgia, Athens, GA, USA; USGS National Wildlife Health Center, Madison, Wisconsin, USA; USDA-APHIS Wildlife Services, Fort Collins, Colorado, USA

^* To whom correspondence should be addressed. Email: Erica.Spackman{at}ars.usda.gov.

	Abstract

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 pathogenic 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 sequence available from GenBank by phylogenetic analysis. Both the HA and NA were phylogenetically distinct from viruses from outside of North America, and from 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 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 infectious doses. Finally, seven H5 viruses, representing different phylogenetic clades were evaluated for their antigenic relatedness by hemagglutination inhibition assay, showing the antigenic relatedness was largely associated with geographic origin. Overall the data supports 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.