New Vaccines Protect Against Asian H5N1 Influenza A Viruses in Domestic Ducks

Scientists are looking at a novel strategy to prevent the spread of pandemic avian influenza. They have developed a vaccine that protects ducks, a known natural reservoir for the virus. They reported their findings in the November 2008 issue of the Journal of Virology

Waterfowl are considered to be the natural reservoir of influenza A viruses due to the isolation of all subtypes from these hosts. Current research indicates that influenza A viruses are continuously evolving within their natural environment and can be transmitted to a variety of animals, including humans. H5N1 avian influenza A viruses are now endemic in domestic poultry in many Asian countries and ducks are believed to be the primary source of infection. Reducing the spread of H5N1 in ducks could play a key role in minimizing the risk of a pandemic outbreak.

In the study researchers first identified dominant pathogenic strains of H5N1 influenza A viruses circulating in Asian poultry and found that four caused symptomatic illness in domestic ducks, but not all were lethal. In addition the researchers reversed the genetics of the viruses in domestic ducks to develop three different inactivated oil emulsion whole-virus H5 influenza vaccines. Following one round of inoculation with the vaccines ducks were completely protected when challenged with a lethal dose of the H5N1 virus.

"The vaccines provided complete protection against the lethal challenge of the homologous and heterologous H5N1 avian influenza A virus with no evidence of morbidity, mortality, or shedding of the challenge virus," say the researchers. "The complete protection offered by these vaccines will be useful for reducing the shedding of H5N1 avian influenza A viruses among vaccinated agricultural avian populations."