Background Avian leukosis virus Subgroup-J (ALV-J) is a rapidly oncogenic evolving retrovirus infecting a variety
of avian species; causing severe economic losses to the local poultry industry.
Methods To investigate ALV-J, a total of 117 blood samples and 57 tissue specimens of different organs were
collected for virological, and pathological identification, serological examinations, molecular characterization,
and sequencing analysis. To the best of our knowledge, this is the first detailed report recorded in broiler flocks
in Egypt. The present study targets the prevalence of a viral tumor disease circulating in broiler flocks in the El-Sharqia,
El-Dakahliya, and Al-Qalyubiyya Egyptian governorates from 2021 to 2023 using different diagnostic techniques
besides ALV-J gp85 genetic diversity determination.
Result We first isolated ALV-J on chicken embryo rough cell culture; showing aggregation, rounding, and degeneration.
Concerning egg inoculation, embryonic death, stunting, and curling were observed. Only 79 serum samples
were positive for ALV-J (67.52%) based on the ELISA test. Histopathological investigation showed tumors consist
of uniform masses, usually well-differentiated myelocytes, lymphoid cells, or both in the liver, spleen, and kidneys.
Immunohistochemical examination showed that the myelocytomatosis-positive signals were in the spleen, liver,
and kidney. The PCR assay of ALV-J gp85 confirmed 545 base pairs with only 43 positive samples (75.4%). Two positive
samples were sequenced and submitted to the Genbank with accession numbers (OR509852–OR509853). Phylogenetic
analysis based on the gp85 gene showed that the ALV-J Dakahlia-2 isolate is genetically related to ALV-EGY/
YA 2021.3, ALV-EGY/YA 2021.4, ALV-EGY/YA 2021.14, and ALV-EGY/YA 2021.9 with amino acid identity percentage
96%, 97%; 96%, 96%; respectively. Furthermore, ALV-J Sharqia-1 isolate is highly genetically correlated to ALV-EGY/YA
2021.14, and ALV-EGY/YA 2021.9, ALV-J isolate QL1, ALV-J isolate QL4, ALV-J isolate QL3, ALV-EGY/YA 2021.4 with amino
acid identity percentage 97%, 97%; 98%, 97%, 97%, 95%; respectively.
Conclusions This study confirmed that ALV-J infection had still been prevalent in broilers in Egypt, and the genetic
characteristics of the isolates are diverse. |
