Role of minor poultry in the ecology and evolution of influenza A viruses

Live bird retail markets have been associated with influenza A viruses since 1924. Live bird markets contain aquatic and terrestrial poultry. Studies have investigated the relationship of influenza virus with the major poultry species: ducks, chickens, quail, and pigeons. The relationship between influenza A viruses and 'minor poultry' species---pheasants, chukar partridges, and guinea fowl---has not been established. It was necessary to gain more knowledge on the interaction between influenza viruses and minor poultry. The research contained in this dissertation explored this avian population by addressing the following: (1) Determining the susceptibility of pheasants and chukar partridges to infection with influenza A viruses of each HA subtype. (2) Characterizing length of shedding of avian influenza A viruses from pheasants (3) Determining the mechanism of prolonged shedding from pheasants.; Results from these studies reinforce the idea that replication of influenza viruses is species dependent. Pheasants were susceptible to infection with nonpathogenic avian influenza viruses of 15 HA subtypes while chukar partridges were less susceptible to infection with avian influenza viruses. Thirteen of the 23 viruses tested were isolated from pheasants for ≥14 days; one virus was shed for 45 days. Prolonged shedding of influenza viruses from pheasants was detectable in cloacal swabs. Clinical disease signs were not observed in pheasants or chukar partridges after infection with nonpathogenic influenza viruses. However, the H5N1 viruses tested caused 100% mortality in pheasants. All birds had high levels of serum neutralizing antibodies by 14 days postinfection regardless of the length of time virus was shed. There was preliminary evidence that influenza virus was maintained in the bursa of pheasants. Antigenic variants emerged after prolonged shedding of influenza virus from pheasants.; The studies in this dissertation provide information to fill in the knowledge gap on the role of minor poultry in the ecology of influenza viruses in the market system. Pheasants serve as asymptomatic perpetuators of influenza and aid in the generation of the genetic diversity of influenza viruses. This provides a strong argument for separation of pheasants and chukar partridges from other poultry in the markets or removal of these birds from live bird markets.