Distinguishing Japanese Spotted Fever and Scrub Typhus, Central Japan, 2004- 2015

Deleterious effects of a combination therapy using fluoroquinolones and tetracyclines for the treatment of Japanese spotted fever: a retrospective cohort study based on a Japanese hospital database

OBJECTIVES

Tetracyclines are the standard treatment for rickettsiosis, including Japanese spotted fever (JSF), a tick-borne rickettsiosis caused by Rickettsia japonica. While some specialists in Japan advocate combining fluoroquinolones with tetracyclines for treating JSF, the negative aspects of combination therapy have not been thoroughly evaluated. Whether fluoroquinolones should be combined with tetracyclines for JSF treatment is controversial. The study aimed to evaluate the disadvantages of fluoroquinolones combined with tetracyclines for JSF treatment.

METHODS

This retrospective cohort study was conducted using a Japanese database comprising claims data from April 2008 to December 2020. The combination therapy group (tetracyclines and fluoroquinolones) was compared with the monotherapy group (tetracycline only) regarding mortality and the incidence of complications.

RESULTS

A total of 797 patients were enrolled: 525 received combination therapy, and 272 received monotherapy. The adjusted odds ratio (OR) for mortality was 2.30 [95% confidence interval (CI): 0.28-18.77] in the combination therapy group with respect to the monotherapy group. According to the subgroup analysis, patients undergoing combination therapy with ciprofloxacin experienced higher mortality rates compared with those receiving monotherapy (adjusted OR = 25.98, 95% CI = 1.71-393.75). Additionally, 27.7% of the combination therapy group received NSAIDs concurrently with fluoroquinolones. The combination therapy with NSAIDs group was significantly more likely to experience convulsions than the monotherapy without NSAIDs group (adjusted OR: 5.44, 95% CI: 1.13-26.30).

CONCLUSIONS

This study found no evidence that combination therapy improves mortality outcomes and instead uncovered its deleterious effects. These findings facilitate a fair assessment of combination therapy that includes consideration of its disadvantages.

Masqueraders Around Disaster: Clinical Features of Scrub Typhus in Fukushima, Japan

Background

Scrub typhus (ST) is endemic in Fukushima, with the largest number of cases reported in Japan from 2009 to 2010. Although ST is highly treatable, its atypical clinical presentation impedes diagnosis, causing delays in treatment.

Methods

We review the clinical features of ST in adults from 2008 to 2017 at Ohta Nishinouchi General Hospital in Fukushima, Japan.

Results

Fifty-five cases (serotype Karp 24, Irie/Kawasaki 21, Hirano/Kuroki 10) of ST were confirmed via serology based on elevated immunoglobulin (Ig)M and IgG and polymerase chain reaction positivity of eschar samples. The mean age was 69 years, and 64% were female. The case fatality rate was 1.8% (1/55). Approximately 70% of cases (38/55) were not diagnosed as ST upon the initial clinic visit. Inappropriate use of antibiotics was identified in 22% of cases (12/55). In terms of atypical clinical features, 1 or more of the manifestations, fever, rash, and eschar, was absent in 31% of cases (17/55). Approximately 11% of cases presented without eschar (6/55; Karp 1, Irie/Kawasaki 1, Hirano/Kuroki 4). Moreover, severe complications were observed with shock and disseminated intravascular coagulation in 7% of cases (4/55), Thus, while 53% of cases presented with the typical triad (29/55), unusual complications and atypical features occurred in 40% (22/55).

Conclusions

Diagnosis of ST becomes clinically challenging in the absence of typical features. In Fukushima, an endemic area of ST, an atypical presentation involving multisystem disease is common.

Human granulocytic anaplasmosis with rash and rhabdomyolysis: A case report

Human granulocytic anaplasmosis (HGA) is a tick-borne infection caused by Anaplasma phagocytophilum. Only seven cases of HGA have been reported in Japan to date. We report the case of a 61-year-old female farmer who developed HGA with rash and rhabdomyolysis. The patient had fever and erythema covering the entire body, including the palms. An induration with an eschar was observed on the right leg, indicating that the patient had been bitten by a tick. Elevated serum creatinine and creatinine kinase levels and hematuria indicated rhabdomyolysis. We suspected Japanese spotted fever, a tick-borne illness caused by Rickettsia Japonica, and administered minocycline and ciprofloxacin for a week. Transient neutropenia and thrombocytopenia were observed, but the symptoms improved. Polymerase chain reaction (PCR) and antibody tests for R. japonica and Orientia tsutsugamushi, which causes scrub typhus, were both negative. The PCR test for severe fever with thrombocytopenia syndrome virus was also negative. Antibodies against A. phagocytophilum-related proteins were detected by western blotting, indicating seroconversion of IgG with paired serum samples, and the patient was diagnosed with HGA. HGA should be suspected in acute febrile patients with a history of outdoor activity and cytopenia, with or without a rash. A testing system and the accumulation of cases in Japan are necessary for the early diagnosis and appropriate treatment of HGA.

Changing trends in Japanese spotted fever epidemiology in Shimane, Japan: A two-decade retrospective study with emphasis on the COVID-19 pandemic era

INTRODUCTION

The objective of this study is to evaluate the epidemiological characteristics of Japanese Spotted Fever (JSF) cases reported through the National Epidemiological Surveillance of Infectious Disease (NESID) system in Shimane Prefecture, Japan, from 2000 to 2022, encompassing the periods before and during the COVID-19 pandemic period.

METHODS

A retrospective analysis was conducted on JSF cases reported to the NESID system in Shimane Prefecture between 2000 and 2022. Population data were obtained from the Statistical Information of Shimane. Poisson regression analysis was employed to examine the relationship between the annual prevalence rate of JSF and the COVID-19 pandemic.

RESULTS

A total of 301 JSF cases were analyzed during the study period. Even the pre-COVID-19 pandemic period, a gradual and significant increase in the prevalence rate was observed (prevalence rate = 1.03, 95% CI: 1.01-1.05; p = 0.01), and a rapid increase was noted since 2020 (prevalence rate = 1.57, 95% CI: 1.39-1.78; p < 0.01). The slope during the pre-COVID-19 pandemic period was estimated to have significantly increased (p < 0.01).

CONCLUSIONS

Our findings suggest that while the prevalence rate of JSF had exhibited a slight increase in the years preceding the COVID-19 pandemic, it demonstrated a more significant increase following the pandemic in Shimane Prefecture. JSF has increased since 2020 and may be linked to COVID-19 pandemic. The COVID-19 pandemic has had a substantial impact on global health, underscoring the importance of investigating the prevalence of specific infectious diseases and other health-related indicators to accurately assess the pandemic's impact.

Analysis of Differences in Characteristics of High-Risk Endemic Areas for Contracting Japanese Spotted Fever, Tsutsugamushi Disease, and Severe Fever With Thrombocytopenia Syndrome

Background

Tick-borne infections, including tsutsugamushi disease, Japanese spotted fever, and severe fever with thrombocytopenia syndrome (SFTS), are prevalent in East Asia with varying geographic distribution and seasonality. This study aimed to investigate the differences in the characteristics among endemic areas for contracting each infection.

Methods

We conducted an ecologic study in Japan, using data from a nationwide inpatient database and publicly available geospatial data. We identified 4493 patients who were hospitalized for tick-borne infections between July 2010 and March 2021. Mixed-effects modified Poisson regression analysis was used to identify factors associated with a higher risk of contracting each tick-borne disease (Tsutsugamushi, Japanese spotted fever, and SFTS).

Results

Mixed-effects modified Poisson regression analysis revealed that environmental factors, such as temperature, sunlight duration, elevation, precipitation, and vegetation, were associated with the risk of contracting these diseases. Tsutsugamushi disease was positively associated with higher temperatures, farms, and forests, whereas Japanese spotted fever and SFTS were positively associated with higher solar radiation and forests.

Conclusions

Our findings from this ecologic study indicate that different environmental factors play a significant role in the risk of transmission of tick-borne infections. Understanding the differences can aid in identifying high-risk areas and developing public health strategies for infection prevention. Further research is needed to address causal relationships.

Prompt diagnosis and appropriate treatment of Japanese spotted fever: A report of three cases

Background

Japanese Spotted Fever (JSF) is a Spotted Fever Group (SFG) rickettsiosis caused by Rickettsia japonica. More than 300 cases are diagnosed annually in Japan, and the number of reported cases has been increasing. Correct diagnoses depend on the triad of symptoms and signs, including fever, rash, and eschar, which can be seen at the site of vector bites. JSF is not life-threatening if treated appropriately without diagnostic delay but there are some fatal cases every year. This negligence leads to disseminated intravascular coagulation (DIC) and multiple organ failure (MOF), and poor prognoses, consequently. Prompt diagnosis of JSF is difficult when the aforementioned triad of signs and symptoms is not initially present.

Case report

This report describes three JSF cases: an 87-year-old woman with fever, shock, pancytopenia, DIC, and MOF; a 79-year-old man with fever and difficulty in movement; and a 78-year-old man with fever, general fatigue, and appetite loss. All patients had a rash and eschar, which led to prompt diagnosis and appropriate treatment immediately. All patients were treated without any complications.

Why should an emergency physician be aware of this?

As mentioned above, JFS can be fatal with delayed diagnoses and treatment initiations. The key for a prompt diagnosis is to recognize the triad of symptoms and signs, which are not often present initially, and it makes JSF diagnosis challenging. Repeated comprehensive physical examinations are essential for prompt diagnosis and improve prognosis of JSF.

Complicated Japanese Spotted Fever With Meningitis in an Older Patient: A Case Report

Japanese spotted fever (JSF) poses a significant public health challenge, mainly due to its atypical presentation in specific demographics. This report details a unique case of JSF in an 89-year-old female who was admitted to a rural hospital exhibiting generalized pain and rapid cognitive decline but no rash. Initially misdiagnosed as polymyalgia rheumatica, her condition was complicated by thrombocytopenia and altered mental state, prompting consideration of tick-borne illnesses. Subsequent serological analysis confirmed JSF despite the absence of its hallmark rash. The patient's condition escalated to include bacteremia and aseptic meningitis. Treatment involved a regimen of minocycline and meropenem, along with endoscopic cauterization of a bleeding rectal ulcer. After treatment, the patient showed improvement and was transferred for rehabilitation. This case highlights the criticality of considering JSF in elderly patients within endemic areas, even when classic symptoms like erythema and petechiae are absent. It underscores the necessity for broad diagnostic perspectives, especially in atypical presentations, and the integration of comprehensive care approaches. The involvement of caregivers and relatives in early detection and seeking medical care promptly is crucial. The report illustrates the complexities in diagnosing and managing advanced JSF cases and stresses the importance of early serological testing and adaptive treatment strategies in managing such challenging cases.

Clinical Characteristics and Diagnostic Prediction of Severe Fever with Thrombocytopenia Syndrome and Rickettsiosis in the Co-Endemic Wakayama Prefecture, Japan

Background and Objectives: The Wakayama prefecture is endemic for two types of tick-borne rickettsioses: Japanese spotted fever (JFS) and scrub typhus (ST). Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne hemorrhagic viral disease with a high mortality rate and is often difficult to differentiate from such rickettsioses. SFTS cases have recently increased in Wakayama prefecture. For early diagnosis, this study aimed to evaluate the clinical characterization of such tick-borne infections in the co-endemic area. Materials and Methods: The study included 64 febrile patients diagnosed with tick-borne infection in Wakayama prefecture between January 2013 and May 2022. Medical records of 19 patients with SFTS and 45 with rickettsiosis (JSF, n = 26; ST, n = 19) were retrospectively examined. The receiver operating curve (ROC) and area under the curve (AUC) were calculated to evaluate potential factors for differentiating SFTS from rickettsiosis. Results: Adults aged ≥70 years were most vulnerable to tick-borne infections (median, 75.5 years; interquartile range, 68.5-84 years). SFTS and rickettsiosis occurred mostly between summer and autumn. However, no significant between-group differences were found in age, sex, and comorbidities; 17 (89%) patients with SFTS, but none of those with rickettsiosis, experienced gastrointestinal symptoms such as vomiting, abdominal pain, and diarrhea. Meanwhile, 43 (96%) patients with rickettsiosis, but none of those with SFTS, developed a skin rash. The AUCs of white blood cells (0.97) and C-reactive protein (CRP) levels (0.98) were very high. Furthermore, the differential diagnosis of SFTS was significantly associated with the presence of gastrointestinal symptoms (AUC 0.95), the absence of a skin rash (AUC 0.98), leukopenia <3.7 × 109/L (AUC 0.95), and low CRP levels < 1.66 mg/dL (AUC 0.98) (p < 0.001 for each factor). Conclusions: Clinical characteristics and standard laboratory parameters can verify the early diagnosis of SFTS in areas where tick-borne infections are endemic.

Nonnegligible Seroprevalence and Predictors of Murine Typhus, Japan

To elucidate the epidemiology of murine typhus, which is infrequently reported in Japan, we conducted a cross-sectional study involving 2,382 residents of rickettsiosis-endemic areas in Honshu Island during August-November 2020. Rickettsia typhi seroprevalence rate was higher than that of Orientia tsutsugamushi, indicating that murine typhus is a neglected disease.

Trends in the Incidence of Japanese Spotted Fever in Japan: A Nationwide, Two-Decade Observational Study from 2001-2020

The worldwide spread of tick-borne diseases (TBDs) has become a public health concern. Therefore, this study aimed to clarify trends in the incidence of Japanese spotted fever (JSF), one of Japan's most prevalent TBDs. Weekly infectious disease reports were used to calculate the annual incidence rates (AIRs) of JSF. Data were stratified by age and sex, and joinpoint regression analysis was performed to estimate the annual percentage change (APC). AIR and APC were geographically compared among the 47 prefectures. A total of 3,453 JSF cases were observed from 2001 to 2020. The AIR per 100,000 population was 0.03 in 2001, which increased approximately 10-fold to 0.33 in 2020. The average APC (AAPC) during the study period was 12.3% (95% CI: 10.7-13.9). By age group, the incidence of JSF increased more rapidly among the older population: 11.5% (95% CI: 10.1-12.9) in those aged ≥ 65 years and 8.9% (95% CI: 6.4-11.5) in those aged < 50 years. Although the AIR over the past two decades was higher in climatically warm regions located in southwestern Japan and on the Pacific coast, increases in the AAPC were notable in colder regions located in eastern Japan. The incidence of JSF continues to increase in Japan, especially among older populations and in eastern prefectures, where the disease has not been previously diagnosed.

Japanese spotted fever with post-infectious encephalitis

Japanese spotted fever (JSF) is a rickettsial disease caused by Rickettsia japonica. To the best of our knowledge, there have only been five reported cases of JSF involving the central nervous system. A 74-year-old man was admitted after 1 week of fever and maculopapular rash. JSF was definitively diagnosed by PCR; however, the patient showed mental disturbance and abnormal behavior. After intravenous immunoglobulin, his mental state and behavior improved. The findings of cerebrospinal fluid analysis, electroencephalography, and ^99 mTcHM-PAO single photon computed emission tomography suggested post-infectious encephalitis. JSF causes post-infectious encephalitis and early treatment is recommended.

Clinical Differentiation of Severe Fever with Thrombocytopenia Syndrome from Japanese Spotted Fever

Severe fever with thrombocytopenia syndrome (SFTS) and Japanese spotted fever (JSF; a spotted fever group rickettsiosis) are tick-borne zoonoses that are becoming a significant public health threat in Japan and East Asia. Strategies for treatment and infection control differ between the two; therefore, initial differential diagnosis is important. We aimed to compare the clinical characteristics of SFTS and JSF based on symptomology, physical examination, laboratory data, and radiography findings at admission. This retrospective study included patients with SFTS and JSF treated at five hospitals in Nagasaki Prefecture, western Japan, between 2013 and 2020. Data from 23 patients with SFTS and 38 patients with JSF were examined for differentiating factors and were divided by 7:3 into a training cohort and a validation cohort. Decision tree analysis revealed leukopenia (white blood cell [WBC] < 4000/μL) and altered mental status as the best differentiating factors (AUC 1.000) with 100% sensitivity and 100% specificity. Using only physical examination factors, absence of skin rash and altered mental status resulted in the best differentiating factors with AUC 0.871, 71.4% sensitivity, and 90.0% specificity. When treating patients with suspected tick-borne infection, WBC < 4000/µL, absence of skin rash, and altered mental status are very useful to differentiate SFTS from JSF.

Effectiveness of fluoroquinolone antimicrobials in addition to tetracyclines for Japanese spotted fever: A retrospective analysis using a national inpatient database

OBJECTIVES

This study aim to evaluate the effectiveness of fluoroquinolone (FQ) antimicrobial therapy in combination with tetracyclines (TCs) in patients with Japanese spotted fever (JSF) using a nationwide inpatient database in Japan.

METHODS

We identified hospitalized patients diagnosed with JSF who were enrolled in the Japanese Diagnosis Procedure Combination inpatient database from July 2010 to March 2021. Patients who received FQ plus TC on the day of admission were compared with patients who received TC alone on the day of admission, using inverse probability of treatment weighting. The primary outcome was in-hospital mortality. Secondary outcomes were in-hospital complications, total hospitalization costs, and length of hospital stay.

RESULTS

We identified 1060 eligible patients. Of these, 434 (41%) received FQ plus TC on the day of admission and 626 (59%) received TC alone on the day of admission. Inverse probability of treatment weighting showed no statistically significant differences between the groups in in-hospital mortality, in-hospital complications, total hospitalization costs, and length of hospital stay.

CONCLUSION

This study did not show any significantly improved effectiveness using FQ antimicrobials in combination with TCs for treating JSF. Clinicians may need to be cautious in administering FQ and TC antimicrobials concomitantly in routine practice.

The clinical course of 239 cases of Japanese spotted fever in Ise Red Cross Hospital, 2006-2019

INTRODUCTION

Although the mortality rates associated with Japanese spotted fever (JSF) are unknown, advances in testing technology have led to an increase in JSF-induced mortality reported in clinical practice. Up-to-date clinical information is essential for accurate diagnosis and prompt treatment of JSF.

METHODS

This retrospective descriptive study included patients with JSF who were treated at the Ise Red Cross Hospital between 2006 and 2019. Diagnostic criteria included positive results of molecular-based tests during the acute phase and/or increased serum-specific antibody titers. This study was performed based on the clinical findings, clinical course, treatment, and prognosis in confirmed cases of JSF.

RESULTS

We investigated 239 patients with a confirmed diagnosis of JSF (48.1% men, mean age 69.2 years). Notably, 237 patients received tetracycline antibiotics, and eight patients died (one patient was misdiagnosed and died without adequate treatment). Four of the remaining patients had a multi-organ failure at the time of admission. However, among the 155 consecutive patients who received effective antibiotic therapy after 2012, we observed two deaths; one patient died of hemorrhage secondary to non-steroidal anti-inflammatory drug-induced duodenal ulcer.

CONCLUSIONS

Our study showed a case fatality rate of 3.3%, which indicates that JSF is a severe illness. Although a few cases of the fulminant disease are reported, early initiation of therapy was shown to improve JSF-induced mortality by approximately 1%. Prompt initiation of antibiotic therapy (even in the absence of genetic test results) is warranted in cases of suspected JSF.

Clinical characteristics of and antibody response to spotted fever group rickettsial infections in South India: Case series and serological cohort study

OBJECTIVE

The clinical and serological characteristics of spotted fever group rickettsial (SFGR) infections in South Asia are poorly understood. We studied the clinical presentation and the IgM/IgG response in cases enrolled at two health care centres in South India.

METHOD

We enrolled 77 patients. Fifty-seven of these patients were recruited at a tertiary care centre, the remaining 20 at a community hospital (secondary care level). Diagnostic tests included IgM and IgG enzyme-linked immunosorbent assay and polymerase chain reaction. Over a period of 1 year, 41 cases were followed up for repeated sero-analysis.

RESULTS

Median age was 9 years (range 1-79). A rash was present in 74% of cases (57/77). In cases aged <15 years, rash was present in 94% (44/47) vs. 43% (13/30) in cases aged ≥15 years. An eschar was found in two cases (3%). Severe infection or complications occurred in 10 cases (13%). These included central nervous system infection (6/77, 8%), kidney injury (3/77, 4%), shock (3/77, 4%), lung involvement (2/77, 3%) and peripheral gangrene (2/77, 3%). IgM antibody levels increased faster after fever onset than IgG antibodies, peaking at 50 and 60 days, respectively. After the peak, IgM and IgG levels showed a slow decline over one year with less than 50% of cases showing persistent IgG antibody levels.

CONCLUSION

Spotted fever group rickettsial infections in South India may be under-diagnosed, as many cases may not develop a rash. The proportion of cases developing severe infection seems lower than for scrub typhus in this region. IgG seroprevalence may substantially underestimate the proportion in a population with past SFGR infection.

Misdiagnosis of scrub typhus as hemorrhagic fever with renal syndrome and potential co-infection of both diseases in patients in Shandong Province, China, 2013-2014

Background

Scrub typhus, caused by Orientia tsutsugamushi, an obligate intracellular gram-negative bacterium, along with hemorrhagic fever with renal syndrome (HFRS), caused by hantaviruses, are natural-focus infectious diseases prevalent in Shandong Province, China. Both diseases have similar clinical manifestations in certain disease stages and similar epidemic seasons, which has caused difficulties for physicians in distinguishing them. The aim of this study was to investigate whether misdiagnosis of scrub typhus as HFRS occurred in patients in Shandong Province.

Methods

Serum samples (N = 112) of clinically suspected HFRS patients from 2013 to 2014 in Shandong Province were analyzed with enzyme-linked immunosorbent assay (ELISA) for antibodies to both hantavirus and Orientia tsutsugamushi.

Results

ELISA showed that 56.3% (63/112) and 8.0% (9/112) of clinically suspected HFRS patients were IgM antibody positive to hantavirus and O. tsutsugamushi, respectively. Among the hantavirus IgM antibody positive patients, 7.9% (5/63) were also IgM antibody positive to O. tsutsugamushi. Among the hantavirus IgM antibody negative sera, 8.2% (4/49) of sera were positive to O. tsutsugamushi.

Conclusions

We concluded that some scrub typhus patients were misdiagnosed as HFRS and co-infection of scrub typhus and HFRS might exist in China. Due to the different treatments for scrub typhus and HFRS, physicians should carefully differentiate between scrub typhus and HFRS and consider administering anti-rickettsia antibiotics if treatment for HFRS alone does not work.

Scrub typhus is caused by O. tsutsugamushi and hemorrhagic fever with renal syndrome (HFRS) is caused by hantavirus. Both diseases have similar manifestations and have their peak epidemic season in the fall, which makes their clinical differentiation difficult to be differentiated from each other clinically. In this study, we found that scrub typhus was indeed misdiagnosed as HFRS and co-infection of O. tsutsugamushi and hantaviruses might exist in China. Owing to different treatments of HFRS and scrub typhus, physicians need pay attention to differentiate them; identify co-infection of HFRS and scrub typhus; and consider administering antibiotics if antiviral treatment alone does not work.

Descriptive epidemiology of rickettsial infections in Japan: Scrub typhus and Japanese spotted fever, 2007-2016

OBJECTIVE

This study aimed to describe the epidemiological and clinical characteristics of endemics of two rickettsial diseases, scrub typhus (ST) and Japanese spotted fever (JSF), in Japan.

METHODS

We conducted a retrospective, descriptive epidemiological assessment of cases notified via national surveillance from 2007-2016.

RESULTS

Over the 10-year period, 4185 ST and 1765 JSF cases were notified; of these, 20 (0.48%) cases of ST and 16 (0.91%) cases of JSF were fatal at the time of reporting. The elderly had higher notification rates and fatalities. While the annual number of ST notifications was stable and cases were reported from a broad geographic range, the number of JSF reports increased three-fold, expanding from the southwest to the east. The seasonality of ST varied by region and was more common during spring/summer in the north and autumn/winter in the south; 78% of cases occurred during autumn/winter, mainly in the southern region. Most of the fatal ST cases occurred in the spring/summer and occurred in the northern region.

CONCLUSION

Our analysis identified seasonal and regional variations in the distribution of rickettsiosis. These variations were most likely to be related to the ecology of the vectors and etiological agents. Knowing the recent epidemiological and clinical features of ST and JSF can support clinical diagnosis and guide preventative activities against these vector-borne diseases.

Scrub typhus mimicking the clinical course of infectious mononucleosis: a case report

Objective: Scrub typhus is a relatively common life-threating disease; its symptoms are non-specific and similar to those of other viral infections. Therefore, scrub typhus might be underdiagnosed.

Patient: Herein, we report a patient with scrub typhus whose clinical course mimicked that of infectious mononucleosis. A 63-year-old male patient with hypertension presented to our hospital complaining of symptoms including prolonged fever, pharyngeal discomfort, and a mild headache. He showed the appearance of a rash after amoxicillin administration. At the same time, he did not show a crusted rash on his body surface.

Results: After a comprehensive examination, Epstein-Barr virus and cytomegalovirus infections were ruled out. We suspected that this patient suffered from scrub typhus on the basis of his usual lifestyle. Finally, polymerase chain reaction analysis showed a positive result for deoxyribonucleic acid of Orientia tsutsugamushi in his blood sample. Fortunately, he recovered naturally with only supportive treatment during his hospitalization.

Conclusion: We should observe and monitor patients with infectious mononucleosis-like symptoms and emphasize the importance of a clinical interview.

Impact of C-Reactive Protein Levels on Differentiating of Severe Fever With Thrombocytopenia Syndrome From Japanese Spotted Fever

Background

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging viral hemorrhagic fever in China, Korea, and Japan. Japanese spotted fever (JSF), which belongs to spotted fever group rickettsioses, is also endemic to Western Japan. Patients with SFTS and those with JSF display many of the same clinical manifestations. Sudden fever, rash, tick bite, and neurological and gastrointestinal symptoms may be seen in both infections, but the frequency and severity of each disease have not been compared and studied. Because laboratory confirmation of pathogens takes time, it is important to predict diagnosis of SFTS vs JSF based on the features of the clinical characteristics at the initial presentation, particularly in primary care settings.

Methods

We conducted a case series review at 4 medical facilities in Miyazaki, Japan. Based on the medical records, clinical and laboratory characteristics were compared between patients with SFTS and those with JSF.

Results

Eighty-one patients were enrolled in this study, including 41 with SFTS and 40 with JSF. The absence of rash (P < .001), leukopenia (P < .001), and normal C-reactive protein (CRP) levels (P < .001) were the variables distinguishing SFTS from JSF. Normal CRP levels (≤1.0 mg/dL) had a 95% sensitivity (84%–99%) and 97% specificity (87%–100%) for SFTS, with a positive likelihood ratio of 37.1 (5.35–257).

Conclusions

Normal serum CRP levels were shown to differentiate SFTS from JSF with a very high probability.

Associations between Japanese spotted fever (JSF) cases and wildlife distribution on the Boso Peninsula, Central Japan (2006-2017)

Populations of large mammals have been dramatically increasing in Japan, resulting in damage to agriculture, forestry, and ecosystems. However, their effects on tick-borne diseases have been poorly studied. Here, we focused on the relationship between Japanese spotted fever (JSF), a tick-borne disease caused by Rickettsia japonica, and populations of large mammals. To explore factors that affected the area in which JSF cases occur, we used generalized linear mixed models (GLMMs). We demonstrated that the expansion of the area of JSF occurrence can be predicted by deer density and geographical factors, which is likely due to differences in landscape structure. However, the associated models have limitations because of the lack of information about the distribution of vectors and reservoirs. To reduce the risk of humans contracting JSF, potential reservoirs should be confirmed.

Predictive variables for hemodialysis and death in Japanese spotted fever, and the association between distance from rivers and incidence

The number of patients with Japanese spotted fever (JSF) and its case fatality rate have been increasing in Japan and other East Asian countries. Better clinical and laboratory biomarkers are needed to avoid misdiagnosing JSF and to predict severe cases. In addition to determining these predictors, we aimed to examine the association between the incidence of JSF and the distance from rivers, in Hiroshima Prefecture, one of the most JSF prevalent areas in Japan. Patients diagnosed with JSF from 2009 to 2017 in two hospitals in Onomichi City in Hiroshima Prefecture were studied, and their clinical characteristics and laboratory data were collected retrospectively from medical charts. A random forest was used to identify predictors of severe JSF leading to hemodialysis or death. A multivariable negative binomial regression model was utilized to analyze the association between the cumulative incidence in each postal code area and the distance from the residential postal code area to the closest river. Out of 82 patients with JSF (mean age at diagnosis, 74.1 ± 10.6 years; 34 (41.5 %) men), 6 cases were regarded as severe (among them 5 hemodialysis patients and 3 deaths). Twenty-eight (34.1 %) patients were misdiagnosed at least once at the initial hospital visit. Laboratory examination showed 34.5 % had atypical lymphocytes, 73.8 % had no eosinophils, 75.6 % had an elevated aspartate aminotransferase (AST) level, and 69.5 % had hyponatremia. Among cases without urine leucocytes, 63.3 % had proteinuria and 63.3 % had hematuria. Low serum total protein was the strongest predictor of severe JSF, followed by high blood urea nitrogen (BUN) and low albumin. Geospatial analysis showed a significant negative association between the cumulative incidence of JSF cases and the distance from rivers in an adjusted model: the cumulative incidence decreased by 0.51 times (95 % CI: 0.30 to 0.86) for every kilometer of distance from the residential postal code area to the closest river. Some laboratory data may be useful in averting misdiagnosis of JSF and in predicting severe cases. Additional studies should be done in order to clarify the mechanism and association of the incidence of JSF with the distance from the nearest river.

Effects of introduced sika deer (Cervus nippon) and population control activity on the distribution of Haemaphysalis ticks in an island environment

The effects of introduced mammal species on the ecology of parasites are often under investigated. The sika deeer, Cervus nippon, is host species of many hard ticks. We collected 8348 ticks on an island where sika deer were introduced. The most representative species was Haemaphysalis megaspinosa (n = 4198; 50.3%), followed by H. longicornis (n = 1945; 23.3%), H. cornigera (n = 1179; 14.1%), H. flava (n = 713; 8.5%), Ixodes turdus (n = 289; 3.7%), I. granulatus (n = 22; 0.3%), and H. hystricis (n = 2; <0.1%) on an island where sika deer were introduced. H. megaspinosa and H. hystricis have not previously been recorded on the Izu islands. The high abundance of H. megaspinosa indicated that the tick species may have been introduced with the sika deer. Furthermore, H. megaspinosa larvae were more abundant at collection sites 21-40 days after sika deer were caught by foot snare traps indicate that engorged female of this tick species were forced to drop off in a very limited area near the foot snare trap. This represented a risk for hunters and people associated with wildlife control visiting the area.

Japanese Spotted Fever with Hemophagocytic Lymphohistiocytosis

Japanese spotted fever (JSF) is an uncommon but potentially fatal infection transmitted by tick bites. We herein report a fulminant case of JSF infection that occurred in an immunocompetent adult that was complicated by disseminated intravascular coagulation and hemophagocytic lymphohistiocytosis (HLH). We discuss the difficulty in making the diagnosis and identifying the complication of HLH in our patient. HLH is a rare complication of rickettsiosis, and this is the first reported case in English of JSF complicated by HLH in an immunocompetent adult. Secondary HLH caused by rickettsiosis requires a different treatment from primary HLH. Rickettsiosis must therefore be considered in patients with HLH.

Rickettsia japonica Infection after Land Leech Bite, Japan

We report a case of Rickettsia japonica infection in an 81-year-old man in central Japan. The patient had fever, rash, and an eschar but no evidence of a tick bite. His symptoms began 8 days after a land leech bite. The land leech is a potential vector of R. japonica.

Spatial epidemiological determinants of severe fever with thrombocytopenia syndrome in Miyazaki, Japan: a GWLR modeling study

Background

Cases of severe fever with thrombocytopenia syndrome (SFTS) have increasingly been observed in Miyazaki, southwest Japan. It is critical to identify and elucidate the risk factors of infection at community level. In the present study, we aimed to identify areas with a high risk of SFTS virus infection using a geospatial dataset of SFTS cases in Miyazaki.

Methods

Using 10 × 10-km mesh data and a geographically weighted logistic regression (GWLR) model, we examined the statistical associations between environmental variables and spatial variation in the risk of SFTS. We collected geospatial and population census data as well as forest and agriculture mesh information. Altitude and farmland were selected as two specific variables for predicting the presence of SFTS cases in a given mesh area.

Results

Using GWLR, the area under the receiver operating characteristic curve (AUC) was estimated at 73.9%, outperforming the classical logistic regression model (72.4%). The sensitivity and specificity of the GWLR model were estimated at 90.9 and 58.7%, respectively. We identified altitude (odds ratio (OR) = 0.996, 95% confidence interval (CI): 0.994–0.999 per one-meter elevation) and farmland (OR = 0.999, 95% CI: 0.998–1.000 per % increase) as useful negative predictors of SFTS cases in Miyazaki.

Conclusions

Our study findings revealed that the risk of SFTS is high in geographic areas where farmland area begins to diminish and at mid-level altitudes. Our findings can help to improve the efficiency of ecological and animal surveillance in high-risk areas. Using finer geographic resolution, such surveillance can help raise awareness among local residents in areas with a high risk of SFTS.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4111-3) contains supplementary material, which is available to authorized users.