Characterization of Spotted Fever Group Rickettsia in Ticks Collected from South Korea

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Recently, numbers of newly emerging spotted fever group Rickettsia spp.were observed in ticks.Here, we explored to determine the prevalence of rickettsia species found in ticks from 2 northeastern provinces (Gyeonggi, and Gangwon) of South Korea.A total of 1,798 Ixodid ticks were collected by tick drag methods from August to September 2009 in two northeastern provinces.204 samples were screened for the rickettsial 17-kDa antigen gene using nested PCR (nPCR), and 25 samples showed positivity.Of the 25 samples, 16 (64%), 11 (44%), and 9 (36%) were positive for rickettsial outer membrane protein A (ompA) gene, outer membrane protein B (ompB) gene, and surface cell antigen 4 (sca4) gene, respectively.BLAST results of ompB, ompA and sca4 sequences were obtained from the two identified genotypes designated as Rickettsia sp.str.koreansis, formerly named as HlR/D91, (from Haemaphysalis longicornis) and InR/D372 (from Ixodes nipponensis).The ompA small part (645bp) of Rickettsia sp.str.koreansis shared 99.8% similarity with Rickettsia sp.FuJ98 (firstly identified in China) while ompA large part (1651bp) of Rickettsia sp.str.koreansis showed 98.8% similarity with R. heilongjiangensis.Further, ompB (1848bp) and sca4 (1705bp) of Rickettsia sp.str.koreansis showed 97.9% and 97.6% sequence similarities with R. hulinensis and R. japonica, respectively, while ompA (small & large parts), ompB, and sca4 derived from Rickettsia sp.InR/D372 clustered with R. monacensis (99.8%) and R. tamurae (99.6%), respectively.These data suggest that the potentially new Rickettsia sp.str.koreansis was closely related to R. japonica, R. heilongjiangensis in northeastern Korea.