Epidemiological characteristics of tick-borne infectious diseases in Hubei Province, 2016-2021 / 中华流行病学杂志

Objective: To understand the epidemiological characteristics of tick-borne infectious diseases (TBID) and the risk factors of severe illness and death in Hubei Province from 2016 to 2021. Methods: Based on the incidence data of fever with thrombocytopenia syndrome (SFTS), tsutsugamushi disease, typhus and other TBID reported during 2016-2021, the epidemiological analysis was conducted. Field investigation results of TBID in areas with high incidence in 2021, logistic regression analysis of population characteristics, epidemiological history and other factors were used to explore the risk factors of severe and fatal cases. In the field vector investigation, free ticks and surface ticks of the host animals in the cases' home and surrounding grassland were monitored and detected. Results: A total of 3 826 TBID cases were reported in Hubei from 2016 to 2021, of which 71.30% (2 728/3 826) were SFTS, 13.04% (499/3 826) were tsutsugamushi disease and 15.66% (599/3 826) were typhus. A total of 44 cases died in 6 years; the fatality rate was 1.15% (44/3 826). In the peak seasons of incidence from May to July, the cases in people engaged in agriculture related work accounted for 84.61% (3 237/3 826). The incidence rate in women was higher than that in men, and the cases aged ≥50 years accounted for 81.02% of the total (3 100/3 826), and the incidence rate increased with age (P<0.001). The TBID cases were distributed in 86 counties and districts in 16 prefectures (municipality). The incidence rates of different areas had significant differences (P<0.05), and there was a certain spatial-temporal clustering and expasion. Bovis microplus and Haemaphysalis longicornis were captured in the field, and the positive rates in host animals and grassland ticks were 10.94% (7/64) and 40.00% (2/5), respectively. Univariate logistic regression analysis results showed that age ≥50 years and leukocyte <2.0×109/L were risk factors for severe illness and death. Conclusions: The TBID reported in Hubei were mainly SFTS, tsutsugamushi disease and typhus. In order to reduce the incidence of TBID, it is necessary to strengthen the prevention and control in women aged ≥50 years and reduce field exposure and tick bites during the epidemic period.

Epidemiological characteristics of typhus in China, 1950-2021 / 中华流行病学杂志

Objective: To analyze the epidemiological characteristics of typhus in China from 1950 to 2021, and discuss the challenges in typhus prevention and control in China and suggest future prevention and control strategies. Methods: Based on the reported data of typhus from 1950 to 2021 in China from the Infectious Disease History Database of China Public Health Science Data Center and the National Notifiable Infectious Disease Reporting Information System of Chinese Center for Disease Control and Prevention, we conducted a descriptive statistical analysis. Mann-Kendall test and circular distribution method were used to analyze the incidence, mortality and case fatality of typhus to reveal the temporal, spatial and population distributions and diagnosis of typhus in China. Results: From 1950 to 2021, a total of 452 965 typhus cases and 7 339 typhus deaths were reported in China, with the cases numbers exceeding 10 000 in 14 years of the 1950s, 1960s and 1980s, respectively. Since 1990s, the reported cases and incidence rate of typhus have decreased dramatically and the most cases were sporadic. However, the reported typhus cases in Anhui, Hubei, Hunan Provinces showed significant uptrends. Although typhus could occur all the year round, but the seasonality was observed with the incidence mainly in summer and autumn. For different provinces from the north to the south, the peaks of typhus' monthly incidence tended to shift to earlier dates. The male to female ratio of the cases was 1.01∶1 (18 529∶18 366). However, more cases occurred in women in recent years. The cases aged ≤9 years accounted for the highest proportion (18.9%), but the number of cases aged ≥50 years showed an upward trend. Most cases were farmers with the proportion increasing year by year. Moreover, the cases in students and scattered-living children also accounted for relatively higher proportions. The median of the interval between onset and diagnosis of typhus was 6 days. Most cases were clinically diagnosed, while the proportion of laboratory-confirmed cases was low and most laboratory cases were confirmed by Well-Felix reaction. Conclusions: Although the incidence and mortality of typhus in China has decreased significantly, the risk for local typhus outbreaks still exists. The prevention and control of typhus still face many challenges. It is indispensable to strengthen the pathogen detection and surveillance for typhus in China.

Correlation between rainfall and the prevalence of scrub typhus: an observation from a tropical endemic country / Correlación entre las precipitaciones y la prevalencia del tifus de matorral: una observación de un país endémico para enfermedades tropicales

The effect of climatological parameter on infectious disease is an interesting issue in clinical epidemiology. Of several parameters, rainfall is reported for its interrelationship with many tropical diseases such as malaria. In this short communication, the authors report the observation on correlation between rainfall and the prevalence of scrub typhus from a tropical endemic country.

El efecto del parámetro climatológico en las enfermedades infecciosas es un tema interesante en la epidemiología clínica. De varios parámetros, se reportan precipitaciones por su interrelación con muchas enfermedades tropicales como el paludismo. En esta breve comunicación, los autores informan de la observación sobre la correlación entre las precipitaciones y la prevalencia del tifus de matorral de un país endémico tropical.

Neuropathic Pain in Guillain-Barre Syndrome Associated with Scrub Typhus

Guillain-Barre syndrome (GBS) is usually characterized by acute areflexic ascending paralysis with minimal sensory involvement. Only a few cases of GBS associated with scrub typhus have been reported. Previous case reports focused on the laboratory findings, pathogenesis, and clinical manifestation. Unlike the previous case, neuropathic pain was a prominent symptom of GBS in our case. We report scrub-typhus-related GBS with a detailed description of the clinical manifestations, especially neuropathic pain, along with results of serial follow-up electrodiagnostic studies.

Annual Fluctuation in Chigger Mite Populations and Orientia Tsutsugamushi Infections in Scrub Typhus Endemic Regions of South Korea

OBJECTIVES: Chigger mites are vectors for scrub typhus. This study evaluated the annual fluctuations in chigger mite populations and Orientia tsutsugamushi infections in South Korea.METHODS: During 2006 and 2007, chigger mites were collected monthly from wild rodents in 4 scrub typhus endemic regions of South Korea. The chigger mites were classified based on morphological characteristics, and analyzed using nested PCR for the detection of Orientia tsutsugamushi.RESULTS: During the surveillance period, the overall trapping rate for wild rodents was 10.8%. In total, 17,457 chigger mites (representing 5 genera and 15 species) were collected, and the average chigger index (representing the number of chigger mites per rodent), was 31.7. The monthly chigger index was consistently high (> 30) in Spring (March to April) and Autumn (October to November). The mite species included Leptotrombidium pallidum (43.5%), L. orientale (18.9%), L. scutellare (18.1%), L. palpale (10.6%), and L. zetum (3.6%). L. scutellare and L. palpale populations, were relatively higher in Autumn. Monthly O. tsutsugamushi infection rates in wild rodents (average: 4.8%) and chigger mites (average: 0.7%) peaked in Spring and Autumn.CONCLUSION: The findings demonstrated a bimodal pattern of the incidence of O. tsutsugamushi infections. Higher infection rates were observed in both wild rodents and chigger mites, in Spring and Autumn. However, this did not reflect the unimodal incidence of scrub typhus in Autumn. Further studies are needed to identify factors, such as human behavior and harvesting in Autumn that may explain this discordance.

Co-Infection of Scrub Typhus and Human Granulocytic Anaplasmosis in Korea, 2006

BACKGROUND: Scrub typhus, severe fever with thrombocytopenia syndrome (SFTS) and human granulocytic anaplasmosis (HGA) are important arthropod-borne infectious diseases in Korea and share a common point that they are transmitted by arthropod bites mostly during outdoor activities and there are considerable overlaps of epidemiologic and clinical features at presentation. We investigated the co-infection of these infections. METHODS: The study subjects were patients with laboratory-confirmed scrub typhus who were enrolled retrospectively in 2006. SFTS virus (SFTSV) infection was confirmed by a reverse transcriptase polymerase chain reaction (PCR) to amplify partial L segment of SFTSV for molecular diagnosis. HGA was confirmed by a nested PCR to amplify 16S rRNA gene of Anaplasma phagocytophilum. Direct sequencing of the positive PCR products was performed. Clinical features of co-infected subjects were described. RESULTS: One-hundred sixty-seven patients with scrub typhus were included in the analysis. Co-infection of A. phagocytophilum was identified in 4.2% of scrub typhus patients (7/167). The route of co-infection was uncertain. The co-infected patients had not different clinical manifestations compared to the patients with scrub typhus only. All the study subjects were negative for SFTSV. CONCLUSION: We found retrospective molecular evidence of the co-infection of scrub typhus and HGA in Korea. HGA may be more prevalent than expected and need to be considered as an important differential diagnosis of febrile patients in Korea.

Recent Increase of Human Granulocytic Anaplasmosis and Co-Infection with Scrub Typhus or Korean Hemorrhagic Fever with Renal Syndrome in Korea

We report 17 patients with human granulocytic anaplasmosis between January 2015 and September 2018 at two tertiary university hospitals in Korea. Monthly incidence peaked in May and June. Among these patients, we identified three who were co-infected with scrub typhus, and one patient with hemorrhagic fever with renal syndrome.

A Study on the Febrile Illness in Autumn among Farmers in Gyeongju-si: Scrub typhus, Leptospirosis, HFRS / 農村醫學 地域保健

OBJECTIVES: This study aimed to assess the status of Scrub typhus, Leptospirosis and HFRS(hemorrhagic fever with renal syndrome) among farmers with febrile illness. METHODS: We involved a total of 841 farmers who had febrile illness(508 and 333 village residents were, respectively, three and four district of Gyeongju city) selected during autumn of 2014 and 2015. Data were collected by survey questionnaires and blood sample examination. RESULTS: Serum response rate for Scrub typhus and Leptospirosis was 1.5% each and 1.9% for HFRS. Serum response rate for Scrub typhus was significantly higher for tick-bite cases(38.5%), while Leptospirosis was significantly higher for those who were in fruit–planting work(23.1%). Similarly, serum response rate was significantly higher for HFRS who were working in venyl green house work(25.0%). CONCLUSIONS: Government authority should develop effective and efficient preventive strategies to create awareness of infectious diseases among farmers. Extending information, education and communication be reached to farmers that could change their perception and help early diagnosis and treatment and reduce the disease burden and its complication.

Survey of Rickettsia spp. and Orientia tsutsugamushi Pathogens Found in Animal Vectors (Ticks, Fleas, Chiggers) in Bangkaew District, Phatthalung Province, Thailand

Rickettsial infections (Rickettsioses) are the causes of acute fever found in Thailand. It is classified as acute febrile illnesses transmitted by bloodsucking arthropod vectors (tick, flea, and chigger). This research investigated pathogens of scrub typhus in vectors from Bangkaew District, Phatthalung Province. A total of 303 pools of vector samples were ticks (Rhipicephalus sanguineus, R. microplus, and Haemaphysalis sp.), fleas (Ctenocephalides felis orientis, C. f. felis, and C. canis), and chiggers (Leptotrombidium deliense, Aschoschoengastia indica, Blankaartia acuscutellaris and Walchia disparunguis pingue) collected from reservoir hosts (dogs and rodents). The 17 and 56 kDa gene of Rickettsia causing scrub typhus were found in 29% of ticks and 98% of flea. DNA sequence analysis reveeled the detected strains were R. asembonensis and Rickettsia sp. cf1 and 5.The chiggers, 1%, were infected with Rickettsia strain TA763, a pathogen of scrub typhus.

Ecthyma gangrenosum and agranulocytosis in a previously healthy 12-month-old girl: Report of 1 case with a literature review

Ecthyma gangrenosum (EG) is a rare skin manifestation which starts with a maculopapular eruption and followed by a necrotic ulcer covered with black eschar. EG usually occurs in immunosuppressed patients with Pseudomonas aeruginosa sepsis. We present a previously healthy 12-month-old girl with EG by P. aeruginosa and agranulocytosis due to influenza A and then rhinovirus infection, without bacteremia. It is important for allergists to culture wound and differentiate EG from other skin disorders including Tsutsugamushi disease and initiate appropriate empiric antipseudomonal antibiotic treatment, and to evaluate for possible immunodeficiency, even in a healthy child.

The Most Common Mite- and Tick-borne Infectious Diseases in Korea: Scrub Typhus and Severe Fever Thrombocytopenia Syndrome / 대한내과학회지

The incidence of mite- and tick-borne infectious disease is increasing with climate change and the development of diagnostic tools. Tick-borne infectious diseases include Lyme disease, anaplasmosis, ehrlichiosis, severe fever with thrombocytopenia syndrome (SFTS), and Japanese spotted fever. Rickettsial pox and scrub typhus are mite-borne infectious diseases. Scrub typhus and SFTS are the most common mite- and tick-borne infectious diseases in Korea, respectively. They are often difficult to diagnose at an early stage of disease. To make a definite diagnosis of mite- and tick-borne infectious disease, polymerase chain reaction (PCR) tests or serologic testing for antibodies during the acute and convalescent periods are necessary. If patients with nonspecific symptoms, such as fever, headache, nausea, and vomiting, have a history of outdoor activity or a tick bite, it is reasonable to consider the possibility of mite- or tick-borne infectious diseases clinically. There are no vaccinations against mite- and tick-borne infectious diseases. Therefore, preventing mite or tick bites is the best way to prevent the diseases.

A Case of Scrub Typhus complicated with a Splenic Infarction

We present a patient with scrub typhus complicated with a splenic infarction. A 40-year-old man visited the emergency medical center complaining of fever for the previous week. He had no past medical history, but reported engaging in outdoor activities. Examination revealed a maculopapular rash on his trunk and an eschar on his epigastrium. Abdominal computed tomography was performed to examine the cause of the tenderness on the left upper quadrant of his abdomen, which revealed a splenic infarct. The patient was diagnosed with scrub typhus based on the results of blood polymerase chain reaction testing, and genetic sequencing confirmed the presence of Orientia tsutsugamushi Boryong. His symptoms improved following doxycycline treatment.

A Case of Scrub Typhus complicated with a Splenic Infarction

We present a patient with scrub typhus complicated with a splenic infarction. A 40-year-old man visited the emergency medical center complaining of fever for the previous week. He had no past medical history, but reported engaging in outdoor activities. Examination revealed a maculopapular rash on his trunk and an eschar on his epigastrium. Abdominal computed tomography was performed to examine the cause of the tenderness on the left upper quadrant of his abdomen, which revealed a splenic infarct. The patient was diagnosed with scrub typhus based on the results of blood polymerase chain reaction testing, and genetic sequencing confirmed the presence of Orientia tsutsugamushi Boryong. His symptoms improved following doxycycline treatment.

Tifus de los matorrales, una enfermedad emergente en Chile / Scrub typhus, an emerging infectious disease in Chile

Resumen El tifus de los matorrales, causado por Orientia tsutsugamushi y transmitido por larvas de ácaros trombicúlideos de roedores silvestres es una rickettsiosis endémica en el Asia Pacífico. Luego del primer caso identificado en Chile en el año 2006, nuestro grupo ha identificado más de 30 casos a partir del año 2015. Los casos se han presentado con un marcado predominio en meses de verano, y su presentación clínica incluye fiebre, exantema y una mancha negra en el sitio de inoculación. Otros hallazgos frecuentes han sido cefalea intensa, sudoración nocturna, aumento de PCR, VHS y transaminasas hepáticas. La gran mayoría de los pacientes se han diagnosticado en el sur de Chile (principalmente la isla de Chiloé), pero recientemente también se han presentado casos en la Región Metropolitana, en personas volviendo de viajes al sur de Chile. Los médicos clínicos deben estar informados de esta enfermedad emergente en el país, de modo de sospecharla e iniciar terapia empírica con doxiciclina. La confirmación de estos casos con los métodos diagnósticos disponibles en Chile contribuirá a una mejor comprensión del rango epidemiológico y la relevancia clínica de esta infección nueva en el país.

Scrub typhus, caused by Orientia tsutsugamushi and transmitted by larvae of trombiculid mites, is an endemic rickettsiosis in the Asia Pacific region. After the first identification of a case in Chile in 2006, more than 30 cases have been diagnosed by our group since 2015. Cases were detected predominantly during the Chilean summer months. Patients presented with fever, rash, and a typical eschar at the inoculation site; other frequent findings were intense headache, night sweats, increased laboratory markers of inflammation and transaminases. The vast majority of cases have been diagnosed in southern Chile (mainly Chiloé Island), although recently some cases were also identified in the central Metropolitan Region in patients returning from trips to southern Chile. Physicians attending Chilean patients should be aware of this emerging infection to be able to initiate empirical therapy with doxycycline. The confirmation of cases by the diagnostic methods available in Chile will contribute to a better understanding of the epidemiological and clinical relevance of this emerging infection in South America.

Mathematical Modeling for Scrub Typhus and Its Implications for Disease Control

BACKGROUND: The incidence rate of scrub typhus has been increasing in the Republic of Korea. Previous studies have suggested that this trend may have resulted from the effects of climate change on the transmission dynamics among vectors and hosts, but a clear explanation of the process is still lacking. In this study, we applied mathematical models to explore the potential factors that influence the epidemiology of tsutsugamushi disease. METHODS: We developed mathematical models of ordinary differential equations including human, rodent and mite groups. Two models, including simple and complex models, were developed, and all parameters employed in the models were adopted from previous articles that represent epidemiological situations in the Republic of Korea. RESULTS: The simulation results showed that the force of infection at the equilibrium state under the simple model was 0.236 (per 100,000 person-months), and that in the complex model was 26.796 (per 100,000 person-months). Sensitivity analyses indicated that the most influential parameters were rodent and mite populations and contact rate between them for the simple model, and trans-ovarian transmission for the complex model. In both models, contact rate between humans and mites is more influential than morality rate of rodent and mite group. CONCLUSION: The results indicate that the effect of controlling either rodents or mites could be limited, and reducing the contact rate between humans and mites is more practical and effective strategy. However, the current level of control would be insufficient relative to the growing mite population.

Predictors of acute myocarditis in complicated scrub typhus: an endemic province in the Republic of Korea

BACKGROUND/AIMS: Scrub typhus is known as a self-limited infectious disease. Cardiac complication is uncommon and usually not life-threatening. Until now, few cases of fulminant myocarditis by scrub typhus have been reported. So, we investigated incidence and predictors of acute myocarditis in severe scrub typhus. METHODS: We retrospectively reviewed 89 patients among 91 scrub typhus confirmed patients who examined an echocardiogram and cardiac biomarkers from 2005 to 2015 in the intensive care unit at our hospital. We excluded two patients who didn’t have electrocardiography. Patients were divided into two groups and compared between scrub typhus with (n = 13) and without (n = 76) acute myocarditis. RESULTS: Age, sex, and underlying diseases were similar between the groups. The existence of eschar and duration of general ache and fever were similar between the groups. However, patients with acute myocarditis had more elevated total bilirubin, high incidence of ST elevations and paroxysmal atrial fibrillation (PAF) than those without acute myocarditis. Receiver operating characteristic analysis showed that the PAF was a predictor of myocarditis with a sensitivity of 70% and specificity of 84%. Predictive power of combination of ST-segment elevation and PAF was significantly associated with myocarditis in the multivariate analysis (odds ratio, 1.57; 95% confidence interval [CI], 1.21 to 11.7; p = 0.041) and area under the curve was 0.947 (95% CI, 0.878 to 0.983; p < 0.001). CONCLUSIONS: Acute myocarditis with scrub typhus may be more common than previously reported. Patients with high bilirubin and PAF are at increased risk of acute myocarditis with scrub typhus. These patients warrant closer follow-up and echocardiogram would be needed.

Survey and Phylogenetic Analysis of Rodents and Important Rodent-Borne Zoonotic Pathogens in Gedu, Bhutan

Rodents are well-known reservoirs and vectors of many emerging and re-emerging infectious diseases, but little is known about their role in zoonotic disease transmission in Bhutan. In this study, a cross-sectional investigation of zoonotic disease pathogens in rodents was performed in Chukha district, Bhutan, where a high incidence of scrub typhus and cases of acute undifferentiated febrile illness had been reported in people during the preceding 4–6 months. Twelve rodents were trapped alive using wire-mesh traps. Following euthanasia, liver and kidney tissues were removed and tested using PCR for Orientia tsutsugamushi and other bacterial and rickettsial pathogens causing bartonellosis, borreliosis, human monocytic ehrlichiosis, human granulocytic anaplasmosis, leptospirosis, and rickettsiosis. A phylogenetic analysis was performed on all rodent species captured and pathogens detected. Four out of the 12 rodents (33.3%) tested positive by PCR for zoonotic pathogens. Anaplasma phagocytophilum, Bartonella grahamii, and B. queenslandensis were identified for the first time in Bhutan. Leptospira interrogans was also detected for the first time from rodents in Bhutan. The findings demonstrate the presence of these zoonotic pathogens in rodents in Bhutan, which may pose a risk of disease transmission to humans.

Research Progress on Leptotrombidium deliense

This article reviews Leptotrombidium deliense, including its discovery and nomenclature, morphological features and identification, life cycle, ecology, relationship with diseases, chromosomes and artificial cultivation. The first record of L. deliense was early in 1922 by Walch. Under the genus Leptotrombidium, there are many sibling species similar to L. deliense, which makes it difficult to differentiate L. deliense from another sibling chigger mites, for example, L. rubellum. The life cycle of the mite (L. deliense) includes 7 stages: egg, deutovum (or prelarva), larva, nymphochrysalis, nymph, imagochrysalis and adult. The mite has a wide geographical distribution with low host specificity, and it often appears in different regions and habitats and on many species of hosts. As a vector species of chigger mite, L. deliense is of great importance in transmitting scrub typhus (tsutsugamushi disease) in many parts of the world, especially in tropical regions of Southeast Asia. The seasonal fluctuation of the mite population varies in different geographical regions. The mite has been successfully cultured in the laboratory, facilitating research on its chromosomes, biochemistry and molecular biology.

Differences in agricultural activities related to incidence of scrub typhus between Korea and Japan / 한국역학회지

OBJECTIVES: The purpose of this study was to establish a basis for improving or strengthening the preventive strategy against scrub typhus in Korea by comparing and analyzing the difference of prevention behaviors contributing to the occurrence of scrub typhus in Japan and Korea. METHODS: The survey was carried out in Jeollabuk-do, which is a high risk and high incidence area, and Fukuoka Prefecture, which is a high risk and low incidence area. The study included 406 Korean farmers and 216 Japanese farmers. Data were collected through face-to-face surveys by interviewers who had completed standardized education. RESULTS: Korean farmers have a higher percentage of agricultural working posture that involved contact with weeds than Japanese farmers (p < 0.05). The frequency and proportion of weeding were lower in Korean farmers than in Japanese farmers (p < 0.05). The level of knowledge about scrub typhus was significantly higher among Korean farmers than among Japanese farmers (p < 0.05). Mostly, the behavior of agriculture work was more appropriate for Japanese farmers than for Korean farmers (p < 0.05). The total average level of agricultural work was lower in Korea than in Japan, lower in men than women, and lower in part-time farmers than full-time farmers (p < 0.05). CONCLUSIONS: This study suggests that it is reasonable to develop and provide a program that can improve the level of preventive behavior taking into consideration the characteristics of the subject in order to reduce the incidence of diseases in high-risk areas for scrub typhus.

Epidemiologic characteristics of scrub typhus on Jeju Island / 한국역학회지

OBJECTIVES: Scrub typhus is the most common febrile disease in Korea during the autumn. Jeju Island is the largest island in South Korea and has a distinctive oceanic climate. This study aimed to identify epidemiologic characteristics of scrub typhus on Jeju Island. METHODS: From January 2011 to December 2016, 446 patients were diagnosed with scrub typhus on Jeju Island. The patients' personal data and the environmental factors that might be related to scrub typhus were investigated and retrospectively analyzed. RESULTS: The median age of the patients was 58-years-old (range, 8 to 91) and 43% of them worked in the agricultural, forestry or livestock industry. Regardless of their job, 87% of the patients had a history of either working outdoors or of other activities before developing scrub typhus. The south and southeast regions of Jeju Island, especially Namwon-eup, showed the highest incidence of scrub typhus. Workers in mandarin orange orchards seemed to be the highest risk group for scrub typhus infection. CONCLUSIONS: Scrub typhus on Jeju Island showed unique characteristics. To efficiently prevent scrub typhus, each year individual regional approaches should be developed based on the epidemiologic characteristics of the disease.