Investigation Of Tick-borne Viruses In Parts Of The Sino-Russian Border

Tick-borne viruses(TBV)are major category of important arboviruses,which circulate in nature through vertebrates and vector ticks.There are currently more than 160 tick-borne viruses known,some of which pose a serious threat to the health of humans and animals.There is a natural foci of tick-borne viruses in the border area between China and Russia.Under the "Belt and Road" initiative,there are increasing activities at the border ports between China and Russia including trade,transportation and travel,which results in increasing risks of cross-border transmission of tick-borne diseases.Therefore,this study conducted an investigation on tick-borne viruses in some border areas between China and Russia,which provides an etiological basis for the monitoring,prevention and control of tick-borne diseases in this area.(1)This study was conducted in 5 urban areas on the Sino-Russian border(Yanbian Korean National Minority autonomous prefecture,Songling District,Jiagedaqi District,Yichun City,and Jiamusi City)from April to May during 2019 to 2020.Tick specimens were collected by using the artificial flag-laying method and extracting from the body surface of the livestock.Collected tick specimens were morphologically identified,and statistical analysis was performed according to the collecting area,collecting time,species,and number;(2)In the study,a rapid detection assay for the TaqMan Reverse Transcription-Polymerase Chain Reaction(RT-PCR)of Tibet Orbivirus(TIBOV)was established.This study also carried out the nucleic acid molecular detection on the collected tick specimens for Severe Fever with Thrombocytopenia Syndrome Virus(SFTSV),Tick-Borne Encephalitis Virus(TBEV),Alongshan Virus(ALSV),Omsk Hemorrhagic Fever virus(OHFV),Langatvirus(LGTV),Powassan Virus(POWV),and Tibet Orbivirus(TIBOV),by using the Real-Time Quantitative PCR Assays;(3)For the specimens with positive nucleic acid screening results in the above-mentioned detection,high-throughput sequencing was used to perform the genetic evolution analysis and the analysis of selection pressure of amino acid characteristic sites,and the origin time and transmission path of Far East subtype TBEV were also analyzed.The results of the study demonstrated that:(1)A total of 7171 tick specimens collected in 5 urban areas along the Sino-Russian border from 2019 to 2020 belonged to 1 family,3 genera and 3 species.Ixodes persulcatus is the dominant tick species,accounting for 45.13%,followed by Dermacentor silvarum at 27.96%,and Haemophilus concinna at 26.91%;(2)Four batches of TBEV nucleic acid were detected as positive,all of which were carried by Ixodes panaxa.Three batches were collected from Songling District of Daxing'an Mountains,with the positive rate being 4.16%(3/72).One batch was collected from Jiamusi City,with the positive rate of TBEV being 1.11%(1/90).Four batches were collected from Songling District and Yichun City.Nucleic acids for SFTSV,POWV,LGTV,OHFV,and TIBOV were all tested negative.The established TaqMan RT-PCR detection assay for Tibet Orbivirus had high sensitivity and strong specificity;(3)A total of four TBEV genome sequences were obtained,and phylogenetic analysis showed that the four TBEVs were all of the Far East subtype.The results of selection pressure analysis showed that the 831 site of the Far East subtype TEBV NS5 gene region was under positive selection pressure.Bayesian phylogenetic analysis showed that the epidemic strains of TBEV in China were mainly Far East Asian type,mainly distributed in the Russian Far East,Japan,Xinjiang Province,Jilin Province and Heilongjiang Province.It was speculated that the origin of Far East type TBEV was originated in Russia,and then spread to the Far East(Northeast China and Japan).Estimating time to the most recent common ancestor(TMRCA)was 1152 years(95%Confidence Interval 721-1751).Conclusion:The Far East subtype tick-borne encephalitis virus is the most important tick-borne virus in some border areas between China and Russia.Alongshan Virus(ALSV)was detected in the Jiagedaqi and Yichun city.No nucleic acid positive of Fever with Thrombocytopenia Syndrome Virus(SFTSV)was detected in the vector investigation.No evidence of prevalence of Omsk Hemorrhagic Fever Virus(OHFV),Langote Virus(LGTV),Powassen Virus(POWV),and Tibet Circovirus(TIBOV)was found on the Sino-Russian border.This survey provides basic data for the prevention and control of tick-borne diseases in some border areas between China and Russia.