Susceptibility of two species of wild terrestrial birds to infection with a highly pathogenic avian influenza virus of H5N1 subtype

The recent epidemic caused by H5N1 highly pathogenic avian influenza (HPAI) viruses has spread over many parts of Asia, Europe and Africa. Wild birds, particularly waterfowl, are considered to play a role in viral dissemination. However, detailed information on whether wild terrestrial birds act as carriers is currently unavailable. To investigate the susceptibility of terrestrial birds to HPAI viruses, two species of wild bird (great reed warbler and pale thrush) that are common in East Asia were infected with H5N1 HPAI virus. The results showed that both species were highly susceptible to the virus. The great reed warbler showed fatal infection with 100% mortality, but the pale thrush survived for longer periods (>8 days) with viral shedding. These findings suggest that there is variation in clinical outcome after infection of wild terrestrial birds, and that some bird species could become subclinical excretors of the H5N1 virus.