Molecular Characterization of the Meq Gene of Marek’s Disease Virus in Central Java and Yogyakarta, Indonesia

Marek’s disease virus serotype 1, a significant poultry pathogen, encodes the Meq oncoprotein, which is crucial for tumorigenesis in chickens. Despite the ongoing presence of Marek’s disease virus serotype 1 in Indonesia, no molecular characterization of field strains has been reported since 2016. Therefore, this study addresses this critical gap, aiming to conduct molecular characterization of the latest Marek’s disease virus serotype 1 from Indonesian isolates and its histopathological features. This study characterizes the Meq genes of MDV-1 from 27 tissue samples from chickens with clinical symptoms of Marek’s disease virus serotype 1, submitted by commercial layers and breeder farms. The methodology comprised histopathological examination of affected tissues using hematoxylin and eosin staining, alongside molecular detection and sequencing analysis of the Meq gene. Histopathological analysis confirmed Marek’s disease through the observation of diffuse lymphocytic infiltration in multiple organs. Comparative sequence analysis of the deduced 282-amino-acid Meq protein from Indonesian isolates against the CVI988 vaccine strain revealed six amino acid substitutions, an amino acid distance of 2.2%, and placement in a distinct phylogenetic cluster. Notably, the Indonesian isolates exhibited 100% amino acid identity and formed a monophyletic group with strains from Vietnam (MDV/Ck/DT/TN and MDV/Ck/DT/TN). These isolates were also identical to earlier Indonesian isolates from North Sumatra (2013) and West Java (2016), with methionine at position 180 identified as a conserved characteristic. Phylogenetically, these isolates clustered most closely with a very virulent pathotype (G2 strain) from China. Analysis of the proline-rich repeat region revealed disruptions in the PPPP motif to P(Q/A)PP, suggesting a potential association with virulent to very virulent pathotypes. This study demonstrates the continued circulation of a genetically stable and distinct MDV-1 strain in Indonesia, which remains divergent from the CVI988 vaccine strain over at least a decade. The findings underscore ongoing evolutionary pressures on MDV-1, with potential implications for disease control in one of Asia’s major poultry-producing regions.

Cite this article as: Salma, I., Santoso, F. P. C., Sutrisno, B., & Wibowo, M. H. (2026). Molecular characterization of the meq gene of Marek’s disease virus in Central Java and Yogyakarta, Indonesia. Acta Veterinaria Eurasia, 52, 0028, doi: 10.5152/actavet.2026.26028.