Pathogenicity of Chinese H5N1 highly pathogenic avian influenza viruses in pigeons

It has long been thought that pigeons are resistant against H5 highly pathogenic avian influenza (HPAI) viruses. Recently, however, highly pathogenic H5N1 avian influenza viruses have demonstrated distinct biological properties that may be capable of causing disease in pigeons. To examine the susceptibility of domestic pigeons to recent H5N1 viruses, we inoculated pigeons using H5N1 viruses isolated in China from 2002 to 2004. Within 21 days following inoculation, all pigeons had survived and fully recovered from temporary clinical signs. However, seroconversion assays demonstrated that several viruses did in fact establish infection in pigeons and caused a certain amount of viral shedding in the oropharynx and cloaca. There was not, however, a definitive relationship between viral shedding and viral origin. Viruses were also inconsistently isolated from various organs of pigeons in infected groups. Pathological examination revealed that the infection had started as respiratory inflammation and caused the most severe lesions in the brain in later stages. These results indicate that pigeons are susceptible to the more recent Asian H5N1 HPAI and could be a source of infection to other animals, including humans.