Avian reovirus (ARV) strains cause a variety of symptoms in chickens, including viral arthritis/tenosynovitis, a disease that has emerged as a significant cause of economic losses in commercial chicken flocks in recent years in various countries, including Egypt. Furthermore, ARV strains are frequently isolated from birds suffering from malabsorption. In the actual study, seventy-five samples were collected in 2021 and 2022 from broiler and vaccinated broiler breeder flocks at different farms in Giza Province, Egypt, with reovirus-like symptoms such as significant weight fluctuation and arthritis/malabsorption. ARV was screened using real-time PCR, and fifteen positive samples were detected (20%), which were then subjected to embryonated chicken egg (ECE) isolation and molecular characterization (11/15 sample) of a partial segment of the sigma (σ)C gene (S1-gene). Phylogenetically, nine strains were found to belong to genotypic cluster IV, with 82–89% identity with Israeli ARV 2018, and two strains belong to genotypic cluster V with a 78% nucleotide identity with Japan ARV 2021. No correlation between lesions and genotype was found. The strains under study had a low sequence identity (43–55%) when compared with various commercial vaccines belonging to genotypic cluster I (e.g., strain S1133). These findings imply that novel ARV genotypes representing clusters IV and V have recently been introduced to Egyptian poultry farms. A homologous vaccine is suggested; because this variation raises the possibility that commercial vaccines may not offer protection against circulating ARVs.

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In recent years, the reintroduction of the infectious bursal disease virus (IBDV), particularly its severe strains, has imposed considerable cost on the Egyptian poultry industry. The goal of the current study was to investigate the molecular features of IBDV in Egypt from June 2019 to April 2021. A total of 30 field samples (bursa of Fabricius) were collected from broiler farms in which the chickens were vaccinated (Transmune 2512 s/c) at hatching. A highly variable region encompassing VP2 gene was targeted for IBDV screening utilizing reverse transcription-polymerase chain reaction (RT-PCR). Of 30 tested samples, 16 were positive by PCR. To isolate the virus, the bursal suspension was injected into 10-11 day embryonated chicken eggs via the chorioallantoic membrane. Five current positive isolates from 2021 were chosen for nucleotide and amino acid (aa) sequence analysis. Phylogenetically, three of the strains under study belonged to the very virulent (vvIBDV) strains, with 97-98% resemblance to Giza 2008 belonging to the (Genogroup 3) IBDV strain. The remaining two strains were identified as a vaccination strain (genotype 1) that matched the winter field 2512 vaccine strain by a similarity percentage of 98. Mutations in the antigenic locations of (P) domain loops were discovered when the sequencing samples were compared to the existing IBD vaccines. The circulating strains were found to be very similar to vvIBDV serotype 1 genotype 3 strains with mutations in the P domain loop providing a potential reason for the circulation of vvIBDV viruses in Egyptian broiler farms despite the vaccination program.