Seroprevalence Survey of H9N2 Avian Influenza Virus in Backyard Chickens around the Caspian Sea in Iran

Since 1998, an epidemic of avian influenza occurred in the Iranian poultry industry. The identified agent presented low pathogenicity, and was subtyped as an H 9 N 2 avian influenza virus. Backyard chickens can play an important role in the epidemiology of H 9 N 2 avian influenza virus infection. Close contact of backyard chickens with migratory birds, especially with aquatic birds, as well as neighboring poultry farms, may pose the risk of transmitting avian influenza virus, but little is known about the disease status of backyard poultry. A H 9 N 2 avian influenza virus seroprevalence survey was carried out in 700 backyard chickens from villages around the Caspian Sea, Northern Iran, using the hemagglutination-inhibition (HI) test. The studied backyard chickens had not been previously vaccinated and showed no clinical signs of disease. The mean antibody titers found were 6.8, 7.5, 5.9, 7.2, 5.7, 6.4, 6.2 and the seroprevalence was 76.2%, 79.5%, 68.18%, 78.27%, 65%, 72.31% and 71.4% as found in seven villages. Overall HI titer and seroprevalence against H9N2 were 6.52 and 72.98%, respectively.