Abstract
Aim:This study aimed to determine the prevalence of layer flock tumor disease in Lower Egypt during the period of 2018-2019 and to undertake molecular characterization and determine the genetic diversity of all identified viruses.Materials and Methods:Forty samples were collected from layer chicken located in six governorates of Lower Egypt during the period of 2018-2019. Samples were taken from tumors in different organs. Tumor tissues were identified by histopathological sectioning and then further confirmed by a reverse-transcription polymerase chain reaction. Finally, genetic evolution of Avian leukosis virus (ALV-J) gp85 gene was studied.Results:All the study samples were negative for Marek’s disease virus, reticuloendotheliosis virus, ALV (A,B,C and D) and 20 samples were positive for ALV-J in backyard in six governrates. Sequencing of ALV-J gp85 gene was performed for six representative samples (one from each governorate), and they were found to be genetically related to prototype virus HPRS-1003 (identity percentage: 91.2-91.8%), but they were from a different group that was similar to the AF88-USA strain (first detected in 2000) with specific mutations, and they differed from a strain that was previously isolated in Egypt in 2005, forming two different subgroups (I and II) that had mutations in the hr1domain (V128F, R136A) and hr2 domain (S197G, E202K).Conclusion:The ALV-J virus was the main cause of neoplastic disease in layer chickens from Lower Egypt in the period of 2018-2019. We found that the genetic evolution of ALV-J gp85 gene was related to prototype virus HPRS-1003 but in a different group with a specific mutation. Further studies are needed to evaluate the antigenicity and pathogenicity of recently detected ALV-J strains.
Highlights
Marek’s disease virus (MDV), Avian leukosis virus (ALV), and reticuloendotheliosis virus (REV), collectively termed as avian tumor viruses, cause severe economic losses in the chicken industry [1].MDV, which belongs to Alphaherpesvirinae subfamily, affects T-lymphocyte and causes nervous symptoms and ocular lesions [2]
Sequencing of ALV-J gp85 gene was performed for six representative samples, and they were found to be genetically related to prototype virus HPRS-1003, but they were from a different group that was similar to the AF88-USA strain with specific mutations, and they differed from a strain that was previously isolated in Egypt in 2005, forming two different subgroups (I and II) that had mutations in the hr1domain (V128F, R136A) and hr2 domain (S197G, E202K)
The ALV-J virus was the main cause of neoplastic disease in layer chickens from Lower Egypt in the period of 2018-2019
Summary
Marek’s disease virus (MDV), Avian leukosis virus (ALV), and reticuloendotheliosis virus (REV), collectively termed as avian tumor viruses, cause severe economic losses in the chicken industry [1].MDV, which belongs to Alphaherpesvirinae subfamily, affects T-lymphocyte and causes nervous symptoms and ocular lesions [2]. Marek’s disease virus (MDV), Avian leukosis virus (ALV), and reticuloendotheliosis virus (REV), collectively termed as avian tumor viruses, cause severe economic losses in the chicken industry [1]. REV, which belongs to the gammaretrovirus genus, causes bursal tumors by affecting pre-B and pre-T lymphocytes. ALV, which belongs to the Retroviridae family, genus Alpharetrovirus [4], is classified into 10 viral subgroups (A-I). The first six subgroups, (A-F), mainly infect chickens and turkeys, and they are classified according to viral envelope, host range, and cross-neutralization of the other uncommon subgroups (F, G, H, and I) of ALVs affected wild birds [5,6]. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/ publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated
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