First report of seroprevalence and genetic characterization of avian orthoreovirus in Egypt.

Recently, the Egyptian broiler industry has experienced an increased incidence of avian reovirus (ARV) infections. However, to date, no studies have been carried out to investigate the epidemiologic status of ARV infections as well as the genetic characteristics of the currently circulating ARV strains. The present study estimates the seroprevalence of ARV infections in Alexandria, El-Behera, Giza, Kafr El-Sheikh, and Gharbia governorates, Egypt, during the period 2017-2018. A total of 150 serum samples from 15 unvaccinated broiler flocks with suspicious ARV infection were screened using a commercial enzyme-linked immunosorbent assay kit. All the tested flocks were found to be positive for ARV-specific antibodies, and the overall seropositivity rate was 80.6%. Meanwhile, 5 (33.3%) flocks were confirmed for the presence of ARV through a reverse transcription-polymerase chain reaction (RT-PCR) assay based on the σA-encoding gene. Phylogenetic analysis based on the nucleotide sequences of the σA-encoding gene revealed that the obtained ARV isolate, designated EGY1, was grouped in the S1113-like cluster of ARV and displayed 100% and 98.7% nucleotide identity with the Chinese MSO1 isolate and the S1133 vaccine strain, respectively. In addition, amino acid alignments with the S1133 vaccine strain revealed that the σA protein of the EGY1 isolate carried the substitutions G81S and A118V. In conclusion, the present study provides the evidence for a ubiquitous distribution of ARV infection in Egypt as well as represents a starting point for genetic characterization of the currently circulating ARV strains.