Detection of Rickettsia japonica From Ticks of Mueui Island Where The First Case of Japanese Spotted Fever Was Found

초록

Rickettsia japonica, one of the member of Spotted fever group Rickettsia, has been recently recognized as a human pathogen in Korean by serologic and microbial studies. Previously we found the first case of Japanese spotted fever and isolated R. japonica from a patient. The patient lived in Mueui Island near Incheon city. Therefore, we had interest on the tick vectors of this island. During March through September 2006, ticks were collected from grass vegetation by flagging vegetation. The survey areas are three sites that are mostly abandoned field near the road. A total 206 ticks were collected from Mueui Island during three visits and all ticks were identified as Haemaphysalis spp. and 29 were adults and 177 were larva. The midgut of individual adult ticks and pooled larval ticks was suspended in 100ul of phosphate-buffered saline and DNA was extracted. The screening for rickettsial groEL gene was performed using nested PCR and the purified PCR products were sequenced. A total of 11/44 (25%) pools of ticks were positive for by nested PCR using primers specific for groEL gene. The nucleotide sequences of groEL gene from11 positive fragment of PCR were determined. The sequences were aligned and a phylogenetic tree was constructed using MEGA software. All nucleotide sequences of 10/11 showed high similarity (96.9-99.8%) with that of R. japonica YH. In the phylogenetic tree 10/11 sequences formed a cluster with that of R. japonica YH. In summary, we examined the rickettsial pathogens harbored by ticks from Mueui island and found that 25% of tick samples were positive for R. japonica.