Epidemiological Investigation On Spotted Fever Group Rickettsiae And Coinfection With Borrelia Burgdorferi Sensu Lato In Several Provinces, China

Spotted Fever is a series of diseases characterised as cute fever and tetter whichare caused by pathogenic spotted fever group rickettsiae. Lyme Disease is caused byBorrelia burgdorferi sesu lato. Both Spotted Fever and Lyme Disease are tick-bornezoonosis.The objective of the study was to investigate present epidemiological condition ofTick-borne Spotted Fever in several provinces of our country. In this study, we haveused the Epidemiological surveys and molecular biological techniques to search foretiologic evidence in tick vectors, animal reservoirs and susceptible animals (orpeople). The investigation results can provide counter measure for working out morecontrolling measure to new tick-borne diseases, and provide scientific theoretical basisto direct the clinical cure.Comparing the infection rates of different rodents and vectors may ascertain thedominant host and major vector in each area. What has important epidemiologicalmeaning for preventing and controlling the infection, prevalence of disease, andreducing error and leakage diagnosis.We selected Heilongjiang,Jilin,Inner Mongolia Autonomous Region,XinjiangUigur Autonomous Region,Zhejiang and Guizhou province as investigable focus tocollect samples. PCR was used to amplify OmpA gene of SFGR from spleen ofrodents in these areas, and the infection rates were compared. At the same time, PCRand IFA were used to detecte coinfection of SFGR and B.b.s.l from rodents,vector andlivestock especially in Jilin province.A total of 575 rodents were detected, the positive rate of SFGR is 12.0%. Theamplification products of positive have been detected in Heilongjiang,Inner MongoliaAutonomous Region,Xinjiang Uigur Autonomous Region,Zhejiang and Guizhouprovince, with the infection rates of 3.1%,21.6%,30.0%,10.8%,21.4% respectively.It is negative in Jilin province. The diversity between the infection rates of north andsouth area is insignificant ( χ 2=0.000,P=0.983).We discovered SFGR in 100 I. persulcatus ticks, with infection rate of 2.0% andthe infection rate of B.b.s.l was 36.0% in I. persulcatus ticks, the coinfection rate ofthe both agents was 2.0%. In 327 D. Silvarum ticks, the positive rates of B.b.s.l andSFGR were 30.9% and 29.1% respectively. 55 ticks (16.8%) were coinfected with thetwo pathogens. The infection rate of SFGR in D. Silvarum ticks is higher than in I.persulcatus ticks, the diversity is significant ( χ 2=30.4,P<0.01);The diversitybetween the infection rates of B.b.s.l in D. Silvarum ticks and I. persulcatus ticks isinsignificant ( χ 2=0.699,P=0.403);The coinfection rate in D. Silvarum ticks is higherthan in I. persulcatus ticks and the diversity is significant ( χ 2=13.287,P<0.01). 13rodents are detected positive of B.b.s.l in 102 rodents collected in Jilin, the positiverate is 12.7%, no coinfection is detected.Exact 200 sera of cattle and 203 sera of sheep are tested by IFA. The positiverates of serological detection of SFGR in cattle and sheep are 18.0% and 19.2%respectively. The positive rates of serological detection of B.b.s.l. in cattle and sheepare 10.0% and 15.8% respectively. The coinfection rates of serological detection incattle and sheep are 5.5% and 7.9% respectively. The diversity among rates of SFGR,B.b.s.l. and coinfection are insignificant ( χ 2=0.098,P=0.755;χ 2=2.978,P=0.084;χ 2=0.914,P=0.339).In summary, we got positive results of SFGR in rodents in Heilongjiang,InnerMongolia Autonomous Region,Xinjiang Uigur Autonomous Region,Zhejiang andGuizhou province. It suggested that epidemiological risk factor of SFGR exist in allthese regions. Coinfection of B.b.s.l and SFGR exist in ticks and sera of livestock inHuichun, Jilin province.The sequence analysis of SFGR positive products showed that the DNAsecquence of the newly detected agent (JL-95) was close to the two previouslydescribed rickettsiae which were detected in Ixodes ricinus from Slovakia (called IRS3and IRS4). Phylogenetic relationships inferred from the comparison of thesesequences with those of other genus Rickettsiae indicate that JL-95,IRS3 and IRS4constitute a new rickettsial genotype and form a separate cluster among the spottedfever group rickettsiae. The sequencing of specific fragment confirmed a new SFGRwhich was distinct with other rickettsiae known in China.The sequence analysis of B.b.s.l showed that the B.b.s.l in JiLin area, which werein high homologous, all belonged to B.garinii genotypes. It suggested that thevariation of 5S-23S rRNA intergenic region of B.b.s.l. is a little in Jilin.This resultprovided primary theoretical basis for developing and empoldering the vaccine ofB.b.s.l in Jilin province.