Department of Life Science, National Taiwan Normal University, Taipei, Taiwan.
Center for Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taipei, Taiwan.
Med Vet Entomol. 2022 Jun;36(2):223-229. doi: 10.1111/mve.12560. Epub 2021 Nov 30.
The genus Rickettsia is the causative agent of several rickettsial diseases that are primarily transmitted by hard ticks. The occurrence of Rickettsia in chigger mites, which are vectors of scrub typhus in the western Pacific region, has been infrequently investigated. We identified Rickettsia spp. in chiggers collected from small mammals in six counties of Taiwan. Moreover, by capitalising on parallel Rickettsia detections on small mammals and their infested ticks and fleas, we were able to identify Rickettsia spp. that suggested more intimate associations with chigger mites. Rickettsia detection rates in 318 pools of chiggers were 21.7% and 22.3% when based on the ompB and gltA gene, respectively. Overall, we identified six (based on the ompB gene) and eight (gltA gene) Rickettsia species. Approximately half of the sequenced species were most similar to Rickettsia sp. clone MB74-1 (ompB gene) and Rickettsia sp. TwKM02 (gltA gene). Furthermore, both species were either infrequently or never identified in small mammals, ticks and fleas, which suggests that chigger mites might be the primary host of both rickettsiae. Whether both species are pathogenic to humans remains to be studied. They may also be microbial endosymbionts of chigger mites, with their potential effects on the pathogenicity of the aetiologic agent of scrub typhus deserving further investigations.
恙虫病东方体是几种立克次体病的病原体，主要通过硬蜱传播。在西太平洋地区，恙螨作为恙虫病的传播媒介，其体内携带恙虫病东方体的情况鲜有研究。我们从台湾六个县的小型哺乳动物中采集的恙螨中鉴定出了立克次体。此外，通过对小型哺乳动物及其寄生的恙螨和跳蚤进行平行的立克次体检测，我们能够鉴定出与恙螨关系更为密切的立克次体。基于 ompB 和 gltA 基因，318 个恙螨池中恙虫病东方体的检出率分别为 21.7%和 22.3%。总体而言，我们基于 ompB 基因鉴定出了六种，基于 gltA 基因鉴定出了八种立克次体。大约一半的测序物种与立克次体 sp. clone MB74-1（ompB 基因）和立克次体 sp. TwKM02（gltA 基因）最为相似。此外，这两个物种在小型哺乳动物、蜱和跳蚤中都很少或从未被鉴定出来，这表明恙螨可能是这两种立克次体的主要宿主。这两种物种是否对人类具有致病性仍有待研究。它们也可能是恙螨的微生物内共生体，其对立克次体病病原体致病性的潜在影响值得进一步研究。
