Two Novel Avian Influenza Virus Subtypes Isolated from Domestic Ducks in North of Iran.

Avian Influenza Viruses (AIV) are the causative agents of Avian Influenza (AI), which is a contagious and zoonotic disease in birds. Among birds, wild waterfowls and ducks are the primary and natural reservoirs of low pathogenic avian influenza viruses (LPAI). This study aimed to identify and differentiate between two AIV subtypes (i.e., hemagglutinin and neuraminidase from domestic ducks by hemagglutinin inhibition (HI) and neuraminidase inhibition (NI) assays. To this end, 962 cloacal swabs were collected from domestic ducks being sold at different Iranian Live Bird Markets in Gilan, Mazandaran, and Golestan provinces, located at the southern coast of the Caspian Sea. The samples were inoculated in 10-day-old embryonated specific pathogen-free chicken eggs, and subsequently, harvested allantoic fluids were subjected to agar gel immunodiffusion, HI, and NI assays. In total, five positive samples, including two H4N2 and three H3N2 AIV subtypes were identified. Isolation of H4N2 and H3N2 viruses has never been reported from Iranian domestic ducks previously. This finding further suggests the diversity of LPAI viruses in Iranian ducks and also shows that the HI and NI assays are highly efficient in determining AIV subtypes.