BACKGROUND: Backyard poultry are at risk of exposure to various viral contagious diseases such as Newcastle (ND) and Avian Influenza (AI). These diseases, in addition to the backyard poultry infection have an influence on villagers’ livelihoods. Also, backyard poultry plays an important role in circulation and survival of these viruses in environment and are considered as a risk factor for the poultry industry. OBJECTIVES: Studying the prevalence level of ND and Influenza H9N2 diseases in backyard chickens in Iran, in 2014-2015. METHODS: A descriptive cross-sectional study was conducted for two years (2014-2015) in backyard chickens with mortalities suspected of infection with ND or AI H9N2 viruses. Each mortality report was considered as one outbreak. For detection of possible ND or influenza virus infection tracheal and lung tissue samples were investigated by RT-PCR reaction test. Results were analyzed statistically by SPSS software. RESULTS: Overall, 121 outbreaks of Newcastle or influenza (H9N2) disease with 25.936 cases of death from 17 provinces were reported in two years. of these, 54 outbreaks (44/6 %) were caused by H9N2 influenza virus, 58 (47/9 %) by velogenic ND virus and 9 (7/4 %) outbreaks were caused by influenza and Newcastle concurrent infection. Hotspot ratio in 2015 was significantly higher than in 2014. In comparison with Newcastle disease alone or concurrent ND and influenza outbreaks, the highest mean mortality rate was observed in H9N2 outbreaks. Outbreaks were reported in all seasons but the rate of occurrence in the months of June and July was significantly higher than the rest of the year. CONCLUSIONS: According to our results ND and H9N2 influenza virus infections are widely distributed in backyard chickens of villages in Iran. So, for implementation of control strategies, education of villagers, vaccination and annual surveillance of backyard poultry seem necessary.

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