Molecular identification of Rickettsia spp. in chigger mites in Taiwan

Abstract

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.

Rickettsia felis and Other Rickettsia Species in Chigger Mites Collected from Wild Rodents in North Carolina, USA

“…In this study, we provide the first evidence of Rickettsia infection in chiggers collected from rodents within North America, a significant extension of recent work finding rickettsial DNA in trombiculid mites from South America and Asia [ 10 , 31 , 32 ]. Nucleotide sequence analyses of Rickettsia -specific 23S-5S IGS, 17 kDa, and gltA gene fragments indicated the amplicons from these chiggers were closely related to those in R. felis , R. conorii , R. typhi , and unidentified Rickettsia species.…”

“…Nucleotide sequence analyses of Rickettsia -specific 23S-5S IGS, 17 kDa, and gltA gene fragments indicated the amplicons from these chiggers were closely related to those in R. felis , R. conorii , R. typhi , and unidentified Rickettsia species. The most frequently detected rickettsial species in our study, Rickettsia felis , is globally distributed and was found in fleas, mosquitoes, ticks, and chigger mites [ 31 ]. There is increasing evidence that chiggers could be vectors of transitional group rickettsiae, because of their discovery in a variety of field-collected chiggers [ 10 , 32 ].…”

Not Only Leptotrombidium spp. an Annotated Checklist of Chigger Mites (Actinotrichida: Trombiculidae) Associated with Bacterial Pathogens

“…Bacteria-positive larvae were obtained from A. agrarius , the Indian mole-rat B. bengalensis Gray, 1835, B. indica , A. roylei , R. rattus , the buff-breasted rat R. tanezumi flavipectus (Milne-Edwards, 1872), R. tanezumi , the Sikkim rat R. andamanensis (Blyth, 1860), R. exulans , R. norvegicus , R. losea , Rattus spp., the small white-toothed rat B. berdmorei (Blyth, 1851), T. belangeri (mentioned as T. belangeri persurae ), T. glis and S. murinus (mentioned as S. murinus fulvo-cinerea) as well as from the moist marshlands (host-questing larvae). The above observations were made in Australia, China, India, Indonesia, Malaysia, Myanmar, Pakistan, Papua New Guinea, Philippines, Singapore, Taiwan (including Pescadores), Thailand and Vietnam [ 10 , 14 , 23 , 40 , 46 , 49 , 51 , 52 , 68 , 78 , 83 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 ].…”

“…Laboratory reared individuals originating from larvae captured in nature were also positive for Mycobacterium sp. Lehmann and Neumann, 1896 (Actinomycetota, Mycobacteriales, Mycobacteriaceae) Infected larvae were obtained from the bodies of A. agrarius , B. indica , R. exulans , R. losea , R. rattus and R. tanezumi captured in Taiwan and Thailand [ 23 , 29 , 84 , 85 , 97 , 105 ].…”

“…Reports come from Japan, Russia (Primorsky Krai), South Korea and Taiwan. [ 34 , 60 , 62 , 63 , 69 , 70 , 97 , 108 , 115 , 118 , 119 , 120 ].…”