Historical epidemics of scrub typhus in Queensland and Papua New Guinea

Undifferentiated febrile diseases (e.g., Mossman fever) from northern Queensland were eventually partially attributed to mite-transmitted rickettsial infections known as scrub typhus or tsutsugamushi fever. Scrub typhus became a major medical threat to military operations in Papua New Guinea during the Second World War and killed more Australian soldiers than malaria in the pre-antibiotic era. Further investigations showed scrub typhus to be an occupational disease of rural workers in north Queensland especially around Cairns and Innisfail. Occasional small epidemics of scrub typhus still occur during military exercises in Queensland, but as scrub typhus is not a reportable disease, its presence in the civilian community is largely unknown. Increased use of serological testing in patients with fever and rash illnesses after exposure in northern Queensland is likely to show that scrub typhus is a modern infection that remains treatable with antibiotics once it is identified.     

Acute respiratory distress syndrome in scrub typhus

Scrub typhus is a mite-borne infectious disease caused by Orientia tsutsugamushi. Acute respiratory distress syndrome (ARDS) is a serious complication of scrub typhus. This study retrospectively reviewed the medical records of 72 patients diagnosed with scrub typhus from January 1998 to August 2006 in Kaohsiung Chang Gung Memorial Hospital in Taiwan. Eight of 72 scrub typhus patients with ARDS were included in the study; the other patients without ARDS were used as controls. The mortality rate for the scrub typhus patients with ARDS was 25%. The eight patients seldom had underlying diseases. Initial presentations of dyspnea and cough, white blood cell count, hematocrit, total bilirubin, and delayed used of appropriate antibiotics use were significant predictors of ARDS. Multivariate analysis showed that albumin, prothrombin time, and delayed use of appropriate antibiotics were independent predictors of ARDS. Identification of these relative risk factors may help clinicians evaluate clinical cases of scrub typhus with ARDS.     

Short report: detection of Orientia tsutsugamushi in clinical samples by quantitative real-time polymerase chain reaction

Orientia tsutsugamushi infection causes scrub typhus, a common zoonosis of rural Asia. Orientia tsutsugamushi was recently detected by a real-time quantitative polymerase chain reaction (qPCR) assay in animal specimens. We evaluated the same qPCR assay in specimens obtained from patients with serologically proven scrub typhus infections. The 47-kDa qPCR assay was more sensitive than was mouse inoculation; it was reactive in whole blood specimens from all 10 isolate-positive patients and in 7 of 17 isolate-negative individuals (P = 0.003, Fisher's two-tailed exact test). As few as 1,076 O. tsutsugamushi copies/microL were detected in whole blood. Four of 7 sera from isolate-proven scrub typhus infections were also reactive by qPCR. The assay was unreactive in all 12 individuals without scrub typhus infection. This is the first demonstration of a sensitive and specific real-time qPCR assay for human scrub typhus infection.     

Comparative evaluation of selected diagnostic assays for the detection of IgG and IgM antibody to Orientia tsutsugamushi in Thailand

We compared the performance of 2 commercially available dipstick assays, 2 enzyme-linked immunosorbent assays (ELISAs), and an indirect immunofluorescent antibody (IFA) assay for the diagnosis of scrub typhus, using the indirect immunoperoxidase (IIP) test as the reference standard. The dipstick assays were the Integrated Diagnostics (Baltimore, MD) Dip-S-Ticks Scrub Recombinant (r56) dipstick test (INDX assay) and the PanBio (Brisbane, Australia) Scrub Typhus IgM and IgG Rapid Immunochromatographic test (PanBio assay). One of the ELISAs used pooled cell lysates of Karp, Kato, and Gilliam strain Orientia tsutsugamushi as antigen (pooled-antigen ELISA), and the other used a recombinant r56 protein as the antigen (recombinant ELISA). With a panel of 123 positive and 227 negative sera, sensitivity and specificity of the assays were as follows: INDX assay, IgG, 60% and 95%, IgM, 60% and 97%; PanBio assay, IgG, 94% and 96%, IgM, 83% and 93%; IFA (1:400 cutoff), IgG, 91% and 96%, IgM, 85% and 98%; pooled-antigen ELISA, IgG (1:1600 cutoff), 97% and 89%, IgM (1:400 cutoff), 94% and 91%; recombinant ELISA, IgG (1:1600 cutoff), 97% and 92%, IgM (1:400 cutoff), 93% and 94%. Because of its excellent performance and use of a standardized, commercially available antigen, the recombinant ELISA is suitable for use in a diagnostic laboratory, where it may be able to replace the IFA and IIP assays. In contrast, the PanBio dipstick assay was easy to perform and did not require sophisticated equipment, making it suitable for use in rural areas where more sophisticated diagnostic tests such as the ELISA and IFA may not be available.     

A serological survey of scrub, tick, and endemic typhus in Sabah, East Malaysia

A seroepidemiological survey of 837 people and 383 febrile patients was performed in rural areas of Sabah. We determined that the rickettsial diseases scrub typhus and endemic typhus were uncommon causes of febrile illness, as was tick typhus, except in forest dwelling peoples. The rate of occurrence of SFGR specific antibody was 16.5% among 412 forest dwellers, indicating that tick typhus may be a frequent cause of illness in this population.     

Short report: prospective evaluation of a multi-test strip for the diagnoses of scrub and murine typhus, leptospirosis, dengue Fever, and Salmonella typhi infection

A multi-test strip dotblot immunoassay for the diagnosis of typhoid fever, scrub typhus, murine typhus, dengue virus infection and leptospirosis was evaluated in Thai adults presenting to hospital with acute, undifferentiated fever. The kit gave multiple positive test results in 33 of 36 patients with defined infections and was therefore not a useful admission diagnostic tool.     

Patient and sample-related factors that effect the success of in vitro isolation of Orientia tsutsugamushi

Orientia tsutsugamushi is the causative agent of scrub typhus infection, a major cause of human disease in rural areas of Southeast Asia. Twenty-six blood samples collected from patients with serologically proven scrub typhus during a six month period were sent to Bangkok (535 km from the clinical site) by road at ambient temperature (average daily temperature range: 27.1-29.1 degrees C) for attempted in vitro isolation in Vero cells. O. tsutsugamushi was isolated from 12 samples (sensitivity 46.7%) with the time to isolation ranging from 16 to 37 days [median 27 days, inter-quartile range (IQR) 22.5-33.5 days]. Patient factors such as days of fever and O. tsutsugamushi IgM antibody titer, transport factors such as transit time, and isolate genotype (Karp and Gilliam/Kawasaki) were assessed to determine their influence on the outcome of in vitro isolation. None of the factors significantly influenced the isolation outcome. This study demonstrates that O. tsutsugamushi can often be isolated in vitro from the blood of scrub typhus patients when transported at ambient tropical temperatures for many days.     

Comparative evaluation of the indirect immunoperoxidase test for the serodiagnosis of rickettsial disease

An indirect immunoperoxidase test was compared with an indirect fluorescent antibody test and the Weil-Felix OXK test for serodiagnosis of scrub typhus by measuring the rickettsial antigen specific activity of IgG, IgM, and whole globulin. Acute and convalescent sera from 50 Rickettsia tsutsugamushi isolate-positive scrub typhus patients and from 45 febrile patients diagnosed as having diseases other than scrub typhus were tested. The receiver operating characteristic for each test showed that the indirect immunoperoxidase and indirect fluorescent antibody tests were more sensitive and specific than the Weil-Felix test using convalescent and acute as well as paired sera. The indirect immunoperoxidase test showed no cross-reactivity when R. tsutsugamushi antigen was tested against sera collected from patients living outside the scrub typhus-endemic area with diseases other than scrub typhus. The indirect immunoperoxidase and indirect fluorescent antibody tests were comparable in measured response to R. tsutsugamushi, R. typhi, and TT-118 (spotted fever group) antigen. Thus the indirect immunoperoxidase test represents a sensitive, specific, reproducible, and practical semiquantitative test for rickettsial disease diagnosis.     

Rapid diagnosis of scrub typhus in rural Thailand using polymerase chain reaction

The aim of this study was to evaluate the use of polymerase chain reaction (PCR) amplification of the O. tsutsugamushi 16S rRNA gene for the diagnosis of scrub typhus in rural Thailand. A prospective study of acute febrile illness in Udon Thani, northeast Thailand, identified 183 patients as having scrub typhus on the basis of immunofluorescent antibody testing (IFA) of paired sera. A further 366 febrile patients admitted concurrently with a range of other diagnoses acted as negative controls. Diagnostic sensitivity and specificity of 16S rRNA PCR was 44.8% and 99.7%, respectively, compared with IFA. PCR positivity was related to duration of symptoms and presence of eschar (P < 0.001, both cases). PCR using primers to amplify a fragment of the 56-kd gene had a sensitivity and specificity of 29.0% and 99.2%, respectively. PCR has a high specificity but low sensitivity for the rapid diagnosis of scrub typhus in this endemic setting.     

Distribution of eschars on the body of scrub typhus patients: a prospective study

Eschar is an important finding for the diagnosis of scrub typhus. The IFA test for possible scrub typhus was performed. The presence or absence of eschar was thoroughly examined. Among the 176 scrub typhus cases confirmed by IFA, 162 (92.0%) cases had eschar; 128 patients (79.5%) had eschars on the front of the body. Eschars were primarily detected in males within 30 cm below the umbilicus (19 patients, 35.8%). Distributions on the lower extremities and the front chest above the umbilicus were 22.6% (12 patients) and 20.8% (11 patients), respectively. A different pattern was seen in females. The most prevalent area was the front chest above the umbilicus, which accounted for 40.7% (44 patients) of all the detected eschars. Our study is the first report of a schematic diagram that shows the differences between the males and females with respect to eschar location in scrub typhus patients.     

Evaluation of tests for serological diagnosis of scrub typhus

Two specific serological tests, a Dot enzyme immunoassay (EIA) and an immunoglobulin (Ig)M enzyme-linked immunosorbent assay (ELISA) using the 56 kDa antigen and the Weil-Felix test were evaluated for diagnosis of scrub typhus. Sensitivity of 100, 86.5 and 43.5% were observed with Dot EIA, IgM ELISA and Weil-Felix test, respectively. False-positive reactions were observed in patients with falciparum malaria, pulmonary tuberculosis, S. viridans septicemia and typhoid fever using Dot EIA and IgM ELISA. Therefore, although Dot EIA and IgM ELISA are useful in the serodiagnosis of scrub typhus, efforts should be made to rule out other febrile illnesses.     

Development of a real-time PCR assay for the diagnosis of scrub typhus cases in India and evidence of the prevalence of new genotype of O. tsutsugamushi

A qualitative syber green real-time PCR with primers designed for a truncated portion of the 56kDa major outer membrane antigen gene of Orientia tsutsugamushi was used to diagnose scrub typhus from the blood or serum of suspected patients. Sixty-six blood and/or sera samples from fever cases, either with high index of suspicion for scrub typhus and/or positive by Weil-Felix test (> or = 1:160), were tested with the PCR. Specificity of the PCR was confirmed by end point melt curve analysis and sequencing of the amplicons. A nested PCR for determination of the serotypes of O. tsutsugamushi was performed on to the samples. In real-time PCR strong positive fluorescence was obtained in 73% of the suspected samples. Serotype-specific PCR amplification of some of the positive samples was indicative of the Kuroki type whereas the rest were non-responsive to this test. Sequence analyses of PCR amplicons indicated the presence of new, previously undescribed type of O. tsutsugamushi in this region. This one-step real-time PCR can be used for the detection and confirmation of scrub typhus, when used independently or in conjunction with, the Weil-Felix test, which is still the only available detection test for scrub typhus in most parts of the developing world. Elaborate studies need to be taken up to further evaluate its suitability as specific molecular tool for the diagnosis of scrub typhus and to delineate the prevalent strain types in these regions for a clear epidemiological understanding of this emerging infectious disease.     

Scrub Typhus: Surveillance,Clinical Profile and Diagnostic Issues in Shandong,China

To elucidate the epidemic status, clinical profile, and current diagnostic issues of scrub typhus in Shandong Province, we analyzed the surveillance data of scrub typhus from 2006 to 2011 and conducted a hospital-based disease survey in 2010. Scrub typhus was clustered in mountainous and coastal areas in Shandong Province, with an epidemic period from September to November. The most common manifestations were fever (100%), eschar or skin ulcer (86.3%), fatigue (71.6%), anorexia (71.6%), and rash (68.6%). Predominant complications included bronchopneumonia, toxic hepatitis, and acute cholecystitis in 21.6%, 3.9%, and 2.9% of the cases, respectively. Severe complications including toxic myocarditis, heart failure, pneumonedema, pleural effusion, and emphysema were first reported in Shandong. Missed and delayed diagnosis of scrub typhus was common in local medical institutions. Alarm should be raised for changes of clinical features and current diagnostic issues of scrub typhus in newly developed endemic areas.     

Differentiating dengue virus infection from scrub typhus in Thai adults with fever

Dengue fever and scrub typhus are common infections in Asia that often present as acute febrile illness of unclear etiology. We prospectively evaluated febrile adults presenting to the outpatient department of a hospital in northern Thailand to attempt to identify distinguishing characteristics between the two infections. Fifty-four patients were infected with scrub typhus and 35 were infected with dengue virus. Dengue virus infection was associated with hemorrhagic manifestations, particularly bleeding from the gums, which was reported by 27% of the dengue patients, but by none of the scrub typhus patients (P < 0.001, by Fisher's exact test). A low platelet count (< 140,000/mm3) and low white blood cell count (< 5,000/mm3) were strongly associated with dengue infections: odds ratio = 26.3 (95% confidence interval [CI] = 7.4-93.2) for platelet count and 8.2 (95% CI = 2.6-25.5) for leukocyte count. Prospective evaluations of the usefulness of these simple criteria to differentiate scrub typhus from dengue infection are needed in other areas, particularly where rapid confirmatory diagnostic tests are not available.     

Possible scrub typhus coinfections in Thai agricultural workers hospitalized with leptospirosis

Possible coinfections with Orientia tsutsugamushi the causative agent of scrub typhus, were prospectively evaluated in rice farmers hospitalized with leptospirosis in Northeast Thailand. Of 22 adults with leptospirosis diagnosed by the microscopic agglutination test, 9 also had serologic evidence of scrub typhus. Of 9 individuals with possible coinfections, 5 had signs or symptoms typical of scrub typhus and atypical of leptospirosis. Patients who appeared to have mixed infections had significantly higher median platelet counts and significantly lower median serum bilirubin and creatinine concentrations (P < 0.05, Mann-Whitney U test) than did individuals with leptospirosis alone. One patient with serologic evidence of scrub typhus and leptospirosis was treated only with penicillin, to which scrub typhus is not sensitive. Respiratory distress worsened during therapy, and the patient died of respiratory failure. Physicians should consider the possibility of scrub typhus infection in leptospirosis patients who respond poorly to treatment or who have atypical disease manifestations.     

Early diagnosis of scrub typhus in Thailand from clinical specimens by nested polymerase chain reaction

The early detection of scrub typhus in Thailand by nested polymerase chain reaction (PCR) is presented. The diagnosis of scrub typhus, from clinical samples obtained from hospitals in the northern part of Thailand, by nested PCR was compared to immunofluorescence (IF) and Weil-Felix (WF) tests. The primer pairs used for the nested PCR were designed on the basis of the nucleotide sequence of the gene that encodes the 56-kDa antigen, and RFLP analysis was used for identification. Clotted blood from 80 patients suspected of scrub typhus infection were tested. With the IF test, antibodies for Orientia tsutsugamushi were observed in 38 patients checking IgM and IgG titers. Only 21 patients showed positive seroconversion while 17 patients were negative. For the WF test, only 13 patients gave a positive seroconversion. In the early stage of infection, 19, 13 and 3 patients were detected with a sensitivity of 90.47% (19/21), 61.90% (13/21) and 14.28% (3/21) by the nested PCR, IF and WF test respectively. Two patients who were negative for seroconvesion by IF and WF were positive by nested PCR. Therefore, this suggests that nested PCR is applicable for specific rapid diagnosis at an early stage of scrub typhus in endemic regions.     

云南省恙虫病与肾综合征出血热混合感染的诊断及分析

目的 调查云南省不明原因发热患者中是否存在恙虫病与肾综合征出血热混合感染病例.方法 采用间接免疫荧光法和胶体金法检测不明原因发热患者血清中的恙虫病东方体(OT)抗体及肾综合征出血热(HFRS)病毒抗体,用巢式PCR扩增患者血液中的OT 基因sta56片断与汉坦病毒(HV)基因L片断.结果 79例患者中,实验室确诊HFRS 5例,恙虫病3例,HFRS与恙虫病混合感染4例;巢式PCR检测到HV L片断核酸2例(DLR2和DLR6), 序列分析两者间的同源性100%,DLR2与老挝汉城病毒L0199株核苷酸序列同源性最高为94.6%, 与中国汉城病毒L99株的同源性80.5%, 与云南汉坦病毒YN06-256的同源性69.8%.结论 首次证实云南省存在恙虫病与肾综合征出血热混合感染病例,其HFRS病原体遗传进化关系与老挝汉城病毒L0199株密切相关.     

Gastrointestinal manifestations of septic patients with scrub typhus in Maharat Nakhon Ratchasima Hospital

Scrub typhus is an acute febrile illness caused by Orientia induced vasculitis, which is common in Asia and the Pacific Islands and is sometimes also encountered in Western countries. Even though it can cause multi-organ dysfunctions, there is limited information regarding the relationship between scrub typhus infection and gastrointestinal dysfunction. Therefore, a cross-sectional study was conducted to discover the gastrointestinal manifestations of septic patients with scrub typhus infection. During the study period, 80 septic cases were recruited, and according to the results of immunofluorescent antibody testing (IFA), 20 (25%) were found to have scrub typhus infection. The most common gastrointestinal symptoms of scrub typhus patients were vomiting 13 (65%), nausea 12 (60%), diarrhea 9 (45%), and hametamesis or melena 5 (25%). Gastrointestinal signs included hepatomegaly 8 (40%), jaundice 7 (35%), and abdominal pain 4 (20%). Elevation of SGOT, SGPT, and alkaline phosphatase were 16 (80%), 14 (70%), and 16 (80%), respectively. Direct bilirubin was elevated in 19 (95%) of the cases and half of the cases had a low serum protein level. Of scrub typhus cases, 8 (40%) had eschars. The sites of eschars were mostly in hidden areas, such as on the back, genitalia and abdomen. Three of the five patients with eschar had hepatomegaly on ultrasound examination. The significant findings of the scrub typhus septic patients with eschar on endoscopic examination were gastritis in two cases, gastritis with gastric erosion in two cases, and one case showed a duodenal ulcer and erosion. The differentiating point for endoscopic findings in scrub typhus compared to the other causes was that the stomach lesions were more frequent and severe than the duodenal lesions. According to our endoscopic findings, physicians should be aware of gastric and duodenal lesions in febrile patients with gastrointestinal symptoms, such as abdominal pain or discomfort and indigestion. Scrub typhus can cause gastrointestinal and liver dysfunction.     

1952-1989年和2006-2017年中国大陆恙虫病流行及时空分布特征

目的 研究并阐明中国大陆恙虫病流行趋势和时空分布特征, 为恙虫病的预防和控制提供参考依据。方法 根据1952-1989年和2006-2017年中国大陆恙虫病疫情报告数据,采用描述性流行病学方法、空间自相关分析和ArcGIS 10.4软件的可视化技术等,全面系统研究中国大陆恙虫病流行及时空分布特征,并确定高风险地区。结果 在1952-1989年和2006-2017年期间,我国累计报道恙虫病病例156 234例,死亡180例。1952-1989年的年均发病率0.13/10万。2006年以后,年均发病率急剧上升,由2006年的0.09/10万上升到2017年的1.62/10万,增长了18倍,年平均增长率为33%。流行季节仍以夏季和秋冬为主,多数病例主要集中在10月,女性发病率高于男性(χ²=168.34, P<0.001)。云南、安徽、广东、福建、江苏、山东、广西和四川8个省(自治区)的病例数最多,占全国总病例数的91.31%。全局空间自相关分析结果表明,在全国范围内恙虫病整体上存在着空间正相关,具有空间聚集性(I=0.085, P<0.05)。局部空间自相关分析结果显示,广西、福建及其周边地区为“热点区域”,是恙虫病高发区。结论 1952-1989年和2006-2017年我国恙虫病发病率存在逐年升高趋势,病例以夏季型和秋冬型为主。空间自相关分析可以及时发现该病的聚集情况并确定高发区和危险区。     

一起鼠型斑疹伤寒爆发疫情中患者血清恙虫病抗体检测

目的 筛查一起鼠型斑疹伤寒爆发疫情患者血清中恙虫病抗体。方法 用间接免疫荧光法对20 份爆发疫情病人血清进行鼠型斑疹伤寒和恙虫病IgG 抗体检测。结果 20 例患者中,鼠型斑疹伤寒抗体阳性13 例,阳性率65%;恙虫病抗体阳性2 例（同时鼠型斑疹伤寒抗体阳性）,阳性率10%。结论 该起鼠型斑疹伤寒爆发疫情患者中存在恙虫病感染,临床上应加强对鼠型斑疹伤寒与恙虫病的诊断与鉴别诊断。