Genetic Diversity Of Tick-borne Zoonoticanaplasma And Rickettsia In Some Areas Of Shaanxi Province

Some species within order Rickettsiales are globally distributed zoonotic pathogen.They are specific intracellular parasitic prokaryotic organisms and belong to the Alpha Proteobacteria.Many members of order Rickettsiales are transmitted periodically among animals through Ixodes.Most mammals canseverse as theirhosts.Although intensive livestock farms has being becoming more and more popular,there are still many traditional farming methods of domestic animals in China and other countries and regions in the world.With the warming of the climate,tick activities become active,which increases the opportunity to be infected by Rickettsiales,endangers human and animal health and causes unnecessary losses.In order Rickettsiales,many members are important new pathogens,which cause anaplasmosis,ehrlichiosis and rickettsioses in humans or animals.In the past two decades,13 human pathogenic pathogens associated with Rickettsiales have been identified in mainland China,including seven species of Spotted Fever Group Rickettsia(SFGR),two species of Ehrlichia,four species of Anaplasma and Candidatus Neoehrlichia mikurensis in the Anaplasmataceae.On the other hand,Xi'an City,the capital of Shaanxi Province,is an epidemic area of hemorrhagic fever with renal syndrome(HFRS),but no hantavirus nucleic acid,antigen and antibody were found in some patients during the laboratory diagnosis of hantaviruses.The symptoms of human Rickettsiales infection are generally mild,occasionally can cause symptoms including hemorrhage and fever,similar to those of hemorrhagic fever with renal syndrome,so these patients with non-hantavirus infection may be caused by Rickettsiales infection.From March 2017 to March 2019,305 whole blood samples of cattle,goats and sheep were collected in Zhouzhi,Lintong,Chang'an and Huyi of Xi'an,Shaanxi Province,and 1120 ticks were collected in Xi'an,Ankang and Baoji cities.Then tick-borne zoonotic Anaplasma and Rickettsia were identified.Rickettsia was identified by amplification of its 16 S rRNA(rrs),17-kDa,gltA and ompA genes;Anaplasma were identified by amplification of its 16 S rRNA(rrs),gltA and gorEL genes,and sequence analysis was performed.Finally,phylogenetic trees were reconstructed to reveal their species and genetically relationship with known isolates.Two hundred and forty-two Ca.R.jingxinensis were detected from tick sampled in Xi'an and Baoji cities.Thirty-five Anaplasma platys-like,two hundred and seventy-two Anaplasma capra,one Anaplasma ovis and fourteen A.phagocytophlium-related species(designed as Ca.A.zhouzhiense and Ca.A.dongdaense)were detected from tick and blood samples in Xi'an and Ankang cities.Through molecular identification of zoonotic Anaplasma and Rickettsia carried by livestock and ticks in Shaanxi Province,the circulation of these pathogens in the local area was clarified,which provided basis for the prevention and control of livestock,information and reference for epidemiological research and control of the disease,as well as theoretical basis for the diagnosis of fever and hemorrhage of unknown origin.