Pathobiological characterization of low-pathogenicity H5 avian influenza viruses of diverse origins in chickens, ducks and turkeys.

We undertook one of the most comprehensive studies on the replication and intraspecies transmission characteristics of low-pathogenicity avian influenza viruses in ducks, chickens and turkeys. Our results indicated that most of these isolates could replicate and be transmitted in poultry without inducing clinical disease. However, differences in transmission to contact control birds were noted, emphasizing the importance of having contact control cage mates in biological characterization experiments. Ducks supported the replication of viruses of wild aquatic bird origin in their respiratory and digestive tracts equally well. The viruses from wild aquatic birds were not effectively transmitted among chickens. In contrast, the wild-bird isolates and viruses of domestic bird origin from live-bird markets and commercial poultry operations replicated and were transmitted more efficiently in turkeys than in chickens or ducks. We also found a lower minimal infectious dose requirement for infection of turkeys compared to chickens and ducks. Our data support an important role of turkeys as being more susceptible hosts for avian influenza viruses than domestic ducks and chickens. These results highlight the role of turkeys as intermediate or bridging hosts in the transmission of influenza viruses from wild birds to land-based domestic poultry or among different land-based bird species.