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PubMed1966

In vitro cultivation of the rickettsial agent of trench fever.

Although trench fever appears to be endemic in many areas of the world, recognition of the disease has been handicapped by the difficulties of making a clinical diagnosis and the unavailability of a simple laboratory procedure to establish the etiology. The author describes a method for the in vitro cultivation of Rickettsia quintana that provides a relatively simple means for the laboratory diagnosis of trench fever. R. quintana can be propagated with ease from the blood of patients directly on blood agar incubated at 37 degrees C for 12-14 days under a gas tension of 5% CO(2) in air. The number of rickettsiae circulating in the patient's peripheral blood can be quantitated. The protracted rickettsiaemia in trench fever makes for a relatively long period during which blood culture can be usefully employed.In the course of studies with the method described, it was found that erythrocytes contain a factor (or, possibly, factors) essential for multiplication of R. quintana; this factor is cryostable and thermostable and may be haemoglobin. Blood serum also promotes multiplication.

Humans↗
PubMed2003

Pathogenic mechanisms of diseases caused by Rickettsia.

The specter of bioterrorism employing genetically engineered Rickettsia resistant to all antibiotics should reawaken the world's desire to elucidate the pathogenesis of typhus and spotted fever rickettsioses in a search for mechanisms vulnerable to interdiction. The pathogenetic sequence includes rickettsial entry into the dermis, hematogenous dissemination to vascular endothelial cells (most critically in brain and lungs), increased vascular permeability, edema, and immunity mediated by NK cells, IFN-gamma, TNF-alpha, RANTES, antibodies, and cytotoxic T lymphocytes. Silverman has demonstrated the role of reactive oxygen species (ROS) produced by R. rickettsii-infected endothelial cells in peroxidative damage to cell membranes in vitro, and Heinzen has described actin-based rickettsial intracellular mobility and intercellular spread. At this point the availability of sequences of rickettsial genomes and excellent animal models of rickettsioses have yielded insufficient progress towards the identification of rickettsial virulence factors and knowledge of the importance of injury mediated by ROS, phospholipase A(2), protease(s) or other mechanisms in vivo. Attention to the rickettsiosis-associated procoagulant state led to determination that hemostatic mechanisms largely prevent major hemorrhage without disseminated intravascular coagulation or thrombosis-mediated ischemia. Particularly lacking is knowledge of early events in vivo at the portal of entry in skin (or lung), of the effects of the inoculum medium (arthropod saliva or feces), mediators produced by infected endothelium under conditions of flow and of the contributions in vivo of immune effectors to pathology, of the role of apoptosis in rickettsial infection, and of the endothelial cell alterations that account for increased vascular permeability. The host cell receptor for the Rickettsia ligand and the mechanism of rickettsial escape from the phagosome need to be elucidated.

Chronic Disease↗
PubMed2004

Application of a reverse line blot assay to the study of haemoparasites in cattle in Uganda.

Recent advances in genomic technology have focused many veterinary researchers on the possibility of producing one multivalent recombinant vaccine against all the haemoparasites that infect cattle in the tropics. Before such a vaccine is developed it is essential to define target cattle populations as well as the range of anti-pathogen vaccines required in order to control disease. To further this objective, we have evaluated a reverse line blot (RLB) assay, which simultaneously detects the principal tick transmitted protozoan and rickettsial cattle pathogens, in different epidemiological scenarios in Uganda. A critical question is the sensitivity, particularly in relation to detecting carrier animals. As Theileria parva is considered to be the most important pathogen in the region, we assessed the sensitivity of the RLB assay for T. parva and showed that 1-2 x 10(3) parasites per ml of blood could be detected-a level comparable with previously developed PCR methods and well below conventional microscopic detection. We applied the RLB assay to evaluate the differences in pathogen profiles between crossbred and indigenous cattle and show that there were different profiles, with a low prevalence of T. parva and Theileria taurotragi in the indigenous cattle compared to a high prevalence in the crossbred cattle. In contrast, we show higher prevalences of Theileria mutans and Theileria velifera in the indigenous compared to the crossbred cattle. Interestingly Anaplasma marginale, Babesia bovis and Babesia bigemina were of low prevalence but a high prevalence of Ehrlichia bovis was seen, raising the question of whether this rickettsial species could be pathogenic in cattle. Analysis of animals with clinical symptoms of East Coast Fever showed that, while T. parva is a major cause of these symptoms, T. mutans and possibly T. taurotragi and T. velifera, may also cause clinical disease. Overall, the results presented here highlight the complexity of tick-borne pathogen infections in cattle in Uganda.

Anaplasmosis↗
PubMed2002

[The Brill-Zinsser disease still occurs in Croatia: retrospective analysis of 25 hospitalized patients].

The article presents epidemiological, clinical, laboratory and therapeutic characteristics of Brill-Zinsser disease (BZD). A total of 25 cases of BZD were retrospectively analyzed during the period from January 1, 1980 through December 31, 2000, and etiology was confirmed by rickettsial complement-fixation test (CFT). The majority of cases 15 (60%) quoted history of primary attack of epidemic typhus during or after the World War II. During the course of the disease in our patients different organic systems were involved. Aseptic meningitis was verified in 21 (84%) patients, rash in 17 (68%), liver lesion in 14 (56%), pneumonitis in 7 (28%), myopericarditis in 7 (28%) and 5 (20%) had renal lesion. Not a single clinical symptom or finding of disease has a diagnostic particularity. However, long term fever, headache, rash and aseptic meningitis, or information of infestation with lice in childhood, or a history of epidemic typhus should arouse a suspicion of this disease, which still occurs in Croatia.

Adult↗
PubMed1979

Exposure of guinea pigs to Rickettsia rickettsii by aerosol, nasal, conjunctival, gastric, and subcutaneous routes and protection afforded by an experimental vaccine.

Guinea pigs were inoculated with Rocky Mountain spotted fever by the aerosol, conjunctival, subcutaneous, intragastric, and intranasal routes. Rickettsial infection was produced by all routes except intragastric. All animals with clinical signs of disease developed agglutinating antibody, and most developed a cell-mediated immune response. Disease produced by all experimental routes (except intragastric) was indistinguishable. The tissue culture-derived inactivated vaccine produced in this laboratory protected guinea pigs against an aerosol challenge.

Administration, Intranasal↗
PubMed2002

Genetic identification of rickettsiae isolated from ticks in Japan.

Following the description in Japan of Japanese spotted fever, caused by Rickettsia japonica, a search for the vector of this disease led to the isolation of several rickettsiae from various tick species. Sixty-three rickettsial isolates were obtained from six different tick species, and six type strains were described by PCR and monoclonal antibody testing. We identified these six strains by amplification and sequencing of the genes encoding 16S rRNA and citrate synthase. We confirmed that the isolates from Dermacentor taiwanensis and Haemaphysalis flava ticks were R. japonica isolates. In Ixodes ovatus, Ixodes persulcatus, and Ixodes monospinosus, we identified a Rickettsia identical or closely related to Rickettsia helvetica, a species that is pathogenic for humans and that to date has only been found in Europe. Finally, we identified a new genotype of unknown pathogenicity, genotype AT, that was isolated from Amblyomma testudinarium ticks and that is closely related to a Slovakian genotype obtained from Ixodes ricinus ticks.

Animals↗
PubMed2000

Pathogenesis of liver lesions caused by experimental infection with Piscirickettsia salmonis in juvenile Atlantic salmon, Salmo salar L.

Piscirickettsia salmonis, the etiologic agent of salmonid rickettsial septicemia (SRS), or piscirickettsiosis, causes substantial economic losses to the salmon industry. The pathogenesis of the disease has not been fully characterized. The aim of this study is to describe the hepatic lesions associated with experimental P. salmonis infection in Atlantic salmon juveniles. Fish were maintained in fresh water and inoculated intraperitoneally (IP), orally, or on the gill surface with P. salmonis. A group of uninfected fish was kept as control. Liver samples from 5 fish in each inoculated group and 3 controls were collected weekly and processed for histological and immunohistochemical examination. Thickening of the liver capsule by inflammatory cells was a characteristic histologic feature of IP inoculated fish. Three weeks post-IP inoculation, 8 fish had died and 2 fish were sampled. Histological changes at this time consisted of vasculitis, presence of fibrin thrombi, vacuolated hepatocytes and focal areas of necrosis. Leukocytes containing intracytoplasmic basophilic microorganisms were seen within hepatic sinusoids. Vasculitis and intracytoplasmic vacuoles were prominent features in fish inoculated orally and on the gill surface. The presence of P. salmonis within hepatocellular vacuoles, endothelial cells, and leucocytes was confirmed by immunohistochemistry. The intracellular location of P. salmonis and the vascular damage seen in infected fish are characteristic of rickettsial infections. Histological lesions induced by experimental infection with P. salmonis using the oral and gill surface routes were similar to those observed in natural outbreaks of piscirickettsiosis. The tropism of P. salmonis for endothelial cells explains the vascular lesions observed in SRS, whereas hepatic lesions are due to ischemic necrosis and direct injury by intracytoplasmic organisms.

Animals↗
PubMed2004

[Spotted fever Rickettsiae. Their immunodominant proteins and immune response].

The organisms of Rickettsia species are gram (-) bacteria that cause severe illnesses in humans and are an important health problem in several countries around the world, including Mexico. The presence of different antigens between species and also in different strains of the same specie is an obstacle for vaccine development and serological diagnosis. There are important advances in the knowledge of the rickettsial antigenic structure and the resulting immune response in infected hosts, including humans. This review covers these topics and provides an overview about the development of vaccines and accessible diagnostic methods for diseases caused by Rickettsia.

Animals↗
PubMed2005

Investigation of an outbreak of scrub typhus in the himalayan region of India.

In Indira Gandhi Medical College, Himachal Pradesh, India, during autumn of 2003 (September-November), more than 100 cases of fever of unknown origin (FUO) were reported with 15 ensuing deaths. In addition to all routine investigations and cultures, the Weil-Felix test was incorporated for the investigation of these cases. Antigen was procured from the Central Research Institute, Kasauli. Forty-six percent (45/96) of the cases demonstrated a > or =1:80 titer of agglutinins against OXK antigen. A team from the National Institute of Communicable Diseases, New Delhi, confirmed the antibodies for scrub typhus in some of the serum samples tested for leptospirosis, dengue fever, and rickettsial infections. Twelve blood samples positive for OXK antigen were sent to the Defense Research Development Establishment, Gwalior, for polymerase chain reaction studies, but none of the samples were positive, as all of the patients were already on broad-spectrum antibiotics and had reported to our hospital after 7-10 days of fever. At our institute, the Weil-Felix test has now been rountinely introduced for the investigation of cases of FUO, and the results until April 2004 (150 cases) revealed the presence of other rickettsial infections prevalent in the region. To evaluate the epidemiology and magnitude of the problem, further prospective studies are required.

Agglutination Tests↗
PubMed1999

Ehrlichia chaffeensis in archived tissues of a white-tailed deer.

White-tailed deer (Odocoileus virginianus) play an integral role in the natural history of Ehrlichia chaffeensis, the causative agent of human monocytic ehrlichiosis (HME). Paraffinized tissues from a white-tailed deer submitted as a diagnostic case to the Southeastern Cooperative Wildlife Disease Study (Athens, Georgia, USA) in October of 198.5 and originally described as infected with an unidentified rickettsial organisim were re-examined by specific nested polymerase chain reaction (PCR) for evidence of infection with Ehrlichia spp. Ehrlichia chaffeensis was identified from the bone marrow and inguinal lymph node of this deer based on amplification of a characteristic sequence-confirmed 16S rDNA fragment from these tissues. Parallel PCR tests on the same samples were negative for 16S rDNA fragments of the agent of human granulocytic ehrlichiosis (HGE) and for an Ehrlichia-like organism widely distributed in white-tailed deer populations. This report describes detection of E. chaffeensis in archived tissue from a deer collected before the index case of human monocytic ehrlichiosis was established.

Animals↗