Genetic Characterization and Subtype Isolation of Circulating Metapneumovirus in Commercial Turkeys in the Central Region.

INTRODUCTION: Rhinotracheitis is an acute respiratory infection in turkeys and is considered a relatively significant economic disease caused by Avian metapneumovirus (AMPV) in poultry species. AMPV is responsible for turkey rhinotracheitis (TRT) and swollen head syndrome (SHS) in chickens, which is usually accompanied by secondary bacterial infections that increase mortality. This virus belongs to the genus Metapneumovirus within the subfamily Pneumoviridae of the family Paramyxoviridae. AMPV has been identified in Africa, Asia, Europe, North America, and South America. In turkeys, depending on the country, AMPV may be the most important viral pathogen causing substantial economic losses. AMPV also causes disease in domesticated poultry. MATERIALS & METHODS: In the present study, a total of 208 samples were collected from 87 flocks of broilers, layers, broiler turkeys, breeder chickens, and indigenous chickens from central Iran (Hamadan, Qazvin, Zanjan and Isfahan) to identify and isolate the virus. These samples were tested using specific primers and reverse transcriptase-polymerase chain reaction (RT- PCR) techniques. Additionally, 4 positive samples were partially sequenced. Positive samples were inoculated into embryonated eggs for virus isolation, and evaluations were conducted post- inoculation. RESULTS: Out of 87 flocks, twenty-eight samples tested positive. Positive samples were mainly swabs from the upper respiratory tract. The positive samples predominantly identified subtype B of the virus, with one sample also testing positive for subtype A. Positive samples were detected in turkeys, broilers, and layer chickens. Both subtypes A and B of the virus were positive and isolated after 3 to 5 sequential inoculations in embryonated eggs. CONCLUSION: The results of this study confirm that PCR with specific primers is an effective and reliable method for identifying and differentiating avian metapneumovirus.