Recently 2018, four strains of infectious bronchitis virus (IBV) were isolated from vaccinated and non-vaccinated broiler flocks from different chicken farms in different cities in Iraq. The pathogenic characters were assessed for the four IBV strains. Test chickens were infected by the four strains releasing an immune response. Noticeable results showed by cross neutralization assays which revealed that strains antigenically distinct from classic IBV strains of H120, M41, Conn, and Gray. Compared to H120 vaccine strain, short insertion, point mutation, and deletion occurred at many positions in the S1 protein of the four strains. Two of the four strains had the motif (HRRRR), which was considered identical to that of the epidemic IBV strains in Iraq. Another two strains had new motifs (HRLRR and RRYRR) emerged in the isolated strains. These Four strains were also genetically different from the vaccine strains and non-Iraqi IBV strains but closely related to large numbers of USA and China, Singapore and India strains. The isolates and 14 reference IBV strains were clustered into three distinct groups (I-III). The four strains were categorized into groups III, forming a big phylogenetic branch, which is closely related to USA IBVs and Singapore IBVs whereas the vaccine strains belonging to group I and II are genetically distant from groups III. The results from this study indicate that different IBV strains circulate in the chicken population in Iraq.
Published Date: 2019-05-24; Received Date: 2019-05-10