The molecular epidemiological study of bovine leukemia virus infection in Myanmar cattle
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Bovine leukemia virus (BLV) is the etiological agent of enzootic bovine leukosis, which is the most common neoplastic disease of cattle. BLV infects cattle worldwide and affects both health status and productivity. However, no studies have examined the distribution of BLV in Myanmar, and the genetic characteristics of Myanmar BLV strains are unknown. Therefore, the aim of this study was to detect BLV infection in Myanmar and examine genetic variability. Blood samples were obtained from 66 cattle from different farms in four townships of the Nay Pyi Taw Union Territory of central Myanmar. BLV provirus was detected by nested PCR and real-time PCR targeting BLV long terminal repeats. Results were confirmed by nested PCR targeting the BLV env-gp51 gene and real-time PCR targeting the BLV tax gene. Out of 66 samples, six (9.1 %) were positive for BLV provirus. A phylogenetic tree, constructed using five distinct partial and complete env-gp51 sequences from BLV strains isolated from three different townships, indicated that Myanmar strains were genotype-10. A phylogenetic tree constructed from whole genome sequences obtained by sequencing cloned, overlapping PCR products from two Myanmar strains confirmed the existence of genotype-10 in Myanmar. Comparative analysis of complete genome sequences identified genotype-10-specific amino acid substitutions in both structural and non-structural genes, thereby distinguishing genotype-10 strains from other known genotypes. This study provides information regarding BLV infection levels in Myanmar and confirms that genotype-10 is circulating in Myanmar.
KeywordsNest Polymerase Chain Reaction Bovine Leukemia Virus Epitope Region Bovine Leukemia Virus Infection Bovine Leukemia Virus Strain
We thank LBVD members and farm owners of Lewe, Pyinmana and Shwe Myo Livestock Zone for assistance with sampling the farms in Myanmar. We are grateful to the Support Unit at the Bio-material Analysis, RIKEN BSI Research Resources Center, for help with sequence analysis. This work was supported by Grants-in-Aid for Scientific Research A (No: 18255013) from the Japan Society for the Promotion of Science, and by a Grant from Integration Research for Agriculture and Interdisciplinary Fields in Japan (No.: 14538311).
Compliance with ethical standards
Conflict of interest
The authors declare no conflict of interest.
Animal handling and research ethics
All animals were handled by veterinarians from the University of Veterinary Science in Yezin Myanmar in strict accordance with good animal practice following the guidelines of the University of Veterinary Science. This experiment is approved by the Committee on the Ethics of Animals for Research at the Faculty of Agriculture, Kagoshima University (Certificate No: H28 NOU 005).
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