Research Structure Design

"Prevention and Control of Avian Influenza in the U.S." Research Structure

• Introduction
• Background and Significance
• Research Designs and Methods
• Specific Aims
• Literature Searched

RESEARCH DESIGN AND METHODS
The majority of influenza viruses that are enzootic in wild aquatic birds are unable to replicate efficiently in chickens. However, multiple subtypes of influenza viruses have been isolated from healthy and diseased chickens (H5N2, H5N1, H7N*, H4N6, H6N*, H9N*, etc.). Occasionally, these viruses have acquired high virulence for chickens. Invariably, it is not known whether the influenza virus was transmitted directly to the chickens from an aquatic bird, or if the virus acquired expanded host-range capabilities by replication in other avian species, prior to infection of the chicken. LBMs have long been the sampling points of convenience for influenza A viruses that replicate efficiently in chickens. Two different scenarios would explain the association of the LBMs with chicken influenza. 1) Chickens in the markets are exposed to multiple influenza virus strains shed in high amounts by ducks or other waterfowl. In this case, the dynamics of bird transit through the markets accelerates the process of screening virus from waterfowl to chickens, with associated selection pressure on those that successfully replicate in chickens. 2) Alternatively, the LBMs could provide additional avian species as intermediate susceptible hosts; e.g. quail, pheasant, turkeys, etc., in which a multistep adaptation of the influenza viruses from waterfowl could occur. We propose an integrated approach to study these two possibilities through direct experimental approaches as well as through prospective epizootiological studies in the LBMs of the Western and Eastern US. This information will be immediately applicable to determine the best intervention strategies in the LBM systems.

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SPECIFIC AIMS