Background Reticuloendotheliosis virus (REV) is an oncogenic immunosuppressive retrovirus that infects different
kinds of avian species; posing significant economic losses to the poultry industry worldwide.
Methods In Egypt, there is an unidentified disease associated with the runting-stunting syndrome with neoplasia,
suspected to be REV, that has been continuously monitored in several breeder flocks. To diagnose and analyze REV
by cell cultures, enzyme-linked immunosorbent assay (ELISA), histopathological investigation, the polymerase chain
reaction (PCR) test, and sequencing analysis, 200 blood samples, and 50 tissue specimens were collected. The current
study targets the occurrence and genetic characteristics of a viral neoplastic disease, resembling REV infection, circulating
in breeder flocks from 2022 to 2023 in the Ismailia, El-Sharqia, and El-Dakahliya governorates.
Result Here, REV was isolated on chicken embryo fibroblast cell culture; exhibiting cell aggregation, rounding,
and cell detachments. Collectively, only 70 serum samples were positive for anti‐REV antibodies with seroprevalence
rates of 35% based on the ELISA test. The histopathological observation demonstrated lymphoreticular tumors
in the liver, spleen, and other examined organs. The immunohistochemical staining method confirmed the REV-positive
signals in all examined organs (liver, kidney, spleen, bursa, ovaries) except for the heart. The PCR assay of the LTR
gene assessed 370 base pairs with only 5 positive samples with a percentage of 16.6%. Three positive samples were
further sequenced and submitted to the Genbank under accession numbers (PP763709, PP763710, PP763711).
Phylogenetic analysis of the REV-LTR gene showed that our three isolates (Sharquia-1-REV, Ismilia-2-REV, Mansoura-
3-REV) are REV subtype III which predominantly circulated in breeders in Egypt. These three isolates are highest similar
to American, Chinese, and Taiwanese REV reference strains, and other Egyptian strains with nucleotide identity percentages
of 100%, 99%, and 99%; respectively, and on the amino acid identity level were with (99–100%), (98%, 99%),
(99%, 100%); respectively.
Conclusions This study established that REV infection was extensively distributed in the breeders and became one
of the causes of the clinical outbreaks of tumors, raising awareness of REV as the causative agent of avian oncogenic
disease in Egypt. |
