Genotype diversity and distribution of Orientia tsutsugamushi in scrub typhus patients and rodents in Shandong, northern China

The Prevalence of Rodents Orientia tsutsugamushi in China During Two Decades: A Systematic Review and Meta-Analysis

Background: Orientia tsutsugamushi is a zoonotic intracellular pathogen that requires parasitism in eukaryotic cells to reproduce. In recent years, tsutsugamushi disease reported in many places nationwide has crossed the Yangtze River, continuously, spreading to the North China. Now this phenomenon has aroused people's attention. Materials and Methods: In this study, meta-analysis was used to analyze the infection of rodents (vectors) in China, to clarify the transmission rule of O. tsutsugamushi. Results: This study included literature from six databases (PubMed, Web of Science, Science Direct, Wanfang, CNKI, and VIP). A total of 55 articles were included in the study from 610 retrieved articles. The total infection rate of O. tsutsugamushi in rodents was 5.5% (1206/20,620, 95% confidence interval [CI]: 0.0553-0.0617). The prevalence of O. tsutsugamushi in rodents before 2013 (7.73%, 95% CI: 4.11-12.37) was higher than after 2013 (2.11%, 95% CI: 0.64-4.41). O. tsutsugamushi spread among a variety of rodents, among which Rattus losea (13.3%, 95% CI: 4.33-26.26), Rattus tanezumi (5.69%, 95% CI: 1.37-12.72), and Apodemus agrarius (5.32%, 95% CI: 2.26-9.58) infection rate was higher. Kawasaki (8.32%, 95% CI: 1.42-20.17), Karp (7.36%, 95% CI: 2.62-14.22), Kato (2.54%, 95% CI: 0.08-8.28), and Gilliam (2.13%, 95% CI: 0.42-5.09) were the main prevalent genotypes in China. The prevalence of O. tsutsugamushi in rodents was seasonal, increasing gradually in summer (2.39%, 95% CI: 0.46-5.77), peaking in autumn (4.59%, 95% CI: 1.15-10.16), and then declining. The positive rate of immunofluorescence assay (25.07%, 95% CI: 8.44-46.88) was the highest among the detection methods, and it was statistically significant (p < 0.05). Based on the subgroup of geographical factors and climatic factors, the probability of O. tsutsugamushi infection in rodents was the highest when the temperature >19℃ (8.20%, 95% CI: 1.22-20.52), the altitude <100 millimeters (7.23%, 95% CI: 3.45-12.26), the precipitation >700 millimeters (12.22%, 95% CI: 6.45-19.50), and the humidity 60-70% (7.80%, 95% CI: 4.17-12.44). Conclusions: Studies have shown that rodents carrying O. tsutsugamushi are common. People should prevent and control rodents in life and monitor rodents carrying O. tsutsugamushi for a long time.

AuNPs/CNF-modified DNA biosensor for early and quick detection of O. tsutsugamushi in patients suffering from scrub typhus

A novel approach has been developed for the detection of 56 kDa tissue-specific antigen (TSA) gene of Orientia tsutsugamushi a causative agent of scrub typhus disease. The approach was developed by immobilization of 5' NH2 labeled ssDNA probe selective to 56 kDa TSA gene, to the surface of AuNPs/CNF modified screen-printed electrode. An electrochemical response was recorded with single stranded genomic DNA (ssDNA) of O. tsutsugamushi isolated from patient sample, using cyclic voltammetry and electrochemical impedance spectroscopy. The electrode surface was characterized by Field-Emission Scanning electron microscope (FE-SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Raman Spectroscopy at each step of fabrication. The DNA biosensor shows optimum response within 50-60 s at room temperature (25 ± 3 °C). The sensor shows higher sensitivity [7849 (µA/cm²)/ng DNA], fast response time (60 s), wider linear range (0.04-2.6 ng) with limit of detection of 0.02 ng/µl of ssDNA sample.

Diagnosis of scrub typhus: recent advancements and challenges

Scrub typhus is a mite-borne, acute febrile illness caused by the bacterium Orientia tsutsugamushi. It is a re-emerging infectious disease of the tsutsugamushi triangle. Scrub typhus is transmitted through bites of contaminated chiggers (larval stage). Diagnosis of scrub typhus is challenging as its symptoms mimic with other acute febrile illnesses. Several methods are effectual for diagnosis of scrub typhus that includes enzyme-linked immunosorbent assay (ELISA), immunofluorescence assay (IFA), immunochromatographic test (ICT), Weil-Felix, polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP). Weil-Felix test was initially used for the diagnosis of scrub typhus in underdeveloped countries but not preferred due to a lack of both specificity and sensitivity. Other immuno-based methods like IFA and ELISA are most outrank for detection of scrub typhus due to their higher sensitivity and specificity, but not vigorous to lay bare the infection at early stages and need the convalescent sampling for verification of positive samples. On another deed, PCR based methods becoming acceptable over era due to its dexterity of early-stage diagnosis with higher specificity and sensitivity but lack its applicability in circumstances of scrub typhus due to the variegated genetic makeup of Orientia tsutsugamushi among its serotypes. The present review focused on various detection methods along with their advantages and disadvantages used in the diagnosis of scrub typhus. A comparison between available methods of diagnosis with challenges in the detection of scrub typhus is also summarized.

Analysis of epidemiological characteristics of four natural-focal diseases in Shandong Province, China in 2009-2017: A descriptive analysis

Background

Natural-focal diseases are serious diseases that endanger human health. They threaten about 100 million people in Shandong Province, and cause illness in thousands of people each year. However, information on the epidemiological characteristics of natural-focal diseases in Shandong Province has been limited. The purpose of the study was to describe and analyze the epidemiological characteristics of natural-focal diseases in Shandong Province, 2009–2017.

Methods

We describe the incidence and distribution of four natural-focal diseases in Shandong Province using surveillance data from 2009–2017.

Results

From 2009–2017, 11123 cases of four natural-focal diseases including 257 deaths were reported in Shandong Province, China. The four natural-focal diseases were severe fever with thrombocytopenia syndrome (SFTS), human granulocytic anaplasmosis (HGA), typhus, and scrub typhus. The high-risk groups of the four diseases were farmers and the elderly. The incidence rate of scrub typhus was significantly higher in females. However, this difference was not seen in the other three diseases. The four diseases were mainly clustered in the middle-southern part of Shandong Province and the Shandong Peninsula. The annual incidence of SFTS and scrub typhus increased, typhus was relatively stable, and HGA declined. However, the range of SFTS expanded, while HGA shrunk, and typhus and scrub typhus were unchanged. The epidemic period of SFTS and HGA was from May to October, typhus was from October to November, and scrub typhus was from September to November. The fatality rates of SFTS, typhus, scrub typhus, and HGA were 9.19%, 0%, 0.01%, and 2.24%, respectively.

Conclusions

Our study described and analyzed the prevalence of natural-focal diseases in Shandong Province, and confirmed that age was closely related to the SFTS fatality rate. This study may help to improve the understanding of the prevalence of natural-focal diseases in Shandong Province in recent years and to better develop accurate prevention and control strategies for natural-focal diseases.

Orientia tsutsugamushi infection in rodents in Anhui Province of China

We conducted an investigation of Orientia tsutsugamushi infection among rodents in non-endemic areas in Anhui Province. Fifty-six (56) rodents including 44 Apodemus agrarius and 12 Niviventer niviventer were trapped and captured in autumn in the fields of three counties in Anhui Province. DNA samples were amplified and sequenced for the 56kDa protein gene of Orientia tsutsugamushi. The overall infection rate in the rodents was 23.2%(13/56). The rate of detection of O. tsutsugamushi in Apodemus agrarius and Niviventer niviventer were 27.3% and 8.3% respectively. Moreover, we identified two genotypes (Karp and Gilliam strains) of Orientia tsutsugamushi in rodents. Our study demonstrated that Apodemus agrarius is the main host for O. tsutsugamushi pathogen and this is the first report of Karp and Gilliam strains in these non-endemic areas in Anhui Province.

Prevalence and Phylogenetic Analysis of Orientia tsutsugamushi in Rodents and Mites from Central India

Orientia tsutsugamushi, the causative agent of scrub typhus in humans, is an obligate intracytosolic bacterium transmitted among animals and to humans by some species of larval trombiculid mites (chiggers) and is hosted mainly by rodents. In this study, we attempted detection of O. tsutsugamushi from blood and tissue samples of rodents trapped from different locations in Central India using PCR targeting the 56 kDa outer membrane protein gene and the 47 kDa high temperature transmembrane protein gene. A total of 59 rodent samples comprising 38 of blood collected from domestic and public surroundings and 21 of tissue from agricultural farm were included in this study. The 56 kDa outer membrane protein gene was detected from 10 of 59 samples by PCR, and the 47 kDa protein gene was detected from 4 of 59 samples by nested-PCR. Mites collected from the rodents were identified as Ornithonyssus bacoti, and one of five pooled samples was found to be positive for O. tsutsugamushi using PCR targeting 56 kDa outer membrane protein gene. Thus, perpetuation of O. tsutsugamushi among rodents and mites was detected constituting a potential public health concern.

Use of eschar swabbing for the molecular diagnosis and genotyping of Orientia tsutsugamushi causing scrub typhus in Quang Nam province, Vietnam

BACKGROUND

Scrub typhus is a rickettsiosis which is caused by Orientia tsutsugamushi and occurs throughout the Asia-Pacific region. Molecular diagnosis of rickettsioses using eschar swabs has recently emerged, and may be very useful for the diagnosis of these diseases in tropical settings.

METHODOLOGY/PRINCIPAL FINDINGS

Quantitative polymerase chain reaction (qPCR) was used to detect O. tsutsugamushi DNA in whole blood and eschar swab specimens of 67 patients who were clinically suspected of scrub typhus in Quang Nam province, Vietnam. Among the 20 patients for whom both eschar and whole blood were obtained, 17 (85%) of the eschar specimens and 5 (25%) of the whole blood specimens tested positive for O. tsutsugamushi. Genetic analysis of the 56-kDa TSA gene sequences demonstrated that the 14 sequences obtained in this study, including 12 eschar swabs and 2 whole blood specimens, were related to 4 groups: Karp, Kawasaki, Gilliam (JG-v and TG-v) and TA716. The majority (9/14; 64.4%) of contemporary O. tsutsugamushi genotypes in Quang Nam province were related to the Karp group.

CONCLUSIONS

These results suggest that polyclonal antigen pools used for serological testing in the future should contain at least Karp, Kawasaki, Gilliam and TA716 antigens for Vietnamese patients, as well as patients who have traveled to Vietnam. qPCR after eschar swabbing should be considered for molecular diagnosis of scrub typhus in endemic patients as well as in travelers, since it is easy to perform and appears very useful for the rapid detection of Orientia tsutsugamushi in the early phase of infection.