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At least 793 records · Page 44Linked to original sources
PubMed1978

Serological evidence for a high incidence of transmission of Rickettsia tsutsugamushi in two Orang Asli settlements in Peninsular Malaysia.

Two communities of Orang Asli (aborigines) in Peninsular Malaysia were observed for evidence of Rickettsia tsutsugamushi infection over periods of 1-8 mo. Sequential sera were examined for antibody by the indirect immunofluorescence test. The incidence of infection in the two self-selected populations in the two communities was calculated to be 3.9% per month and 3.2% per month.

Adolescent↗
PubMed1985

Immunological studies of experimental tsutsugamushi disease in congenitally athymic (nude) mice.

Athymic mice were taken ill and died from infection with the high virulence as well as the low virulence strains of Rickettsia tsutsugamushi, and they did not improve in spite of tetracycline therapy. Moreover, neither 7S nor IgM antibody was detected by immunofluorescent antibody method in serum samples of athymic mice infected with the high virulence strain. Although immune serum-transfer exhibited some protective effect in athymic mice infected with the high virulence strain, it was far lower than in euthymic mice. Although both athymic and euthymic mice having received non-immune T-lymphocytes were taken ill and died, the mice having received immune T-lymphocytes survived infection with the high virulence strain. This protective capacity of T-lymphocytes was weak by 10 days after immunization of donor mice, became firm after a month and lasted as long as 12 months without decay. For athymic mice infected with the low virulence strain, not only immune but also non-immune T-lymphocytes from euthymic mice exhibited significant protective effect. By treatment of immune T-lymphocytes with anti-Thy-1.2 or anti-Lyt-1.2 alloserum, the protective capacity was lost entirely, and considerably diminished by treatment with anti-Lyt-2.2 alloserum in a homologous system using the high virulence strain. The results show that the inhibition of progress of tsutsugamushi disease is principally dependent on cellular immune mechanism(s) and that the production of antibody against R. tsutsugamushi is thymus-dependent.

Animals↗
PubMed1995

Eradication of Rickettsia tsutsugamushi from patients' blood by chemotherapy, as assessed by the polymerase chain reaction.

The presence of Rickettsia tsutsugamushi DNA in peripheral blood mononuclear cells of eight patients with tsutsugamushi disease was determined by the polymerase chain reaction during antibiotic treatment with minocycline or doxycycline. Rickettsia tsutsugamushi DNA was detectable in all samples from these patients collected the day before treatment began. After the initiation of chemotherapy, all samples tested positive on the third or fourth day, and one sample tested positive on the eighth day, showing a slow action of the drugs against the rickettsia within cells. Immune responses against R. tsutsugamushi also seemed to be important for eradication of the pathogens, as suggested by patients' high antibody titers.

Aged↗
PubMed1999

Seroepidemiologic survey of Orientia tsutsugamushi, Rickettsia typhi, and TT118 spotted fever group rickettsiae in rubber estate workers in Malaysia.

The seroprevalence of Orientia tsutsugamushi, Rickettsia typhi, and TT118 spotted fever group (SFG) rickettsiae in 300 rubber estate workers in Slim River, Malaysia was determined in December 1996 and March 1997. In December, which was the wet season, 23.3%, 3.0%, and 57.3% of the population had antibodies detected against the three rickettsiae, respectively. The highest seropositive rate of 40% was detected for single infection with SFG rickettsiae, followed by a rate of 15.3% for both O. tsutsugamushi and SFG rickettsiae among the rubber estate workers. Subjects less than 21 years old had a lower seroprevalence of SFG rickettsiae compared with the other age groups. Indians had a higher seroprevalence of O. tsutsugamushi compared with other ethnic groups. Rubber tappers had a higher seroprevalence of SFG rickettsiae compared with other occupational groups. During the dry season in March 1997, there was a significant increase in the seroprevalence of R. typhi. The seroconversion rates for IgM against O. tsutsugamushi, R. typhi, and SFG rickettsiae were 5.7%, 12.3%, and 15.1%, respectively, during the four-month period. Significant variations of antibody titers towards the three rickettsiae was noted among subjects who were bled twice. This suggests a significant and continual exposure of rubber estate workers to the three rickettsiae.

Adolescent↗
PubMed1979

Experimental Rickettsia tsutsugamushi infections in dogs.

Dogs were infected intravenously and intradermally with the Gilliam and Karp strains of R. tsutsugamushi. Although the development of clinical signs was related to the dose of the organism, Gilliam-infected dogs developed severer infections than those infected with Karp. Specific antibodies were demonstrated in sera of experimentally infected dogs.

Animals↗
PubMed1979

Comparison of experimental Rickettsia tsutsugamushi infections in silvered leaf (Presbytis cristatus) and cynomolgus (Macaca fascicularis) monkeys.

Both silvered leaf and cynomolgus monkeys were infected with the Gilliam, Karp and Kato strains of Rickettsia tsutsugamushi. The two species developed similar clinical syndromes, but the antibody responses were greater in cynomolgus monkeys. In both species of monkeys, the Gilliam strain induced more severe clinical manifestations. At 10 months post-infection, silvered leaf monkeys were immune to homologous intradermal (id) challenge. Cynomolgus monkeys, at 15 months post-infection, were relatively resistant to homologous intravenous challenge, but not to a homologous or heterologous id challenge.

Animals↗
PubMedDate not supplied

The effect of mouse age on the determination of Rickettsia tsutsugamushi virulence.

The effect of age on the susceptibility of ICR mice to lethal intraperitoneal (ip), Rickettsia tsutsugamushi infections was tested with five virulent strains--Karp, Kato, Gilliam, TA763, and TH1817--and three strains of reduced virulence--TA678, TA686, and TA716. Susceptibility differences were noted only in the ICR mice inoculated with two of the strains of reduced virulence, TA716 and TA678. With both strains, mice in the 12-weeks and younger age groups had lower death rates than did mice in the 21-weeks and older age groups. Also, CBA/CaJ mice of varying ages were inoculated intravenously with large doses of the Gilliam strain to determine the effect of age on susceptibility to acute death syndrome (ADS). A progressive increase in ADS resistance was seen in the 4-, 8-, 12-, and 16-week-old age groups. This study indicates that the age of mice used to test the virulence of R. tsutsugamushi strains may be an important consideration, especially when testing the ip lethality of strains of reduced virulence.

Age Factors↗
PubMed1985

Pathology of toxic death in mice following intravenous injection of Rickettsia tsutsugamushi strain gilliam: examination by light and scanning electron microscopy.

The pathologic manifestations of the toxic death elicited by the iv injection of mice with Rickettsia tsutsugamushi strain Gilliam were examined by light and scanning electron microscopic techniques to ascertain the cause of death. Light microscopic examinations of hematoxylin and eosin-stained sections of organs suggested the presence of fluid in the lungs; this was confirmed by an increase in the weight of the lungs of moribund mice. Scanning electron microscopy of blood cells demonstrated a marked crenation of erythrocytes from these mice. Death appears to be the result of shock brought on by vascular collapse secondary to plasma leakage.

Animals↗
PubMed1986

Suppression of lymphocyte responsiveness during acute Rickettsia tsutsugamushi infection in mice.

Lymphocytes from Inbred Balb/cyJ mice infected subcutaneously with 10(3) MLD50 of Rickettsia tsutsugamushi Karp strain were unresponsive to rickettsial antigens and phytohemagglutinin in the lymphocyte transformation assay between 11 and 28 days post-infection. There was, however, no correlation between this suppressed responsiveness to rickettsial antigens and the immune capacity to resist a normally lethal ip challenge with the Karp strain. Fourteen days after infection, these mice survived a potentially lethal Karp challenge. Naive recipients of day 14 post-infection mouse splenic lymphocytes also were partially protected against ip challenge. Karp strain-specific anti-rickettsial antibody reached a peak geometric mean titer of 260 during the period of apparent cellular unresponsiveness. However, day 14 post infection mice showed a fourfold decrease of antibody response to a T-dependent antigen, which suggests the presence of T-dependent antibody suppression in these mice.

Animals↗
PubMed1987

Evidence for infection caused by spotted fever group Rickettsia in Kyushu, Japan.

Of 50 cases that gave negative immunofluorescence reaction with Rickettsia tsutsugamushi among patients with suspected tsutsugamushi disease encountered in Miyazaki Prefecture during the last four years, three showed a significant rise in the antibody titer to Rickettsia montana, a species of spotted fever group. This paper reports evidence for the occurrence of the rickettsial infection of the spotted fever group in Kyushu, Japan.

Adult↗