ABSTRACT
Objective To understand the condition of tick carrying CRT(Candidatus rickettsia tarasevichiae) and compound infection with SFTSV(Sever fever thrombocytopenia syndrome virus) in Yanbian area of Jilin province. Methods Free ticks were collected from 6 counties including Yanji, Wangqing, Hunchun, Dunhua, Antu and Helong in the Korean Autonomous Prefecture of Jilin Province(Yanbian Prefecture) by using the flagging, and they were classified morphologically. The CRT and SFTSV in ticks were detected by Nest PCR(Nested polymerase chain reaction) and Real Time RT-PCR(Real-time Quantitative polymerase chain reaction) methods. Target DNA sequencing was performed for CRT positive products, and the homology of gene sequence and phylogenetic relationship were analyzed. Results A total of 1032 ticks were collected in this study, including ixodes persulcatus (35.56%) and dermacenter silvarum (20.64%). haemaphysalis japonica (20.45%), haemaphysalis longicornis (10.47%), haemaphysalis concinna (8.33%),others( 4.55%). The CRT was detected from the Ixodes persulcatus, Haemaphysalis longicornis, Haemaphysalis japonica Dermacentor silvarum. The MIR(Minimum infection rate per 100 ticks) of CRT was 10.47%.The SFTSV was detected from the Haemaphysalis-concinna, Haemaphysalis-japonica,Ixodes-persulcatus,Haemaphysalis-longicornis,Dermacentor-silvarum. The MIR of SFTSV was 2.52 %. Three species of ticks, including Ixodes persulcatus(2.45%), Haemaphysalis japonica(1.42%), and dermacentor silvarum(0.47%), had CRT and SFTSV compound infections, and the MIR of two pathogens compound infections was 1.26 %. In this study, the gene sequence of CRT positive PCR products ompA and 17kDa with nucleotide sequence of Xinyang plant of HeNan XinYang strain (KX365196.1),had homology of 100%. Phylogenetic analysis showed that CRT ompA and the HeNan XinYang strain (KX365196.1) gene sequences formed a cluster in Yanbian, while the 17 kDa gene formed an independent branch. Conclusions For the first time, CRT was detected from free ticks in Yanbian area of Jilin Province, and it was found that Ixodes persulcatus may be the main medium of transmission of the pathogen. At the same time, it was found that CRT and SFTSV have compound infection in ticks of Yanbian area. Therefore, it can be clearly identified that Yanbian area in Jilin Province is the natural source of CRT, and there are two pathogenic compound infections in the local ticks.
ABSTRACT
Objective To mastered the distribution characteristics of Haemaphysalis longicornis in the Tumen River basin along the border between Russia, Korea and Northeast China, and understand the status of Haemaphysalis longicornis carrying the virus of fever with thrombocytopenia syndrome (SFTS), then, isolate the virus and analyze its genetic characteristics. Method Ticks were collected from Hunchun, Tumen, Helong and Longjing cities in the Tumen River basin of Jilin Province from April to September, 2017. Haemaphysalis longicornis was selected and grouped. SFTS virus was detected by real-time quantitative polymerase chain reaction (RT-qPCR). Virus isolation was carried out in Vero cells, besides, S,M,L gene segments were amplified . The homology of S, M and L gene segments was compared, phylogenetic tree was established, and their gene characteristics were analyzed. Result Haemaphysalis longicornis mainly distributed in Hunchun and Tumen City in the lower reaches of Tumen River. It was the dominant species in the two counties, reaching 71.85% and 87.62% respectively. A virus named YBHC-TICK2-2017/CHINA was isolated from Haemaphysalis longicornis collected in Hunchun. The sequences of S segment (1 746 bp), M segment (3 336 bp) and L segment (6 376 bp) of the virus were 98.00%-99.00%, homologous to those of SFTS virus isolates from China and Korea recorded in National Center for Biotechnology Information (NCBI) Gen Bank. Phylogenetic tree analysis showed that the S segment gene sequence of the virus strain was divided into a cluster with Jilin strain (KT890282) in China, and M segment and L segment gene sequence with Jiangsu strain (KR230781) in China. Conclusions Haemaphysalis longicornis are widely distributed in the lower reaches of the Tumen river. It was the first time that SFTS virus was isolated from Haemaphysalis longicornis in this area, suggesting that this area is important for SFTS prevention.