Tick-borne Pathogent Investigation In Inner Mongolia Forest Area

Background:Tick-borne infectious diseases is a kind of tick-borne natural foci disease,tick vector transmission of a wide range of pathogens(including bacteria,viruses,rickettsia,spirochetes,etc.),animal host wide.The prevalence of complex links,and susceptible to the natural environment,socio-economic conditions,several tick-borne infectious diseases often coexist in the same foci,a vector ticks can carry two or more pathogens,greatly increased host animals and human complex infection probability,easily lead to disease epidemic and outbreaks.Since 1982,33 emerging tick-borne agents have been reported in China[1-7],including three species in the family Anaplasmataceae,three species of Ehrlichia,eight species of spotted fever group rickettsiae,six species of Borrelia burgdorferi sensu lato,eleven species of Babesia,the virus causingsevere fever with thrombocytopenia syndrome,and 15 of the33 new tick-borne agents have been reported to cause human disease(The location and time of the first confirmation of each new tick-borne infectionsare givenin Appendix 1[93]).Lyme disease(LD)is a tick-borne infectious disease caused by the Borrelia burgdorferi sensu lato(Bb)in the 1970 s.More than 70 countries have reported this disease or Natural foci,also known as "Second AIDS" in the United States.The World Health Organization has classified it as a new infectious disease that needs to focus on prevention and treatment research.Since 1986,we found Lyme disease natural foci in China,the etiology confirmed 19 provinces,municipalities and autonomous regions exist Lyme disease natural foci,9 kinds of ticks can carry Borrelia burgdorferi sensu lato,sheep,cattle,dogs,rabbits and 8 species of wild mice have a natural infection.In recent years,Lyme disease has a thousand cases reported each year,which harm and seriousness has received increasing attention.Spot fever is a general term known as acute fever and systemic rash,which caused by the spotted fever group Rickettsiae(SFGR).SFGR is a globally distributed,strictly vascular endothelial cell parasitic gram-negative bacilli,which is the largest and most complex group in Rickettsia.So far,19 kinds of SFGRhave been found to cause human infection.China has more than10 provinces,municipalities and autonomous regions confirmed SFGR infection,andthe incidence of areas and scope continue to expand and change.In recent years,China and the rest of the world continue to find new species of SFGR and the resulting Spot fever.Inner Mongolia Daxinganling area is rich in natural resources,ecosystem species and diverse,and its unique geographical advantages and natural landscape suitable for ticks habitat,so it is one of the main epidemic areas of tick-borne infectious diseases in China [8].In recent years,with the adjustment of industrial structure and natural forest protection project in Inner Mongolia forest area,the forest harvesting quantity has been decreasing year by year,and the exploitation of forest resources has been gradually increased,and the local economy has been continuously developed.With the increase of people entering the forest area,people were tick bites and the probability of infection is increasing,and the incidence is getting higher and higher.As a result,tick-borne diseases are extremely threatening to people in tourism,camping,economic development,field production activities,military training and national defense construction in Inner Mongolia.Objective: Through this study,we can further understand the infection of Borrelia burgdorferi sensu lato and SFGR in the Daxinganling area of Inner Mongolia,supplement and improve the diversity and complexity of the pathogenic pathogen of the ticks,and provide the basis for our better control of tick-borne diseases.Methods: In this study,We selected Bilahe forest area(N49 ° 25'48.52 ",E123 ° 32'15.82"),Kuduer forest area(N50 ° 01'35.64 ",E121 ° 36'58.73")and Qiqian forest area(N52 ° 11'45.30 ",E120 ° 46'21.42")of Inner Mongolia as the investigation point,widely collected Ixodes persulcatus,Dermacentor silvarum and Haemaphysalis conicinna and other kinds of ticks,used the method of polymerase chain reaction(PCR)to study the infection and genotyping of Borrelia burgdorferi sensu lato and SFGR.Results: In this study,We collected a total of 792 ticks in the Beilahe,Kuduer and Qiqian,including Ixodes persulcatushas 723(91.29%),Dermacentor silvarumhas48(6.06%),Haemaphysalis conicinna has 21(2.65%).Both the Kuduer and Qiqian forest area are dominated by Ixodes persulcatus(?2=202.405,p=0.000),suggesting that Ixodes persulcatus is one of the main vectors of tick-borne diseases in this area.PCR analysis showed that the positive rate of tick-borne Borrelia burgdorferi sensu lato was 35.35%,Wherein Ixodes persulcatus,Dermacentor silvarum,Haemaphysalis conicinnawas 276(38.17%),2(4.17%),2(9.52%).Genotyping results showed that there were five genotypes: B.garinii type,positive ticks 212(positive rate 26.77%);B.afzelii type,positive ticks 53(positive rate 6.69%);B.miyamotoi type,positiveticks13(Positive rate 1.64%);B.spielmanii type,positiveticks 1(Positive rate0.12%);Borrelia sp.NM517 type,positiveticks 1(Positive rate 0.12%).Among them,B.miyamotoi,spielmanii and B.sp.NM517 were the first discoveries in China.Statisticalanalysis showed that B.garinii was the dominant genotype of Borrelia burgdorferi sensu lato in the China Daxing'anling area(? 2=19.433,p=0.013).In addition,the SFGR positive rate of ticks was 40.4%,wherein Ixodes persulcatus,Dermacentor silvarum,Haemaphysalis conicinna was283(39.14%)?28(58.33%)?9(42.86%).Genotyping results showed that there were three genotypes:Candidatus Rickettsia tarasevichiae(CRT)positive ticks 284(positive rate35.86%);R.raoultiipositive ticks 33(positive rate 4.17%);R.helongjiangiipositive ticks 3(positive rate 0.38%).According to the statistical test,there were significant differences in the positive infection of different genotypes of SFGR in three forest areas of Daxing'anling(?2=82.474,p=0.000).CRT was the dominant genotype of SFGR which was found in both the Kuduer and Qiqian forest areas,but R.raoultiiwas the dominant genotype in the Bilahe forest area.According to statistical analysis,There was significant difference in the infection of three different types of SFGR(?2=251.838,p=0.000),CRT was the dominant genotype of SFGR which was found inIxodes persulcatus and Haemaphysalis conicinna,but R.raoultii was the dominant genotype in Dermacentor silvarum.The study also foundTicks exist Borrelia burgdorferi sensu lato and SFGR complex infection,the combined infection rate was 14.52%(115).Conclusion: In this study,we combined with field investigation,laboratory testing,integrated application description of epidemiology,analytical epidemiology and other methods,to conducted an in-depth investigation into the infection of tick-borne pathogens in the Daxing'anlingarea of Inner Mongolia.The survey found that Ixodes persulcatus is the local dominant tick.Ticks can be isolated or mixed with the Spirochetes(B.garinii?B.afzelii?B.miyamotoi?B.spielmanii?B.sp.NM517)and SFGR(CRT?R.raoultii?R.heilongjiangii)infection.We first discovered the three genotypes of B.miyamotoi,B.spielmanii and B.sp.NM517 in the Spirochetes.B.miyamotoi belongs to Borrelia recurrentis,is mainly parasitic inIxodidae,and often with B.afzelii,B.garinii and other genotypes mixed infection in ticks.B.spielmanii belongs to the genus Borrelia burgdorferi sensu lato,is a new type of human pathogenic pathogens.The sequence similarity of B.sp.NM517 sequence to B.Theileri strain KAT 16 s ribosomal RNA is 98.77%,which is also a new genotype,but it has not yet been isolated and cultured,which needs further study.The results of this study not only complement and improve the diversity of tick-borne pathogens in the Daxing'anling area of Inner Mongolia,but also provide a new idea for better control of tick-borne infectious diseases.