Short report: prevalence of antibodies against spotted fever, murine typhus, and Q fever rickettsiae in humans living in Zambia. (1/103)

The causative agents of rickettsial diseases (Rickettsia conorii, R. typhi, and Coxiella burnetii) have been reported throughout the African continent. However, there have been no reports on epidemiologic surveys of these infections in Zambia. This study was designed to clarify the prevalence of three rickettsioses in 377 humans in Zambia. The seroprevalence of antibodies against R. conorii, R. typhi, and C. burnetii was 16.7%, 5.0%, and 8.2%, respectively. The rates of antibody positivity against R. conorii and C. burnetii were higher in the eastern (23.1% and 11.8%) and western (16.8% and 7.4%) areas of Zambia than in the northern (3.0% and 3.0%) area of this country. There was little difference among the three areas in the distribution of antibodies against R. typhi. Since cattle breeding is more extensive in the western and eastern areas than in the northern area, it is thought that cattle-breeding areas are foci of R. conorii and C. burnetii infections in Zambia.  (+info)

Differential up-regulation of circulating soluble selectins and endothelial adhesion molecules in Sicilian patients with Boutonneuse fever. (2/103)

In 150 patients with Boutonneuse fever (BF), caused by Rickettsia conorii, we studied the plasma levels of soluble L-selectin (sL-selectin), vascular cell adhesion molecule-1 (sVCAM-1), intercellular adhesion molecule-1 (sICAM-1) and E-selectin (sE-selectin) in various phases of disease to clarify their role in disease evolution. Results indicate that during the acute phase of BF there is a significant increase in the serum levels of sL-selectin, sE-selectin, sVCAM-1 and sICAM-1. sL-selectin and sVCAM-1 returned to normal levels in the third week of disease, whereas sE-selectin and sICAM-1 persisted at significantly high levels even after the third week. The secretion of these soluble CAMs in BF is mainly the result of leucocyte expression and endothelial cell activation, but secretion also appears to mediate anti-inflammatory activities, moderating leucocyte adhesion and reducing in particular lymphocyte and monocyte infiltration. Only sL-selectin serum levels were found to correlate with the acute phase of infection characterized by fever.  (+info)

Epidemiological characteristics of spotted fever in Israel over 26 years. (3/103)

During the summer of 1997, 2 confirmed and several suspected fatal cases of spotted fever (SF) occurred in previously healthy young adults in Israel. This unusual cluster of events stimulated the current study. The incidence of SF in Israel from 1971-98 was analyzed. Incidence increased until 1980, declined until 1994, and increased slightly from 1994-97. Incidence was higher during the summer, among children aged 0-9 years, and in rural settlements in central Israel. From 1971-1997, 31 deaths were reported, mostly in the elderly. The deaths that occurred in 1997 are a reminder that, despite the fact that morbidity due to SF is described mainly in children, SF can have a rapidly fatal outcome in healthy young adults. Thus, even during periods of low incidence, careful monitoring and high awareness for prompt diagnosis and treatment are needed.  (+info)

New Rickettsiae in ticks collected in territories of the former soviet union. (4/103)

Dermacentor nuttallii from Siberia, Rhipicephalus sanguineus from Crimea, and Rh. pumilio from the Astrakhan region were infected with Rickettsia sibirica (12%), R. conorii (8%), and the Astrakhan fever agent (3%), respectively. Three new Rickettsiae of the R. massiliae genogroup were identified in ticks by 16S rDNA, gltA, and ompA sequencing.  (+info)

Short report: isolation and identification of two spotted fever group rickettsial strains from patients in Catalonia, Spain. (5/103)

Two rickettsial strains, 16B (previously isolated) and FB1, were isolated from blood from patients with Mediterranean spotted fever in Catalonia, Spain. These are the only 2 human rickettsial isolates of the spotted fever group obtained so far in Spain. These strains were identified by the polymerase chain reaction and sequence analysis of a fragment of the outer membrane protein A (ompA) gene. The partial ompA sequence was found to be 100% identical with that of Rickettsia conorii (Malish 7 strain) for both strains. These results confirm the presence of R. conorii in Catalonia, despite the fact that in a previous study, no R. conorii were isolated, but a new rickettsial strain of the spotted fever group (Bar29) was isolated from dog ticks (Rhipicephalus sanguineus) in Catalonia. Further studies are necessary to get a better knowledge of the epidemiology of rickettsiae in Catalonia.  (+info)

The rickettsial outer-membrane protein A and B genes of Rickettsia australis, the most divergent rickettsia of the spotted fever group. (6/103)

The genes for rickettsial outer-membrane protein A (rOmpA), a distinguishing feature of spotted fever group (SFG) rickettsiae, and rOmpB, a genus-specific protein, were identified and sequenced in Rickettsia australis. The amino acid sequences of domains I, III and IV of the R. australis rOmpA share close homology with those of rOmpA of other SFG rickettsiae, but the repeat region (domain II) is dramatically different from that of other known SFG rOmpA. R. australis rOmpB is more similar to rOmpB of other SFG rickettsiae than to that of typhus group rickettsiae.  (+info)

Critical role of cytotoxic T lymphocytes in immune clearance of rickettsial infection. (7/103)

Cytotoxic T-lymphocyte (CTL) activity developed against the major infected target cells of rickettsial infections, endothelial cells and macrophages. Spleen cells from mice immune to Rickettsia conorii exerted specific major histocompatibility complex (MHC) class I-matched CTL activity against R. conorii-infected SVEC-10 endothelial cells, with peak activity on day 10. Similarly, spleen cells from Rickettsia australis-immune mice exerted specific CTL activity against an R. australis-infected macrophage-like cell line. Gamma interferon (IFN-gamma) gene knockout mice were more than 100-fold more susceptible to R. australis infection than wild-type C57BL/6 mice. MHC class I gene knockout mice were the most susceptible, more than 50,000-fold more susceptible to a lethal outcome of R. australis infection than wild-type C57BL/6 mice. These results indicate that CTL activity was more critical to recovery from rickettsial infection than were the effects of IFN-gamma. The observation that perforin gene knockout mice were more than 100-fold more susceptible than wild-type C57BL/6 mice indicates that perforin-mediated activity accounts for a large component, but not all, of the CTL-mediated antirickettsial effect. CTL activity was expressed by immune CD8 T lymphocytes. Adoptive transfer of immune CD8 T lymphocytes from IFN-gamma gene knockout mice into R. australis-infected IFN-gamma gene knockout mice dramatically reduced the infectious rickettsial content in the organs, confirming that CD8 T lymphocytes provide immunity against rickettsiae besides that provided by the secretion of IFN-gamma. CTLs appear to be crucial to recovery from rickettsial infection.  (+info)

Rickettsia felis: molecular characterization of a new member of the spotted fever group. (8/103)

In this report, placement of Rickettsia felis in the spotted fever group (SFG) rather than the typhus group (TG) of Rickettsia is proposed. The organism, which was first observed in cat fleas (Ctenocephalides felis) by electron microscopy, has not yet been reported to have been cultivated reproducibly, thereby limiting the standard rickettsial typing by serological means. To overcome this challenge, several genes were selected as targets to be utilized for the classification of R. felis. DNA from cat fleas naturally infected with R. felis was amplified by PCR utilizing primer sets specific for the 190 kDa surface antigen (rOmpA) and 17 kDa antigen genes. The entire 5,513 bp rompA gene was sequenced, characterized and found to have several unique features when compared to the rompA genes of other Rickettsia. Phylogenetic analysis of the partial sequence of the 17 kDa antigen gene indicated that R. felis is less divergent from the SFG rickettsiae than from the TG rickettsiae. The data corroborate results from previous reports that analysed the citrate synthase, 16S rRNA, rompB (135 kDa surface antigen), metK, ftsY, polA and dnaE genes that placed R. felis as a member of the SFG. The organism is passed trans-stadially and transovarially, and infection in the cat flea has been observed in the midgut, tracheal matrix, muscle, hypodermis, ovaries and testes.  (+info)