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Seroprevalence of scrub typhus infection in patients with pyrexia at some malaria clinics in three western provinces of Thailand.

In Thailand, the epidemiological data on scrub typhus infection represents only "the tip of an iceberg" especially in malaria clinics where patients come to seek attention because of other febrile illnesses that may have initial clinical signs that are indistinguishable from malaria. The objectives of this study were to determine the prevalence of antibody titers to Orientia tsutsugamushi, and its various strains, among patients at some malaria clinics in three western provinces of Thailand. The sample was represented by 200 patients from 6 malaria clinics in Ratchaburi, Petchaburi and Kanchanaburi provinces between June and November, 1994. Blood specimens were collected with their consent. Immunofluorescent antibody assays (IFA) were used for measuring IgM and IgG antibody titers for scrub typhus infection. The results showed that the prevalence rate for scrub typhus infection (IgM and/or IgG titer > or = 50) was 59.50% (119 cases). The immunofluorescent antibody response to various strains of O. tsutsugamushi showed that co-infections with the Karp, the Gilliam and the Kato strains were the most common (found in 68.10% of cases). Geometric mean antibody titers (GMT) were highest for the Karp strain, followed by the Gilliam then Kato strains. In conclusion, this study indicates that the prevalence rate of scrub typhus is not rare in these areas.

Adolescent↗

PubMed2006

Epidemiology of scrub typhus in eastern Taiwan, 2000-2004.

The epidemiology of scrub typhus in eastern Taiwan was studied by analyzing the data from the CDC Web reporting system. A total of 1,396 cases with 403 confirmed cases were reported in the period of 2000 to 2004. The cases were commonly found in all counties with the highest number in Yuli Township, Hualien County (53 cases) and Taitung City, Taitung County (40 cases). Monthly changes in the number of cases showed epidemic periods in the spring with a peak in May, and again in the fall, with an October-November peak. The occurrence of disease varied with age, gender, and occupation. Our results showed that the infection rates in the elderly (50-69 years old), males (62.8%), and farmers (25.6%) were higher than those in other age groups, females, and other occupations. Five major clinical symptoms, fever, headache, eschar, rash, and lymphadenopathy, were observed in 90.1, 61.9, 23.1, 21.6, and 10.7% of the cases, respectively. Almost 90% (89.3%) of the cases showed 1-3 clinical symptoms and some showed 4-5 symptoms (10%). Only one patient with no symptoms (0.8%) was found. This paper reports the status of scrub typhus in eastern Taiwan, and suggests that a health education program could train individuals to self-recognize the disease symptoms.

Adolescent↗

PubMed2006

ARDS complicating scrub typhus in Sub-Himalayan region.

Scrub typhus is a febrile illness widely endemic in Asia caused by Rickettsiae tsutsugamushi in which humans are accidental hosts. If there is delay in the initiation of the appropriate antimicrobial therapy patient may present with serious complications. We report three cases that presented in emergency with acute respiratory distress syndrome and history of fever for more than one-week duration. On investigation all the three patients were positive for Weil Felix reaction and showed dramatic response to doxycycline.

Adult↗

PubMed2005

Clinical study of 20 children with scrub typhus at Chiang Rai Regional Hospital.

20 children, diagnosed with scrub typhus who attended Chiang Rai Regional Hospital during a period of 6 months from June 2003 to December 2003, were studied prospectively. All cases were serologically proved to be scrub typhus by using Dipstick or indirect immunofluorescent antibody (IFA) technique. The most common clinical feature was eschar (75%). Others included hepatomegaly (65%), cough (60%), lymphadenopathy (40%), tachypnea (35%), constipation (25%), abdominal pain (20%), edema (20%), splenomegaly (15%), vomiting (15%), rash (15%) and petichia (5%) respectively. Chest radiography showed abnormalities in 85% with mostly bilateral interstitial infiltrations. Elevated of SGOT: SGPT were detected in 18 (90%) and 15 (75%) cases. Hypoalbuminemia was detected in 12 (60%) cases. Complete blood count showed PMN leukocytosis (> 60%) in 12 (60%) cases, lymphocytosis (> 40%) and atypical lymphocytosis (> 5%) in 1 (5%) case each and thrombocytopenia in 16 (80%) cases. The Weil-Felix test was positive in 1 (5%) case. Complications were pneumonia with or without pulmonary edema, meningitis and shock. Chloramphenicol and doxycycline were successfully treated and roxithromycin was not effective.

Adolescent↗

PubMed1988

Evaluation of the whole blood lymphocyte transformation assay for scrub typhus exposure: adaptability to field sample collection.

The optimal conditions for the determination of exposure to scrub typhus by the whole blood lymphocyte transformation assay was 7 days culture of 10% blood in RPMI 1640 medium supplemented with 10% human AB-negative serum and L-glutamine with 50-200 micrograms protein/ml of Karp, Kato, or Gilliam strain membrane antigen. A simple exponentially decaying linear model shows the decrease in lymphocyte viability, the ability of sensitized cells to be stimulated with PHA mitogen, and the corresponding decrease in stimulation by scrub typhus antigens with increasing time of preincubation on ice. The lower limit of stimulation index for the detection of scrub typhus by whole blood lymphocyte transformation assay was 4.0 with a type I error of 1%.

Antigens, Bacterial↗

PubMed2025

Proteome Profiling in Cerebrospinal Fluid Reveals Increased Levels of Peroxiredoxin 2 Discriminating Japanese Encephalitis Virus and Scrub Typhus Infection.

Japanese encephalitis virus (JEV) and scrub typhus (ST) are major etiological agents of acute encephalitis syndrome (AES) in India and South Asia. The pathophysiological changes at the molecular level caused by JEV and ST have yet to be studied in detail. The cerebrospinal fluid (CSF) proteomic landscape is a critical indicator of CNS pathology. Here, we conducted label-free quantitative proteomics on CSF from AES patients (n = 15) to identify etiology-specific differentially expressed proteins (DEPs) linked to encephalitis. The key DEPs were validated via ELISA in CSF (n = 49) and serum (n = 33). Our findings revealed 50 proteins exhibited differential expression across JEV and ST groups, with a notable subset of three proteins, PRDX2, KLK6, and TTR. PRDX2 and KLK6 were markedly elevated in JEV CSF (AUC: 0.8933 and 0.9689) but not in ST or non-JEV AES, while TTR was reduced in JEV yet elevated in ST (AUC: 0.5619 vs. 0.8238). Further, PRDX2 upregulation was validated in JEV-infected mouse brains and cortical neurons. Overexpression of PRDX2 in human neuroblastoma cells correlated with enhanced antiviral gene expression, p-STAT1, p-AKT (ser473), and viral replication. Thus, our comprehensive proteomic analysis of CSF identifies PRDX2 as an important circulatory protein, differentially expressed between JEV and ST, with high specificity and enhancing viral propagation, underscoring its role in viral propagation and pathogenesis.

Humans↗

PubMed1996

Scrub typhus infections poorly responsive to antibiotics in northern Thailand.

BACKGROUND: Rickettsia tsutsugamushi, the aetiological agent of scrub typhus, is common in Asia and readily infects visitors to areas where disease transmission occurs. Rapid defervescence after antibiotic treatment is so characteristic that it is used as a diagnostic test for R tsutsugamushi infection. Reports from local physicians that patients with scrub typhus in Chiangrai, northern Thailand responded badly to appropriate antibiotic therapy prompted us to do a prospective clinical evaluation and antibiotic susceptibility testing of human rickettsial isolates. METHODS: The clinical response to doxycycline treatment in patients with early, mild scrub typhus in northern Thailand was compared with the results of treatment in Mae Sod, western Thailand. Prototype and naturally occurring strains of R tsutsugamushi were tested for susceptibility to chloramphenicol and doxycycline in mice and in cell culture. FINDINGS: By the third day of treatment, fever had cleared in all seven patients from Mae Sod, but in only five of the 12 (40%) from Chiangrai (p < 0.01). Median fever clearance time in Chiangrai (80 h; range 15-190) was significantly longer than in Mae Sod (30 h; range 4-58; p < 0.005). Conjunctival suffusion resolved significantly more slowly in Chiangrai (p < 0.05). Antibiotics prevented death in mice infected by Chiangrai strains of R tsutsugamushi less often than after infection by the prototype strain (p < 0.05). Only one of three Chiangrai strains tested in cell culture was fully susceptible to doxycycline. INTERPRETATION: Chloramphenicol-resistant and doxycycline-resistant strains of R tsutsugamushi occur in Chiangrai, Thailand. This is the first evidence of naturally occurring antimicrobial resistance in the genus Rickettsia.

Administration, Oral↗

PubMed2005

Development and evaluation of a latex agglutination test for the rapid diagnosis of scrub typhus.

The purpose of this research was to develop a simple and rapid diagnostic test for scrub typhus using a latex agglutination test (LAT) to detect antibodies against Orientia tsutsugamushi. Five strains of O. tsutsugamushi were propagated in L929 cells. The rickettsiae were purified and concentrated with percoll density gradient centrifugation. A suitable concentration of O. tsutsugamushi soluble antigen was used to sensitize latex to prepare the latex antigen. The specificity, sensitivity, and accuracy of the latex antigen were assessed. The LAT, indirect immunofluorescent antibody test (IFA), and Weil-Felix agglutination test (WF) were compared by testing 109 acute febrile illness cases and 100 confirmed non-scrub typhus cases (50 other febrile disease cases and 50 healthy controls). By using the IFA as the standard reference method, the overall sensitivity, specificity, and accuracy of the LAT were 89.1, 98.2, and 93.6%, respectively. By contrast, the sensitivity of the WF, compared with the IFA, was only 47.3%, while the specificity and accuracy were 92.6 and 69.7%, respectively. Thus, the LAT described here is another important alternative test for the diagnosis of scrub typhus.

Antibodies, Bacterial↗

PubMed1979

Vectors of scrub typhus and their hosts on a mature oil palm estate.

L. (L.) deliense was the predominant vector of scrub typhus in a mature oil palm estate, but a small number of L. (L.) fletcheri (0.1% from rodents) and L. (L.) vivericola (0.02% from rodents and 8.0% from black plates) was also collected. Although good correlation between L. (L.) deliense collected from rodents and from black plates was not established, either method may serve as a general indicator of population fluctuations over a period of time. For the most part, the vectors of scrub typhus were limited to litter piles, and thus, the possibility of contracting scrub typhus within this type of habitat was minimal.

Animals↗

PubMed2003

Epidemiological studies on host animals of scrub typhus of the autumn-winter type in Shandong Province, China.

In order to elucidate the host animals of scrub typhus in Shandong Province, epidemiological studies on host rodents of the autumn-winter type scrub typhus were carried out from 1995 to 2002 at four localities in the Shandong Province. Based upon ecological observations of the composition, seasonal fluctuation of animal hosts, isolation of Orientia tsutsugamushi, detection and identification of serotypes of antibodies to O. tsutsugamushi were conducted. Two thousand eight hundred and eighty-four rodents and insectivores were captured, including 2,055 Apodemus agrarius (71.26%), 408 Cricetulus triton (14.15%), 64 C. barabensis (2.22%), 12 Crocidura suaveolens (0.42%), 313 Rattus (R.) norvegicus (10.85%), 32 Mus (M.) musculus (1.11%). A. agrarius was predominant in the field and the seasonal fluctuation was correlated significantly to that of scrub typhus (r=0.810, p<0.005). R. norvegicus was predominant indoors. The average capture rate per year in the field was 12.76% from 1995 to 1997. Of the total 2,884 rodents and insectivores captured out- and in-doors, 527 were living rodents (including 335 A. agrarius, 119 C. triton, 6 C. barabensis, 2 C. suaveolens, 63 R. norvegicus and 2 M. musculus, and 15,467 chigger mites were collected from them. Two hundred and fifty-three of 335 A. agrarius were parasitized by chiggers, showing 75.52% (253/335) of the infestation rate and 17.53 of the chigger index; 106 C. triton were parasitized by chiggers, showing 89.08% (106/119) infestation rate and 75.93 of the chigger index. The average antibody positive rate of rodents was 14.78%. The seasonal change of the antibody positive rate was higher during December-February (the second year), and varied from 20% to 28%, but the level of antibodies remained relatively low (5.26-16.67%) during March-November. The results of serotyping with 47 antibody-positive sera were as followings: 39 sera were Gilliam types, 7 sera were Karp types, 1 serum was Kato type. Twelve strains of O. tsutsugamushi were isolated from A. agrarius (8 strains), C. triton (3 strains) and R. norvegicus (1 strain), out of the isolated 12 strains, 10 were Gilliam strains, 2 were Karp strains. A. agrarius and R. norvegicus were the main host animals in out- and indoors respectively.

Animals↗

PubMed1980

Prevention of scrub typhus. Prophylactic administration of doxycycline in a randomized double blind trial.

We conducted a prospective randomized double blind study on the effects of doxycycline as a prophylactic antibiotic against scrub typhus. A total of 1,125 military subjects was followed for periods as long as 5 months of exposure in a hyperendemic focus in the Pescadores Islands of Taiwan. Oral 200 mg doses of doxycycline (Vibramycin) or placebo were given once each week throughout the trial. The incidence rate of scrub typhus in the placebo group was 2.5 times greater than that of the group taking doxycycline (P = 0.11). When subjects who failed to comply with scheduled administration of doxycycline were removed from the analysis, the incidence rate of scrub typhus in the control group was five times greater than that in the drug group (P = 0.04). The rates of infection with Rickettsia tsutsugamushi and of sick call reports were the same in experimental and control groups. The drug was well tolerated in pretrial tests and complaints were negligible during the conduct of the trial. Doxycycline appears to be an excellent antibiotic for the prevention of scrub typhus among personnel exposed to high risk of infection with R. tsutsugamushi.

Dose-Response Relationship, Drug↗

PubMed2003

Laboratory diagnosis of two scrub typhus outbreaks at Camp Fuji, Japan in 2000 and 2001 by enzyme-linked immunosorbent assay, rapid flow assay, and Western blot assay using outer membrane 56-kD recombinant proteins.

Two scrub typhus outbreaks occurred among U.S. Marines training at Camp Fuji, Japan, between October 25 and November 3, 2000 and October 17 and November 30, 2001. Nine cases in approximately 800 Marines in 2000 and eight cases in approximately 900 Marines in 2001 (approximate attack rates = 1.1% and 0.9%, respectively) reported with signs and symptoms of fever, rash, headache, lymphadenopathy, myalgia, and eschar. Serologies and rapid response to doxycycline treatment indicated they had scrub typhus. Sixty-four convalescent serum samples (18 suspected cases and 46 negative controls) from U.S. Marines training at Camp Fuji during the outbreaks were assessed by enzyme-linked immunosorbent assay (ELISA), rapid flow assay (RFA), and Western blot assay for evidence of infection with Orientia tsutsugamushi, the causative agent of scrub typhus. All but one suspected case had serologic evidence of scrub typhus and all 46 control sera were non-reactive to O. tsutsugamushi antigens. The recombinant 56-kD antigen (r56) from the Karp, Kato and Gilliam strains of O. tsutsugamushi in an ELISA format provided better results than Karp r56 alone (ELISA and RFA) or whole cell antigen preparation from Karp, Kato and Gilliam (ELISA).

Adult↗

PubMed1986

Laboratory animal models for human scrub typhus.

A wide variety of animals have been utilized in an attempt to provide the information necessary to bring scrub typhus to the point where it is no longer a threat to man. The laboratory mouse is usually the animal of choice for the study of this disease. The discovery that certain strains of inbred mice are genetically resistant to Rickettsia tsutsugamushi, the agent of scrub typhus, has opened new avenues in the study of the immune response to the disease. The cynomolgus monkey, Macaca fascicularis, appears to be the best animal model for the study of scrub typhus as it occurs in humans and should be useful in the development of an efficacious vaccine.

Animals↗

PubMed2002

Acute scrub typhus in Northern Thailand: EKG changes.

The electrocardiographic (EKG) manifestations of scrub typhus were prospectively evaluated in 29 adult patients who acquired Orientia tsutsugamushi infection in Chiang Rai, Northern Thailand. EKGs were normal in 22 of the 29 patients (76%); minor non-specific changes were found in the other 7 patients; ie ST segment/T wave changes (10%), U waves (7%), and premature ventricular contractions (4%). These results suggest that EKG changes in scrub typhus acquired in areas of diminished antibiotic susceptibility are similar to those observed in O. tsutsugamushi infection acquired elsewhere.

Acute Disease↗

PubMed1990

[Serodiagnosis of scrub typhus by dot-blot method].

Microimmunofluorescence (IF) and immunoperoxidase tests are generally used for the serodiagnosis of scrub typhus. While these tests give satisfactory results in the hands of experienced personnel, they can be troublesome for inexperienced technicians. To develop a simpler diagnostic method, dot-blot assay was examined in this study. Six antigenically distinctive strains of Gilliam, Karp, Kato, Shimokoshi, Kawasaki and Kuroki of Rickettsia tsutsugamushi and a strain of Rickettsia sibirica were dotted on a nitrocellulose sheet by a dot-blot instrument. The sheets were treated with patient sera, followed by peroxidase-conjugated anti-human immunoglobulin-antibody and then with the substrate of the enzyme, and the color development on the dots was compared by naked eye observation. By this procedure, anti-rickettsial antibody-positive patient sera showed clear color development on at least one, usually several dots, while the very faint color was observed by the treatment with antibody-negative sera. On the other hand, it was ascertained that the antigens on nitrocellulose sheets were stable for at least 4 months at room temperature. Therefore the diagnostic kits were prepared, and the practical application of this procedure for diagnosis of scrub typhus were tested in Shizuoka and Miyazaki Prefectural Pabulic Health Laboratories. The results indicated a very good comparability between the dot-blot assay and IF-tests, and this dot-blot method was ascertained as a simple and useful method for the scrub typhus serodiagnosis.

Adolescent↗

PubMed1998

Performance of a dot blot immunoassay for the rapid diagnosis of scrub typhus in a longitudinal case series.

A rapid dipstick test for scrub typhus was prospectively evaluated in Chiangrai, northern Thailand. Sera from 162 patients with fever of unclear etiology were tested by a dot blot immunoassay using two different antigen concentrations. Dipsticks coated with lower concentration of antigen lacked sensitivity compared with the indirect immunoperoxidase test. Dipsticks with higher antigen concentration had increased sensitivity that was equivalent to that of the immunoperoxidase test. By increasing the antigen concentration on the dipstick, sensitivity increased from 67% to 100%, positive predictive value increased from 90% to 93%, and negative predictive value rose from 92% to 100%. The specificity of both antigen concentrations was 98%. This study establishes that scrub typhus can be confirmed serologically by use of a dipstick assay and that serodiagnosis can be effectively tailored to a target population.

Adult↗

PubMed2001

Early diagnosis of scrub typhus with a rapid flow assay using recombinant major outer membrane protein antigen (r56) of Orientia tsutsugamushi.

The variable 56-kDa major outer membrane protein of Orientia tsutsugamushi is the immunodominant antigen in human scrub typhus infections. We developed a rapid immunochromatographic flow assay (RFA) for the detection of immunoglobulin M (IgM) and IgG antibodies to O. tsutsugamushi. The RFA employs a truncated recombinant 56-kDa protein from the Karp strain as the antigen. The performance of the RFA was evaluated with a panel of 321 sera (serial bleedings of 85 individuals suspected of scrub typhus) which were collected in the Pescadore Islands, Taiwan, from 1976 to 1977. Among these 85 individuals, IgM tests were negative for 7 cases by both RFA and indirect fluorescence assay (IFA) using Karp whole-cell antigen. In 29 cases specific responses were detected by the RFA earlier than by IFA, 44 cases had the same detection time, and 5 cases were detected earlier by IFA than by RFA. For IgG responses, 4 individuals were negative with both methods, 37 cases exhibited earlier detection by RFA than IFA, 42 cases were detected at the same time, and 2 cases were detected earlier by IFA than by RFA. The sensitivities of RFA detection of antibody in sera from confirmed cases were 74 and 86% for IgM and IgG, respectively. When IgM and IgG results were combined, the sensitivity was 89%. A panel of 78 individual sera collected from patients with no evidence of scrub typhus was used to evaluate the specificity of the RFA. The specificities of the RFA were 99% for IgM and 97% for IgG. The sensitivities of IFA were 53 and 73% for IgM and IgG, respectively, and were 78% when the results of IgM and IgG were combined. The RFA test was significantly better than the IFA test for the early detection of antibody to scrub typhus in primary infections, while both tests were equally sensitive with reinfected individuals.

Antibody Specificity↗

PubMed1995

In vitro effectiveness of azithromycin against doxycycline-resistant and -susceptible strains of Rickettsia tsutsugamushi, etiologic agent of scrub typhus.

In an effort to find a potential alternative treatment for scrub typhus, we evaluated the effectiveness of the standard drug doxycycline and the new macrolide azithromycin against a doxycycline-susceptible strain (Karp) and a doxycycline-resistant strain (AFSC-4) of Rickettsia tsutsugamushi. The antibiotics were tested in an in vitro assay system in which infected mouse fibroblast cells (L929) were incubated for 3 days in various concentrations of the drugs. Rickettsial growth was evaluated by direct visual counts of rickettsiae in Giemsastained cells or by flow cytometry. Initial tests were conducted at the concentration of each antibiotic considered to be the upper breakpoint for susceptibility (16 micrograms/ml for doxycycline and 8 micrograms/ml for azithromycin). Growth of both Karp and AFSC-4 was strongly inhibited with both antibiotics, as measured by visual counts, although the percentage of cells infected with AFSC-4 in the presence of doxycycline was three times greater than the percentage of cells infected with Karp but was only 60% as great as the percentage of cells infected with Karp in the presence of azithromycin. Flow cytometry confirmed that rickettsial growth occurred in the absence of antibiotics, but it failed to detect it in the presence of high concentrations of either drug. Visual counts of rickettsial growth at lower concentrations of the antibiotics (0.25 to 0.0078 microgram/ml) showed that the Karp strain was 16 times more susceptible that the AFSC-4 strain to doxycycline. Azithromycin was much more effective than doxycycline against AFSC-4, inhibiting rickettsial growth at 0.0156 microgram/ml to levels below that achieved by 0.25 microgram of doxycycline per ml. Azithromycin was also more effective than doxycycline against the Karp strain, causing greater reductions in the number of rickettsiae per cell at lower concentrations. If in vivo testing confirms the in vitro effectiveness of azithromycin, it may prove to be the drug of choice for the treatment of scrub typhus in children and pregnant women, who should not take doxycycline, and in patients with refractory disease from locations where doxycycline-resistant strains of R. tsutsugamushi have been found. When tested in an in vitro assay system, azithromycin was more effective than doxycycline against doxycycline-susceptible and -resistant strains of R. tsutsugamushi.

Animals↗