Spotted Fever Group Rickettsiae in Inner Mongolia, China, 2015–2016

We found Rickettsia raoultii infection in 6/261 brucellosis-negative patients with fever of unknown origin in brucellosis-endemic Inner Mongolia, China. We further identified Hyalomma asiaticum ticks associated with R. raoultii, H. marginatum ticks associated with R. aeschlimannii, and Dermacentor nuttalli ticks associated with both rickettsiae species in the autonomous region.

Brucellosis, a zoonotic disease, is highly endemic to Inner Mongolia, China, and is increasing in workers in agriculture or animal husbandry (5). However, some agriculture workers with brucellosis-like symptoms, including general malaise and fever, were seronegative for Brucella spp. We suspected that fever of unknown origin among brucellosis-seronegative patients might be caused by tickborne pathogens. We identified 6 cases of human R. raoultii infections in brucellosis-seronegative patients in western Inner Mongolia, and we investigated exposure to ticks infected with SFGR.
We detected gltA amplicons from 6/261 (2.3%) blood samples (Table). All 6 patients had strong malaise and mild fever of 36.8°C -37.3°C but no rash. Five of these patients also had arthralgia and vomiting.
Sequence and phylogenetic analysis showed that the sequences of 6 nearly full-length (1.1 kb) gltA amplicons with were identical to each other and to R. raoultii gltA (GenBank accession no. DQ365803). We further analyzed ompA and 16S rDNA in gltA-positive samples. All 6 samples were PCR positive for both genes; 552-bp sequences of the amplicons were identical to sequences of R. raoultii ompA (GenBank accession no. AH015610), and 389-bp sequences of the amplicons were identical to sequences of R. raoultii 16S rDNA (GenBank accession no. EU036982). PCR results were negative for the genes Anaplasma phagocytophilum p44/msp2, Ehrlichia chaffeensis p28/omp-1, and Borrelia spp. flaB. An indirect immunofluorescence assay showed that IgM and IgG titers against R. japonica were 40-80 for IgM in 3 patients and 160 for IgG in 2 patients.
Recently, human cases of R. raoultii infection have been reported in China, including northeastern Inner Mongolia (1,4). Potential vectors for R. raoultii are Dermacentor spp. ticks in Europe, Turkey, and northern Asia and Haemaphysalis spp. and Amblyomma sp. ticks in southern Asia (7,8). Other studies have identified Hyalomma spp., Rhipicephalus spp., and Amblyomma sp. ticks as potential vectors for R. aeschlimannii (7,8); human cases of R. aeschlimannii infection have been reported in Italy and Morocco (7,9). We detected R. raoultii in H. asiaticum as well as D. nuttalli ticks, but in Mongolia, R. raoultii has been detected only in D. nuttalli ticks, and not H. asiaticum ticks (10). We identified D. nuttalli ticks as another potential vector for R. aeschlimannii. Our work contributes to the knowledge of the epidemiology, clinical characteristics, and known tick vectors associated with R. raoultii and R. aeschlimannii. S potted fever group rickettsiae are tickborne, obligatory intracellular, gram-negative bacteria with a worldwide distribution. However, the distribution of each species of spotted fever group rickettsiae is limited to geographic areas by their specific tick vectors. Japanese spotted fever is a severe rickettsiosis caused by Rickettsia japonica bacterium (1,2), which has been present in Japan since 1984 and isolated from patients in other countries of Asia (e.g., South Korea, the Philippines, and Thailand) over the past decade (3,4). In this study, we present information on an R. japonica isolate acquired from a febrile patient and R. japonica seroprevalence in Anhui Province in eastern China.

RESEARCH LETTERS
On August 7, 2013, a 61-year-old man from Shucheng County, Lu'an City, China, in the Dabie Mountain area of Anhui Province (online Technical Appendix Figure 1, https:// wwwnc.cdc.gov/EID/article/24/11/17-0264-Techapp1. pdf) with fever and headache for 1 week was admitted into Shucheng County People's Hospital. The patient reported several tick bites 10 days before the onset of his illness. At admission, the patient was conscious and had fever (39.0°C); he did not have jaundice, and no bleeding was found on his skin or mucosal membranes. A papular rash with papules 0.1-0.5 cm in diameter was noted all over his body (online Technical Appendix Figure 2). Blood cell counts showed the patient had leukocytosis (10.34 × 10 9 cells/L), increased neutrophils (87.5%), and a platelet count within reference range (130 × 10 9 /L). Blood chemistry testing revealed a urea nitrogen concentration of 9.12 mmol/L (reference range 2.9-8.2 mmol/L), creatinine of 0.758 mg/dL (67 µmol/L, reference range 53-106 µmol/L), C-reactive protein of 77.5 nmol/L (reference range 0.76-28.5 nmol/L), and an erythrocyte sedimentation rate of 22 mm/h (reference range 0-20 mm/h). A urine test showed a procalcitonin concentration of 0.806 ng/ mL (reference range <0.15 ng/mL) and an interleukin 6 concentration of 52 pg/mL (reference range <1.8 pg/mL). The patient had rough lung breath sounds, and computed tomography showed inflammatory infiltrates in the middle right lung and lower left lung lobe, bullae on the upper left lung lobe, and emphysematous changes. The patient was suspected to have a rickettsial infection and was given minocycline and meropenem on the day of his admission. Two days later, on August 9, 2013, the patient's fever subsided (36.2°C), and he was discharged.
A blood sample taken from the patient 1 day after admission was inoculated onto THP-1 and Vero E6 cells; after 10 days, cytopathic effect was visible by light microscopy with only the THP-1 cells. Diff-Quick (Thermo Fisher Scientific, Kalamazoo, MI, USA)-stained smears of THP-1 cells showed Rickettsia-like bacilli in the cytoplasm. Electron microscopy showed the bacilli localized to the cytoplasm and nucleus and had the typical ultrastructure of Rickettsia bacteria. This species was highly pleomorphic