Investigation of Avian Influenza Viruses (H9N2-H5nx) in Pigeons during Highly Pathogenic Avian Influenza Outbreaks in Iran, in 2016

Avian influenza (AI) virus (H9N2 and H5 subtypes) infections in birds cause major concerns around the world. The majority of the avian species, such as domestic, pet, and wild birds, are natural and experimental hosts of avian influenza viruses. There are global concerns about members of the Columbidae family, namely pigeons or doves, for their role as the potential interspecies bridge in influenza A viruses ecology. The acquired scientific data in this regard is still not clear since there are doubts about whether or not they transmit viruses between susceptible populations, and spread viruses among farms during outbreaks. To monitor H5 and H9 influenza virus infection status in the rural, backyard, and domestic birds, an annual active surveillance program was performed from September to October 2016. In December 2016, an outbreak of highly pathogenic avian influenza (HPAI) virus subtype H5N8 was detected in a layer farm in Tehran province, Iran. The present research was conducted to study H9N2 or H5 infections in pigeons within HPAI H5N8 2016 outbreaks and annual national AI surveillance in Iran. For this purpose, cloacal swabs and tissue samples (trachea, lung, brain, liver, heart, pancreas, and cecal tonsil) were collected and examined by real-time reverse transcription-polymerase chain reaction (RT-PCR) method and virus isolation. Results of the tests performed on the swab and tissue samples were negative for H5 nor H9N2 viruses. The samples in real-time RT-PCR that after three passages still showed negative results in HA and molecular tests were considered negative. Moreover, the Newcastle disease virus was isolated in most of the samples taken from dead pigeons, after inoculation in embryonated chicken eggs.