ACTA VETERINARIA ET ZOOTECHNICA SINICA ›› 2019, Vol. 50 ›› Issue (2): 354-363.doi: 10.11843/j.issn.0366-6964.2019.02.013

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Isolation of Bluetongue Virus Serotype 9 Strain in China for the First Time

LI Zhanhong, WANG Jinping, YANG Heng, LIAO Defang, SONG Jianling, GAO Lin, HE Yuwen, LI Huachun*   

  1. Yunnan Tropical and Subtropical Animal Virus Diseases Laboratory, Yunnan Animal Science and Veterinary Institute, Kunming 650224, China
  • Received:2018-07-06 Online:2019-02-23 Published:2019-02-23

Abstract:

The study aims to isolate bluetongue virus (BTV) endemic in Yunnan Province of China and to understand the genetic and infection characteristics of the isolated BTV. Virus isolation was performed by inoculation method of "Embryos-C6/36 cells-BHK-21 cells" with BTV nucleic acid positive blood samples collected from sentinel cattle. Serotype of the isolated virus was decided by micro-neutralization test and sequencing the ORF regions of Segment 2 and Segment 6. The proliferation characteristics of isolated virus in BHK-21 cells were determined by the tests of growth curve and plaque formation. The viral load and neutralizing antibody of infected animal were analyzed by qRT-PCR and neutralization test. Results were as follows:In August 2013, BTV strain of V013/YN/2013 was isolated form sentinel cattle in Mangshi, Yunnan Province. Micro-neutralization test showed that V013/YN/2013 belonging to serotype of BTV-9. Further sequence analysis confirmed the identity of isolated virus by correlation with other isolated BTV-9 strains belonging to Eastern topotype and showed closest relationship with BTV-9 strains isolated from Japan and Australia. The results of growth curve and plaque formation showed that the proliferation capacity of V013/YN/2013 is significantly higher than BTV-9 reference strain. Although specific neutralizing antibodies are produced in infected animals, the presence of the virus in the blood can be continuously detected, suggesting that the virus can cause a long-lasting infection in cattle. This study reported for the first time the isolation of an BTV-9 strain V013/YN/2013 belonging to Eastern topotype in China, these results will provide a basis for further whole-genome sequencing, establishment of diagnostic methods, epidemiological investigation and pathogenicity study of BTV-9 in China.

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