Avidity of IgG to Rickettsia prowazekii and the presence of specific IgM in blood sera for retrospective analysis of the 1998 epidemic typhus outbreak in Russia.

The authors applied a new methodological approach based not only on the study of IgM/IgG to Rickettsia prowazekii in sera, but also on the estimation of the avidity index of specific IgG. The data allowed the authors to draw new conclusions about the 1998 epidemic typhus outbreak in Russia.

Seroprevalence of Scrub Typhus, Typhus, and Spotted Fever Among Rural and Urban Populations of Northern Vietnam.

AbstractRickettsial infections are recognized as important causes of fever throughout southeast Asia. Herein, we determined the seroprevalence to rickettsioses within rural and urban populations of northern Vietnam. Prevalence of individuals with evidence of prior rickettsial infections (IgG positive) was surprisingly low, with 9.14% (83/908) testing positive to the three major rickettsial serogroups thought to circulate in the region. Prevalence of typhus group rickettsiae (TG)-specific antibodies (6.5%, 58/908) was significantly greater than scrub typhus group orientiae (STG)- or spotted fever group rickettsiae (SFG)-specific antibodies (P < 0.05). The majority of TG seropositives were observed among urban rather than rural residents (P < 0.05). In contrast, overall antibody prevalence to STG and SFG were both very low (1.1%, 10/908 for STG; 1.7%, 15/908 for SFG), with no significant differences between rural and urban residents. These results provide data on baseline population characteristics that may help inform development of Rickettsia serological testing criteria in future clinical studies.

Molecular and serological evidence of flea-associated typhus group and spotted fever group rickettsial infections in Madagascar.

BACKGROUND: Rickettsiae are obligate intracellular bacteria responsible for many febrile syndromes around the world, including in sub-Saharan Africa. Vectors of these pathogens include ticks, lice, mites and fleas. In order to assess exposure to flea-associated Rickettsia species in Madagascar, human and small mammal samples from an urban and a rural area, and their associated fleas were tested. RESULTS: Anti-typhus group (TGR)- and anti-spotted fever group rickettsiae (SFGR)-specific IgG were detected in 24 (39%) and 21 (34%) of 62 human serum samples, respectively, using indirect ELISAs, with six individuals seropositive for both. Only two (2%) Rattus rattus out of 86 small mammals presented antibodies against TGR. Out of 117 fleas collected from small mammals, Rickettsia typhi, a TGR, was detected in 26 Xenopsylla cheopis (24%) collected from rodents of an urban area (n = 107), while two of these urban X. cheopis (2%) were positive for Rickettsia felis, a SFGR. R. felis DNA was also detected in eight (31%) out of 26 Pulex irritans fleas. CONCLUSIONS: The general population in Madagascar are exposed to rickettsiae, and two flea-associated Rickettsia pathogens, R. typhi and R. felis, are present near or in homes. Although our results are from a single district, they demonstrate that rickettsiae should be considered as potential agents of undifferentiated fever in Madagascar.

A murine model of infection with Rickettsia prowazekii: implications for pathogenesis of epidemic typhus.

Epidemic typhus remains a major disease threat, furthermore, its etiologic agent, Rickettsia prowazekii, is classified as a bioterrorism agent. We describe here a murine model of epidemic typhus that reproduced some features of the human disease. When BALB/c mice were inoculated intravenously with R. prowazekii (Breinl strain), they survived but did not clear R. prowazekii infection. Immunohistological analysis of tissues and quantitative PCR showed that R. prowazekii was present in blood, liver, lungs and brain 1 day after infection and persisted for at least 9 days. Importantly, infected mice developed interstitial pneumonia, with consolidation of the alveoli, hemorrhages in lungs, multifocal granulomas in liver, and hemorrhages in brain, as seen in humans. Circulating antibodies directed against R. prowazekii were detected at day 4 post-infection and steadily increased for up to 21 days, demonstrating that R. prowazekii lesions were independent of humoral immune response. R. prowazekii-induced lesions were associated with inflammatory response, as demonstrated by elevated levels of inflammatory cytokines including interferon-gamma, tumor necrosis factor and the CC chemokine RANTES in the lesions. We concluded that the BALB/c mouse strain provides a useful model for studying the pathogenic mechanisms of epidemic typhus and its control by the immune system.

Survey of three bacterial louse-associated diseases among rural Andean communities in Peru: prevalence of epidemic typhus, trench fever, and relapsing fever.

Typhus and other louse-transmitted bacterial infections in Peruvian sierra communities are known to occur but have not recently been assessed. In this study, 194 of 1,280 inhabitants of four villages in Calca Province in the Urubamba Valley were included. Thirty-nine (20%) of the 194 volunteers had antibodies to Rickettsia prowazekii, whereas 24 (12%) had antibodies to Bartonella quintana and 2 against Borrelia recurrentis. There was a significant correlation between the presence of infesting ectoparasites and antibodies to R. prowazekii, as well as between antibodies to R. prowazekii and ectoparasite infestation and fever in the previous 6 months. The proportion of inhabitants infested with ectoparasites was significantly higher in the highest-altitude village than in the other three villages. Two volunteers' antibody levels suggested a recent typhus infection, but only B. quintana DNA was amplified from lice. Epidemic typhus remains extant in the area, and B. quintana infections were encountered and documented for the first time in South America.

Structure of the acid-labile galactosyl phosphate-containing O-antigen of the bacterium Proteus vulgaris OX19 (serogroup O1) used in the Weil-Felix test.

The structure of the O-specific polysaccharide chain of Proteus vulgaris OX19 lipopolysaccharide which determines the O1 specificity of Proteus and is used in the Weil-Felix test for diagnostics of rickettsiosis was established. On the basis of 1H- and 13 C-NMR spectroscopy, including two-dimensional correlation spectroscopy (COSY), H-detected 1H, 13C heteronuclear multiple-quantum coherence (HMQC), and rotating-frame nuclear Overhauser effect spectroscopy (ROESY), it was found that the polysaccharide consists of branched pentasaccharide repeating units containing D-galactose, 2-acetamido-2-deoxy-D-glucose, 2-acetamido-2-deoxy-D-galactose, and 2-acetamido-2,6-dideoxy-D-glucose (QuiNAc, two residues), which are connected to each other via a phosphate group (P): [formula: see text]. The polysaccharide is acid-labile, the glycosyl phosphate linkage being cleaved at pH 4.5 (70 degrees C) to give a phosphorylated pentasaccharide with a galactose residue at the reducing end. Structural analysis of the oligosaccharide and a product of its dephosphorylation with 48% hydrofluoric acid using 1H- and 13C-NMR spectroscopy and electrospray ionization mass spectrometry confirmed the structure of the polysaccharide.

Serological response of patients suffering from primary and recrudescent typhus: comparison of complement fixation reaction, Weil-Felix test, microimmunofluorescence, and immunoblotting.

Microimmunofluorescence and Western immunoblotting were compared with the classical complement fixation reaction and the Weil-Felix test to study the serological responses of patients to Rickettsia prowazekii and both Proteus vulgaris OX19 and OX2 during primary and recrudescent typhus infections. The serological response to R. prowazekii was found to be similar during primary and recrudescent typhus, and all sera examined contained antibodies to the same R. prowazekii cell structures. Immunoglobulin G (IgG) and IgM were found to be the dominant anti-R. prowazekii immunoglobulins in all sera tested and were found to be directed against the 100-kDa protein and the lipopolysaccharide. IgA antibodies, when present, were mainly against the 100-kDa protein. For P. vulgaris, IgG antibodies recognized the proteins and lipopolysaccharides of both OX19 and OX2 serotypes; IgM antibodies were directed against the P. vulgaris OX2 lipopolysaccharide. In addition, donor blood sera, which were negative by microimmunofluorescence, were found to contain IgG immunoglobulins reacting with R. prowazekii protein antigens of 135, 60, and 47 kDa by western immunoblotting.

A clinico-epidemiological study of epidemic typhus in Africa.

Epidemic, louse-borne typhus persists in the rugged, mountainous areas of Ethiopia and much of northeastern and central Africa as well as in the rural highlands of Central and South America, where the conditions of living favor the harboring of body lice and where antibiotic treatment and effective louse-control measures are unavailable. The historical significance and current epidemiology of typhus, including the reservoir of Rickettsia prowazekii in flying squirrels in the United States, are reviewed, and the clinical presentation, laboratory findings, and hospital course in the cases of 60 patients admitted with epidemic, louse-borne typhus to the St. Paul's Hospital in Addis Ababa, Ethiopia, are described. Treatment of this disease with oral doxycycline, tetracycline, or chloramphenicol prevents complications and results in prompt resolution of symptoms.

Serological study of louse borne and flea borne typhus in Addis Ababa.

A total of 500 subjects (288 males and 212 females) were tested in Addis Ababa, Ethiopia, in Virology and Rickettsiology Division of the National Research Institute of Health, in 1987, for anti R. prowazekii using Complement Fixation Test (CFT). Out of these 58 subjects (41 males and 17 females) were also tested for anti R. typhi using the same test. The study population included three groups. Group I included 200 patients referred to the National Research Institute of Health (NRIH) for the Weil-Felix test for the diagnosis of typhus. Group II consisted of 200 patients with febrile illness visiting the Outpatient Department (OPD) of St. Paul's Hospital. Group III included 100 blood donors' serum samples included from previous collections. The blood donors had no sign of febrile illness during the collection of the blood samples. The results showed that anti R. prowazekii was detected in 38 subjects (7.6%). The sex ratio among the positive subjects indicated that there were 32 males (22%) and 6 females (2.8%). From the 58 subjects who were also tested for anti R-typhi only 7 (5 males and 2 females) (12%) were found to be positive. Only one person was found to be positive both for anti R. prowazekii and anti R-typhi. From 200 samples (Group-I) tested both by the Weil-Felix test and by Complement Fixation Test for anti R. prowazekii only 4 samples were positive by both test, thus showing very low percent agreement.(ABSTRACT TRUNCATED AT 250 WORDS)