Epidemiology Of Tick-Borne Encephalitis In China And Investigation Of Tick-Borne Virus In Northern China

Background: As the specific blood-feeding ectoparasitic animal,ticks can spread a variety of pathogens by biting humans and animals,which seriously threatens human health and animal husbandry production and has a great impact on public health.Therefore,understanding the epidemiological characteristics of tick-borne encephalitis in China and carrying out relevant surveys of tick-borne viruses will provide a scientific basis for the prevention and control of tick-borne viral infections in China.Methods:(1)The epidemiological characteristics of tick-borne encephalitis in China were systematically analyzed by the data of tick-borne encephalitis(TBE)cases reported nationwide from 2007 to 2018;(2)Tick-borne specimens were collected in Heilongjiang and Xinjiang by manual flag laying method and livestock body surface picking method.(3)A study on method of tick species identification based on molecular markers of mitochondrial COI(COI)and 16 Sr DNA(16S r DNA)was established;(4)Molecular screening for tick-borne encephalitis virus(TBEV),Powassan virus(POWV),Langat virus(LGTV)and Omsk Hemorrhagic Fever virus(OHFV),fever with thrombocytopenia syndrome virus(SFTSV),and Alongshan virus(ALSV)was carried out based on real-time fluorescence reverse transcription polymerase chain reaction(real time RT-PCR)on tick specimens from Heilongjiang,Xinjiang,and Almaty areas associated with the Belt and Road in China.Results:(1)From 2007 to 2018,a total of 3364 TBE cases were reported in mainlanChina,with an annual incidence of 0.09 to 0.44/100,000.Among the TBE cases,the Northeast region accounted for 89.92%(41.94% in Da Xing An Ling,8.70% in Xiao Xing An Ling,and 39.21% in Chang Bai Shan).TBE cases were mainly male(67.03%),and the age group was mainly concentrated in the age of 40 to 49.The TBE cases in Da Xing An Ling were dominated by domestic workers and forestry workers,and the TBE cases in Xiao Xing An Ling and Chang Bai Shan were dominated by domestic workers and farmers.Most TBE cases occur from April to August of each year,with a peak in June.The laboratory confirmed rate of TBE was the highest in Da Xing An Ling,and the laboratory confirmed cases were mainly concentrated in Inner Mongolia Forestry General Hospital,accounting for 45.42% of the confirmed cases in China.(2)A total of 2545 tick specimens were collected in this study,including 1850 ticks(including 288 Dermacentor silvarum and 16 Ixodes persulcatus ticks)in the Gagdachi area of the Da Xing An Ling,Heilongjiang Province,China;384 ticks(Hyalomma detritum)in the Gurtu Wenquan County,Wusu City,Xinjiang Province,and 221 ticks(including 105 Hyalomma detritum,47 Haemaphysalis punctata and 69 Dermacentor marginatus)in the Almaty area of Kazakhstan;(3)Morphological and molecular biological classification studies of ticks identified a total of 5 tick species(Ixodes persulcatus,Dermacentor silvarum,Dermacentor marginatus,Hyalomma detritum,Haemaphysalis punctate)belonging to 4 genera(Ixodes,Dermacentor,Hyalomma,and Haemaphysalis)in 1 family(Ixodes),which made up for the shortcomings of morphological identification methods.(4)TBEV,SFTSV,OHFV,LGTV,POWV,and ALSV were negative in tick specimens from Gagdachi,Heilongjiang,Gurtu,Xinjiang,and Almaty,Kazakhstan.Conclusions: In summary,the incidence of TBE in China is mainly concentrated in the Da Xing An Ling,Chang Bai Shan and Xiao Xing An Ling.Tick specimens were negative for TBEV,SFTSV,OHFV,LGTV,POWV,and ALSV in Gagdachi,Heilongjiang,Gurtu,Xinjiang,and Almaty,Kazakhstan,considering that there have been no case reports of POWV,OHFSV,and LGTV infection in China,it is considered that there has been no importation of POWV,OHFSV and LGTV viruses.The mitochondrial COI and 16 S r DNA molecular markers established in this study can be accurately applied to the molecular biological identification of ticks,providing a powerful supplement to traditional species morphological identification methods.The above provides important basic data for the prevention and control of tick-borne encephalitis and related tick-borne viral diseases in China.