Pham X D, Otsuka Y, Suzuki H, Takaoka H
Department of Infectious Disease Control, Oita Medical University, Hasama, Japan.
J Med Entomol. 2001 Mar;38(2):308-11. doi: 10.1603/0022-2585-38.2.308.
The current study surveyed the 56-kDa type-specific antigen (TSA) gene DNAs of Orientia tsutsugamushi (Hayashi) in approximately 4.000 unengorged chiggers obtained from the soil or ground surface in an endemic and a nonendemic area of the Tsutsugamushi disease in Oita Prefecture, southwestern Japan, by nested polymerase chain reaction (PCR). Serotypes of O. tsutsugamushi were identified by restriction fragment-length polymorphism (RFLP) analysis. In the endemic area, 242 pools from five species [234 pools of Leptotrombidium scutellare (Nagayo, Miyagawa, Mitamura, Tamiya and Tenjin), two L. pallidum (Nagayo, Miyagawa, Mitamura and Tamiya), four L. kitasatoi (Fukuzumi & Obata), one L. fuji (Kuwata, Berge and Philip), and one Neotrombicula japonica (Tanaka, Kaiwa, Teramura and Kagaya)] were tested, and eight (seven pools of L. scutellare and one N. japonica) were positive for O. tsutsugamushi. Among the seven positive pools of L. scutellare, the distribution of serotypes was as follows: Kuroki (4), Gilliam (1), Karp (1), and Kawasaki (1). The first two serotypes (Kuroki and Gilliam) were identified for the first time in this species. In the nonendemic area, 128 pools from eight species were tested, and 13 were positive for O. tsutsugamushi. The positive rate was as follows: L. pallidum (4/41). L. kitasatoi (1/18), Gahrliepia saduski Womersley (2/10), L. fuji (4/50), L. himizu (Sasa, Kumada, Hayashi, Enomoto, Fukuzumi and Obata) (1/2), and Miyatrombicula kochiensis (Sasa, Kawashima and Egashira) (1/3). The latter three species were shown for the first time to harbor O. tsutsugamushi. All ofthe positive pools were Kuroki, except for two pools (one L. pallidum and one L. fuji), which were Gilliam (this serotype was also detected for the first time in L. pallidum). Further analysis revealed no differences in the nucleotide sequences (125 bp of variable domain 1 of TSA gene) of the same serotypes (i.e., Kuroki and Gilliam) among the positive samples. These data indicate that O. tsutsugamushi was widely distributed in various trombiculid species, even in the nonendemic area. The data are also suggestive of a possible horizontal transmission of O. tsutsugamushi among trombiculid species.
本研究通过巢式聚合酶链反应（PCR），对从日本西南部大分县恙虫病流行区和非流行区的土壤或地面采集的约4000只未饱血恙螨体内的恙虫东方体（林氏）56-kDa型特异性抗原（TSA）基因DNA进行了检测。通过限制性片段长度多态性（RFLP）分析鉴定恙虫东方体的血清型。在流行区，对来自5个种类的242个恙螨样本池[234个小板恙螨（长与、宫川、三村、田宫和天神）样本池、2个苍白恙螨（长与．宫川、三村和田宫）样本池、4个北里恙螨（深津和小幡）样本池、1个富士恙螨（桑田、贝格和菲利普）样本池和1个日本新恙螨（田中、河轮、寺村和加贺谷）样本池]进行了检测，其中8个样本池（7个小板恙螨样本池和1个日本新恙螨样本池）的恙虫东方体呈阳性。在7个阳性的小板恙螨样本池中，血清型分布如下：黑木型（4个）、吉列姆型（1个）、卡尔普型（1个）和川崎型（1个）。前两种血清型（黑木型和吉列姆型）首次在该种类中被鉴定出来。在非流行区，对来自8个种类的128个恙螨样本池进行了检测，其中13个样本池的恙虫东方体呈阳性。阳性率如下：苍白恙螨（4/41）、北里恙螨（1/18）、萨杜斯基嗜螨恙螨（2/10）、富士恙螨（4/50）、日见恙螨（笹、熊田、林、榎本、深津和小幡）（1/2）和小川真恙螨（笹、川岛和江头）（1/3）。后三个种类首次被发现携带恙虫东方体。除了2个样本池（1个苍白恙螨样本池和1个富士恙螨样本池）为吉列姆型（该血清型也首次在苍白恙螨中被检测到）外，所有阳性样本池均为黑木型。进一步分析显示，阳性样本中相同血清型（即黑木型和吉列姆型）的核苷酸序列（TSA基因可变区1的125 bp）没有差异。这些数据表明，恙虫东方体广泛分布于各种恙螨种类中，即使在非流行区也是如此。这些数据还提示恙虫东方体在恙螨种类之间可能存在水平传播。
