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PubMed1976

Experiments on chickens placed on ground endemic of classical scrub typhus in Akita prefecture, Japan.

The chicken is available as a bait animal for the study of vector mites and has been found to be infected by chigger mite bite in an area endemic of scrub typhus. L. pallidum and L. palpale were reconfirmed to be zoophilic for the chicken. It is suggested a walking bird can serve as a vector--carrying mites from one place to another. R. orientalis can persist subclinically for a certain period in the spleen and liver of chickens placed on the ground endemic of scrub typhus. Specimens of L. pallidum, 22 in number, collected from chickens placed on the ground of an endemic area in Akita Prefecture were found rickettsia-positive. Both strains isolated from bait chickens and L.pallidum collected from host chickens were identified as a Kato type of R. orientalis.

Animals↗
PubMed1976

Experiments on chickens placed on ground endemic of classical scrub typhus in Akita Prefecture, Japan.

The chicken is available as a bait animal for the study of vector mites and has been found to be infected by chigger mite bite in an area endemic of scrub typhus. L. pallidum and L. palpale were reconfirmed to be zoophilic for the chicken. It is suggested a walking bird can serve as a vector--carrying mites from one place to another. R. orientalis can persist subclinically for a certain period in the spleen and liver of chickens placed on the gound endemic of scrub typhus. Specimens of L. pallidum, 22 in number, collected from chickens placed on the ground of an endemic area in Akita Prefecture were found rickettsia-positive. Both strains isolated from bait chickens and L.pallidum collected from host chickens were identified as a Kato type of R. orientalis.

Animals↗
PubMed1988

Scrub typhus pneumonitis: an entity which is frequently missed.

Four cases of scrub typhus pneumonitis are reported. Diagnosis was confirmed by positive Weil-Felix OX-K reaction and immunofluorescent antibody test for Rickettsia tsutsugamushi. Two patients presented with atypical pneumonia and two had overwhelming pneumonia resembling adult respiratory distress syndrome. All patients made a full recovery after appropriate treatment.

Adult↗
PubMed1989

[Scrub typhus: an imported case seen in Milan].

The Authors describe a scrub typhus case imported from Indo-China and observed in Milan, which is probably the first case reported in Italy. The patient, on holiday journey, exposed herself unwisely to the danger of catching the infection. The diagnosis was based on clinical grounds and Weil-Felix reaction. The problems of the diagnosis reliability and of the imported diseases are briefly discussed as well.

Adult↗
PubMed2006

Evaluation of tests for serological diagnosis of scrub typhus.

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

Antibodies, Bacterial↗
PubMedDate not supplied

Comparative evaluation of four serodiagnostic tests for scrub typhus in Thailand.

The commercial dot-blot enzyme-linked immunosorbent assay Dip-S-Ticks dipstick test was compared with the indirect immunoperoxidase (IIP) and Weil-Felix (WF) tests for the diagnosis of scrub typhus, using the indirect immunofluorescent antibody test (IFA) as the reference standard. With a panel of 117 positive and 75 negative sera, the dipstick test was 94% sensitive and 98.7% specific at a cut-off value of one or more positive dots. The IIP was 90.6% sensitive and 100% specific at a cut-off titre of 1:400, and was more sensitive than the IFA with acute sera (79.6% vs. 68.5% at a titre > or = 1:400). All 3 were superior to the WF, which lacked sensitivity. The dipstick assay was easy to perform and did not require sophisticated electrical equipment, and the results were available within one hour. It is therefore suitable for use in rural Thailand, where scrub typhus is common.

Agglutination Tests↗
PubMed1979

Gamma-irradiated scrub typhus immunogens: broad-spectrum immunity with combinations of rickettsial strains.

Scrub typhus immunogens were prepared from Rickettsia tsutsugamushi strains Karp, Kato, Gilliam, Kostival, and Buie by exposing frozen infected yolk sac suspensions to 300 krad of gamma radiation. Mouse protection tests showed that each of the irradiated immunogens protected C3H/HeDub mice against high challenge levels of Karp and Gilliam, but that none of these single-strain immunogens were capable of protecting against all five of the challenge strains. Broad-spectrum protection was achieved by using combinations of three strains of irradiated rickettsiae in a vaccination regimen of three injections at 5-day intervals. A comparison of vaccination efficacy employing three such combinations (Karp-Gilliam-Kato, Karp-Kostival-Kato, and Buie-Kostival-Kato) indicated that both sequential administration of strains on successive vaccination days and multiple injections of trivalent mixtures produced protective responses superior to those obtained with single-strain immunogens. Trivalent mixtures of rickettsiae exhibited a striking synergistic effect on the immune response of C3H/HeDub mice and elicited a protective response against Kato challenge that could not be obtained with any single-strain immunogen. Mice vaccinated with the trivalent Karp-Gilliam-Kato immunogen resisted challenge with more than 10(3) 50% mouse lethal doses of Karp and Gilliam for 12 months, and were resistant to similar levels of challenge with Kato and Buie for 6 months.

Animals↗
PubMed1980

Leptotrombidium (Leptotrombidium) Umbricola, new species, a probable vector of scrub typhus in Peninsular Malaysia.

Leptotrombidium (Leptotrombidium) umbricola, described here as a new species, is a member of the L. (L.) deliense group and most closely resembles L. (L.) vivericola. L. (L.) umbricola was collected from the ground surface and from animal hosts, in similar habitats to the scrub typhus vector, L. (L.) deliense. The host and habitat distribution records and the Rickettsia tsutsugamushi infection rates within unengorged specimens suggest that L. (L.) umbricola may be an important vector of scrub typhus in Peninsular Malaysia.

Animals↗
PubMed1977

Host defenses in experimental scrub typhus: role of spleen and peritoneal exudate lymphocytes in cellular immunity.

Lymphocytes obtained from spleens or peritoneal exudates of immune donor mice were evaluated for their ability to passively confer protection on recipients subsequently challenged with virulent scrub typhus rickettsiae. Peritoneal exudate lymphocytes (PELs) injected intraperitoneally were able to transfer complete protection against rickettsial challenge by 5 days after immunization, whereas splenic lymphocytes (SpL's) required 15 days to exhibit similar resistance. When immune lymphocytes were transferred intravenously, cells from both anatomical compartments required 15 days after immunization before they were able to completely protect recipients. PELs maintained this protective capacity for 2 weeks, but the passive immunity induced by intravenously transferred SpL's rapidly diminished to insignificant levels. It was particularly interesting that the protective effect of SpL's could be dramatically reduced by the concomitant presence of a mineral oil-induced peritoneal exudate. Almost total abrogation of resistance was observed when SpL's obtained from exudate-bearing mice were transferred intravenously. The protective capacity of both PELs and SpL's was resistant to 1,200 rads of gamma radiation at 7 to 10 days after immunization, but resistance was transient and by 3 weeks was undetectable. It was not possible to determine from this study whether the transferred lymphocytes were proximate mediators of protection in scrub typhus infection of mice or whether they served to recruit the host's own defenses, or both. However, it was possible to conclude that PEL's and SpLs exhibited functional heterogeneity and that PELs were more efficient mediators of protection.

Animals↗
PubMed1982

Transmission of scrub typhus to human volunteers by laboratory-reared chiggers.

Laboratory-reared, Rickettsia tsutsugamushi-infected Leptotrombidium arenicola and L. fletcheri chiggers were fed on 1 and 2 human volunteers respectively. All subjects developed typical clinical signs and symptoms of scrub typhus beginning days 8-10 post chigger attachment (PCA); these included fever, severe headache, myalgia, regional lymphadenopathy, and eschar. The two L. fletcheri subjects developed a transient generalized rash on days 3-4 after the onset of fever, and these two individuals also appeared to suffer a more severe clinical disease. Rickettsemias were detected in all three volunteers beginning on day 7 PCA, 1-3 days before the onset of clinical disease. Rises in indirect fluorescent antibody titers occurred starting on days 13-19 PCA (day 4-11 post fever) and in Weil-Felix OXK titers starting on days 26-22 PCA (days 7-14 post fever). These results strongly suggest that the use of laboratory-reared chiggers is a reliable means of transmitting scrub typhus infections to volunteers.

Adult↗
PubMed1980

Scrub typhus survey of Biak and Owi islands: ectoparasites of small mammals and rickettsial isolations.

A survey of smnall mammals and their ectoparasites was conducted on the islands of Biak and Owi, Indonesia, in August 1976. Two species of chiggers known to serve as vectors of scrub typhus were found: Leptotrombidium (Leptotrombidium) deliense from Rattus exulans, R. ruber, and R. r. septicus; L. (L.) flectcheri from R. exulans, R. leucopus and R. r. septicus. Rickettsia tsutsugamushi was isolated from the spleens of R. exulans and R. r. septicus. The favored ecotype of the chigger and rat hosts of R. tsutsugamushi appeared to be coarse, low-lying native vegetation on a porous coralline soil. These and similar nearby coral islands should be considered high risk areas for scrub typhus.

Animals↗
PubMed2006

Orientia tsutsugamushi in eschars from scrub typhus patients.

To verify the value of eschars for the diagnosis of scrub typhus and to characterize genotypes of Orientia tsutsugamushi in patients, we examined eschars and blood specimens of 7 patients from Shandong Province, People's Republic of China, for O. tsutsugamushi by polymerase chain reaction targeting the Sta56 gene. All 7 eschars and acute-phase blood samples were positive, while no specific DNA amplicons were obtained from the 7 convalescent-phase blood samples collected after antimicrobial drug therapy. The findings indicate that patients' eschars can be used for detection and genetic characterization of O. tsutsugamushi during the convalescent phase.

Adult↗
PubMed1997

Prevalence of genotypes of Orientia tsutsugamushi in patients with scrub typhus in Miyazaki Prefecture.

The genotypes of Orientia tsutsugamushi in patients with scrub typhus in Miyazaki Prefecture were examined by polymerase chain reaction (PCR) and the restriction fragment length polymorphism method. Specific patterns for genotypes Irie, Hirano, Tazume and Yoshimura were detected in 26, 6, 5 and 2 of 39 DNA samples obtained from peripheral blood mononuclear cells, respectively. DNA sequences of the PCR products from the Tazume strain were genetically very close to the Hirano strain and the Yoshimura strain was also very close to the Karp strain. Furthermore, the DNA sequences from the Irie and Tazume strains were completely homologous to the reported sequences of the Kawasaki and Kuroki strains, respectively.

Base Sequence↗
PubMed1991

Recent studies on scrub typhus and Rickettsia tsutsugamushi in Shandong Province--China.

In an outbreak of scrub typhus occurred 138 cases in 1986 in Menying County of Shandong Province of China which were confirmed through clinical and epidemiological surveys and laboratory techniques. In the endemic areas, the predominant species of mite is Leptotrombidium (L.) scutelarae and the predominant rodent is Apodemus agrarius, which may be the main vector and reservoir. Several strains of Rickettsia tsutsugamushi (R.T.) were obtained from mites, wild mice and patients, of which 3 human strains (SDH871, SDH875, SDH878) cause illness and some deaths in mice, except SDH871. The LD50 of SDH878 is 3.4. Cross-protection was observed among the strains, SDH871, SDH878, and prototype strain karp. Also the antibodies in mucoid peritoneal fluid were detectable with high titer. Shandong R.T. belongs to the serotype of the Gilliam strain.

Adult↗
PubMed1974

Transmission of Rickettsia orientalis to man by Leptotrombidium akamushi at a scrub typhus endemic area in Akita Prefecture, Japan.

During the summer seasons of 1956 through 1970, 93 larval trombiculid mites were removed from 386 individuals who had been bitten by chiggers in Jumonji, Akita Prefecture. All 87 larvae that were available for examination were identified as Leptotrombidium akamushi. Infestation of man occurred predominantly during July and August, but the period extended from June to November. The duration of attachment was approximately 1 to 3 days. Usually only 1 chigger was found on a victim but on occasion as many as 7 were removed at one time. Scrub typhus developed in 45 (11.7%) of the 386 farmers bitten by chiggers. Although patients with scrub typhus may have sustained multiple bites, only one eschar was found. However, 76% of the patients did not recognize a bite either at the site where an eschar subsequently appeared or elsewhere prior to the onset of disease. If it is assumed that workers who did not subsequently become ill were equally unaware of chigger bites, then the probable incidence of disease in chigger victims was 3.1%. The minimum infectivity rate of L. akamushi larvae in Akita Prefecture was estimated to be 2.3%. Based upon the assumption that infection was transmitted as the result of a single bite, the infective rate of chiggers attacking man was calculated to be 2.5%.

Arachnid Vectors↗
PubMed1950

[Scrub Typhus].

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4-Aminobenzoic Acid↗
PubMed2005

Scrub typhus vaccine candidate Kp r56 induces humoral and cellular immune responses in cynomolgus monkeys.

A truncated recombinant 56-kDa outer membrane protein of the Karp strain of Orientia tsutsugamushi (Kp r56) was evaluated in cynomolgus monkeys (Macaca fascicularis) for immunogenicity and safety as a vaccine candidate for the prevention of scrub typhus. This recombinant antigen induced strong humoral and cellular immune responses in two monkeys and was found to be well tolerated. Antigen-specific immunoglobulin M (IgM) and IgG were produced to almost maximal levels within 1 week of a single immunization. Peripheral blood mononuclear cells from vaccinated animals showed an induction of antigen-specific proliferation and gamma interferon production. The Kp r56 was not as efficient as infection with live organisms in preventing reinfection but was able to reduce the inflammation produced at the site of challenge. This report describes the results of the first systematic study of the immunogenicity of a recombinant scrub typhus vaccine candidate in a nonhuman primate model.

Animals↗
PubMed1980

Rodent and scrub typhus survey in a ricefield at Kramat Tunngak area, Tanjung Priok, Jakarta, Indonesia.

Trapping of small mammals in a ricefield at Kramat Tunggak around Tanjung Priok in Jakarta city, was carried out from July 1977 through June 1978. Of three species of rodents, R.argentiventer was found to be the predominant species in the ricefield. R.r.diardii was an intermittent resident, and the presence of R.norvegicus was interesting observation. S.murinus, a house shrew, was also present. R.argentiventer was the dominant species during the periods when the rice grains were available as a source of food. Infestation with Gamasid mites and non-vector chiggers was found common in all rodent species examined. R. argentiventer was the only species found infested with the classical scrub typhus vector (L. (L.) deliense). The density and mean chigger-load of the scrub typhus vector chiggers were found to be high in stages 4 and 5 of the ricefields when the micro-habitats were favourable. The oriental rat flea (X. cheopis) was found infesting all species of rodents.

Agriculture↗