title: Molecular detection of Rickettsia species in ticks collected from the southwestern provinces of the Republic of Korea.
abstract: Rickettsiae constitute a group of arthropod-borne, Gram-negative, obligate intracellular bacteria that are the causative agents of diseases ranging from mild to life threatening that impact on medical and veterinary health worldwide.
  
  
  
  A total of 6,484 ticks were collected by tick drag from June-October 2013 in the southwestern provinces of the Republic of Korea (ROK) (Jeollanam, n = 3,995; Jeollabuk, n = 680; Chungcheongnam, n = 1,478; and Chungcheongbuk, n = 331). Ticks were sorted into 311 pools according to species, collection site, and stage of development. DNA preparations of tick pools were assayed for rickettsiae by 17 kDa antigen gene and ompA nested PCR (nPCR) assays and the resulting amplicons sequenced to determine the identity and prevalence of spotted fever group rickettsiae (SFGR).
  
  
  
  Haemaphysalis longicornis (4,471; 52 adults, 123 nymphs and 4,296 larvae) were the most commonly collected ticks, followed by Haemaphysalis flava (1,582; 28 adults, 263 nymphs and 1,291 larvae), and Ixodes nipponensis (431; 25 adults, 5 nymphs and 401 larvae). The minimum field infection rate/100 ticks (assuming 1 positive tick/pool) was 0.93% for the 17 kDa antigen gene and 0.82% for the ompA nPCR assays. The partial 17 kDa antigen and ompA gene sequences from positive pools of H. longicornis were similar to: Rickettsia sp. HI550 (99.4-100%), Rickettsia sp. FUJ98 (99.3-100%), Rickettsia sp. HIR/D91 (99.3-100%), and R. japonica (99.7%). One sequence of the partial 17 kDa antigen gene for H. flava was similar to Rickettsia sp. 17kd-005 (99.7%), while seven sequences of the 17 kDa antigen gene obtained from I. nipponensis ticks were similar to R. monacensis IrR/Munich (98.7-100%) and Rickettsia sp. IRS3 (98.9%).
  
  
  
  SFG rickettsiae were detected in three species of ixodid ticks collected in the southwestern provinces of the ROK during 2013. A number of rickettsiae have been recently reported from ticks in Korea, some of which were identified as medically important. Results from this study and previous reports demonstrate the need to conduct longitudinal investigations to identify tick-borne rickettsiae and better understand their geographical distributions and potential impact on medical and veterinary health, in addition to risk communication and development of rickettsial disease prevention strategies.
authors.affiliation: Division of Zoonoses, National Institute of Health, Centers for Disease Control and Prevention, Cheongju-si, Chungcheongbuk-do, 28159, Republic of Korea.
authors.forename: Yoontae
authors.initials: Y
authors.lastname: Noh
authors.affiliation: Division of Zoonoses, National Institute of Health, Centers for Disease Control and Prevention, Cheongju-si, Chungcheongbuk-do, 28159, Republic of Korea.
authors.forename: Yeong Seon
authors.initials: YS
authors.lastname: Lee
authors.affiliation: 5th Medical Detachment, 168th Multifunctional Medical Battalion, 65th Medical Brigade, Unit 15247, Yongsan US Army Garrison, Seoul, APO AP 96205-5247, Republic of Korea.
authors.forename: Heung-Chul
authors.initials: HC
authors.lastname: Kim
authors.affiliation: 5th Medical Detachment, 168th Multifunctional Medical Battalion, 65th Medical Brigade, Unit 15247, Yongsan US Army Garrison, Seoul, APO AP 96205-5247, Republic of Korea.
authors.forename: Sung-Tae
authors.initials: ST
authors.lastname: Chong
authors.affiliation: Public Health Command District-Korea, 65th Medical Brigade, Unit 15281, Yongsan US Army Garrison, Seoul, APO AP 96205-5281, Republic of Korea.
authors.forename: Terry A
authors.initials: TA
authors.lastname: Klein
authors.affiliation: Viral and Rickettsial Diseases Department, Naval Medical Research Center, Silver Spring, MD, 20910, USA.
authors.forename: Ju
authors.initials: J
authors.lastname: Jiang
authors.affiliation: Viral and Rickettsial Diseases Department, Naval Medical Research Center, Silver Spring, MD, 20910, USA.
authors.forename: Allen L
authors.initials: AL
authors.lastname: Richards
authors.affiliation: Division of Zoonoses, National Institute of Health, Centers for Disease Control and Prevention, Cheongju-si, Chungcheongbuk-do, 28159, Republic of Korea.
authors.forename: Hae Kyeong
authors.initials: HK
authors.lastname: Lee
authors.affiliation: Division of Zoonoses, National Institute of Health, Centers for Disease Control and Prevention, Cheongju-si, Chungcheongbuk-do, 28159, Republic of Korea. tenksy@korea.kr.
authors.forename: Su Yeon
authors.initials: SY
authors.lastname: Kim
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000235:genetics; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D026863:Ixodidae / Q000382:microbiology*; D007814:Larva; D008297:Male; D009758:Nymph; D056910:Republic of Korea; D012281:Rickettsia / Q000145:classification* / Q000302:isolation & purification*
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C078167:OMPA outer membrane proteins
keywords: 17 kDa antigen gene; Ixodid ticks; Rickettsia; Spotted fever group rickettsiae; ompA