In this study, the reticuloendotheliosis (REV) infection status was monitored through antibody determination and molecular detection in chickens in different provinces of Egypt. We investigated the occurrence and genetic characteristics of REVs in chickens' flocks from January 2019 to March 2021 as a PCR test examined 39 commercial chicken farms (27 layers and 12 broiler breeders) from 11 provinces of Egypt. Results showed six farms (15.4%) were REV-positive in 3 provinces (AL Sharqia, Al Menya, and Al Behera). Four REV-positive farms were genetically sequenced.
24 of these 39 farms (18 layers and 6 broiler breeders) were examined by ELISA test for antibodies detection against REV and ALV (subtype A and B). 22 farms (91.7%) were REV antibodies positive in all 11 provinces tested (Al Sharqiyah, Al Monofiya, Al Daqahlia, Al Gharbia, Al Qualiobia, Al Beheira, Giza, Damietta, Kafr El Sheikh, Bani Suief and El Minya), 3 farms (12.5%) were ALV (subtype A and B) antibodies positive from Al Beheira governorates. Molecular detection of REV was differentiated from other neoplastic viruses MD, ALV (subtype A, B, C, D, and J), from 39 farms, seven farms were positive for MDV (5 of them were seropositive for REV), one farm positive for ALV.J (the farm was seropositive for REV), all farms were negative for ALV.
Our results demonstrated that REV was extensively distributed in different regions of Egypt. Phylogenetic analysis of the partially sequenced envelope glycoprotein gene showed that REV was most closely related to strains from China, Taiwan, Thailand, and the USA. The REV strains were clustered into REV subtype III. This finding indicates that REV subtype III was predominantly circulated in Egyptian chicken flocks. Our findings raise awareness about REV-induced diseases as the causative agent of runting and oncogenic disease in chickens and highlight the incidence of REV infection among some commercial chicken flocks in Egypt.