Abstract
Tick-borne spotted fever group (SFG) rickettsioses were neglected in Taiwan. The study reported a seroepidemiological survey of SFG rickettsiae in residents in Gongliao District, Northeast Taiwan. Blood samples were examined for antibodies against SFG rickettsiae by enzyme-linked immunosorbent assay and immunofluorescence assay. Risk factors were assessed using logistic regression. Ticks parasitizing dogs were collected within a 2 km radius from the houses of seropositive participants, and PCR was performed to detect possible tick-borne pathogens. Of 1108 participants, 75 (6.8%) had antibodies against SFG rickettsiae. Residents were more likely to be seropositive if they were older than 65 years, recruited by Dr. Enjoy’s Clinic, or resided in Jilin village. A total of 184 ticks including 5 species (Rhipicephalus sanguineus, Rhipicephalus haemaphysaloides, Dermacentor auratus, Haemaphysalis hystricis, Haemaphysalis ornithophila) were collected. Rickettsia spp. were detected in 6.5% (12/184) of ticks. Rickettsia sp. TwKM01 was found in 6 R. sanguineus and 4 R. haemaphysaloides; while Rickettsia sp. TwKM03 was identified in 1 R. sanguineus. Moreover, gene-based pairwise analysis indicated identification of a putative new species, Rickettsia sp. Da-1, in D. auratus. These findings provided evidence of SFG rickettsiae infection in ticks and suggested SFG rickettsiae exposure in the residents.
Highlights
Rickettsiae are obligate intracellular Gram-negative bacteria belonging to the orderRickettsiales [1]
Genus Rickettsia was classified into 3 groups: spotted fever group (SFG)
Further genetic evidence has suggested the addition of a transitional group (TRG) along with the ancestral group (AG) rickettsiae [4]
Summary
Rickettsiae are obligate intracellular Gram-negative bacteria belonging to the orderRickettsiales [1]. Genus Rickettsia was classified into 3 groups: spotted fever group (SFG). Rickettsiae, typhus group (TG) rickettsiae, and scrub typhus group based on serology [2]. The scrub typhus group was designated as a new genus, Orientia [3]. Further genetic evidence has suggested the addition of a transitional group (TRG) along with the ancestral group (AG) rickettsiae [4]. SFG rickettsiae and AG rickettsiae are primarily transmitted by ticks; while TG rickettsiae and TRG rickettsiae are associated with fleas, chiggers, or lice [5]. In Taiwan, the notifiable rickettsial diseases cover scrub typhus, epidemic typhus, and murine typhus. Scrub typhus and murine typhus led to 300–500 and 20–60 confirmed cases each year, respectively; while epidemic typhus has not been documented since World
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