A new record of avian reovirus genogroup clusters isolated and molecularly characterized in chickens in Egypt

Background

The global poultry industry has been experiencing increasing condemnation at slaughterhouses since 2011, due to the emergence of avian reovirus (ARV) variant strains. Recently seven ARV genogroup clusters were identified based on the σC sequence of the S1 segment that was used as a genetic marker to characterize and classify ARV.

Results

Among ninety-seven suspected broilers, breeders, and commercial grandparent’s homogenates, ARV was PCR confirmed in thirty-five (36%). Samples were collected from different governorates in Egypt, including Giza–Ismailia–Sharqia–Menoufia, and Behira, between 2020 and 2023. A viral isolation trial was performed on weak positive samples, successfully isolating sixteen samples on the LMH cell line forming the characteristic giant cells of ARV infection. Partial sequencing and phylogenetic analysis of the σC gene of ten ARV PCR positive samples revealed the circulation of ARV genogroup clusters 1, 2, 4, and 5, eight samples being distinguished from commercially available vaccine strains with a low percentage of nucleotides and amino acid identities.

Conclusions

This research demonstrated that the ARV isolates were distinct compared to commercially available vaccine strains based on partial σC sequence. Detection, isolation, and classification of ARV as genogroups 1, 2, 4, and 5 are recorded. A vigilant surveillance to evaluate the ARV situation in Egypt is urgent. We recommend re-evaluating the ARV commercial vaccines by challenging them with circulating Egyptian field isolates, as well as their cross-protection. In addition, the development of autologous vaccines from both classical and variant strains to provide optimal protection.