Distribution And Molecular Characteristics Of Tick Species And Tick-borne Rickettsiae,Xinjiang Border Areas

Background: Xinjiang Uygur Autonomous Region(XUAR),which is located in the northwest of China,with 5600 km border line,accounts for about a quarter of the national land border and neighboring Mongolia and other 7 neighboring countries.XUAR is an important channel of the ancient Silk Road in history,is China’s advocacy of "The Belt and Road" north line to Central Asia and Europe’s important land portal link.Tick-borne rickettsiae can be spread through international trade by livestock,birds and wild animal migration,causing infection and outbreak of human and animal rickettsial diseases.The aim of this study is to know about tick species identification,investigation and molecular distribution characteristics of tick borne rickettsiae in border areas of XUAR for preventing tick borne pathogens transmitting and make a foundation of international co-operation.Methods: Ticks were collected in 14 counties in XUAR border between March to July in 2014-2016.Morphology and molecular biology methods based on 16 S rRNA,COI,12 S rRNA were conducted to identify the species of questing ticks.Multilocus sequence typing method was carried out for the Rickettsiae detection and Polymerase Chain Reaction(PCR)were carried based on 17 kDa,ompA,omp B,gltA,sca1,sca4 and 16 S rRNA genes.Positive samples were further processed for sequencing and sequence statistica lanalysis.Phylogenetic trees of concatenated sequence of Rickettsiae species in China border were conducted to determine the evolutionary relationships.Results: A total of 1279 ticks were collected in 14 XUAR border areas.Morphology and molecular biology results showed that the questing ticks belong to three genera and five species,including Haemaphysalis punctata,H.Erinacei,Dermacentor nuttalli,D.marginatus and Rhipicephalus turanicus.The average positive rate of rickettsiae species was 41.28%(528/1279).Rickettsia raoultii,R.massiliae,R.aeschlimannii,R.slovaca,R.sibirica,R.conorii subsp.indica and Candidatus R.barbariae were co-existed in XUAR border areas and the positive rates were between 6.25% and 77.92% and the positive rates of ticks were between 6.25% and 46.10%.Conclusions: Rhipicephalus turanicus is the advantage tick species of xinjiang border region,throughout almost the entire south border and some of the north border area.H.erinacei is the rare tick species,only distributed in China-kazakhstan border.Xinjiang border areas present high rates for Spotted fever group rickettsiae species.Rickettsia raoultii was detected in the H.erinacei from Vormela peregusna for the first time.Four novel rickettsiae species for China were detected in xinjiang border areas which includes R.aeschlimannii,R.massiliae,R.conorii subsp.indica and Candidatus R.barbariae,expanded the China rickettsial species from six to ten.R.sibirica and R.aeschlimannii variants were discovered,named R.sibirica strain Xinjiang and R.aeschlimannii strain China,respectively.This survey covers almost all border counties and cities in Xinjiang,provides a scientific framework for early disease monitoring system of our country and provides a basic information for international cooperation.In the future,tick-borne rickettsiae species detection and prevention of travelers,migratory birds,transportation of livestock,and wild animals in the border should be tested for further investigation.