Molecular identification of reovirus in broiler type flocks in Golestan province, Iran

Background: Avian reovirus (ARV) has a global distribution in nature and most clinical signs are found in broiler type chickens. Aims: This study was conducted to detect and identify reovirus infections from vaccinated breeder chickens and their progenies. Methods: A total of 20 tissue and blood samples were collected from vaccinated broiler breeders and their progenies with gastrointestinal or performance problems during peak production. Antibody titers were measured by indirect enzyme-linked immunosorbent assay (ELISA) tests. RNA extraction from tissue samples was performed and cDNA was prepared and directly used in the polymerase chain reaction (PCR). Nucleotide sequences were bilaterally determined using internal primers. The analysis of the nucleotide sequences and their related amino acids was performed by the specialized Molecular Evolutionary Genetics Analysis software (6th version). Results: The virus variant was detected in two vaccinated broiler breeders and five broiler flocks. The vaccine strains in breeder flocks included S1133, SS412, 1733, 2408 belonging to genotype 1 from the reovirus phylogenetic tree. Sequence 7 from the isolated reovirus based on the σC revealed that they were different from the reovirus vaccine, and that 6 isolates belonged to genotype 1 of the phylogenetic tree while 1 isolate belonged to branch 4 of the phylogenetic tree. Conclusion: The study showed that the new reovirus strain isolated from vaccinated birds differs from common strains used in the vaccines. It is therefore essential to prevent the effects of the field reovirus on the performance of industrial poultry, by updating and inventing new commercial vaccines, live and killed, against the reovirus.