Genetic Diversity Of Tick-borne Zoonotic Anaplasma And Rickettsia In Some Areas Of Chengde

Ticks are a kind of blood sucking arthropods,which have strong reproductive capacity and are difficult to kill.They are considered to be important vectors of many causative agents in nature,and have important research value in the field of medicine.Ticks can transmit pathogens to human or animals they parasitize in the process of sucking blood,leading to the spread of infectious diseases between human and animals.Anaplasmas and Rickettsia belong to Rickettsiales,which are obligate intracellular bacteria,The infected arthropods,such as ticks,fleas and mites,transmit the pathogens to human beings,causing zoonotic infectious diseases with different severity,ranging from mild to life-threatening.In recent years,with the increasing of the incidence rate of tick-associated rickettsiosis and anaplasmosis year by year,the studies on tick-borne Anaplasma and Rickettsia also increased and new tick-borne pathogens were discovered continuously.Since the 80 s of last century,more than ten pathogens have been identified in Chinese mainland,including at least 7 Anaplasma and 8 spotted fever group Rickettsiae in Rickettsia.Tick-associated rickettsiosis and anaplasmosis have got more and more attentions in vector-borne diseases in Chinese mainland.Chengde is the central city connecting Beijing,Tianjin,Liaoning and Inner Mongolia,and its topography is characterized by mountains densely covered with green vegetation,providing convenience for the survival of ticks.To data,three tick species,including Haemaphysalis longicornis,Dermacentor silvarum and Ixodes persulcatus,have been found in Chengde city.These ticks are important vectors of Rickettsiales.In order to protect people's health,it is urgent to carry out the research on tick-borne pathogens of Rickettsiales in Chengde.Objective:To better understand the infection of Anaplasma and Rickettsia in ticks in parts of Chengde city;to identify the species and genetic characteristics of Anaplasma and Rickettsia carried by ticks in Chengde;to provide more sufficient theoretical basis for the diagnosis of patients with with fever or fever with hemorrhage of unknown origin;to provide data for the epidemiological study of tick-borne Anaplasma and Rickettsia.Method:A total of 336 ticks were collected from the body surface of domestic animal in Liugou and Sangou towns in Chengde city.The ticks were taken back to the laboratory for identification of Anaplasma and Rickettsia.The16 S r RNA(rrs),gro EL,glt A,msp2 and msp4 genes of Anaplasma were amplified.The obtained sequences were compared with the known sequences,and the 16 S r RNA(rrs),gro EL,glt A and omp A genes of Rickettsia.The phylogenetic tree of above-mentioned genes was reconstructed.Result:1.From 336 samples of Haemaphysalis longicornis in Liugou town and Sangou town of Chengde,85 were Anaplasma positive and 58 were Rickettsia positive.Including 28(8.3%)Anaplasma capra and 57(16.9%)A.ovis,and 12(3.6%)Rickettsia sibirica,21(6.3%)R.raoultii and 25(7.4%)Candidatus R.jingxinensis.2.The phylogenetic trees based on the gro EL,glt A,msp2 and msp4 genes of Anaplasma and omp A gene of Rickettsia were reconstructed,suggesting genetic diversity of Anaplasma and Rickettsia detected in this area.Conclusion:In Chengde,at least two Anaplasma species of and three Rickettsia species are circulating,with high infection rate.The Anaplasma and Rickettsia strains present high genetic diversity.It is necessary to further expand the investigation areas of natural foci of Rickettsiales in Chengde,and carry out the studies on their infection in human.