Genotyping Of Coxiella Burnetii Carried By Ticks And Rats In Some Regions In China

Objective Coxiella burnetii is the agent of a worldwide distributed zoonotic disease called Q fever.Its broad host range includes domestic and wild animals as well as humans,it can be disseminated through aerosols,and its pathogenicity is maintained by its extraordinary resistance to desiccation and the effects of physical and chemical factors encountered in the environment.The U.S.Centers for Disease Control and Prevent has classified C.burnetii as a potential bioterrorism agent.In recent years,Q fever becomes an increasing threat to humans and causes enormous economic losses.Ticks and rats,with a variety of species,are widely distributed in China and both of them are common natural reservoirs of C.burnetii.However,the current researches related to C.burnetii in China are commonly focus on nucleic acid and antibody detection in host,and there is a lacking information of systematic molecular epidemiological research for C.burnetii,reflecting limited information of the distribution and the dominant genotypes of C.burnetii carried by hosts in various regions,as well as it is difficult for the genotypes comparison of different isolates of this pathogen,and then to find outbreak associations by combining epidemiological investigation and to trace the source of infection.To prevent Q fever outbreaks,it is important to monitor prevalence of C.burnetii in ticks and rats so as to establish effective prevention and control measures.In this study,the prevalence of C.burnetii in ticks and rats in some regions of China were detected,and then the genotypes of C.burnetii in positive samples and Q fever patients were analyzed.MethodsFirstly,ticks and wild rats were collected in Shandong,Yunnan,Guangxi,Jiangxi,Tibet and Anhui province,and genome DNA samples were extracted for the identification of the host species by molecular biology.Secondly,genus-specific PCR was used for the detection of the presence of C.burnetii in samples,and the positive samples were further subject for phylogenetic analysis.Finally,C.burnetii in positive samples were genotyped by multispacer sequence typing(MST)and multilocus variable number tandem repeats analysis(MLVA).ResultsA total of 266 ticks and 240 rats were collected from wild fields in Shandong,Yunnan,Guangxi,Tibet,Jiangxi and Anhui province.Results of molecular biology and morphological species identification revealed that all ticks were belonged to Haemaphysalis Iongicornis,and the rats included Rattus tanezumi,Rattus nitidus,Rattus andanmanensis,Eothenomys miletus,Apodemus chevrieri,Niviventer confucianus,Apodemus latronum,Apodemus agrarius,and Rattus norvegicus.C.burnetii was detected in 50 H.Iongicornis and 45 rats by PCR combined with sequencing,and the highest positive rate(48.98%)was detected in E.miletus from Yulong Yunnan,as well as rats from Menglain Yunnan,Anhui and Jiangxi and ticks from Shandong carry C.burnetii,with infection rates of 15.09%,16.67%,13.33% and 18.80% respectively,while C.burnetii was not detected in rats collected from Guangxi and Tibet.In addition,rickettsia infections were detected in rats in Jiangxi and Anhui,both with infection rate 3.33%;Orientia tsutsugamushi infections were detected in rats in Guangxi,with infection rate 28.57%;Ehrlichia infections were detected in rats in Menglian,Yunnan,with infection rate 1.89%.Genotyping results showed that the MST type of C.burnetii in A.chevrieri and R.tanezumi in Yunnan province,A.agrarius in Anhui province and H.Iongicornis in Shandong province was MST16 and two new MST genotypes were found in A.chevrieri and R.tanezumi from Yunnan province,while the MLVA type of C.burnetii in R.tanezumi in Yunnan and Q fever patients was MLVA 1.ConclusionsC.burnetii was detected from rats in Yunnan,Anhui and Jiangxi province and from ticks in Shandong province.The genotypes of C.burnetii in collected samples were MST type 16 and MLVA type 1,and two new MST genotypes have been identified in rats from Yunnan.The results of this study help for the better understanding of the distribution and genetic diversity of C.burnetii in China and provide data support for the traceability of Q fever in China.