Incidence Of Scrub Typhus Research Articles

Study on the characteristics of temporal distribution and the epidemic trend of autumn-winter type scrub typhus under time series analysis

To explore the characteristics of temporal distribution and epidemic trend of autumn-winter type scrub typhus using the time series analysis. Based on the data of scrub typhus collected from Shandong Diseases Reporting Information System from 2006 to 2011, both spectral analysis and moving average analysis were used to analyze the annual data of scrub typhus while scrub typhus incidence in 2012 - 2014 was forecasted. Seasonal decomposition analysis was applied to analyze the monthly data from January of 2006 to October of 2011, followed by Autoregressive Integrated Moving Average Model (ARIMA) which was constructed to forecast case number in November and December of 2011 and compared to the actual incidence. The results of spectral analysis showed that the prevalence of autumn-winter type scrub typhus had a feature of '3-year-periodicity'. A long-term up-trend was confirmed by method of moving average analysis, with annually case numbers of 310, 337 and another number of 366 forecasted for 2012 to 2014, respectively, with the annual increase rate as 9% per-year. Data from analysis of monthly data of scrub typhus showed that through multiple seasonal decomposition analysis, the results indicated that the prevalence of this disease possessed a typical autumn-winter type. The seasonality indexes for scrub typhus in October and November were 8.454 and 2.230, respectively, while others were less than 1.000. The ARIMA(0,1,1) (0,1,0)(12) model of (1-B)(1-B(12))X(t) = (1-0.811B)u(t) that was used to forecast the prevalence of autumn-winter type scrub typhus and was constructed with the residual error of 16 lags as white noise. The Box-Jenkins test statistic for the model was 3.116, giving a P value of 0.999. The model fitted the data well. Good accordance was achieved between the observed values and the forecasted values of scrub typhus in November and December of 2011 which was produced by the ARIMA model, and all observed values were within the forecasted 95%CI. The prevalence of autumn-winter type scrub typhus showed a 3-year-periodicity, with a long-term up-trend, and the case numbers of 2012 to 2014 were forecasted, rising on the end with an increasing rate of 9% per year, which occurred seasonally with October as the peak time in every year. The ARIMA(0,1,1) (0,1,0)(12) model seemed to be quite appropriate in predicting the autumn-winter type scrub typhus.

Scrub Typhus without Eruption

A 72-year-old woman presented with a chief complaint of fever for 5 days. Her blood pressure was 120/70 mmHg, and her body temperature was 38°C (axillary). Physical examination showed that her chest was clear, and her liver and spleen were not palpable. No skin rash was observed, but an eschar on her chest was discovered (Figure 1). Routine laboratory tests revealed normal leukocyte and platelet counts, elevated C-reactive protein level (10.2 mg/dL), and elevated aspartate aminotransferase (AST) 285 U/L and alanine aminotransferase (ALT) 185 U/L. Orientia tsutsugamushi infection was confirmed by indirect immunofluorescent antibody test. Immunoglobulin (Ig) M/IgG titers of Kato, Karp, and Gilliam strains were 80/160, 160/160, and 40/80, respectively. Figure 1. An eschar over her left upper chest was a clue to diagnose scrub typhus without skin rash. She was successfully treated with minocycline. Scrub typhus is often acquired during outdoor work such as farming, forestry, collecting edible wild plants, and recreation. About 400 cases of scrub typhus were reported annually in recent years in Japan. The largest number of cases was in Kyushu followed by Tohoku-Hokuriku and Kanto areas. There were two peaks of incidence of scrub typhus in Japan, a large peak in November and a small peak in May. Males and females were almost equally affected. The peak incidence was in the age group of 70–74 years.1 As a result of population aging in this country, young people move to cities for work, and elderly people, spending more time in outdoor activities than other age groups, may be more likely to be exposed to infected mites. Fever, skin rash, and eschar are three major clinical symptoms of scrub typhus. Individuals of Caucasian and Japanese ancestry are more likely to develop a rash compared with other racial groups, like Southeast Asians, who contract the disease.2 However, it is imperative to find evidence of an eschar to diagnose this condition. Empiric antimicrobial treatment, usually a tetracycline class antibiotic, will produce rapid amelioration of the clinical symptoms of scrub typhus and may also prevent fatal complications.

Report on the rate of Orientia tsutsugamushi infection in Hapcheon and Miryang, Korea

Most of the epidemic spread is closely related to the growth environment of insects or rodents as mediators. Climate changes make their growth environment change resulting in an epidemic infection increase. Even though the incidence of scrub typhus is increasing, little is known about scrub typhus compared with other infectious diseases in Korea. The tsutsugamushi infection prevalence of Orientia tsutsugamushi carried by tick was projected for surveillance from April to September in 2011. Chigger mites were collected at Miryang (Mt. Gaji) and Hapcheon (Gaya‐myeon) by the Sherman live trap and hanging method. Each collected samples were identified by microscope. Genomic DNAs were purified using CTB extraction kit and amplified by PCR using INNOPLEX TSUTSU detection kit.The number of chigger mites was highest in April, and then gradually declined. No chigger mites were collected in July (1st week) and August (1st week). However, chigger mites were collected again after September. We detected Orientia tsutsugamushi from samples collected in May (2nd week) using INNOPLEX TSUTSU detection kit. There has been no sign of an epidemic disease caused by climate change with the exception of tsutsugamushi infection in Korea until now. But, it is gradually requiring continuous monitoring, and the development of protective technology and emergency system for rapid, accurate diagnosis and treatment.

Epidemiology of 67 scrub typhus cases in Beijing

Objective To understand the epidemiological characteristics of 67 scrub typhus cases in Beijing. Methods The analysis was conducted on the temporal-spatial distributions of 67 scrub typhus cases in Beijing with SPSS software. Results As of October 2010, a total of 67 cases of scrub typhus were reported, Most cases were farmers (73.1%) with the mean age of 5214 years. The male to female ratio of the cases was 1 ∶ 1. Up to 92.5% of the cases were local people who lived in Pinggu districts in Beijing. The affected area in pinggu were in expansion in recent 3 years. Conclusion The incidence of scrub typhus peaks in October in Beijing, and the incidence had increased for 3 consecutive years. It is suggested to conduct population based serological surveillance of scrub typhus, establish host animal and trombiculid mite surveillance system and conduct health education among high risk population in Beijing to minimize the risk of scrub typhus epidemic.

The potential effect of exotic Pacific ratsRattus exulanson vectors of scrub typhus

Summary1. The role and influence of exotic species in indigenous vector‐borne diseases are important but remain understudied. Ascertaining whether disease vectors prefer exotic vs. native hosts has important implications for human health. Moreover, evaluating whether exotic hosts are intrinsically less susceptible to vectors, or whether vector loads can vary with environment, is instructive for possible disease dynamics in the face of range expansion of exotic species.Rattus exulanshas recently been recorded for the first time in eastern Taiwan, where scrub typhus is prevalent. We assessed the role ofR. exulansas a host for chiggers (larval trombiculid mites), and the degree to which vector loads ofR. exulansexhibited spatial variation.2. We deployed live traps in two villages in Taiwan that differed in human population density and in the incidence of scrub typhus. We recovered and tallied chiggers from small mammals, and identified over one‐fifth of chiggers from each host to species. Chiggers were assayed forOrientia tsutsugamushi(OT) infection with nested‐PCR.3. R. exulanswas the most common small mammal species captured (31·4% total captures), and supported about one‐fifth of total chiggers recovered.Leptotrombidium imphalumdominated the chigger assemblage of most native species (>90%), butGahrliepiaspp. was commonly found inR. exulans(39·1%). We detected OT in the genusLeptotrombidium(39%) but not in theGahrliepia. Prevalence and loads of chiggers inR. exulanswere about 5× and 17× higher, respectively, in the less densely populated village; a similar trend also occurred with nativeR. losea.4. Synthesis and applications. Currently,R. exulansappears to play a relatively minor role in supporting chiggers. However, the fact that both prevalence and loads of chiggers inR. exulansvary greatly with environment, along with the abundance of most exotic species and the ecological flexibility ofR. exulans, implies a potential health risk as this species expands to areas with more chiggers. Our study suggests that a clearer understanding of interactions among native and exotic hosts and native parasite species can facilitate prediction of the impact of exotic hosts on the dynamics of vector‐borne diseases.

Epidemiological Characteristics of Scrub Typhus in Korea, 2009

ObjectivesCurrently, the incidence of scrub typhus has increased in urban areas. In this study, we described the epidemiological characteristics of scrub typhus cases reported in the urban areas of Korea in 2009. MethodsWe analysed the case investigation reports of scrub typhus cases that were collected in Korea in 2009. Specially, the different risk factors such as fieldwork and outdoor activity were compared to urban and rural areas, and six urban cities. Statistical analysis was performed using χ2 test. ResultsA total of 4,461 cases (including 1,663 suspected cases) were analysed in this study. Among these, the case reports of 4,254 cases had complete addresses. The cases with outdoor activities were 720 (85.2%) in urban areas. In Daegu and Daejeon, the number of cases participated in outdoor activities was 32 (34.4%) and 23 (31.5%), respectively. In other urban areas, cases with outdoor activities were more than 85%. ConclusionThe most common infection risk factor was outdoor activity in urban areas. However, the proportion and distribution of outdoor activities were different in urban areas. These results will be used to establish strategies for effective prevention and management in urban areas.

Correlations Between Climate Change-Related Infectious Diseases and Meteorological Factors in Korea

Infectious diseases are known to be affected by climate change. We investigated if the infectious diseases were related to meteorological factors in Korea. Scrub typhus, hemorrhagic fever with renal syndrome (HFRS), leptospirosis, malaria and Vibrio vulnificus sepsis among the National Notifiable Infectious Diseases were selected as the climate change-related infectious diseases. Temperature, relative humidity and precipitation were used as meteorological factors. The study period was from 2001 through 2008. We examined the seasonality of the diseases and those correlations with meteorological factors. We also analyzed the correlations between the incidences of the diseases during the outbreak periods and monthly meteorological factors in the hyper-endemic regions. All of the investigated diseases showed strong seasonality; malaria and V. vulnificus sepsis were prevalent in summer and scrub typhus, HFRS and leptospirosis were prevalent in the autumn. There were significant correlations between the monthly numbers of cases and all the meteorological factors for malaria and V. vulnificus sepsis, but there were no correlation for the other diseases. However, the incidence of scrub typhus in hyper-endemic region during the outbreak period was positively correlated with temperature and humidity during the summer. The incidences of HFRS and leptospirosis had positive correlations with precipitation in November and temperature and humidity in February, respectively. V. vulnificus sepsis showed positive correlations with precipitation in April/May/July. In Korea, the incidences of the infectious diseases were correlated with meteorological factors, and this implies that the incidences could be influenced by climate change.

Characterisation of Orientia tsutsugamushi genotypes from wild rodents and chigger mites in Korea

Orientia tsutsugamushi is a causative agent of scrub typhus, and a Gram-negative obligate intracellular bacterium that is transmitted to humans by the bite of infected Leptotrombidium mites. In Korea, the incidence of scrub typhus has increased remarkably in recent years. A total of 6022 cases of scrub typhus were reported in 2007, and the incidence of scrub typhus infection was 13.2 cases per 100 000 persons. To develop a national strategy for the control and prevention of this disease that is based upon scientific data, we surveyed the infection rate and analysed the distribution of O. tsutsugamushi genotypes among wild rodents and engorged chigger mites in Korea. The specimens used in the present study were obtained from rodents because rodents have been recognised as a natural reservoir of O. tsutsugamushi and a host of chigger mites. At monthly intervals between August 2005 and July 2007, Sherman live traps were used to capture wild rodents living in four regions of Korea. Specimens were obtained from two areas in southern Korea, Chogye in Chollanam province and Ganjeon in Gyeongsangnam province, and from two areas in the middle region of Korea, Jangan and Songsan in Gyeonggi province. Chigger mites were collected from the wild rodents that had been captured. The 56-kDa genes of O. tsutsugamushi were collected from the blood or spleens of the wild rodents, and were detected from the pools of 30 chigger mites by nested PCR amplification, which was carried out as described by Furuya et al. [1]. In the present study, genotypes were determined by PCR-RFLP using DdeI. Analysis of the nucleotide sequence homology among the nested PCR products was performed using the CLUSTALX (http://clustal.org) and Tree Explorer (Tamura; http://evolgen.biol.metrou.ac.jp/TE/TE_man.html) programs in order to confirm the genotype in cases that could not be determined by RFLP. The rates of positivity among wild rodents from Chogye, Ganjeon, Jangan and Songsan, were 4.5% (12 ⁄266), 5.0% (10 ⁄201), 12.4% (25 ⁄202) and 5.0% (13 ⁄258), respectively, as shown in Table 1. To monitor the infection rate in mites, we calculated the MPR (minimum positive rate) using the equation: number of positive mites ⁄total number of mites examined. The MPRs were 0.6% (6 ⁄1071), 0.3% (12 ⁄4215), 0.9% (26 ⁄2893) and 1.3% (85 ⁄6752) in Chogye, Ganjeon, Jangan and Songsan respectively. The rates of positivity for O. tsutsugamushi were 6.5% (60 ⁄927) and 0.9% (129 ⁄14 931) in the wild rodents and chigger mites, respectively. In a previous study, Ree et al. [2] analysed the incidence of O. tsutsugamushi by IFA and PCR using 4315 individual mites collected from eight localities in Korea and reported that the infection rate was 1.5%, which was slightly higher than the result reported in the present study. From these results, we were able to determine that there is a high risk of scrub typhus infection in the natural environment of Korea. The Boryong genotype was the most common, at a rate of 76.7% in wild rodents and 82.9% in chigger mites, followed by the Gilliam (10%), Pajoo (8.3%) and Karp (5%) genotypes in the wild rodents and the Karp (11.6%), Pajoo (3.1%), Yoncheon (1.6%) and Kawasaki (0.8%) genotypes in the chigger mites. The Kato genotype was not detected in any of the specimens. The geographical distribution of the Boryong genotype was slightly higher in southern Korea than in mid-Korea, while the Gilliam, Karp and

Impacts of Climate on the Incidence of Scrub Typhus

Impacts of Climate on the Incidence of Scrub Typhus

ミャンマーで感染し帰国後発症した輸入つつが虫病の1 例

Scrub typhus is widespread in rural south and southeastern Asia and the western Pacific. The scrub typhus incidence is the highest among vector-borne diseases in Japan, but imported cases are extremely rare. A 49-year-old man admitted for persistent fever, headache, and rash after returning from Myanmar had been exposed to mosquito and tick bites while doing a 12-day forest inventory in Myanmar. On admission, he had a generalized maculopapular rash but no apparent eschars characteristic of scrub typhus. Blood examination and abdominal ultrasonography showed elevated liver enzymes, thrombocytopenia, and hepatosplenomegaly. Repeated blood smears and blood cultures were negative for malaria infection and bacteremia. Dengue fever was denied by both PCR and serology. The patient deteriorated on the ninth day and suffered complications of rhabdomyolysis, pneumonia, and enteritis. Based on a tentative diagnosis of typhoid fever or rickettiosis, we administratered ceftriaxone and minocycline, which dramatically reduced clinical signs and symptoms. After discharge on day 19, immunofluorescence assay showed significantly increased antibodies for Orienta tsutsugamushi serotype Gilliam, first discovered in Myanmar. All serological results were negative for other rickettioses, leptospirosis and Q fever. Given the many travelers from Japan visiting endemic scrub typhus areas, we must recognize cases of imported scrub typhus among those travelers with fever and rash returning from endemic areas.

Spring Scrub Typhus, People's Republic of China

Spring Scrub Typhus, People's Republic of China

B10 石川県能登半島における2004年ツツガムシ病発生とタテツツガムシの初確認

B10 石川県能登半島における2004年ツツガムシ病発生とタテツツガムシの初確認

Population indices of chiggers ( Leptotrombidium deliense) and incidence of scrub typhus in Chinese military personnel, Pescadores Islands of Taiwan, 1976–1977

Larval Leptotrombidium deliense were recovered from live-trapped Suncus murinus, Rattus rattus and R. norvegicus captured in the Pescadores Islands of Taiwan during 1976 and 1977. Weekly and monthly indices of chigger infestation expressed as a percentage of hosts infested and the number of chiggers per host for S. murinus and Rattus spp. were calculated. Close correlations were observed between monthly indices of L. deliense measured for S. murinus and Rattus spp. and the number of laboratory-confirmed cases of scrub typhus per month. Weekly indices from S. murinus correlated more closely with number of cases than did weekly indices from Rattus spp. The critical level of chigger infestation necessary for a single case of scrub typhus in a month was estimated at 0·69 chigger per S. murinus and 0·68 chigger per Rattus spp. The weekly index of chigger infestation necessary for a single case of scrub typhus during a week was calculated at 0·47 chiggers per shrew. Critical levels of chigger infestations expressed as percentages of hosts infested were not calculated.

Correlation of scrub typhus incidence with temperature in the Pescadores Islands of Taiwan.

Correlation of scrub typhus incidence with temperature in the Pescadores Islands of Taiwan.

Scrub typhus: a common cause of illness in indigenous populations

An explanation was sought for the disparity between the low reported incidence of scrub typhus and the high prevalence of antibody to Rickettsia tsutsugamushi in the rural population of Malaysia. A combination of isolation of the organism, titration of antibody by indirect immunofluorescence, and the Weil-Felix test was used to confirm infections. Scrub typhus was found to be very common, causing 23% of all febrile illnesses at one hospital. The infection was particularly prevalent in oil-palm workers, causing an estimated 400 cases annually in a population of 10,000 people living on one plantation. The clinical syndrome, whether mild or severe, was difficult to distinguish from that due to other infections. Eschars, rashes and adenopathy were uncommon. When used to examine early sera, the Weil-Felix test failed to confirm the diagnosis in most infections.

The incidence and distribution of scrub typhus in North Queensland.

SummaryIn the four years 1951–1955, 199 cases or probable cases of scrub typhus were recognized in North Queensland. The geographical distribution was discontinuous along the Pacific Coast from near Thursday Island (10.6° S.), where cases have not previously been reported, to Mackay (21.1° S.). All but four occurred between Cooktown (15.5° S.) and Ingham (18.7° S.). Most cases arose in a narrow belt close to the sea, and all within 40 miles of it. Some arose on the Atherton Tableland at an elevation of 2000 to 3000 feet.The scrub typhus region has an abundant rainfall and high humidity. Like the potential rain forest region, it is approximately bounded by the 60‐inch isohyet. The mean annual temperature in the scrub typhus region ranges from 80.7° F. at Thursday Island to 68.1° F. at Atherton. The boundary of the region is not related to any isotherm.The existence of foci of high and persisting endemicity, noted in other countries, is evident also in North Queensland. They offer opportunities for intensive ecological studies and for evaluation of preventive measures.The highest monthly incidence was from March to July. The seasonal variation appears to be determined primarily by the rainfall—the wet season is from January to April—but modified by the occupational or recreational activities that take people into endemic foci.Infection was associated with occupation in about 65 %—mainly timber‐cutting, scrub‐clearing and fruit‐farming—and in 18% with recreation. In 17% the significant activity was not defined.

All-Purpose Repellent Mixtures as Clothing Treatments against Chiggers

of the serious annoyance these mites cause people in outdoor areas. The most desirable method of preventing attacks is to destroy the chiggers in their natural habitats by means of insecticidal sprays or dusts. However, this is usually impracticable or impossible because areas of infestation are generally too scattered and the number of persons affected is too small to justify the expense of area-control measures. Under certain conditions also, particularly in military operations, persons may be required to enter infested areas before such measures could be taken. In such cases reliance must be placed entirely on personal protection. The high incidence of scrub typhus (tsutsugamushi disease) in the Pacific theater of operation during World War II brought into prominence the need for effective methods of protecting military personnel from attacks by mites. Early tests at the Orlando, Florida, laboratory of the Bureau of Entomology and Plant Quarantine (Madden et al., 1944) demonstrated that the standard insect repellents, especially dimethyl phthalate, would prevent chigger attachments when applied to clothing. Just as the war ended benzyl benzoate was adopted by the Army as the standard material for treating uniforms. This material was shown (Snyder and Morton, 1946) to be effective through at least two soap-and-water washings, whereas dimethyl phthalate became ineffective after a single rinsing in cool water. The search for new and better clothing treatments for protection against chiggers, as well as against ticks, fleas, and mosquitoes, has been continued since 1944. Studies have shown that mixtures of several good repellents are effective against a wider range of species and on more persons than any one repellent used alone. For this reason a number of mixtures were tested against mosquitoes, ticks, fleas, and chiggers. From

Use of Dimethylphthalate Impregnated Clothing as Protection Against Scrub Typhus

SummaryThe incidence of scrub typhus in three groups of troops operating in an area where one of the probable vectors of this disease was found and where various degrees of protection against the mite was used has been analyzed. Troops with no protection had the highest incidence of the disease, as compared with a lower incidence in troops where clothes were sprayed with dimethylphthalate, and lowest in the group whose clothes had been actually impregnated with a 5 per cent emulsion of dimethylphthalate. There were no instances of dermatitis.It is considered that this experience offers evidence indicative of the high degree of protection against scrub typhus provided by clothes impregnated with dimethylphthalate.