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Objective: To explore the existence of spotted fever group Rickettsiae (SFGR) in Guangdong province., Methods: Sera were tested to find the SFGR in population and host animals. The target samples were screened by polymerase chain reaction (PCR), and Rickettsiae was isolated with embryonated hen eggs and identified by serological tests., Results: Eight hundred and sixty people in natural condition and 321 of mice were determined. The mean positive rate of healthy population was 3.84%. To compare results among elected places, Fisher's exact test was applied. The difference was suggestive (P < 0.01), and there was no significant difference between mountain and plain areas. There was also no significant difference between mountain and plain areas (P > 0.05). Positive rate of mice was 4.67%, with Rattus fulvescens, Rattus edwardsi, Bandicota indica 11.59%, 12.90%, 3.13% respectively. It was the first time that SFGR antibodies in Rattus fulvescens, Rattus edwardsi, Bandicota indica were reported. A total number of 321 mice spleens and 394 ticks from the surface of mice body were collected. Two strains of SFGR, GDFK58-2000 and GDFK59-2000, were isolated in the ticks from the body surface of 2 Rattus fulvescens. They were identified as Rickettsia sibirica by serological tests. Five hundred thirty-three bp OmpA gene fragments of the two strains were cloned and sequenced. Compared with other relevant strains in Genbank, the rates of homology of nucleotide sequences of GDFK58-2000 and GDFK59-2000 and other Rickettsia sibirica strains were from 99.6% to 100%, and the homology of amino acid speculated was 100%., Conclusion: It has been proved that epidemic areas of north Asia tick-transmitted SFGR, did exist in Guangdong province confirmed by hostanimals, transmission vectors and aetiology.

PCR/RFLP technique was used to detect spotted fever group rickettsiae (SFGR) in ticks and small mammals collected in eleven scenic spots of Beijing suburb. We not only detected Rickettsia sibirica in D. sinicus and hedgehog collected nearby the Museum of Aviation, but also isolated two strains of SFGR from them, named as BJ-95 strain and BJH-95 strain respectively. The two strains were identified as R. sibirica by SDS-PAGE, Western blot and PCR/RFLP. The results demonstrated the existence of horizontal transmission of R. sibirica between ticks and small mammals and showed the most scenic spots except the vicinity of Museum of Aviation being investigated were safe to North Asia Fever. This is the first report on the isolation of R. sibirica in hedgehogs.

It was the first time that a primer pairs derived from the 190KDa protein antigen gene of R. rickettsii were used to amplify SFGR DNA in ticks, tick ova, larva, tick faeces and rodent organs which were collected in Hebei, Heilongjiang, Hainan and Beijing. A 532bp fragment was respectively amplified from above samples. The results were partially in concordance with data obtained through rickettsiae isolation. It was suggested that PCR is a rapid, specific, sensitive and practical method for detection of SFGR in endemic foci.