Research examines influenza virus in wild birds in Norway

Discoveries made in the characterization of influenza A virus in wild birds in Norway could lead to a better understanding of the epidemiology and host adaptation of the virus, according to a recent study.

Ragnhild Tønnessen, a researcher with the Norwegian School of Veterinary Science, examined bird samples from Norway's Rogaland County during the hunting seasons of 2005 through 2007 and 2009 through 2010. Wild birds, especially gulls and ducks, are natural hosts for influenza A viruses which can cause disease in humans and animals. In rare cases, some viruses of the H5 and H7 subtypes can mutate and become highly pathogenic, such as highly pathogenic H5N1 virus.

Tønnessen conducted multiple experiments to learn more about how the influenza A virus infects ducks and gulls. She found that influenza virus subtypes typically found in gulls, such as H13 and H16, can stay infectious in water for several months under different temperature and salinity conditions.

Tønnessen also found that the H16N3 influenza virus obtained from a herring gull could only cause a limited infection in chickens. Influenza A infections in domestic chickens typically cause mild disease.

To determine why influenza viruses of the H13 and H16 subtypes primarily infect gulls, Tønnessen examined if the internal proteins of the viruses had certain amino acid compositions related to host adaptation. While several signatures that could be related to host adaptation were detected, Tønnessen said their importance should be further evaluated in experimental studies.